bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hemodynamic evaluation before and after closure of fenestrated Fontan. An acute study of changes in oxygen delivery.
Authors: Hijazi Z M , Fahey J T , Kleinman C S , Kopf G S , Hellenbrand W E 
Published: June 2012

BACKGROUND
Acute changes in hemodynamics and oxygen delivery accompanying temporary occlusion of atrial defects in 14 patients after a fenestrated Fontan procedure were evaluated at a median interval of 32 days after surgery to identify candidates for permanent transcatheter closure of their defects.

METHODS AND RESULTS
Patients ranged in age from 9 months to 33 years and in weight from 7.9 to 69 kg. Right atrial (RA), left atrial (LA), and aortic pressures, mixed venous (SmvO2) and aortic (SaO2) oxygen saturation, and whole-body oxygen consumption (VO2) were measured, and systemic blood flow (Qs), systemic oxygen transport (SOT), and oxygen extraction were calculated before and after occlusion. SmvO2, VO2, and RA pressures did not change, but SaO2 increased from 84 +/- 6% to 95 +/- 3% (p less than 0.05), and LA pressures fell from 5.1 +/- 3.6 to 3.7 +/- 2.2 mm Hg (p less than 0.05). Qs fell from 2.4 +/- 0.7 to 1.8 +/- 0.41.min-1.m-2 (p less than 0.05), SOT fell from 425 +/- 154 to 366 +/- 112 ml.O2.min-1.m-2 (p less than 0.05), and oxygen extraction increased from 0.40 +/- 0.12 to 0.46 +/- 0.13 (p less than 0.05). Only one patient did not undergo definitive closure of his defect because of a marked decrease in Qs and SOT with a significant rise in RA pressure.

CONCLUSIONS
Although delayed closure of an atrial defect in these patients improved morbidity and mortality, the complete separation of the venous and systemic circulations was accomplished at the expense of decreased Qs and oxygen delivery despite the improved level of arterial oxygenation. The resting levels of oxygen extraction are elevated and will be associated with decreased exercise capability. The long-term benefits of closure of these fenestrations are yet to be shown.
Adrenergic effects on reentrant ventricular rhythms in subacute myocardial infarction.
Authors: Butrous G S , Gough W B , Restivo M , Yang H , el-Sherif N 
Published: June 2012

BACKGROUND
Reentry has been shown to be a mechanism of ventricular arrhythmias elicited by programmed premature stimulation in the subacute ischemic period of dogs subjected to myocardial infarction. The spatial distribution of refractoriness in these hearts has been shown to play an important part in the formation of functional arcs of conduction block during programmed ventricular stimulation. Because the adrenergic nervous system influences cardiac arrhythmias and myocardial infarction can directly affect sympathetic innervation in the heart, we investigated the role of the sympathetic nervous system on reentry in the canine heart 4 days after infarction.

METHODS AND RESULTS
The influences of adrenergic stimuli on the initiation of reentrant ventricular excitation were studied using a 128-channel computerized recording system in the canine heart 4 days after ligation of the left anterior descending coronary artery. Bilateral stimulation of the ansae subclavia preferentially improved conduction of premature beats in the normal zones. This corresponded to an improvement in excitability, as measured by a decrease in stimulus strength at the same premature coupling interval as control. Consequently, the effective refractory period was preferentially shortened at normal sites but not at ischemic sites. Both of these changes contributed to a shift of the arc of functional conduction block toward more normal tissue. As a result, sites proximal to the arc of functional conduction block had more time to recover excitability and thereby were available to be reexcited by the distal activation wave front. Conversely, intravenous infusion of norepinephrine preferentially shortened the effective refractory period of sites in the ischemic zone, thereby indicating that denervation hypersensitivity had occurred at these sites. The spatial dispersion of refractoriness and the arc of functional conduction block were significantly reduced in size. As a consequence, previously inducible reentrant rhythms were no longer inducible.

CONCLUSIONS
Sympathetic stimulation can be considered an arrhythmogenic intervention, whereas norepinephrine infusion may be considered antiarrhythmic in this experimental model.
Contribution of localized calcium deposits to dissection after angioplasty. An observational study using intravascular ultrasound.
Authors: Fitzgerald P J , Ports T A , Yock P G 
Published: June 2012

BACKGROUND
Atherosclerotic plaque fracture and dissection of the arterial wall are frequent concomitants of the balloon angioplasty process. The composition and morphology of plaque within the vessel may be critical in determining the extent of plaque fracture and dissection during balloon angioplasty. To examine this potential association in the clinical setting, we studied patients with intravascular ultrasound imaging after balloon angioplasty.

METHODS AND RESULTS
Forty-one patients were studied with intravascular ultrasound after angioplasty in both peripheral and coronary arteries. Ultrasound images representing the target lesion cross section were digitized, stored on computer, and analyzed off-line. The presence of intralesional calcium and the relative size of dissection for each lesion was computed. Thirty-one patients (76%) had ultrasound evidence of significant dissection or plaque fracture immediately after balloon dilation. In 23 of 31 (74%) of the lesions, the ultrasound scans showed significant localized calcium deposits within the plaque substance. In 87% of these cases, the dissections were adjacent to the calcific portion of the vessel wall. In addition, the relative size of dissections referenced to the neolumen area were significantly larger (p less than or equal to 0.002) in the calcified vessels (27.5 +/- 12.3%) compared with the size of the dissections in lesions without calcium (11.2 +/- 5.8%).

CONCLUSIONS
The presence of calcium within the vessel wall appeared to be significantly associated with both the location and size of the dissected tissue arm from the vessel wall. These data suggest that localized calcium deposits have a direct role in promoting dissection, presumably by increasing shear stresses within the plaque.
Association between heart rate and atherogenic blood lipid fractions in a population. The Tromsø Study.
Authors: Bønaa K H , Arnesen E 
Published: June 2012

BACKGROUND
Prospective epidemiological studies indicate that elevated heart rate may carry increased risk for coronary heart disease. Little is known about the relation between heart rate and serum lipid and lipoprotein concentrations in the general population.

METHODS AND RESULTS
We assessed anthropometric and life-style determinants of heart rate and examined the association between heart rate and serum lipid and lipoprotein concentrations in a cross-sectional study of 9,719 men and 9,433 women 12-59 years old. Stratified and multivariate analyses were used to detect possible modification of effect and to control for confounding variables. Heart rate was positively associated with male sex and smoking, decreased with body height and physical activity, and showed a U-shaped relation to body mass index. In both sexes, there was a significant progressive increase in age-adjusted levels of total cholesterol, non-high density lipoprotein (HDL) cholesterol, and triglycerides and a decrease in HDL cholesterol with heart rate. Men with heart rate greater than 89 beats per minute had 14.5% higher non-HDL cholesterol and 36.3% higher triglyceride levels than men with heart rate less than 60 beats per minute. The corresponding differences in women were 12.5% and 22.2%. The associations remained significant when anthropometric and life-style factors were controlled for. The slopes relating total and non-HDL cholesterol level to heart rate were steeper with advancing age.

CONCLUSIONS
Increases in heart rate correlate with higher levels of atherogenic serum lipid fractions in the general population. Alterations in aortic impedance and/or autonomic influences may underlie these associations.
Effect of intravenous adenosine infusion on myocardial perfusion and function. Hemodynamic/angiographic and scintigraphic study.
Authors: Ogilby J D , Iskandrian A S , Untereker W J , Heo J , Nguyen T N , Mercuro J 
Published: June 2012

BACKGROUND
Myocardial perfusion imaging during adenosine-induced hyperemia with dipyridamole or adenosine is an accepted method to diagnose coronary artery disease (CAD) and risk assessment. The mechanism of perfusion abnormality may be caused by disparate flow responses or coronary steal. This study examined the relation between 201Tl perfusion pattern and hemodynamic/angiographic changes during intravenous adenosine infusion.

METHODS AND RESULTS
Patients with suspected CAD underwent sequential hemodynamic, coronary arteriographic, and left ventriculographic studies simultaneously with 201Tl imaging during adenosine infusion (140 micrograms.kg-1.min-1 for 6 minutes). There were 33 patients with CAD and 12 patients without CAD. The 201Tl images (using single-photon emission computed tomography) were abnormal in 31 patients with CAD (sensitivity, 94%) and normal in the patients without CAD (specificity, 100%). In patients with and without CAD, there were significant increases in heart rate and cardiac output (p less than 0.0001) and decreases in systemic vascular resistance and blood pressure (p less than 0.0001). There was a 77 +/- 38% increase in pulmonary capillary wedge pressure in normal subjects and a 125 +/- 83% increase in patients with CAD (p = 0.02). ST segment depression was observed in 11 patients with CAD (33%). In CAD patients, there was no change in percent diameter or area stenosis measured quantitatively during adenosine infusion. In 15 patients, contrast left ventriculography was repeated during adenosine infusion. In these patients, 201Tl perfusion defects were seen in 31 of 75 segments (41%) whereas only six of 75 segments (8%) developed regional wall motion abnormality (p less than 0.001); the remaining segments showed either no change or improved function. The left ventricular ejection fraction did not change significantly (73% versus 75%).

CONCLUSIONS
There is a disparity between the effects of adenosine on left ventricular perfusion and function; most patients with CAD have perfusion defects whereas the global and regional systolic function remains unchanged or improves. Diastolic left ventricular dysfunction is a probable mechanism of the increase in pulmonary capillary wedge pressure.
Abnormal left ventricular intracavitary flow acceleration in patients undergoing aortic valve replacement for aortic stenosis. A marker for high postoperative morbidity and mortality.
Authors: Aurigemma G , Battista S , Orsinelli D , Sweeney A , Pape L , Cuénoud H 
Published: June 2012

BACKGROUND
We examined the clinical and echocardiographic characteristics of patients undergoing aortic valve replacement for aortic stenosis whose continuous wave Doppler studies showed abnormal intracavitary flow acceleration.

METHODS AND RESULTS
The clinical and Doppler echocardiographic records of 53 consecutive patients undergoing aortic valve replacement for aortic stenosis were reviewed. Doppler echocardiography was performed at a mean of 6.6 days (range, 0-22 days) after surgery. Thirteen patients (group 1) had a dagger-shaped high-velocity systolic flow signal indicative of abnormal intracavitary flow acceleration on their postoperative Doppler study; group 2 comprised 40 aortic stenosis patients who underwent aortic valve replacement but had no postoperative evidence of abnormal intracavitary flow acceleration. Group 1 postoperative abnormal intracavitary flow velocities ranged from 1.8 to 6.8 m/sec (mean, 4.9 +/- 0.9 m/sec): Resulting dynamic gradients ranged from 10 to 184 mm Hg (mean, 104.6 +/- 32 mm Hg). Compared with group 2, group 1 patients had a distinctive ventricular geometry with more-pronounced hypertrophy, smaller cavities, and higher ejection fraction. Systolic anterior motion of the mitral valve did not accompany abnormal intracavitary flow acceleration in any patient. Six of 13 group 1 patients suffered postoperative hemodynamic compromise characterized by severe hypotension despite adequate pulmonary capillary wedge pressures; group 1 postoperative mortality was significantly greater than that seen in group 2 patients (38% versus 12%, p less than 0.05).

CONCLUSIONS
Abnormal intracavitary flow acceleration after aortic valve replacement for severe aortic stenosis is associated with a distinctive ventricular geometry and supernormal systolic function but not systolic anterior motion of the mitral valve. Such flow acceleration appears to be a marker for increased postoperative morbidity and mortality. Preoperative and postoperative Doppler echocardiography may be useful in risk stratification and guiding therapy.
Long-term effects of percutaneous laser balloon ablation from the canine coronary sinus.
Authors: Schuger C D , McMath L , Abrams G , Zhan H , Spears J R , Steinman R T , Lehmann M H 
Published: June 2012

BACKGROUND
Radiofrequency catheter ablation of left-sided accessory pathways is becoming the first line of therapy for patients with symptomatic Wolff-Parkinson-White syndrome. Nevertheless, alternative ablation techniques merit development, at least as supplementary modalities for cases in which conventional ablation approaches may prove unsuccessful. We recently reported the short-term results with transcatheter laser balloon ablation from the coronary sinus in a canine model, proving that the procedure is feasible for the potential ablation of left-sided accessory pathways. We now report the effects of percutaneous transcatheter laser balloon ablation in a chronic canine model.

METHODS AND RESULTS
Twenty adult mongrel dogs were studied. After baseline coronary arteriography, left ventriculography, and coronary sinus angiography were obtained, 15 dogs received two or three consecutive laser doses from the coronary sinus of 30-40 W for 15-30 seconds, for a total cumulative energy of 1,200-2,400 J. The five remaining animals underwent a procedure consisting of balloon sham inflation without laser exposure and served as controls. After a mean follow-up of 6 weeks, the angiographic procedures were repeated, and the animals were killed. The mean extent of the fibrotic lesion was 15 mm long, 6 mm wide, and 4.5 mm deep and involved the coronary sinus wall, atrium, and, frequently, the summit of the posterior left ventricular wall. Six animals (four in the study group and two in the control group) showed asymptomatic narrowing of the coronary sinus lumen but always with total angiographic reconstitution due to extensive collateral circulation. The circumflex artery and mitral valve were intact angiographically and histologically in all animals.

CONCLUSIONS
Percutaneous transcatheter laser balloon ablation via the coronary sinus produces a lesion that may be anatomically well suited for left-sided accessory pathway ablation. Although coronary sinus narrowing may occur, adverse physiological effects are unlikely due to the development of extensive collateral circulation. Systematic clinical studies of this new approach to catheter ablation appear warranted.
Postextrasystolic potentiation and its contribution to the beat-to-beat variation of the pulse during atrial fibrillation.
Authors: Hardman S M , Noble M I , Seed W A 
Published: June 2012

BACKGROUND
Beat-to-beat variations in the pulse during atrial fibrillation (AF) have conventionally been attributed to time-dependent changes in filling. We have explored the possibility that they are dependent on the intrinsic myocardial interval force relation.

METHODS AND RESULTS
Left ventricular (LV) contractility (maximum rate of rise of pressure, LV dP/dtmax) and ascending aortic blood velocity were measured during cardiac catheterization in 15 patients with AF. Beats preceded by an interval of less than 500 msec were excluded from analysis to reduce the confounding influence of incomplete mechanical restitution. The LV dP/dtmax was then related to the prepreceding interval. An inverse relation consistent with postextrasystolic potentiation was obtained in all 15 patients (Spearman's rank correlations, -0.56 to -0.86; p less than or equal to 0.0001). This relation was confirmed in three patients during pacing that overrode the AF and introduced single-interval variations into steady-state pacing. The ECG sequences from six of the AF patients were used to drive isometrically contracting guinea pig papillary muscle and human right ventricular tissue (n = 7); the same inverse relation was demonstrated. On a beat-by-beat basis, the maximum rate of rise of force in the isolated muscle correlated well with LV dP/dtmax in the patients (r = 0.50-0.86, p less than or equal to 0.0001). The relation of the integral of aortic velocity (AVI, proportional to stroke volume) to prepreceding interval was also inverse, whereas important correlations were demonstrated between LV dP/dtmax and AVI (Spearman's rank correlations, 0.27-0.95; p less than or equal to 0.0001).

CONCLUSIONS
This study demonstrates that postextrasystolic potentiation contributes to the characteristic beat-to-beat variation of the pulse in AF.
Mechanoenergetic effects of pimobendan in canine left ventricles. Comparison with dobutamine.
Authors: Hata K , Goto Y , Futaki S , Ohgoshi Y , Yaku H , Kawaguchi O , Takasago T , Saeki A , Taylor T W , Nishioka T 
Published: June 2012

BACKGROUND
We hypothesized that the effect of pimobendan (UD-CG 115 BS) to increase calcium sensitivity of contractile protein might result in less myocardial oxygen consumption (VO2) in comparison with dobutamine when they enhance ventricular contractility to the same extent. To examine this hypothesis, we compared the effects of pimobendan and dobutamine on left ventricular contractility and energetics using the frameworks of Emax (contractility index) and the relation between VO2 and PVA (systolic pressure-volume area, a measure of left ventricular total mechanical energy).

METHODS AND RESULTS
We measured VO2, Emax, PVA, and force-time integral (FTI) in excised, cross-circulated, nonfailing dog hearts. The slope of the VO2-PVA relation reciprocally indicates the efficiency from PVA-dependent VO2 to the total mechanical energy (contractile efficiency). The VO2 intercept of the VO2-PVA relation, i.e., PVA-independent VO2, reflects energy utilization for excitation-contraction coupling. The ratio of FTI to PVA-dependent VO2 can be called contractile economy. Both drugs comparably enhanced Emax. Although the contractile economy was greater by 14 +/- 19% (p less than 0.05) for pimobendan than for dobutamine, the contractile efficiency was similar between the two drugs. Oxygen cost of contractility, defined as the slope of the relation between the PVA-independent VO2 and Emax, was the same between the two drugs. Other mechanoenergetic effects of both drugs were similar except for a greater coronary vasodilating effect of pimobendan.

CONCLUSIONS
Pimobendan has almost the same mechanoenergetic effects as dobutamine but slightly greater contractile economy and coronary vasodilation. The calcium-sensitizing effect of pimobendan did not save the oxygen cost of contractility.
Spatial and temporal linking of epicardial activation directions during ventricular fibrillation in dogs. Evidence for underlying organization.
Authors: Damle R S , Kanaan N M , Robinson N S , Ge Y Z , Goldberger J J , Kadish A H 
Published: June 2012

BACKGROUND
It remains controversial as to whether electrical activation during ventricular fibrillation (VF) is organized. To detect the presence of organization in VF, the direction of epicardial activation (EA) at multiple sites was examined by using vector mapping. If VF is not a random process, EA direction at a given site should be related to adjacent sites and prior beats.

METHODS AND RESULTS
Thirteen dogs with healing myocardial infarction (MI) and four dogs without MI had VF induced by programmed stimulation. Using a plaque electrode array with a 2.5-mm interelectrode distance, 91 vector loops were created for each "beat" of VF. Direction of maximum EA was determined at each site for the first 10 consecutive beats of VF and for 10 consecutive beats recorded 5 seconds after VF was established. Spatial and temporal linking of EA directions was evaluated by the ability of activation direction at a given site to be predicted by activation directions at eight adjacent sites for the index beat and at eight adjacent sites and the site of interest for the preceding beat using stepwise linear regression. The strength of the model as reflected by the correlation coefficient (r) indicated the degree of linking. We determined 1) changes in the degree of linking over time during a given episode of VF (using a paired-difference t test), 2) differences in the degree of linking between the anterior and posterolateral walls in animals with (n = 4) and without (n = 4) MI (using two-way ANOVA), and 3) the effect of repeated inductions (n = 10) on the degree of linking (using one-way ANOVA with repeated measures). During 57 episodes of VF, r for each model ranged from 0.64 to 0.88 during the transition to VF to 0.39-0.78 during established VF (p < 0.0001 for the difference). The presence of MI, the site of recording, and repeated inductions did not affect the degree of linking. For each episode, spatial linking was more prominent than temporal linking.

CONCLUSIONS
Electrical activation during VF is organized. The degree of linking of EA directions during VF is not affected by the presence of MI, the site of recording, or repeated inductions of VF. During the first 5 seconds of VF, the degree of linking decreases.