bluuebunny/crossref_metadata_2025 huggingface dataset:
Exercise-induced ST-segment depression in patients without restenosis after coronary angioplasty. Relation to preprocedural impaired left ventricular function.
Authors: Beregi J P , Bauters C , McFadden E P , Quandalle P , Bertrand M E , Lablanche J M
Published: June 2012

BACKGROUND

ST-segment depression during exercise testing is frequently observed in the absence of restenosis after coronary angioplasty.

METHODS AND RESULTS

We studied the determinants of this phenomenon in 70 consecutive patients with unstable angina related to a single left anterior descending coronary artery lesion who had successful angioplasty without restenosis (< 50% stenosis by quantitative angiography). We compared preangioplasty clinical, angiographic, and hemodynamic variables in the group with positive (ExT Pos, n = 35; ST depression, 2.3 +/- 0.9 mm) and negative (ExT Neg, n = 35; ST depression, 0.3 +/- 0.5 mm) results on exercise testing at follow-up angiography. At this time, minimal lumen diameter (1.7 +/- 0.4 mm) and mean residual stenosis (34 +/- 11%) in the ExT Pos group were not significantly different from the values (1.9 +/- 0.5 mm, 38 +/- 10%) in the ExT Neg group. Before angioplasty, the ExT Pos group had a lower ejection fraction (63 +/- 8% versus 68 +/- 9%, P < .05), more marked anterior hypokinesis estimated by the extent of anterior wall contraction on quantitative ventriculography (P < .05), and a greater end-systolic volume (30 +/- 11 versus 25 +/- 9 mL/m2, P < .05) than the ExT Neg group. At follow-up angiography, regional anterior wall motion was normal in 68 patients (97%). Anterior hypokinesis before angioplasty was strongly associated (P < .01) with a positive exercise test at control (71% compared with 31% in patients with normal wall motion before angioplasty).

CONCLUSIONS

In the absence of significant epicardial stenosis after angioplasty, ST-segment depression is strongly associated with the presence of preprocedural regional ventricular dysfunction that has recovered at follow-up angiography.
Forearm vascular responsiveness to alpha 1- and alpha 2-adrenoceptor stimulation in patients with congestive heart failure.
Authors: Indolfi C , Maione A , Volpe M , Rapacciuolo A , Esposito G , Ceravolo R , Rendina V , Condorelli M , Chiariello M
Published: June 2012

BACKGROUND

The alpha-adrenergic component of the sympathetic nervous system plays a major role in the pathophysiology, clinical manifestations, and natural history of human congestive heart failure (CHF). However, the functional integrity of vascular alpha 1- and alpha 2-adrenoceptors in CHF remains to be elucidated. The present study was designed to assess the vascular responsiveness of alpha 1- and alpha 2-adrenoceptors in patients with CHF.

METHODS AND RESULTS

To evaluate alpha 1- and alpha 2-adrenoceptor responsiveness, we studied the effects of the regional infusion into the brachial artery of increasing doses of phenylephrine (a selective alpha 1-adrenoceptor agonist) and BHT 933 (a selective alpha 2-adrenoceptor agonist) on vascular responses in 12 healthy subjects and in 24 patients with CHF secondary to primary dilated cardiomyopathy or ischemic heart disease. Left ventricular ejection fraction was measured by radionuclide angiography, and forearm blood flow was determined by venous occlusion plethysmography. Phenylephrine reduced forearm blood flow in normal subjects from 5.2 +/- 0.9 to 2.5 +/- 0.6 mL per 100 mL of tissue/min (P < .05) at the highest dose (-50.8 +/- 4.8% versus baseline). A similar vasoconstriction was obtained in patients with CHF (from 3.5 +/- 0.5 to 1.5 +/- 0.2 mL per 100 mL of tissue/min (P < .05) (-58.7 +/- 5.0% versus baseline). The dose-response curves produced by phenylephrine in the two groups were comparable. The highest dose of BHT 933 reduced forearm blood flow in normal subjects from 5.3 +/- 0.9 to 2.3 +/- 0.6 mL per 100 mL of tissue/min (P < .05) (-59.0 +/- 4.9% versus baseline). In patients with CHF, a similar vasoconstriction was obtained (from 4.2 +/- 0.8 to 1.5 +/- 0.3 mL per 100 mL of tissue/min, P < .05, -62.1 +/- 6.5% versus baseline). The dose-response curves produced by BHT 933 also were comparable in the two groups. In patients with CHF, plasma concentrations of norepinephrine were significantly higher than in normal subjects.

CONCLUSIONS

The results of the present study demonstrate that alpha 1- and alpha 2-adrenoceptor stimulations produced an equivalent vasoconstriction in patients with CHF and in normal subjects. This indicates that the vascular responsiveness to alpha-adrenoceptor agonists may be preserved in the limb vessels of patients with CHF.
Catheter-induced mechanical conduction block of right-sided accessory fibers with Mahaim-type preexcitation to guide radiofrequency ablation.
Authors: Cappato R , Schlüter M , Weiss C , Siebels J , Hebe J , Duckeck W , Mletzko R U , Kuck K H
Published: June 2012

BACKGROUND

Accessory pathways originating at the tricuspid annulus that exhibit decremental antegrade conduction properties (Mahaim-type preexcitation) are amenable to radiofrequency (RF) current catheter ablation. However, a reliable and reproducible strategy for mapping and ablation of these fibers is lacking.

METHODS AND RESULTS

Eleven patients with preexcited atrioventricular tachycardia involving a decrementally conducting antegrade accessory pathway underwent complete electrophysiological evaluation and subsequent attempts at RF catheter ablation. Mechanical conduction block at the subannular level of the atrial input to the accessory fiber was induced by catheter manipulation in 8 patients, in 2 of them during atrial fibrillation. RF current was delivered, after resumption of preexcitation, to the site of mechanical block during atrial pacing (n = 6) or atrial fibrillation (n = 2) and eliminated the accessory pathway in all 8 patients. In another patient, mechanical block was not observed, but ablation of the atrial accessory fiber insertion was achieved at the subannular level during atrioventricular tachycardia. The anatomic site of ablation along the tricuspid annulus was anterolateral (n = 1), lateral (n = 3), or posterolateral (n = 5). Failures were encountered in the first patient of the series in whom ablation attempts were directed at the ventricular insertion of the accessory fiber and in a patient in whom ablation of the atrial insertion was attempted at the supraannular level. Recurrence of preexcitation within 12 hours was observed in 5 of 6 patients in whom ablation had been achieved during atrial pacing. Eventually successful repeat sessions were performed the following day using a simplified ablation approach. Thus, a median of 5 RF pulses (range, 1 to 26) per accessory fiber eliminated conduction in 9 (82%) of the 11 patients in 1.9 +/- 0.9 sessions. During a follow-up of 9.5 +/- 2.3 months, preexcitation recurred in 1 patient.

CONCLUSIONS

The atrial origin of accessory connections with Mahaim-type preexcitation is apparently confined to the anterolateral-to-posterolateral region of the tricuspid annulus. Mechanical conduction block in the atrial input to the accessory fiber induced at the subannular level by catheter manipulation provides an optimal marker to locate the ablation site, even during atrial fibrillation. To expose early recurrence of antegrade accessory pathway conduction, intermittent atrial pacing in the 12 hours after ablation is advisable; in cases of recurrence, a repeat procedure can readily be performed using just the ablation catheter advanced to the target site at the tricuspid annulus.
Role of spin echo and cine magnetic resonance imaging in presurgical planning of heterotaxy syndrome. Comparison with echocardiography and catheterization.
Authors: Geva T , Vick G W , Wendt R E , Rokey R
Published: June 2012

BACKGROUND

Patients with heterotaxy syndrome frequently have complex congenital cardiac and noncardiac malformations requiring detailed diagnostic evaluation by noninvasive as well as invasive imaging modalities for management planning. Recent advances in magnetic resonance imaging (MRI) techniques allow detailed delineation of cardiovascular anatomy and blood flow in young infants with rapid heart rates. The present study was undertaken to prospectively evaluate the role of MRI in the presurgical evaluation of patients with heterotaxy syndrome.

METHODS AND RESULTS

Between January 1 and December 31, 1992, 14 consecutive patients with heterotaxy syndrome and complex congenital heart disease were enrolled in a prospective protocol. After evaluation by echocardiography and cardiac catheterization, a tentative management plan was recorded. Subsequently, a MRI study was performed and surgical planning was reevaluated. MRI was found to be comparable to echocardiography in terms of length of examination and sedation requirements. Surgical planning was altered in four patients because MRI provided additional data not evident on echocardiography and catheterization. Comparison of diagnostic yield between echocardiography, catheterization, and MRI showed that MRI is superior to echocardiography and often to catheterization in delineation of systemic and pulmonary venous anatomy and their relation to mediastinal structures. When the anatomic and hemodynamic data obtained by echocardiography and MRI were considered together, cardiac catheterization data were necessary only to determination of pulmonary vascular resistance before Fontan operation.

CONCLUSIONS

MRI provides excellent anatomic and functional information that in some patients was not available by echocardiography or catheterization. Combined with echocardiography, MRI provides the high-quality diagnostic information necessary for management planning in most patients with heterotaxy syndrome. Cardiac catheterization is indicated when determination of pulmonary vascular resistance is necessary for decision making or when an interventional procedures is indicated.
Myocardial and cerebral hemodynamics during tachyarrhythmia-induced hypotension in the rat.
Authors: Hagendorff A , Dettmers C , Danos P , Pizzulli L , Omran H , Manz M , Hartmann A , Lüderitz B
Published: June 2012

BACKGROUND

The different vulnerabilities of heart and brain to hypotension and hypoxia have been discussed. Hemorrhagic or cardiogenic hypotension appears to cause greater cerebral lesions than drug-induced hypotension. The present model was established to evaluate myocardial blood flow (MBF) and function of the heart and cerebral blood flow (CBF) during tachyarrhythmias and to characterize the capacity of blood flow regulation in the heart and brain during tachycardia-induced borderline hypotension.

METHODS AND RESULTS

MBF and CBF were determined with radiolabeled microspheres. Coronary and central venous oxygen tensions were measured to estimate myocardial and cerebral oxygen consumption (MVO2 and CVO2). Measurements were performed in 62 Sprague-Dawley rats during sinus rhythm and high-rate left ventricular pacing and after hemorrhage. In control rats, MBF and CBF were 5.08 +/- 1.07 and 1.09 +/- 0.29 mL.g-1.min-1. MBF increased (7.21 +/- 1.98 mL.g-1.min-1, P < .05), whereas CBF decreased (0.99 +/- 0.29 mL.g-1.min-1, P = NS) during normotensive high-rate pacing. MBF and CBF dropped to 4.27 +/- 2.24 mL.g-1.min-1 (P = NS) and 0.68 +/- 0.29 mL.g-1.min-1 (P < .05) during pacing-induced borderline hypotension and decreased further during severe hypotension (1.77 +/- 0.81 mL.g-1.min-1, P < .01; 0.45 +/- 0.18 mL.g-1.min-1, P < .01). During borderline hypotension due to hemorrhage, MBF and CBF were 4.05 +/- 0.95 mL.g-1.min-1 (P = NS) and 0.71 +/- 0.23 mL.g-1.min-1 (P < .05). MVO2 and CVO2 were 72.7 +/- 15.4 and 12.7 +/- 3.3 mL.100 g-1.min-1 in control rats. MVO2 increased during normotensive pacing (100.3 +/- 27.4 mL.100 g-1.min-1, P = NS). Mean MVO2 was reduced during pacing-induced borderline hypotension (64.1 +/- 35.6 mL.100 g-1.min-1, P = NS) and severe hypotension (29.8 +/- 15.4 mL.100 g-1.min-1, P < .05). CVO2 decreased in correlation to CBF. Coronary and cerebrovascular resistance and autoregulation indexes indicated a maintenance of MBF regulation and a failure of CBF regulation during borderline hypotensive tachycardias. These results show a dissociation of MBF and CBF after onset of hypotensive tachycardias. Thus, brain tissue appears to be jeopardized at an earlier stage than myocardial muscle during tachyarrhythmias.

CONCLUSIONS

The proposed hypotension model is suitable to analyze tachyarrhythmia-induced hemodynamic changes and end-organ perfusion in the presence of myocardial dysfunction. It has the potential to test therapeutic strategies in the treatment of tachycardias.
Decreased platelet deposition and smooth muscle cell proliferation after intramural heparin delivery with hydrogel-coated balloons.
Authors: Azrin M A , Mitchel J F , Fram D B , Pedersen C A , Cartun R W , Barry J J , Bow L M , Waters D D , McKay R G
Published: June 2012

BACKGROUND

In vitro and in vivo studies have demonstrated both anticoagulant and antiproliferative effects of heparin. The purpose of this study was to assess the effect of local intramural delivery of heparin, using heparin-coated hydrogel balloons, on platelet deposition and early smooth muscle cell proliferation after in vivo balloon angioplasty.

METHODS AND RESULTS

The effects of local heparin delivery were assessed during balloon angioplasty of porcine peripheral arteries. All balloon dilatations were performed with oversized hydrogel balloons coated with a known quantity of heparin. Balloon dilatations in contralateral vessels with uncoated hydrogel balloons served as study controls. The pharmacokinetics of heparin delivery were assessed using 3H-heparin to quantitate heparin wash-off from the balloon surface, heparin delivery to the arterial wall, and intramural persistence of drug. Platelet deposition at 1 hour after balloon injury was quantified using 111In-labeled platelets. Smooth muscle cell proliferation was assessed 6 to 7 days after angioplasty with immunohistochemical staining for proliferating cell nuclear antigen. 3H-heparin wash-off from the hydrogel balloon surface occurred rapidly, with approximately 95% of the heparin coating disappearing within 10 seconds in the intact circulation. Approximately 2% of heparin on the balloon surface was delivered intramurally at the time of angioplasty. Intramural heparin dissipated rapidly, although small amounts of intramural heparin could still be detected for at least 48 hours. In comparison to control vessels, there was less 111In-platelet deposition (P = .002) and less medial smooth muscle cell proliferation (P = .03) in heparin-treated vessels.

CONCLUSIONS

Local intraluminal delivery of heparin at the time of balloon angioplasty with heparin-coated hydrogel balloons results in intramural deposition of drug that persists for at least 48 hours. This in vivo technique significantly decreases platelet deposition and early smooth muscle cell proliferation after angioplasty injury.
Potential importance of tissue angiotensin-converting enzyme inhibition in preventing neointima formation.
Authors: Rakugi H , Wang D S , Dzau V J , Pratt R E
Published: June 2012

BACKGROUND

Angiotensin II (Ang II) induces vascular smooth muscle cell migration and growth in vitro and induces DNA synthesis in vascular smooth muscle in vivo. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists inhibit neointimal hyperplasia in many experimental models of restenosis. However, recent clinical trials (MERCATOR and MARCATOR) reported that treatment with low (antihypertensive) doses of an ACE inhibitor (cilazapril) failed to prevent restenosis. Because ACE activity is induced in the neointima after injury, we hypothesize that the inhibition of neointimal development may be dependent on the suppression of tissue ACE activity, which in turn is dependent on the dose of the ACE inhibitor.

METHODS AND RESULTS

To test this hypothesis, we treated rats with increasing doses of an ACE inhibitor, quinapril, before injury of the carotid artery. Blood pressure, serum and tissue ACE activity, and neointimal area were measured. The results demonstrated a dose-dependent inhibition by quinapril of serum and tissue ACE activities and neointima formation. However, the IC50s for blood pressure reduction and serum ACE inhibition were significantly lower than that observed for the suppression of neointima formation. The degree of neointimal formation showed a better correlation with residual tissue ACE than with serum ACE or blood pressure.

CONCLUSIONS

These results demonstrate a dissociation of the ability of an ACE inhibitor to decrease blood pressure and inhibit circulating ACE activity from its ability to inhibit tissue ACE activity. These results suggest that the need for a higher dose of an ACE inhibitor for the inhibition of neointima formation may be due to the relative difficulty in inhibiting tissue ACE activity.
Resolution of pace mapping stimulus site separation using body surface potentials.
Authors: Green L S , Lux R L , Ershler P R , Freedman R A , Marcus F I , Gear K
Published: June 2012

BACKGROUND

Several studies have related 12-lead ECG waveform during ventricular tachycardia to ECG waveform during ventricular pacing to identify ablation sites for therapy of ventricular tachycardia. QRS isopotential maps and QRS isointegral maps derived from body surface isopotential maps have also been correlated with left ventricular pacing sites with the same objective. The comparison process used is subjective and only semiquantitative. Improved accuracy of catheter placement may improve success rates of ablation therapy.

METHODS AND RESULTS

This animal study was performed to determine the spatial resolution with which left ventricular pacing sites could be distinguished by body surface isopotential mapping. Potentials were recorded from 64 evenly spaced thoracic leads. Hexapolar or octapolar pacing catheters with 2-mm interelectrode spacing were placed percutaneously in the left ventricle in each of six dogs, and bipolar endocardial pacing was performed using each pair of adjacent electrodes. QRS isopotential maps of each pacing site for each catheter placement were cross-correlated by computer. Difference maps for each pair of pacing sites were calculated lead by lead and time instant by time instant, and root-mean-square voltage differences were calculated. Results indicated that correlation coefficients and root-mean-square error of voltage differences monotonically decrease and increase, respectively, with stimulus site separation. Both measures were significantly different (P < .05) for separations of 4 mm or more.

CONCLUSIONS

A method of quantitative comparison of body surface potential maps can be used in normal hearts to localize ventricular pacing sites within a 4-mm range. The method may have utility in determining potential ablation sites for therapy of ventricular tachycardia or preexcitation syndromes.
Exercise-induced enhancement of immune function in the rat.
Authors: Kaufman J C , Harris T J , Higgins J , Maisel A S
Published: June 2012

BACKGROUND

There have been many anecdotal reports that regular, moderate exercise confers some protective immunity against infection. There has been little scientific evidence to support this. It is also unclear whether training alters lymphocyte trafficking from the spleen to the periphery after a bout of exhaustive exercise.

METHODS AND RESULTS

To determine the effect of moderate training on in vivo antibody production, using rats as an animal model, we gradually trained 18 rats using a swimming protocol for a 4-week period after injection and booster with Keyhole limpet hemocyanin antigen. There were 9 age-matched controls. At the conclusion of training, both groups underwent a short-term exhaustive swim. The trained group showed marked enhancement of IgM and IgG production. After short-term exercise, both groups had acute lymphocytosis, mainly T(suppressor)/cytolytic and natural killer cells with decreases in T(helper) (trained), B cells, and the Th-to-Ts ratio. The changes in the splenocyte subsets were the opposite of the changes in the peripheral blood. With respect to function, after exhaustive exercise, there was a slight increase in mitogenesis and interleukin-2 receptor expression to concanavalin A (untrained more than trained) compared with controls.

CONCLUSIONS

Regular, moderate training enhances antibody production to specific de novo antigen both early and late. In addition, short-term exercise leads to selective release of immune cells from the spleen and results in slightly enhanced function of splenocytes. Direct stimulation by the sympathetic nervous system and catecholamines is the proposed mechanism for the changes seen after short-term exercise and possibly antibody production during training.
Heart rate variability as a prognostic tool in cardiology. A contribution to the problem from a theoretical point of view.
Authors: Moser M , Lehofer M , Sedminek A , Lux M , Zapotoczky H G , Kenner T , Noordergraaf A
Published: June 2012

BACKGROUND

Recent clinical studies have proposed standard deviation of heart rate as a diagnostic tool for the outcome of cardiac infarction. Mathematical analysis of heart rate variability shows that heart rate is influenced by different frequency components derived from different parts of the autonomous nervous system. In the experimental part of this study, we investigated the possibility of calculating a variable describing the parasympathetic branch of the autonomous nervous system exclusively.

METHODS AND RESULTS

In 60 healthy volunteers, heart rate was measured to 1 millisecond during two different conditions: 5 minutes of rest, and 5 minutes of intermittent handgrip dynamometry; the latter is known to increase sympathetic arousal selectively. Heart rate was found to be lower at rest (65.9 +/- 9.7 beats per minute) than during dynamometry (72.8 +/- 10.4 beats per minute, P < .001). Respiratory sinus arrhythmia (RSA) calculated from the mean absolute differences between successive heart beats showed no significant change (3.01 +/- 1.62 beats per minute at rest versus 2.97 +/- 1.30 beats per minute during dynamometry). In contrast, standard deviation increased from 5.19 +/- 1.98 to 9.22 +/- 3.56 beats per minute (P < .001).

CONCLUSIONS

It can be concluded from these data as well as from other plots presented in this article that RSA is a measure of the parasympathetic vagal tone, whereas standard deviation is increased by both sympathetic and parasympathetic arousal. Clinical evidence and data from physiological experiments are presented to show that a selective measure of vagal tone like RSA may offer advantages over standard deviation as a prognostic tool in cardiology.
Reduced heart rate variability and mortality risk in an elderly cohort. The Framingham Heart Study.
Authors: Tsuji H , Venditti F J , Manders E S , Evans J C , Larson M G , Feldman C L , Levy D
Published: June 2012

BACKGROUND

The prognostic implications of alterations in heart rate variability have not been studied in a large community-based population.

METHODS AND RESULTS

The first 2 hours of ambulatory ECG recordings obtained on original subjects of the Framingham Heart Study attending the 18th biennial examination were reprocessed to assess heart rate variability. Subjects with transient or persistent nonsinus rhythm, premature beats > 10% of total beats, < 1 hour of recording time, processed time < 50% of recorded time, and those taking antiarrhythmic medications were excluded. The associations between heart rate variability measures and all-cause mortality during 4 years of follow-up were assessed. There were 736 eligible subjects with a mean age (+/- SD) of 72 +/- 6 years. The following five frequency domain measures and three time domain measures were obtained: very-low-frequency power (0.01 to 0.04 Hz), low-frequency power (0.04 to 0.15 Hz), high-frequency power (0.15 to 0.40 Hz), total power (0.01 to 0.40 Hz), the ratio of low-frequency to high-frequency power, the standard deviation of total normal RR intervals, the percentage of differences between adjacent normal RR intervals that are > 50 milliseconds, and the square root of the mean of the squared differences between adjacent normal RR intervals. During follow-up, 74 subjects died. In separate proportional hazards regression analyses that adjusted for relevant risk factors, very-low-frequency power (P < .0001), low-frequency power (P < .0001), high-frequency power (P = .0014), total power (P < .0001), and the standard deviation of total normal RR intervals (P = .0019) were significantly associated with all-cause mortality. When all eight heart rate variability measures were assessed in a stepwise analysis that included other risk factors, low-frequency power entered the model first (P < .0001); thereafter, none of the other measures of heart rate variability significantly contributed to the prediction of all-cause mortality. A 1 SD decrement in low-frequency power (natural log transformed) was associated with 1.70 times greater hazard for all-cause mortality (95% confidence interval of 1.37 to 2.09).

CONCLUSIONS

The estimation of heart rate variability by ambulatory monitoring offers prognostic information beyond that provided by the evaluation of traditional risk factors.
Magnetic resonance imaging of the iliofemoral arteries after balloon dilation angioplasty of aortic arch obstructions in children.
Authors: Burrows P E , Benson L N , Babyn P , MacDonald C
Published: June 2012

BACKGROUND

We wished to determine the nature and incidence of changes in the iliofemoral arteries after balloon dilation angioplasty (BDA) for aortic arch obstruction in children and to determine the reliability of gradient magnetic resonance imaging (MRI) in their detection.

METHODS AND RESULTS

Sixty-three children, including 62 with and 1 without arch obstruction, underwent MRI of the iliofemoral vessels. Of these, 36 patients had undergone transfemoral BDA (7 after previous transfemoral diagnostic catheterization), 12 had undergone diagnostic transfemoral catheterization but not BDA, and 15 had no history of femoral arterial catheterization. The iliofemoral arteries were normal on MRI in all 15 children without catheterization. Among the 36 children who had undergone BDA, the ipsilateral iliofemoral artery was normal in 15, mildly narrowing in 7, and severely stenotic or occluded in 14 (39%), including 6 of 9 patients treated for acute femoral artery thrombosis and 8 with no history of femoral artery thrombosis. Two patients had documentation of progressive obstruction. Six patients had concordant conventional angiography. There was a significant correlation between the number of balloon catheters used for the angioplasty and severe occlusive changes. Nine of 19 patients who had undergone diagnostic transfemoral catheterization had severe obstructive changes on MRI; 8 of 9 weighed < 10 kg at catheterization.

CONCLUSIONS

Obstructive lesions of the iliofemoral arteries are common after transfemoral BDA of arch obstructions (58%) and can be reliably evaluated with gradient MRI. Catheter size and manipulation are the main contributing factors.
Physical conditioning decreases norepinephrine-induced vasoconstriction in rabbits. Possible roles of norepinephrine-evoked endothelium-derived relaxing factor.
Authors: Chen H I , Li H T , Chen C C
Published: June 2012

BACKGROUND

Physical activity can reduce sympathetic tone and may be beneficial to human health. Whether the vascular responses to norepinephrine (NE), an adrenergic vasoconstrictor, could be altered by chronic exercise was unclear. We therefore conducted this study to investigate the effects of endurance exercise training on NE-induced vasoconstrictive response in healthy rabbits. Possible mechanisms were also studied.

METHODS AND RESULTS

Twenty-four male New Zealand White rabbits were used for this study. They were divided into two groups: control and training. The training group was trained on a treadmill with running speed of 0.88 km/h at a 0 degree grade for 10 to 60 minutes per day, for 5 days a week for a total of 8 weeks. At the end of the experiments, thoracic aortae (3 mm long) were isolated. The vascular tension was measured with a force transducer. The dose-response relation of NE-induced vasoconstriction was determined and compared for control (n = 5) and trained (n = 6) groups. To verify the possible involvement of endothelium-derived relaxing factor (EDRF) in the alteration of NE-induced vasoconstriction after exercise training, we compared the vascular responses to NE in endothelium-intact, N omega-nitro-L-arginine (L-NNA, 10(-4) mol/L)-pretreated, or denuded vessel segments (n = 4 for each experiment of each group). EDRF release in the presence or absence of NE was also evaluated by the increased tension induced by hemoglobin (10(-5) mol/L), an EDRF scavenger (n = 6 for the control group and n = 8 for the trained group). In addition, vascular responses to some specific adrenergic agonists (ie, phenylephrine, an alpha 1-agonist, and clonidine, an alpha 2-agonist) were also studied to see if a specific adrenergic receptor was involved (n = 4 for each experiment of each group). Our results indicated that (1) [NE]ED50 of the thoracic aorta was elevated by exercise training; (2) in the presence of NE, EDRF release from the thoracic aorta, assessed by addition of hemoglobin or L-NNA, was higher in the trained group than in the control group; (3) both phenylephrine (10(-8) mol/L) and clonidine (10(-6) mol/L) could evoke vasorelaxation that would be inhibited by L-NNA; and (4) in addition to causing vasoconstriction, NE could stimulate EDRF release, possibly via alpha 1- and alpha 2-receptors of endothelial cells.

CONCLUSIONS

Our data suggest that exercise training may decrease NE-induced vasoconstrictive response and may increase NE-stimulated EDRF release.
Unexpected interaction between beta-adrenergic blockade and heart rate variability before and after myocardial infarction. A longitudinal study in dogs at high and low risk for sudden death.
Authors: Adamson P B , Huang M H , Vanoli E , Foreman R D , Schwartz P J , Hull S S
Published: June 2012

BACKGROUND

Heart rate (HR) variability is a marker of tonic cardiac autonomic activity and contributes in assessing risk for sudden death after myocardial infarction. Recent clinical observations have indicated that attenuation of HR variability, which occurs after myocardial infarction, may be transient. This study addresses the issue of whether autonomic control of heart rate recovers at different rates after myocardial infarction in subjects at high and low risk for ventricular fibrillation (VF).

METHODS AND RESULTS

Thirty dogs, 22 with myocardial infarction and 8 sham-prepared animals, completed the study. Changes and recovery in cardiac autonomic activity after myocardial infarction were examined by measuring HR variability before and at defined intervals during the first 30 days after infarction. Each HR variability measurement was made before and after beta-blockade in dogs at high (n = 10) and low (n = 12) risk for VF. Arrhythmia risk was determined on the basis of development of VF during exercise and transient myocardial ischemia 30 days after infarction. No sham-prepared animals developed VF. Preinfarction measurements of HR variability were not different between the groups before beta-blockade, but HR variability increased much more in response to beta-blockade in animals destined to be resistant compared with susceptible animals (289 +/- 26 to 369 +/- 35 msec, delta 27.7%, versus 270 +/- 36 to 283 +/- 34 milliseconds, delta 4.8%, respectively, P < .01). Immediately after infarction, HR variability was significantly attenuated in all dogs, but in the resistant dogs it recovered to pre-myocardial infarction levels within 10 days. After the infarction, beta-blockade did not increase HR variability in either group of animals. Postoperative increases in HR variability from beta-blockade were preserved in the sham group. Susceptible animals were characterized by a persistent attenuation of HR variability throughout the 30 days.

CONCLUSIONS

The depression in HR variability produced by myocardial infarction has a clearly different temporal recovery pattern between low- and high-risk animals. After myocardial infarction, beta-adrenergic blockade does not alter HR variability, thus preserving its predictive value. Before myocardial infarction, however, beta-blockade increases HR variability only in the animals destined to be at low risk for lethal arrhythmias after the infarction. The recovery pattern of HR variability after myocardial infarction may contribute to the early recognition of individuals at high risk for sudden death.
Stress echocardiography in the detection of myocardial ischemia. Head-to-head comparison of exercise, dobutamine, and dipyridamole tests.
Authors: Beleslin B D , Ostojic M , Stepanovic J , Djordjevic-Dikic A , Stojkovic S , Nedeljkovic M , Stankovic G , Petrasinovic Z , Gojkovic L , Vasiljevic-Pokrajcic Z
Published: June 2012

BACKGROUND

Exercise and pharmacological stress echocardiography have emerged as convenient alternatives to myocardial scintigraphy. The objective of this study was to compare in the same patients the diagnostic values of exercise, dobutamine, and dipyridamole stress echocardiography tests for detection of myocardial ischemia.

METHODS AND RESULTS

We performed exercise (maximal treadmill Bruce protocol), dobutamine (up to 40 micrograms/kg per minute) and dipyridamole (up to 0.84 mg/kg over 10 minutes) stress echocardiography tests, in random sequence and on separate days, in 136 consecutive patients. All patients underwent coronary angiography. Significant coronary artery disease was defined by quantitative coronary angiography as a lesion with a diameter stenosis > or = 50%. A stress echocardiogram was considered positive when new or worsening of preexisting wall motion abnormality was observed. Most of the patients (94%) were receiving the same antianginal medication for each stress test; 59 patients were receiving concomitant beta-blocker therapy. The prevalence of coronary artery disease was 87.5%, with 108 patients having one-vessel coronary artery disease. Peak heart rate and systolic blood pressure were higher with exercise than with dobutamine or dipyridamole (P < .01). Sensitivity of exercise, dobutamine, and dipyridamole stress echocardiography was 88%, 82%, and 74% (dipyridamole versus exercise, P < .01), respectively. Specificity was 82%, 77%, and 94%, respectively. The overall accuracy was 87%, 82%, and 77% (dipyridamole versus exercise, P < .01), respectively. The accuracy of dipyridamole was higher (P = .02) in the group of patients not receiving beta-blockers (84%) than in the patients receiving beta-blocker therapy (66%), whereas the accuracy of exercise and dobutamine were only slightly higher in the patients not receiving beta-blockers. Significant side effects occurred in 3%, 11%, and 1% of patients during exercise, dobutamine, and dipyridamole tests, respectively.

CONCLUSIONS

Despite the different hemodynamic effects, exercise, dobutamine, and dipyridamole echocardiography have high overall diagnostic values. In this group of patients with a predominance of one-vessel coronary artery disease, the overall diagnostic accuracy of stress echocardiography tests was higher for exercise than for dobutamine or dipyridamole. Concomitant beta-blocker therapy significantly decreased the accuracy of the dipyridamole stress echocardiography test. Pharmacological stress testing (dipyridamole without beta-blockers) can therefore be used as an efficient option for detection of myocardial ischemia in patients who are unable or poorly motivated to exercise adequately.
Conjoint high triglycerides and low HDL cholesterol across generations. Analysis of proband hypertriglyceridemia and lipid/lipoprotein disorders in first-degree family members.
Authors: Sprecher D L , Hein M J , Laskarzewski P M
Published: June 2012

BACKGROUND

To discern whether hypertriglyceridemia (hyper-TG, TG > 95th percentile) and hypoalphalipoporteinemia (hypoalpha, high-density lipoprotein [HDL-C] < or = 10th percentile) are jointly transmitted in families, we studied 385 probands with marked elevations in TG or cholesterol levels (TG or cholesterol > 99th percentile in a previous visit) and their 2072-first-degree relatives in the Lipid Research Clinics' Family Study. Repeat TG measurement, with exclusion criterion of TG < or = 95th percentile, resulted in 162 probands with hyper-TG.

METHODS AND RESULTS

When the proband demonstrated the conjoint trait (CT; ie, TG > 95th percentile, HDL-C < or = 10th percentile, n = 82), an average of 10.6% of first-degree relatives conjointly expressed hyper-TG and hypoalpha in contrast to only 4.1% of first-degree relatives of a proband who expressed high TG levels with normal HDL-C levels (TG > 95th percentile, HDL-C > 10th percentile, n = 80). Hyper-TG was expressed in 24.2% of first-degree relatives of probands with CT. However, hyper-TG was expressed in only 14.4% of first-degree degree relatives of probands with hyper-TG alone. CT probands and their family members tended to have more reported cardiac events and symptoms (P = .02 and .09, respectively) than those subjects associated with hyper-TG alone.

CONCLUSIONS

The differences in HDL-C-TG abnormalities between families related to hyper-TG probands with or without hypoalpha indicate that bottom decile HDL-C is not simply secondary to hyper-TG. A familial interaction is suggested between HDL-C and TG levels consistent with the transmission of hyper-TG and hypoalpha among first-degree relatives. Among subjects and their families with hyper-TG, those who in addition have low HDL-C demonstrate a tendency for more coronary artery disease than do those with normal HDL-C levels.
Vasodilatory effects of C-type natriuretic peptide on forearm resistance vessels are distinct from those of atrial natriuretic peptide in chronic heart failure.
Authors: Nakamura M , Arakawa N , Yoshida H , Makita S , Hiramori K
Published: June 2012

BACKGROUND

C-type natriuretic peptide (CNP) is a newly identified peptide that is structurally related to atrial natriuretic peptide (ANP). Although it has been suggested that CNP is released from the endothelium for the regulation of local vascular tone, no data are available concerning the vasodilatory response to CNP in humans.

METHODS AND RESULTS

Strain-gauge plethysmography was used to determine the vasodilatory effects of intra-arterially infused CNP compared with the effects of ANP infusion in 11 patients with chronic heart failure (CHF) and 11 age-matched healthy controls. Graded doses of CNP and ANP (8, 16, 32, and 48 pmol.min-1.dL-1 tissue volume) were administered randomly into the nondominant brachial artery, and forearm blood flow (FBF) was measured. No significant changes in systemic blood pressure and heart rate were found during the study. Both the absolute and percent FBF responses to ANP relative to the baseline value were significantly lower in CHF patients than in healthy controls (P < .01), whereas the responses to CNP were similar. The calculated forearm spillover of cyclic GMP (cGMP) was significantly lower in CHF patients receiving the highest dose of ANP (P < .02), whereas changes in cGMP spillover after the equimolar dose of CNP were significantly higher (P < .02), despite the lesser potency of CNP.

CONCLUSIONS

In patients with CHF the peripheral vasodilatory effect of ANP is attenuated, but CNP-induced peripheral vasorelaxation is preserved, with CNP being less potent for equimolar doses.
Activation of angiotensinogen and angiotensin-converting enzyme gene expression in the left ventricle of senescent rats.
Authors: Heymes C , Swynghedauw B , Chevalier B
Published: June 2012

BACKGROUND

During senescence, the plasma angiotensin II concentration is decreased, but the regulation of intracardiac angiotensin II synthesis has never been investigated. The purpose of this work was to determine the cardiac content of both angiotensinogen (ANG) and angiotensin-converting enzyme (ACE) mRNAs in 24-month-old Wistar rats.

METHODS AND RESULTS

Total cardiac RNAs and known amounts of ANG and ACE mRNA transcripts, used as standards, were hybridized on slot blots with specific cDNA probes. The quantities of ANG and ACE mRNA were evaluated from the regression lines obtained with fragments of ANG and ACE mRNA in vitro transcripts. With aging, while the overall plasma renin-angiotensin system (RAS) activity decreased, in the left ventricle (LV) the amounts of ANG and ACE mRNAs were increased by fivefold (P < .01) and 2.5-fold (P < .01), respectively, compared with young adult controls. By contrast, in the right ventricle (RV) the same mRNA levels remained unchanged. In parallel, we also found an enhanced expression of the atrial natriuretic factor (ANF) in the LV but not in the RV.

CONCLUSIONS

During senescence, the depressed circulating RAS activity is in contrast to the increase of both ANG and ACE mRNA levels in the LV. Such an upregulation in both gene activities is more likely to be related to the age-associated changes in arterial compliance rather than to hormonal changes, since (1) this regulation is found only in the LV and (2) the same pattern of regulation is also observed for the ANF mRNA level.
A prospective investigation of elevated lipoprotein (a) detected by electrophoresis and cardiovascular disease in women. The Framingham Heart Study.
Authors: Bostom A G , Gagnon D R , Cupples L A , Wilson P W , Jenner J L , Ordovas J M , Schaefer E J , Castelli W P
Published: June 2012

BACKGROUND

Sinking prebeta lipoprotein is a putative marker for elevated levels of lipoprotein (a). Although prospective data suggest that increased plasma lipoprotein (a) is an independent risk factor for coronary heart disease in men, no prospective studies are available in women.

METHODS AND RESULTS

From 1968 through 1975, sinking prebeta lipoprotein was determined by paper electrophoresis in 3103 women Framingham Heart Study participants who were free of prevalent cardiovascular disease. A sinking prebeta lipoprotein band was detectable in 434 of the women (14%) studied. The median follow-up interval was approximately 12 years. Incident cardiovascular disease was associated with band presence using a proportional hazards model that included age, smoking, body mass index, systolic blood pressure, glucose intolerance, low- and high-density lipoprotein cholesterol, and ECG left ventricular hypertrophy. Multivariable adjusted relative risk estimates (with 95% confidence intervals) for outcomes in the band present versus absent groups were as follows: myocardial infarction (82 events), 2.37 (1.48 to 3.81); intermittent claudication (62 events), 1.94 (1.07 to 3.50); cerebrovascular disease (83 events), 1.88 (1.12 to 3.15); total coronary heart disease (174 events), 1.61 (1.13 to 2.29); and total cardiovascular disease (305 events), 1.44 (1.09 to 1.91). A subset analysis indicated that band presence was 50.9% sensitive and 95.4% specific for detecting plasma lipoprotein (a) levels of > 30 mg/dL, the threshold value linked to increased cardiovascular disease risk in men.

CONCLUSIONS

Sinking prebeta lipoprotein was a valid surrogate for elevated lipoprotein (a) levels in Framingham Heart Study women. Band presence and, equivalently, elevated plasma lipoprotein (a), was a strong, independent predictor of myocardial infarction, intermittent claudication, and cerebrovascular disease. Confirmation of these findings in other longitudinal studies of women is needed.
Transcatheter ablation of posteroseptal accessory pathways using a venous approach and radiofrequency energy.
Authors: Dhala A A , Deshpande S S , Bremner S , Hempe S , Sra J S , Blanck Z , Akhtar M , Jazayeri M R
Published: June 2012

BACKGROUND

The efficacy of transcatheter ablation of atrioventricular (AV) accessory pathways (APs) located in the posteroseptal region using a right atrial approach and radiofrequency energy was evaluated.

METHODS AND RESULTS

Fifty consecutive patients with APs in the posteroseptal region underwent radiofrequency catheter ablation. Manifest preexcitation was present in 36 patients and a concealed AP in 14. In 18 patients (group 1), the ventriculoatrial (VA) interval during orthodromic tachycardia was prolonged by 21 +/- 7 milliseconds (range, 10 to 30 milliseconds) with functional left bundle-branch block. In 16 patients (group 2), functional left bundle-branch block caused no VA interval prolongation. The remaining 16 patients (group 3) had no inducible left bundle-branch block during orthodromic tachycardia. Functional right bundle-branch block was induced in 30 patients with no effect on the VA interval. In group 1, of 14 patients with manifest preexcitation during sinus rhythm, 10 patients had a positive delta wave in lead V1. Of 10 group 2 patients with manifest preexcitation, only 5 had a positive delta wave in lead V1. In group 3, of 12 patients with manifest preexcitation, 7 exhibited a positive delta wave in lead V1. All posteroseptal APs were successfully ablated, and this was achieved via a right atrial approach in 48 patients and left ventricular approach in only 2. Successful sites were at the posteroseptal region of the tricuspid annulus (30 patients), within the terminal 1 cm of the coronary sinus including its ostium (16 patients), and at the inferomedial aspect of the right atrium posterior to the coronary sinus ostium (2 patients). The posteroseptal region of the left ventricle was the site of successful ablation in 2 patients. Six patients with a recurrence of AP conduction required a repeat ablation, with successful results in 5. Thirty-five patients had a complete electrophysiological evaluation 2 to 3 months after their successful ablation and were found to have no functioning AP. In 49 patients with a final successful ablation, no recurrence of symptoms was noted during a mean follow-up period of 12 +/- 9 months. Complications occurring in 3 patients were cardiac tamponade requiring surgical drainage and repair of a right ventricular tear, pericardial effusion with no hemodynamic consequence that spontaneously resolved, and a transient 2:1 atrioventricular block.

CONCLUSIONS

These data suggest that posteroseptal APs are amenable to successful ablation using a right atrial approach. Success was achieved in 47 cases (94%) in this series even though the ECG and/or electrophysiological characteristics of the posteroseptal APs of some patients were suggestive of "left-sided" pathways.
Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt.
Authors: Montano N , Ruscone T G , Porta A , Lombardi F , Pagani M , Malliani A
Published: June 2012

BACKGROUND

The powers of the low-frequency (LF) and high-frequency (HF) oscillations characterizing heart rate variability (HRV) appear to reflect, in their reciprocal relationship, changes in the state of the sympathovagal balance occurring during numerous physiological and pathophysiological conditions. However, no adequate information is available on the quantitative resolution of this methodology.

METHODS AND RESULTS

We studied 22 healthy volunteers (median age, 46.5 years) who were subjected after a rest period to a series of passive head-up tilt steps randomly chosen from the following angles: 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. From the continuous ECG, after appropriate analog-to-digital conversion, a personal computer was used to compute, with an autoregressive methodology, time and frequency domain indexes of RR interval variability. Spectral and cross-spectral analysis with the simultaneously recorded respiratory signal excluded its contribution to LF. Age was significantly correlated to variance and to the absolute values in milliseconds squared of very-low-frequency (VLF), LF, and HF components. The tilt angle was correlated to both LF and HF (expressed in normalized units [nu]) and to the LF-to-HF ratio (r = .78, -.72, and .68; respectively). Lower levels of correlation were found with HF (in ms2) and RR interval. No correlation was present between tilt angle and variance, VLF, or LF (in ms2). Individual analysis confirmed that the use of nu provided the greatest consistency of results.

CONCLUSIONS

Spectral analysis of HRV, using nu or LF-to-HF ratio, appears to be capable of providing a noninvasive quantitative evaluation of graded changes in the state of the sympathovagal balance.