bluuebunny/crossref_metadata_2025 huggingface dataset:
Left ventricular regional relaxation and its nonuniformity in hypertrophic nonobstructive cardiomyopathy.
Authors: Hayashida W , Kumada T , Kohno F , Noda M , Ishikawa N , Kojima J , Himura Y , Kawai C
Published: June 2012

BACKGROUND

Regional nonuniformity has been suggested to be closely related to left ventricular (LV) relaxation in diseased heart. The purpose of the present study was to assess LV global and regional relaxation in patients with nonobstructive hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

Left ventriculography was conducted simultaneously with pressure micromanometry in 10 normal control subjects and 11 patients with nonobstructive HCM. LV silhouettes in the right anterior oblique projection were divided into eight regions, and regional wall stress during isovolumic relaxation was computed for six regions from the midventricle to the apex. In HCM patients, isovolumic relaxation time (IRT) and the time constant of LV pressure decrease (Tp) were greater than in control subjects (IRT, 84 +/- 13 versus 66 +/- 6 msec; Tp, 51 +/- 8 versus 36 +/- 5 msec, respectively; p less than 0.01). In HCM patients, the (-)dP/dt upstroke pattern was convex-downward, and dP/dt(20/60), the ratio of dP/dt values 20 and 60 msec after peak (-)dP/dt, was less than in control subjects (1.46 +/- 0.16 versus 2.15 +/- 0.14, p less than 0.01). These findings suggest that there is impaired LV relaxation in HCM patients. End-systolic regional wall stress was lower, and the time constant of regional stress decrease (Tst) was prolonged for each region in HCM patients compared with control subjects. In the HCM group, Tst tended to be more prolonged in regions with increased wall thickness than in regions with normal wall thickness (60 +/- 15 versus 50 +/- 11 msec, p less than 0.01). The coefficient of variation for Tst values in six areas of the left ventricle was calculated in each subject and was greater in HCM patients than in control subjects (13 +/- 7% versus 7 +/- 3%, p less than 0.05), indicating regional nonuniformity in Tst during isovolumic relaxation in HCM patients.

CONCLUSIONS

Significant correlations existed between the coefficients of variation for Tst and Tp (r = 0.80, p less than 0.01), IRT (r = 0.79, p less than 0.01), and dP/dt(20/60) (r = -0.67, p less than 0.05) in the HCM group. Thus, regional nonuniformity is closely related to the impairment of LV relaxation in HCM.
Body surface distribution of abnormally low QRST areas in patients with left ventricular hypertrophy. An index of repolarization abnormalities.
Authors: Hirai M , Hayashi H , Ichihara Y , Adachi M , Kondo K , Suzuki A , Saito H
Published: June 2012

BACKGROUND

QRST isointegral maps (I-maps) have been useful in detecting repolarization abnormalities. We investigated the body surface distribution of abnormally low QRST areas in patients with left ventricular hypertrophy (LVH) and the relation of the abnormalities in I-map to the severity of LVH as assessed by echocardiography.

METHODS AND RESULTS

QRST area departure maps were constructed from electrocardiographic (ECG) data recorded in patients with LVH and precordial negative T waves resulting from aortic stenosis (AS) (10 patients), aortic regurgitation (AR) (12 patients), or hypertrophic cardiomyopathy (HCM) with asymmetric septal hypertrophy (22 patients). Fifty normal subjects served as controls. The I-map was constructed from 87 body surface electrocardiograms recorded simultaneously at a sampling interval of 1 msec. The area where the QRST area was smaller than normal limits (mean -2 SD) was designated the "-2 SD area." The echocardiographic left ventricular (LV) mass was calculated by Devereux's method. Patients with large LV masses due to AS or AR had 2 SD areas located over the left anterior chest or the midanterior chest, respectively. The 2 SD area was located over the left shoulder and left anterior chest and had a lingual shape in patients with HCM. The sum of QRST area values less than the normal range (sigma QRST) was significantly correlated with LV mass in patients with AS or AR (r = 0.83 and r = 0.69, p less than 0.01 and p less than 0.05). However, there was no significant correlation between sigma QRST and the severity of LVH in patients with HCM. sigma QRST divided by the number of electrodes in the 2 SD area was significantly greater in patients with HCM than in those with AS or AR.

CONCLUSIONS

These findings suggest that abnormalities in patients with HCM are manifest even in mild LVH and that there is a greater disparity of repolarization in hypertrophied left ventricles due to HCM than in LVH due to aortic valve disease. QRST isointegral departure maps may provide ECG evidence of LV mass of patients with AS or AR and of susceptibility to malignant arrhythmias in patients with HCM.
Importance of two-dimensional echocardiographic assessment of left ventricular systolic function in patients presenting to the emergency room with cardiac-related symptoms.
Authors: Sabia P , Abbott R D , Afrookteh A , Keller M W , Touchstone D A , Kaul S
Published: June 2012

BACKGROUND

This prospective study was designed to test the hypothesis that the assessment of left ventricular systolic function at the time of emergency room (ER) presentation provides valuable diagnostic and prognostic information in patients with cardiac-related symptoms.

METHODS AND RESULTS

The study is based on a 2-year follow-up of 171 consecutive patients evaluated in the ER for such symptoms. In the course of follow-up, one third of the patients (55 of 171) suffered a major cardiac event. For those with left ventricular systolic dysfunction (LVSD), the age-adjusted rate of early events (occurring within 48 hours of presentation) was more than eight times higher than for those without LVSD (26.9% versus 3.3%, p less than 0.01). For events occurring after 48 hours of ER presentation, LVSD was associated with a nearly fourfold excess of cardiac events (23.9% versus 6.4%, p less than 0.01). Other than advanced age, the most important confounder for early events included an abnormal electrocardiogram diagnostic for acute myocardial infarction. Confounders for late events included advanced age and a history of hypertension. LVSD on two-dimensional echocardiography (2DE) was the only finding associated with early and late events after controlling for other risk factors. In addition, the prediction of these events derived from the combination of historical, clinical, electrocardiographic, and 2DE findings was significantly improved when accounting for the presence or absence of LVSD (p less than 0.01).

CONCLUSIONS

We conclude that the 2DE assessment of left ventricular systolic function provides valuable diagnostic and prognostic information in subjects presenting to the ER with cardiac-related symptoms.
Transvenous coronary ultrasound imaging. A novel approach to visualization of the coronary arteries.
Authors: Sudhir K , Fitzgerald P J , MacGregor J S , DeMarco T , Ports T A , Chatterjee K , Yock P G
Published: June 2012

BACKGROUND

Catheter-based ultrasound is a new imaging modality to examine endovascular detail in the coronary circulation. This technique requires direct placement of the catheter in the arterial segment of interest.

METHODS AND RESULTS

We examined the feasibility of a less invasive approach by imaging the coronary arterial circulation by using a 5F (30 MHz) imaging catheter placed in the cardiac venous system. Using simultaneous fluoroscopy, we studied anesthetized closed-chest dogs (n = 6) and human subjects undergoing right heart catheterization (n = 11). After cannulation of the coronary sinus, the circumflex coronary artery (Cx) was visualized from the great cardiac vein (GCV), and on advancing the catheter into the anterior interventricular vein (AIV), the left anterior descending artery (LAD) was identified. Where artery and vein were parallel to each other, circular cross-sectional images of the coronary artery were obtained, whereas oblique and transverse orientation of artery to vein produced ellipsoid images or long-axis images. In the dogs, ultrasound-determined cross-sectional area of the coronary arteries (4.81 +/- 0.18 mm2) correlated closely with angiography (4.77 +/- 0.21 mm2) (r = 0.91, p less than 0.001). In humans, the Cx was readily visualized from the GCV in all subjects but because of anatomic variability, the LAD was seen less consistently from the AIV (73%). There was significant correlation between ultrasound-determined cross-sectional areas of the coronary arteries (8.25 +/- 0.34 mm2) with those from angiography (8.59 +/- 0.3 mm2) (r = 0.82, p = 0.001) in humans. In all subjects, the ultrasound transducer could be safely advanced into the AIV to the cardiac apex. Limitations of the technique include ultrasonic penetration problems, caused in part by the large size of human coronary veins and variability in artery-vein relations.

CONCLUSIONS

We conclude that transvenous imaging of coronary arteries with intravascular ultrasound is a less invasive, promising new approach to the study of structure and morphology in the coronary vasculature.
Response of relatively refractory canine myocardium to monophasic and biphasic shocks.
Authors: Daubert J P , Frazier D W , Wolf P D , Franz M R , Smith W M , Ideker R E
Published: June 2012

BACKGROUND

Certain biphasic waveforms defibrillate at lower energies than monophasic waveforms, although the mechanism is unknown.

METHODS AND RESULTS

The relative ability of monophasic and biphasic shocks to stimulate partially refractory myocardium was compared because defibrillation is thought to involve stimulating relatively refractory myocardial tissue. Shocks of 25-125 V were given during regularly paced rhythm in 11 open-chest dogs. Computerized recordings of shock potentials, and of activations before and after the shocks, were made at 117 epicardial sites. To quantify the shock field strength, the shock potential gradients were calculated at the electrode sites. Monophasic action potential (MAP) electrode recordings, obtained in five dogs, confirmed direct myocardial excitation by the shock, that is, activations beginning during the shock. Tissue was directly excited up to 4 cm from the shocking electrode, and the area directly excited increased as the shock was made stronger or given less prematurely. In six dogs, strength-interval curves for direct excitation were determined from plots of potential gradient versus refractoriness at each electrode site. The biphasic curves were located to the right of the monophasic curves by 8 +/- 4 msec, indicating a lesser ability to excite refractory myocardium. When the gradient at the directly excited border was at least 3.8 +/- 1 V/cm, conduction failed to propagate away from the directly excited zone after the shock, and MAP recordings made near the border showed a shock-induced graded response. This graded response, which prolonged repolarization, may have been responsible for the failure of conduction from the directly excited zone. Although better for defibrillating, the biphasic waveform was thus less effective than the monophasic one in exciting relatively refractory myocardium.

CONCLUSIONS

These results indicated that waveform selection for defibrillation should not be guided solely by the ability of the waveform to stimulate tissue, as these two properties can be discordant.
Desensitization of myocardial beta-adrenergic receptors during cardiopulmonary bypass. Evidence for early uncoupling and late downregulation.
Authors: Schwinn D A , Leone B J , Spahn D R , Chesnut L C , Page S O , McRae R L , Liggett S B
Published: June 2012

BACKGROUND

Cardiopulmonary bypass (CPB), a process routinely used during cardiac surgery, is a potent stimulant to the release of endogenous catecholamines. Hence, we tested the hypothesis that CPB results in myocardial beta-adrenergic receptor (beta AR) desensitization.

METHODS AND RESULTS

We obtained canine transmyocardial left ventricular biopsies before, during (155 minutes), and after CPB (pre-CPB, CPB, and post-CPB, respectively) and determined beta AR density, proportion of beta 1AR to beta 2AR, and beta AR coupling capacity to adenylyl cyclase. Beta AR density was stable at 112 +/- 14 fmol/mg (pre-CPB) and 103 +/- 9 fmol/mg (CPB) but decreased post-CPB to 84 +/- 7 fmol/mg. The ratio of beta 1AR to beta 2AR (determined by two-site fit for [125I]-iodocyanopindolol competition binding with the beta 1AR selective antagonist ICI89.406) remained constant throughout (60 +/- 3: 40 +/- 3 pre-CPB, 55 +/- 3: 44 +/- 3 CPB, and 61 +/- 2: 39 +/- 2 post-CPB), revealing that both beta 1AR and beta 2AR subtypes were downregulated. A different pattern was noted in the functional properties of these receptors during CPB. Decreased maximal isoproterenol-stimulated adenylyl cyclase activity (252 +/- 14 to 216 +/- 12 pmol/30 min/mg), submaximal isoproterenol-stimulated adenylyl cyclase activity (183 +/- 10 to 157 +/- 11 pmol/30 min/mg), and zinterol-stimulated adenylyl cyclase activity (187 +/- 11 to 159 +/- 11 pmol/30 min/mg, a measure of beta 2AR subtype activation) were noted during CPB, at the time when weaning from CPB takes place. However, this desensitized pattern was found to be completely reversed by 30 minutes post-CPB, with adenylyl cyclase activities returning to pre-CPB levels or slightly higher. Control dogs that did not receive CPB showed no change in beta AR density or adenylyl cyclase activity.

CONCLUSIONS

These data suggest that myocardial beta AR desensitization does occur during CPB in healthy, nonischemic canine myocardium and that this pattern is reversed 30 minutes after discontinuation of CPB. In addition, a slower process of beta AR downregulation persists after discontinuation of CPB. Because successful weaning from CPB is a critical process during myocardial surgery, these findings have potentially important implications in the management of such patients.
Ventricular tachycardia rate and morphology determine energy and current requirements for transthoracic cardioversion.
Authors: Kerber R E , Kienzle M G , Olshansky B , Waldo A L , Wilber D , Carlson M D , Aschoff A M , Birger S , Fugatt L , Walsh S
Published: June 2012

BACKGROUND

The electrical current and energy required to terminate ventricular tachyarrhythmias are known to vary by arrhythmia: Ventricular tachycardia (VT) is generally considered to require less energy than ventricular fibrillation (VF). The hypothesis of our study was that current requirements for transthoracic termination of VT are further determined by VT rate and QRS complex morphology.

METHODS AND RESULTS

We prospectively studied 203 patients who received a total of 569 shocks for VT or VF by following a current-based protocol. This protocol recommended shocks for VT beginning at 18 A (70 +/- 22 J) and shocks for VF beginning at 25 or 30 A (137 +/- 52 J or 221 +/- 70 J). The ventricular tachyarrhythmias were subclassified as monomorphic VT (MVT): uniform QRS complex morphology on surface electrocardiogram and heart rate greater than 100 beats per minute; polymorphic VT (PVT): nonuniform QRS complex morphology and heart rate less than or equal to 300 beats per minute; or VF: nonuniform QRS complex morphology and heart rate greater than 300 beats per minute. We found that shocks of 18 A and 25 A for terminating MVT had success rates of 69% and 82%, respectively, whereas such low-current shocks were less successful for PVT (33% at 18 A) and for VF (19% at 18 A, 53% at 25 A). High-current shocks of 35 A and 40 A were equally successful for the three ventricular tachyarrhythmias. Subdividing MVT revealed that slower MVT (heart rate less than 200 beats per minute) had a significantly better success rate with low-current shocks of 18 A and 25 A than did faster MVT (greater than 200 beats per minute) (89% versus 72% success, p less than 0.01). Bundle branch block morphology, QRS axis, and duration of ventricular tachyarrhythmia did not alter current requirements.

CONCLUSIONS

Heart rate and electrocardiographic degree of organization of ventricular tachycardia are important determinants of transthoracic energy and current requirements for cardioversion and defibrillation. Transthoracic termination of MVT requires relatively low current or energy, but PVT behaves more like VF and requires higher electrical current or energy.
Trends in survival of hospitalized myocardial infarction patients between 1970 and 1985. The Minnesota Heart Survey.
Authors: McGovern P G , Folsom A R , Sprafka J M , Burke G L , Doliszny K M , Demirovic J , Naylor J D , Blackburn H
Published: June 2012

BACKGROUND

The Minnesota Heart Survey is a population-based study designed to monitor and explain trends in cardiovascular mortality, morbidity, and risk factors. As part of this effort, a 50% sample of patients hospitalized for myocardial infarction (MI) in the seven-county Twin Cities (Minneapolis and St. Paul) metropolitan area was reviewed in 1970, 1980, and 1985. Those with a validated definite MI were followed for 4-year mortality. The purpose was to determine whether the improved survival observed between 1970 and 1980 was extended to the 1980-1985 period.

METHODS AND RESULTS

Crude 28-day mortality in men changed from 18% in 1970 to 12% in 1980 to 13% in 1985; in women it changed from 27% in 1970 to 22% in 1980 to 18% in 1985. After adjustment for severity factors (e.g., age, previous MI, and admission heart rate and systolic blood pressure), 28-day mortality was significantly lower in 1980 than in 1970 in men (RR, 0.66; 95% CI, 0.47, 0.92) and in women (RR, 0.69; 95% CI, 0.46, 1.04), but no change occurred from from 1980 to 1985 (p greater than 0.25). After adjustment for severity indicators, 4-year survival was better in 1980 than in 1970 for men (RR, 0.67; 95% CI, 0.54, 0.83) and for women (RR, 0.72; 95% CI, 0.54, 0.98), but there was no significant change from 1980 to 1985 (p greater than 0.25).

CONCLUSIONS

These results suggest that improvements in survival among hospitalized MI patients contributed to the overall decline in coronary heart disease mortality in the Twin Cities area between 1970 and 1980 but not between 1980 and 1985.
Lipoprotein profile in men with peripheral vascular disease. Role of intermediate density lipoproteins and apoprotein E phenotypes.
Authors: Sentí M , Nogués X , Pedro-Botet J , Rubiés-Prat J , Vidal-Barraquer F
Published: June 2012

BACKGROUND

The role of lipoprotein disturbances in the development of peripheral vascular disease (PVD) has not been sufficiently clarified.

METHODS AND RESULTS

The relations among concentrations of intermediate density lipoproteins (IDL), apoprotein (apo) B, apo E, and other lipoproteins were studied in 102 men with PVD and 100 healthy men who formed the control group. Patients with PVD had significantly higher levels of serum triglycerides, very low density lipoprotein (VLDL) cholesterol, VLDL triglycerides, VLDL proteins, IDL cholesterol, and IDL triglycerides and lower levels of high density lipoproteins (HDL) than controls. Serum cholesterol and triglycerides were normal in 30 patients (cholesterol, less than 5.2 mmol/l; triglycerides, less than 2.3 mmol/l), who had significant increases in IDL triglycerides and significant decreases in HDL cholesterol compared with the 47 controls, who had normal cholesterol and triglyceride levels. Patients with more severe distal involvement showed higher cholesterol and triglycerides carried by IDL and a greater reduction in HDL cholesterol. Smoking patients with PVD showed increased VLDL cholesterol and VLDL triglycerides and lower HDL concentrations. Apo E polymorphism in our study population does not differ from that reported for other European populations. Alleles epsilon 2 and epsilon 4 had a major impact on serum triglycerides and VLDL lipids in our patients with PVD.

CONCLUSIONS

Lipoprotein disturbances are a major risk factor for PVD. IDL abnormalities play an important role in the development and severity of PVD and should also be considered a vascular risk factor in normocholesterolemic and normotriglyceridemic patients.
Early postoperative reduction of monoclonal antimyosin antibody uptake is associated with absent rejection-related complications after heart transplantation.
Authors: Ballester M , Obrador D , Carrió I , Moya C , Augè J M , Bordes R , Martí V , Bosch I , Bernà-Roqueta L , Estorch M
Published: June 2012

BACKGROUND

Detection and treatment for rejection after transplantation are based on the identification of myocyte damage upon endomyocardial biopsy. Noninvasive detection of such damage is possible with 111In-labeled monoclonal antimyosin antibodies (MAA). Although the presence and degree of MAA uptake parallels the rejection activity detected by biopsy, the relation between the degree of uptake and the occurrence of severe rejection-related complications has not been previously assessed.

METHODS AND RESULTS

Two hundred forty-seven MAA studies were performed coinciding with biopsies in 52 patients 1-71 months after transplantation. A heart-to-lung ratio (HLR) was used as a measure of relative MAA uptake, with an HLR of 1.55 discriminating normal from abnormal studies. Of the 247 antimyosin studies, 149 coincided with absent, 38 with mild, and 60 with moderate rejection at biopsy. HLR was 1.68 +/- 0.27, 1.79 +/- 0.22, and 1.91 +/- 0.33 in the three biopsy groups, respectively (p less than 0.0001). Two hundred thirty-eight of 247 antimyosin studies coexisted with absent rejection-related complications; in nine of 247 patients, such complications were detected (five congestive heart failure episodes due to rejection and four episodes of vascular occlusion, which resulted in five deaths), and mean HLR was 1.74 +/- 0.3 and 2.1 +/- 0.16 in the two groups, respectively (p less than 0.0001). No complications were noted in 193 studies of patients with HLR of less than 2.00, whereas in nine of 45 with HRL of 2.00 or greater, complications occurred (p less than 0.0001). None of the 23 patients prospectively followed since surgery who had a gradual decrease in MAA uptake during the first 3 months showed rejection-related complications, whereas persistent uptake was associated with complications in five of nine patients (p less than 0.001).

CONCLUSIONS

No rejection-related complications are seen coinciding with HLR of less than 2.00, whereas patients who have complications have an HLR of more than 2.00. The early 3-month pattern of decreasing MAA uptake is associated with a clinical course free of rejection-related complications, whereas a persistent pattern is a signal of the possibility of such complications.
Coronary angioplasty performed within the thrombolysis in Myocardial Infarction II study.
Authors: Baim D S , Diver D J , Feit F , Greenberg M A , Holmes D R , Weiner B H , Williams D O , Schweiger M J , Brown B G , Frederick M M
Published: June 2012

BACKGROUND

Percutaneous transluminal coronary angioplasty (PTCA) of the infarct-related artery was performed within 42 days of recombinant tissue-type plasminogen activator (rt-PA) administration in 1,414 of the 3,534 patients who participated in the Thrombolysis In Myocardial Infarction (TIMI) II study. Primary angiographic success was obtained in 88.7%, with bypass surgery within 24 hours in 3.3% and death within 24 hours in 0.7% of patients. By 1 year, 25.1% of the 1,414 patients had sustained one or more adverse outcomes including death (3.6%), reinfarction (8.4%), or the need for further revascularization (20%).

METHODS AND RESULTS

Despite these generally favorable results, multivariate testing identified several anatomic and clinical subgroups as having an increased risk ratio (RR) for adverse outcome: Unsuccessful PTCA was more common in patients undergoing protocol-assigned PTCA within 2 hours of rt-PA administration (RR, 2.7; p less than 0.001) and in patients over age 70 years (RR, 1.7; p = 0.034). The need for further revascularization within 1 year was increased in the 30.4% of patients with multivessel disease (RR, 2.5; p less than 0.001), patients with prior angina (RR, 1.4; p less than 0.006), or those undergoing ischemia-driven PTCA within 15 hours of rt-PA administration (RR, 1.7; p = 0.022). The risk of death or recurrent infarction within 1 year was increased by the presence of multivessel disease (RR, 1.6; p = 0.007) or prior angina (RR, 1.5; p = 0.014).

CONCLUSIONS

These observations do not necessarily apply to patients undergoing primary PTCA (or PTCA after other thrombolytic agents); however, they do offer a unique yardstick against which to evaluate the results of PTCA in myocardial infarction.
Incidence and mechanism of interruption of reentrant ventricular tachycardia with rapid ventricular pacing.
Authors: Aizawa Y , Niwano S , Chinushi M , Tamura M , Kusano Y , Miyajima T , Kitazawa H , Shibata A
Published: June 2012

BACKGROUND

Information concerning the electrophysiological characteristics of the reentrant circuit is still limited. To understand the incidence and mechanism of pacing-induced interruption of ventricular tachycardia (VT), rapid pacing was performed to entrain VT, and the local electrogram at the VT origin and the surface electrocardiogram were analyzed.

METHODS AND RESULTS

Among 25 patients, evidence of transient entrainment was confirmed in 20 patients, but the critical paced cycle length at which VT was interrupted was obtained in 13 patients when the paced cycle length was decreased in steps of 10 msec. During pacing at the critical cycle length (defined as block cycle length), changes in the local electrogram at VT origin were confirmed in all of the 13 patients; that is, 1) a change in morphology and 2) a change in the timing of activation: a sudden shortening in the stimulus to local electrogram time (third entrainment criterion by Waldo). The two changes mean that the exit is activated from a different direction (retrograde capture) because of an orthodromic block in the slow conduction zone. The QRS complex in the surface electrocardiogram showed a change in configuration from the fusion complex to the fully paced one at the same time when the exit was captured antidromically.

CONCLUSIONS

Based on our observations in these patients, ventricular tachycardia interruption is very often associated with orthodromic block in the reentrant circuit at a critical cycle length of rapid pacing.
Acute hibernation and reperfusion of the ischemic heart.
Authors: Downing S E , Chen V
Published: June 2012

BACKGROUND

Recovery from prolonged low-flow ischemia was studied in isolated, isovolumically beating neonatal piglet hearts (n = 11) and compared with controls (n = 5).

METHODS AND RESULTS

Hearts were perfused with red blood cell-enhanced Krebs-Henseleit buffer with physiological oxygen-carrying capacity. Left ventricular mechanical function was assessed with a fluid-filled balloon. Measurements of peak systolic pressure, pressure-rate product (PRP), and +dP/dtmax were obtained at various filling pressures. Myocardial oxygen delivery and metabolism (MVO2) and lactate uptake were measured at 30-minute intervals. Control data were obtained with coronary flow (CF) set at 2 ml.min-1.g-1. CF was then reduced to 0.2 ml.min-1.g-1 for 2 hours. Thereafter, reperfusion was instituted at control levels. Hearts not subjected to ischemia were studied at identical time intervals. In these, function remained at greater than 80% after more than 3.5 hours of study. Reduction of CF to 10% was accompanied by an abrupt diminution in function (pressure-rate product) and MVO2 to 20% of control and by lactate release. These measures remained constant for the full 2 hours of ischemia. Incremental return of CF caused a lockstep increase in mechanical function and metabolism. At 30 minutes of reperfusion, PRP was 78% of time-matched controls (p = 0.05), and dP/dtmax did not differ. Increasing calcium to 5 mmol/l returned PRP (and dP/dtmax) to preischemia levels. Myocardial ATP and creatine phosphate concentrations were identical in both groups, although glycogen was lower in the ischemic hearts.

CONCLUSIONS

Acute hibernation is associated with protection of the in vitro heart from prolonged normothermic ischemia. Systolic function was only modestly lower, and velocity (dP/dtmax) did not differ from control hearts. The minimal "stunning" was fully reversible with calcium.
Mechanism of global functional recovery despite sustained postischemic regional stunning.
Authors: Lawrence W E , Maughan W L , Kass D A
Published: June 2012

BACKGROUND

The mechanisms whereby reperfusion of a 20-minute coronary occlusion result in global functional recovery despite persistent regional dysfunction were studied in 11 open-chest reflex-blocked dogs.

METHODS AND RESULTS

Pressure-volume and pressure-thickness relations were simultaneously determined before, during, and after reperfusion of left anterior descending artery (LAD) occlusion. Wall thickness was determined by sonomicrometry in both ischemic and remote regions. Chamber systolic function was assessed by end-systolic pressure-volume relations (ESPVR) obtained by conductance catheter and defined by a slope (Ees) and volume shift at a common end-systolic pressure (delta Ves). LAD occlusion produced regional systolic thinning (-7 +/- 6%) and global left ventricular dysfunction (ESPVR shifted rightward (delta Ves = +8.6 +/- 5.1 ml, p less than 0.001) with no Ees change). After nearly 1 hour of reperfusion, LAD region thickening remained markedly reduced at 4 +/- 7% (versus 23 +/- 8%, control), yet chamber systolic function fully recovered (ESPVR shifted back leftward delta Ves = -8.9 +/- 6.5 ml). Ischemia induced a leftward shift and systolic thinning of LAD region pressure-thickness relations. Reperfusion returned end-systolic pressure-thickness relations halfway to their control position and diastolic relations fully to control position. This was primarily due to increased passive stiffening in about half the hearts and a partial return of active function in the remaining ones. The net effect was to eliminate systolic thinning over a physiological loading range, thus normalizing chamber systolic performance. Reflex activation, remote hyperfunction, or altered chamber loading did not account for the postreperfusion disparity between global and regional function.

CONCLUSIONS

These data suggest a mechanism to account for greater functional benefits of reperfusion beyond that anticipated from regional wall motion analysis.
Syncope associated with supraventricular tachycardia. An expression of tachycardia rate or vasomotor response?
Authors: Leitch J W , Klein G J , Yee R , Leather R A , Kim Y H
Published: June 2012

BACKGROUND

Syncope in patients with supraventricular tachycardia has been suggested to be an ominous finding, predictive of rapid rates during tachycardia.

METHODS AND RESULTS

To explore the mechanism of syncope during supraventricular tachycardia, tachycardia was induced in the supine position and after passive head-up tilting to 60 degrees in 13 patients with atrioventricular (AV) node reentry, eight patients with AV reentry, and one patient with atrial tachycardia. Tilt testing was also performed in sinus rhythm for 30 minutes (the last 15 minutes with isoproterenol infusion). Mean +/- SEM age was 38 +/- 3 years, and 11 patients had a history of syncope (median number of syncopal episodes, three; range, one to 30). The cycle length of tachycardia when upright was shorter than when supine (297 +/- 9 compared with 357 +/- 10 msec, p less than 0.001), and mean blood pressure fell to a greater extent after the onset of tachycardia (fall in mean blood pressure, 53 +/- 6 compared with 24 +/- 3 mm Hg, p less than 0.001). Mean blood pressure correlated significantly with tachycardia cycle length when supine (r = 0.58, p = 0.005) but not when tilted upright (r = 0.18, p = 0.45). Syncope occurred in seven patients during upright tachycardia. These seven patients had a greater fall in mean blood pressure with upright tachycardia than the 15 patients without syncope (fall in mean blood pressure, 70 +/- 4 compared with 45 +/- 5 mm Hg, p = 0.01), but there was no difference in the tachycardia cycle length (311 +/- 10 compared with 290 +/- 11 msec, p = 0.29). Six of the seven patients with tachycardia-induced syncope also had syncope with tilt testing in sinus rhythm compared with four of the 15 patients without tachycardia-induced syncope (p = 0.02).

CONCLUSIONS

These data support the view that syncope during supraventricular tachycardia is related to vasomotor factors and does not predict a more rapid tachycardia rate.
Regional myocardial perfusion and glucose metabolism in experimental left bundle branch block.
Authors: Ono S , Nohara R , Kambara H , Okuda K , Kawai C
Published: June 2012

BACKGROUND

Several authors have reported cases in which 201Tl scintigraphy demonstrated perfusion abnormality in the septum of patients with left bundle branch block (LBBB) and normal coronary arteriogram. The mechanism of this abnormality, however, remains to be clarified.

METHODS AND RESULTS

To determine whether LBBB itself induces abnormal myocardial perfusion and ischemia and to elucidate its mechanism, we used an in vivo animal model. LBBB was induced by right ventricular pacing in 17 open-chest dogs. We examined myocardial perfusion and glucose uptake using 201Tl and 18F-labeled 2-fluoro-2-deoxy-D-glucose. 201Tl activity in the septum was reduced to 74.7 +/- 14.5% of its maximal activity, and mean activity was 86.5 +/- 5.3% in the free wall (p less than 0.05). 18F activity in the septum was also reduced compared with that in the free wall (67.4 +/- 12.1% versus 88.0 +/- 5.2%, p less than 0.05). Regional myocardial blood flow was significantly reduced in the septum compared with the free wall, averaging 0.53 +/- 0.18 ml/min/g versus 0.84 +/- 0.14 ml/min/g, respectively (p less than 0.01). Systolic thickening in the septum was reduced from 1.36 +/- 0.20 to 0.98 +/- 0.04 (p less than 0.01) after the induction of LBBB, and the intramyocardial pressure in the septum in diastolic phase, in which the major flow of left anterior descending coronary artery (LAD) exists, increased from 26.6 +/- 10.5 to 57.8 +/- 22.2 mm Hg (p less than 0.02). Mean aortic pressure, LAD flow, and lactate extraction rate showed no significant change.

CONCLUSIONS

LBBB itself may reduce myocardial perfusion and glucose uptake in the septum because of impaired systolic thickening and augmented intramyocardial pressure in the septum; however, this is not necessarily related to septal ischemia.
Factors related to end-systolic volume are important determinants of peak early diastolic transmitral flow velocity.
Authors: Courtois M , Mechem C J , Barzilai B , Ludbrook P A
Published: June 2012

BACKGROUND

Three important determinants of left ventricular (LV) peak early diastolic filling rate, which is related directly to the magnitude of the transmitral pressure difference, are the rate of LV isovolumic pressure fall (T1/2), left atrial (LA) pressure at mitral valve opening (X1), and end-systolic volume (ESV).

METHODS AND RESULTS

To delineate the relative degrees to which these factors contribute to the magnitude of peak early diastolic filling rate, we measured LA and regional intra-LV pressures with micromanometers, LV volume with contrast angiography, and peak transmitral flow velocity (E) with transesophageal Doppler echocardiography in 16 anesthetized closed-chest dogs. E did not correlate significantly with either X1 (r = -0.255) or T1/2 (r = -0.281). Multivariate analysis, with E entered as the dependent variable and X1 and T1/2 as independent variables, also failed to reach significance (R = 0.310). E correlated significantly with ESV (r = -0.633, p less than 0.009). Using multivariate analysis, the major determinants of ESV were found to be LV contractility (+dP/dt), afterload (aortic diastolic pressure, AOdias), and preload (end-diastolic volume, EDV) (R = 0.848, p less than 0.001). E correlated significantly with two of the determinants of ESV (+dP/dt and AOdias) (R = 0.906, p less than 0.001); however, the addition of EDV did not significantly improve the multivariate relation (R = 0.911). To determine whether X1 or T1/2 would add significantly to the above multivariate relation, these factors were entered individually along with +dP/dt and AOdias as third independent variables. Neither the addition of X1 (R = 0.906) or T1/2 (R = 0.926) resulted in a significant improvement in the prediction of E.

CONCLUSIONS

Our observations confirm the importance of factors related to ESV as important determinants of early diastolic filling. These relations suggest that the process of early diastolic function is intimately related to systolic function.
Energy conversion efficiency in human left ventricle.
Authors: Kameyama T , Asanoi H , Ishizaka S , Yamanishi K , Fujita M , Sasayama S
Published: June 2012

BACKGROUND

Left ventricular mechanical efficiency is one of the most important measures of left ventricular pump performance. Several clinical studies, however, have shown that mechanical efficiency does not fall substantially as the heart fails. To clarify the insensitivity of mechanical efficiency to the change in pump performance, we analyzed human left ventricular mechanical efficiency, applying the concept of left ventricular systolic pressure-volume area (PVA).

METHODS AND RESULTS

PVA correlates linearly with myocardial oxygen consumption per beat (MVO2): MVO2 = a.PVA+b, and represents the total mechanical energy of contraction. We determined MVO2-PVA relation and external work in 11 patients with different contractile states. We also calculated the energy transfer from MVO2 to PVA (PVA/MVO2 efficiency), that from PVA to external work (work efficiency), and mechanical efficiency (external work/MVO2). Left ventricular pressure-volume loops were constructed by plotting the instantaneous left ventricular pressure against the left ventricular volume at baseline and during pressure loading. The contractile properties of the ventricle were defined by the slope of the end-systolic pressure-volume relation (Ees). Pressure elevation raised external work by 41.4%, PVA by 71.2%, and MVO2 by 54.5%. These changes were associated with a decrease in work efficiency and an increase in PVA/MVO2 efficiency. The opposite directional changes in these two efficiencies rendered the mechanical efficiency constant. The slope, a, of the relation between MVO2 and PVA was relatively constant (2.46 +/- 0.33) over the range of 0.8-8.8 mm Hg/ml of Ees, but the oxygen axis intercept, b, tended to decrease with the reduction in Ees. PVA/MVO2 efficiency correlated inversely (r = -0.66, p less than 0.05) with Ees, whereas work efficiency correlated linearly with Ees (r = 0.91, p less than 0.01).

CONCLUSIONS

Mechanical efficiency is not appreciably affected by changes in loading and inotropic conditions as long as the left ventricular contractility is not severely depressed.
Low high density lipoprotein level is associated with increased restenosis rate after coronary angioplasty.
Authors: Shah P K , Amin J
Published: June 2012

BACKGROUND

To determine the relation of post-percutaneous transluminal coronary angioplasty (PTCA) restenosis to serum lipid fractions and to circulating levels of endogenous tissue plasminogen activator (t-PA) and its rapid inhibitor (PAI-1), 68 patients with coronary artery disease who underwent a successful PTCA were studied.

METHODS AND RESULTS

During a mean follow-up of 9 months (range, 7-11 months), 28 (41%) patients developed restenosis. A low high density lipoprotein (HDL) cholesterol level was independently and strongly related to both the risk of restenosis (p less than 0.001) and to the time of restenosis (p = 0.03). The mean HDL cholesterol level was 33 +/- 12 mg% in the restenosis group compared with 45 +/- 12 mg% in the nonrestenosis group (p less than 0.001). Restenosis developed in 22 of 34 (64%) patients with an HDL cholesterol less than or equal to 40 mg% compared with six of 34 (17%) patients with an HDL cholesterol greater than 40 mg% (p less than 0.002). The only other variable that was significantly related to restenosis was a low PAI-1 level (p = 0.04).

CONCLUSIONS

The strong relation between a low HDL cholesterol level and the risk of restenosis suggests that lipid fractions could be important in the pathogenesis and prevention of restenosis.
Electrophysiological findings and long-term follow-up of patients with the permanent form of junctional reciprocating tachycardia treated by catheter ablation.
Authors: Chien W W , Cohen T J , Lee M A , Lesh M D , Griffin J C , Schiller N B , Scheinman M M
Published: June 2012

BACKGROUND

The permanent form of junctional reciprocating tachycardia (PJRT) commonly presents as recurrent drug-refractory, narrow-complex tachycardia. We studied the efficacy and safety of catheter ablation in treating these patients.

METHODS AND RESULTS

Six patients with the diagnosis of PJRT were treated at our institution with direct-current catheter ablation. The study cohort comprised three men and three women with a mean age of 33.8 +/- 4.5 years. The mean time from onset of symptoms to ablation was 129 +/- 44.7 months. All failed multiple drug therapy (mean number of drugs failed was 5.3 +/- 0.5). The left ventricular ejection fractions were calculated by echocardiography and were greater than 60% in all except two patients, whose ejection fractions were 25% and 32%. Symptom duration was significantly longer in those with depressed ejection fraction compared with normal patients (258 versus 64.5 months, p less than 0.01). Electrophysiological findings revealed evidence of an atrioventricular reciprocating tachycardia involving retrograde decremental conduction over an accessory pathway localized to the posteroseptal area. Five patients received two direct-current shocks (250 +/- 16.7 J per shock) via paired electrodes from a catheter positioned just outside the coronary sinus os to a patch placed between the scapulae or on the anterior chest wall. One patient received a single direct-current shock of 300 J. The only complication was the development of complete atrioventricular block in one patient. This patient had previously undergone permanent pacemaker insertion for the sick sinus syndrome. The mean hospital stay after ablation was 2.2 days. Mean peak creatinine phosphokinase after ablation was 352 +/- 58.1 units/l and the MB fraction was 12 +/- 2%. Follow-up echocardiograms or gated nuclear studies showed improvement of ejection fraction in the two patients who presented with depressed ejection fractions. After a mean follow-up of 35.8 +/- 10.3 months, all patients remained free of tachycardia without antiarrhythmic drugs.

CONCLUSIONS

We conclude that catheter ablation by using direct current energy appears to be an effective treatment in patients with PJRT.
Imaging of vascular injury with 99mTc-labeled monoclonal antiplatelet antibody S12. Preliminary experience in human percutaneous transluminal angioplasty.
Authors: Miller D D , Rivera F J , Garcia O J , Palmaz J C , Berger H J , Weisman H F
Published: June 2012

BACKGROUND

To evaluate the in vivo safety, biodistribution, and diagnostic accuracy of a monoclonal Fab' antibody (S12) that is specific for the platelet membrane glycoprotein (GMP-140) expressed during platelet activation at vascular injury sites, 11 peripheral percutaneous transluminal angioplasty (PTA) patients (age, 61 +/- 8 years) with severe vascular disease had serial 99mTcS12 radionuclide imaging at 5 and 90 minutes, 4-6 hours, and 20-24 hours after a total of 23 angiographically successful PTA procedures. No acute allergic reactions or hematologic toxicity occurred.

METHODS AND RESULTS

The average PTA percent angiographic diameter stenosis (DS) at all 23 sites decreased from 85 +/- 12% to 12 +/- 11%, with a mean before-to-after-PTA change of 73 +/- 14% (p less than 0.01). The mean radionuclide image-derived ratio of 99mTc S12 activity in PTA versus contralateral non-PTA arterial segments for all angioplasty sites was 1.6 +/- 0.5. Vascular 99mTc S12 antibody activity was qualitatively evident in the majority (78%) of PTA sites at 4-6 hours after injection. 99mTc S12 target-to-background (muscle) ratio equaled 2.3 +/- 0.6 at PTA sites. Nine PTA sites (39%) had residual 99mTc S12 activity at 24 hours after injection (mean PTA site-to-contralateral artery ratio, 1.5 +/- 0.4). The mean vascular 99mTc S12 activity ratios in 10 procedurally complicated (defined as extensive dilation [greater than 2 cm] or grade I or greater arterial dissection) and 13 uncomplicated PTA segments were 1.9 +/- 0.5 versus 1.2 +/- 0.1, respectively (p less than 0.01). The associated before-to-after-PTA angiographic improvement was significantly less in procedurally complicated PTA sites (66 +/- 12% versus 80 +/- 12% DS; p less than 0.01).

CONCLUSIONS

99mTc S12 activity is significantly increased at angiographically patent PTA sites that are procedurally complicated and are associated with less significant before-to-after-PTA angiographic improvement. 99mTc S12 monoclonal Fab' antibody imaging permits noninvasive identification of local vascular platelet activation resulting from angioplasty balloon injury in humans.
Pericardial adaptation in severe chronic pulmonary hypertension. An intraoperative transesophageal echocardiographic study.
Authors: Blanchard D G , Dittrich H C
Published: June 2012

BACKGROUND

The pericardium both limits cardiac distension and accentuates ventricular interdependence. Although this effect appears minimal under normal circumstances, the pericardium markedly restricts acute cardiac enlargement. Animal studies have demonstrated gradual pericardial adaptation and expansion in chronic volume overload and cardiomegaly, but the pericardial response in humans with cardiac hypertrophy and enlargement has not been examined fully. To investigate this further, 14 patients with right ventricular hypertrophy and cardiomegaly secondary to chronic pulmonary thromboembolic disease and severe pulmonary hypertension were studied during pulmonary thromboendarterectomy.

METHODS AND RESULTS

Simultaneous intraoperative transesophageal Doppler echocardiography and direct biventricular hemodynamic measurements were performed at steady state immediately before and after pericardiotomy. All hemodynamic variables showed no significant change before and after pericardiotomy, including heart rate (76 +/- 16 versus 75 +/- 15 beats per minute), mean pulmonary arterial pressure (46.3 +/- 11.1 versus 45.5 +/- 11.7 mm Hg), cardiac index (1.8 +/- 0.5 versus 2.0 +/- 0.6 l/min/m2), left ventricular end-diastolic pressure (5.9 +/- 5.7 versus 7.1 +/- 5.0 mm Hg), and right ventricular end-diastolic pressure (7.9 +/- 6.6 versus 8.0 +/- 6.7 mm Hg). Similarly, there were no significant changes in all Doppler echocardiographic parameters, including right ventricular end-diastolic area (23.2 +/- 5.7 versus 22.6 +/- 5.4 cm2), left ventricular end-diastolic area (15.3 +/- 5.9 versus 15.5 +/- 4.4 cm2), the position of the interventricular septum, and the Doppler-derived mitral inflow measures of diastolic function.

CONCLUSIONS

The pericardium appears to have little influence on the marked cardiac and septal deformations seen in patients with chronic, severe right ventricular pressure overload and cardiomegaly. This study confirms that the human pericardium is capable of adapting over time to changes in cardiac size and geometry.