bluuebunny/crossref_metadata_2025 huggingface dataset:
Coronary wedge pressure in relation to spontaneously visible and recruitable collaterals.
Authors: Meier B , Luethy P , Finci L , Steffenino G D , Rutishauser W
Published: June 2011

Coronary angiography demonstrates only collateral arteries that are already in use (spontaneously visible collaterals). Percutaneous transluminal coronary angioplasty (PTCA) provides an opportunity to uncover collaterals ready to become functional in case of occlusion of the recipient artery (recruitable collaterals). The incidence of recruitable collaterals and their relation to the distal pressure in the occluded artery (coronary wedge pressure) during a 30 sec or longer balloon occlusion was assessed in 57 coronary arteries of 49 patients undergoing PTCA for a proximal coronary stenosis or occlusion. Collateral to 75% of the arteries were present. Spontaneously visible collaterals were four times as frequent as recruitable collaterals. Coronary wedge pressure was significantly higher in arteries with spontaneously visible and recruitable collaterals (41 +/- 12 and 36 +/- 12 mm Hg, respectively) than in arteries without collaterals (18 +/- 4 mm Hg). A coronary wedge pressure of 30 mm Hg or higher was found exclusively in the presence of collaterals. Electrocardiographic changes during balloon occlusion were found more frequently with arteries without collaterals than with arteries with spontaneously visible or recruitable collaterals. Chest pain was more frequent in patients without collaterals or with recruitable collaterals than in those with spontaneously visible collaterals. Major in-hospital events occurred in three patients with collaterals, with a salutary influence of the collaterals in two. The coronary wedge pressure allows prediction of recruitable collaterals. Their clinical impact remains to be investigated in long-term studies on large patient populations.
Impairment of cardiopulmonary baroreflex after cardiac transplantation in humans.
Authors: Mohanty P K , Thames M D , Arrowood J A , Sowers J R , McNamara C , Szentpetery S
Published: June 2011

There is ample evidence for efferent cardiac denervation in patients after cardiac transplantation. However, little is known regarding the effects of the cardiac deafferentation that also results. We examined responses to graded lower-body negative pressure and thus cardiopulmonary baroreceptor unloading in 23 patients 3 to 12 months after cardiac transplantation and compared their responses with those of nine normal subjects. Responses of mean arterial pressure, forearm vascular resistance, and plasma norepinephrine were assessed during lower-body negative pressure and the cold pressor test. Reflex increases in forearm vascular resistance (1.5 +/- 1, 5.0 +/- 1.4, and 6.4 +/- 2.1 vs 14.5 +/- 4.5, 20.3 +/- 6.5, and 34 +/- 11 units) and plasma norepinephrine (42 +/- 12, 58 +/- 15, and 62 +/- 13 vs 49 +/- 14, 94 +/- 25, and 173 +/- 36 pg/ml) during lower-body negative pressure (at -10, -20, and -40 mm Hg) were strikingly smaller in cardiac transplant patients than in normal subjects. The impaired responses of the cardiac transplant patients were not the result of a nonspecific depression of cardiovascular reflexes, since increases in mean arterial pressure (12 +/- 3 vs 10 +/- 2 mm Hg), forearm vascular resistance (19.5 +/- 3.4 vs 18 +/- 5.8 units), and plasma norepinephrine (56 +/- 8 vs 42 +/- 11 pg/ml) during cold pressor test were not significantly different in the two groups. Furthermore, the impaired responses were not caused by the immunosuppressive agents used to treat the cardiac transplant patients, since patients with renal transplants on similar regimens had augmented forearm vasoconstrictor responses.(ABSTRACT TRUNCATED AT 250 WORDS)
Early postinfarction ischemia: clinical, angiographic, and prognostic significance.
Authors: Bosch X , Théroux P , Waters D D , Pelletier G B , Roy D
Published: June 2011

Early ischemia, defined as angina with transient ST-T changes during hospitalization, 24 hr or more after an acute myocardial infarction (MI), was observed in 79 (18%) of a consecutive series of 449 patients surviving an MI and catheterized a mean of 10 +/- 3 days after admission. Three clinical factors present 24 hr after admission could identify patients at low, medium, and high risk of factors had a risk greater than 50% and the 118 patients with Q wave MI, no previous angina, and absence of risk factors had a risk of less than 8%. The angiographic correlates of early ischemia were number of vessels with 70% or more stenosis (2.1 +/- 0.8 vs 1.7 +/- 0.8/patient, p less than .0001), number of diseased coronary artery segments (2.8 +/- 1.4 vs 2.1 +/- 1.2, p less than .0001), left anterior descending coronary involvement (77% vs 62% of patients, p = .01), number of normally contractile segments at jeopardy because of a coronary stenosis (1.9 +/- 1.3 vs 1.3 +/- 1.1/patient, p less than .0002), collateral circulation at jeopardy (24% vs 15% of patients, p less than .005), and fewer collateral vessels distal to a tight stenosis (59 vs 72% of patients, p = .04). The stepwise logistic regression retained one angiographic and two clinical independent predictors of early ischemia: number of diseased vessels (p = .0008), presence of a non-Q wave MI (p = .0027), and previous angina (p = .017).(ABSTRACT TRUNCATED AT 250 WORDS)
Paradoxical hypertension after repair of coarctation of the aorta in children: balloon angioplasty versus surgical repair.
Authors: Choy M , Rocchini A P , Beekman R H , Rosenthal A , Dick M , Crowley D , Behrendt D , Snider A R
Published: June 2011

The incidence and possible causes of paradoxical hypertension were evaluated in eight children who underwent balloon dilatation and seven children who underwent surgical repair of coarctation of the aorta. Both procedures resulted in a significant reduction in the coarctation gradient. Both systolic and diastolic blood pressures increased in the surgical group after repair, whereas systolic pressures decreased and diastolic pressures remained unchanged after balloon angioplasty. In the surgical group, but not in the balloon angioplasty group, plasma catecholamines and plasma renin activity rose during the first 2 days after relief of the coarctation. The data presented in this report support the hypothesis that the sympathetic nervous system and the renin angiotensin system are important mediators of the paradoxical hypertension that occurs after surgical repair of coarctation. Furthermore, balloon angioplasty of coarctation of the aorta does not stimulate either system and thus paradoxical hypertension is not a complication of this procedure.
Cardiovascular and neurohumoral postural responses and baroreceptor abnormalities during a course of adjunctive vasodilator therapy with felodipine for congestive heart failure.
Authors: Kassis E , Amtorp O
Published: June 2011

Studies in patients with congestive heart failure (CHF) have demonstrated an abnormal beta-adrenergic reflex vasodilation during orthostatic tilt. Baroreflex modulation of vascular resistance in patients with CHF was investigated during therapy with a vasoselective calcium antagonist, felodipine. Eight patients on conventional therapy for severe CHF were studied after a 3 week course of additional felodipine or placebo treatment under randomized, double-blind, and crossover conditions. Forearm subcutaneous vascular resistance (FSVR) was estimated with use of the local 133Xe washout. Aortic pulsatile stretch, expressed as the systolic distension in percent of diastolic diameter, was calculated from echocardiographic measurements of aortic root diameters. At 3 weeks, felodipine reduced the arterial pressure, systemic vascular resistance, and FSVR, preserved cardiac filling pressures and heart rate, and increased cardiac output, stroke volume, and aortic pulsatile stretch. Upright tilt (45 degrees) was used to study baroreflex-mediated cardiovascular responses. The unloading of cardiopulmonary baroreceptors during upright tilt was substantial and about equal during both treatment courses, but the pulse pressure was maintained during the placebo and decreased during the felodipine period. During tilt, the patients on placebo failed to increase heart rate and their FSVR, systemic vascular resistance, and arterial mean pressure were decreased, whereas during tilt after felodipine, heart rate and systemic vascular resistance increased to maintain arterial mean pressure and FSVR also tended to increase. Both the stroke volume and aortic pulsatile stretch increased during tilt in patients on placebo but they decreased in those on felodipine. The tilt caused increments in circulating norepinephrine and epinephrine levels during both treatment regimens. Regulation of FSVR during the sympathetic stimulation of orthostatic stress was further elucidated. Proximal neural blockade caused an increase in FSVR during tilt in patients on placebo and a decrease in FSVR during tilt in those on felodipine. Local beta-adrenoceptor blockade caused similar increments in FSVR during tilt in patients on both treatments. Combined proximal and local blockade still increased FSVR during tilt in those on placebo, but caused no change in FSVR during tilt in those on felodipine. This study demonstrates that felodipine normalizes baroreflex control of vascular resistance in patients with CHF.(ABSTRACT TRUNCATED AT 250 WORDS)
The effect of inotropic stimulation on normal and ischemic myocardium after coronary occlusion.
Authors: Buda A J , Zotz R J , Gallagher K P
Published: June 2011

During acute myocardial ischemia, there exists a zone of myocardial dysfunction that surrounds the central ischemic area that has been termed the functional border zone. We hypothesized that this nonischemic but dysfunctional myocardium may respond to an inotropic challenge. To address this issue, we studied 11 open-chest dogs during acute left circumflex (LCx) occlusion. Simultaneous two-dimensional echocardiograms and radioactive microsphere injections were used to create circumferential left ventricular flow-function maps at the papillary muscle level. Serial studies were performed at baseline, 15 min after LCx occlusion, and after the infusion of dobutamine during LCx occlusion. After occlusion, wall thickening decreased from 52 +/- 8% (mean +/- SEM) to -5 +/- 5% (p less than .01) in the central ischemic zone. The extent of left ventricular dysfunction measured 170 +/- 11 degrees while the subendocardial hypoperfusion zone was 130 +/- 9 degrees (p less than .05), resulting in a functional border zone of 40 +/- 11 degrees. During the infusion of dobutamine, wall thickening did not change in the central ischemic zone but increased adjacent to the functional border zone (p less than .01) and in the normal zone (p less than .05), reducing the extent of the functional border zone to 19 +/- 16 degrees (p less than .05). After dobutamine, the slope of transition of wall thickening from nonischemic to ischemic zones, measured directly from the left ventricular function map, increased on the free wall border (0.71 +/- 0.11 to 0.95 +/- 0.10, p less than .02) to a greater extent than on the septal border (0.60 +/- 0.08 to 0.73 +/- 0.06, p = .07). We conclude that nonischemic myocardium adjacent to ischemic tissue responds to inotropic challenge, dobutamine produces a significant decrease in the size of the functional border zone, and dynamic changes in wall thickening after inotropic intervention are greater in the functional border zone of the lateral free wall than at the septal border of the ischemic area.
Effects of activation sequence and anisotropic cellular geometry on the repolarization phase of action potential of dog ventricular muscles.
Authors: Osaka T , Kodama I , Tsuboi N , Toyama J , Yamada K
Published: June 2011

The influence of activation sequences on action potential configuration, especially in the repolarization phase, was examined in isolated canine ventricular muscles. Action potentials were recorded from the epicardial surface in the center of a preparation having nearly uniform fiber orientation (25 X 25 mm). Stimuli applied just adjacent to the recording site produced nearly centrifugal propagation. An activation sequence either parallel (longitudinal) or perpendicular (transverse) to the long axis of the muscle fibers was produced by peripheral stimulation. Action potential duration at -60 mV (APD-60 mV) during centrifugal propagation was significantly longer than that during longitudinal propagation. Further shortening of APD-60 mV was observed during transverse propagation. When a collision of longitudinal or transverse wavefronts (longitudinal or transverse collision) was produced at the action potential recording site, the shortest APD was recorded. During centrifugal propagation, action potential mapping around the stimulating electrodes revealed that APD-60 mV shortened gradually as the recording site was moved further from the stimulation site. The spatial gradient of APD was steeper in the transverse than in the longitudinal direction, causing a distortion in the repolarization sequence and the recovery of excitability near the center of the tissue. Premature stimuli applied to an area near the central stimulation site induced one-way block and circus movement of the wavefront, indicating reentry of excitation. We concluded that the activation sequence and anisotropic cellular geometry substantially affect APD, and that such a change contributes to the spatial inhomogeneity of refractoriness leading to reentrant arrhythmias.
Age-related valvular regurgitation: a study by pulsed Doppler echocardiography.
Authors: Akasaka T , Yoshikawa J , Yoshida K , Okumachi F , Koizumi K , Shiratori K , Takao S , Shakudo M , Kato H
Published: June 2011

To assess the prevalence of valvular regurgitation in the aged, we studied 176 apparently healthy volunteers with no history or physical evidence of cardiac abnormality. Their ages ranged from 40 to 90 (66 +/- 14, mean +/- SD) years. We examined these subjects by pulsed Doppler echocardiography combined with two-dimensional echocardiography to determine the prevalence of valvular regurgitation. Regurgitation began to appear in subjects in their fifties, increasing in prevalence with advancing age (r = .81, p less than .001), and was documented in all over age 80. Similarly, regurgitation involving more than one valve appeared in those 60 years and older, and was very common (89%) in subjects in their eighties. With each type of valvular regurgitation, the prevalence of each type of regurgitation increased with aging, but this tendency was most prominent for aortic regurgitation. We conclude that (1) single or multivalvular regurgitation as detected by pulsed Doppler echocardiography is very common in the aged and may be considered a normal finding in the absence of other evidence of heart disease, and (2) the high prevalence of regurgitation in the aged must be taken into account when Doppler examinations are being performed.
Review of lipid-lowering clinical trials in relation to observational epidemiologic studies.
Authors: Tyroler H A
Published: June 2011

A review of the experimental clinical trials and observational cohort evidence relating serum cholesterol level and its reduction to risks of coronary heart disease (CHD) discloses strong similarities among the quantitative and qualitative relationships found in these studies. Not only are the risk functions similar, but the percent reduction observed is the same as that predicted from the population experience and is proportional to the degree of cholesterol lowering. Furthermore, the risk function is continuous from the highest to the lowest serum cholesterol levels studied. These findings confirm the lipid hypothesis and indicate that lowering serum cholesterol reduces CHD risk. The understanding and control of CHD requires a dual approach: (1) identification and treatment of high-risk individuals, and (2) modification of environmental and behavioral determinants to achieve more favorable distributions of serum cholesterol in populations.
Reversal of exertional hypotension by prolonged exercise training in selected patients with ischemic heart disease.
Authors: Martin W H , Ehsani A A
Published: June 2011

The effect of prolonged intense endurance exercise training on exertional hypotension was investigated in 16 patients with coronary artery disease who had a 10 mm Hg or greater fall in systolic blood pressure (SBP) during progressive exercise testing. Training consisted of walking, running, or cycling at 50% to 60% of peak oxygen uptake (peak VO2) for 30 min 3 days per week for an initial 3 months and was followed by an additional 9 months of similar exercise performed at 70% to 90% of peak VO2 for 50 to 60 min 5 days per week. The 1 year program resulted in a 41% increase in peak VO2 and lower heart rate and blood pressure responses to submaximal work. Before conditioning, SBP attained a maximal value of 162 +/- 5 mm Hg but fell 21 +/- 3 mm Hg, to 141 +/- 7 mm Hg, at peak effort (p less than .01). After training, maximal SBP was achieved at a faster heart rate (157 +/- 5 vs 132 +/- 6 beats/min; p less than .001) and was 7.4% higher (174 +/- 6 vs 162 +/- 5 mm Hg; p less than .005), while SBP at peak exercise had increased by 21% (171 +/- 6 vs 141 +/- 7 mm Hg; p less than .001) and ST segment depression was slightly reduced. Left ventricular ejection fraction (LVEF) before training declined from 56 +/- 4% at rest to 52 +/- 3% at peak exercise (p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)
Long-term control of Chagas disease in Venezuela: effects on serologic findings, electrocardiographic abnormalities, and clinical outcome.
Authors: Acquatella H , Catalioti F , Gomez-Mancebo J R , Davalos V , Villalobos L
Published: June 2011

To evaluate the long-term effects (20 years) of a Chagas control program (CCP) in Venezuela, a prospective serologic evaluation was carried out from 1981 to 1984 on 5771 inhabitants (8%) of Roscio county. This region was selected as a representative area where the national CCP was implemented effectively. Comparison with a serologic survey performed in the same region before the CCP disclosed a reduction in seropositive subjects from 47.8% to 17.1% (p less than .001), most marked amongst children and teenagers from 29.9% to 1.9%, suggesting that transmission of the disease had diminished. Similar seropositivity changes after the CCP were observed nationwide. Because decreased superinfection would also be expected to occur, we tried to ascertain whether the clinical outcome of seropositive individuals living in Roscio county had improved. The mean age of seropositive subjects between both surveys increased significantly from 34.9 +/- 17.3 to 46.7 +/- 15.1 years (p less than .001). Additionally, we examined clinically and obtained electrocardiograms from 775 seropositive subjects. They were classified as asymptomatic (group A, n = 614) or as symptomatic, having mild-to-moderate heart symptoms (group B, n = 99) or having advanced congestive heart failure (group C, n = 62). Their electrocardiograms were compared with those of 923 seronegative subjects collected simultaneously and with published data obtained before the CCP. Comparison of the age-related rates of electrocardiographic abnormalities of seropositive individuals before and after the CCP showed that they did not differ significantly by linear regression analysis, by the Kruskal-Wallis test, or by the normal approximation to the binomial distribution.(ABSTRACT TRUNCATED AT 250 WORDS)
Detection of transient myocardial ischemia by computer analysis of standard and signal-averaged high-frequency electrocardiograms in patients undergoing percutaneous transluminal coronary angioplasty.
Authors: Abboud S , Cohen R J , Selwyn A , Ganz P , Sadeh D , Friedman P L
Published: June 2011

Electrocardiographic manifestations of transient myocardial ischemia were studied, in 11 patients undergoing angioplasty (PTCA) of a left anterior descending coronary artery stenosis, by the visual inspection of the standard surface electrocardiogram (S-ECG) and the intracoronary ECG (IC-ECG) as well as computer-assisted analysis of the S-ECG. Cross-correlation analysis (CCA) performed by computer was used to compare beat-to-beat variability in ST-T morphology of the S-ECG during different stages of PTCA. CCA was also applied to the signal-averaged high-frequency QRS (SA-HFQ). All patients developed angina during balloon inflation, accompanied by transient marked ST-T changes in IC-ECG in 10 of 11 patients (90%). Visual inspection of S-ECG revealed transient ST-T changes in only 6 of 11 (54%). In contrast, CCA of the S-ECG revealed transient ST-T changes in 9 of 11 (82%). Analysis of SA-HFQ revealed that balloon inflation was associated with a marked reduction in the calculated root-mean-square (RMS) voltage for such signals (2.31 +/- 1.04 microV) as compared with RMS values before (3.27 +/- 1.12 microV, p less than .05) PTCA or after conclusion of PTCA (3.79 +/- 1.39 microV, p less than .01). Balloon inflation was also accompanied by changes in waveform morphology of the SA-HFQ, including the development of new or more prominent time zones of reduced amplitude in 10 of 11 individuals (90%). Such zones may represent slow conduction in regions of the heart rendered ischemic during PTCA. CCA of the S-ECG and of SA-HFQ appears to detect evidence of transient ischemia with greater sensitivity than simple visual inspection of S-ECG, and may therefore prove to be of use in the evaluation of patients with chest pain of uncertain origin.
Beneficial effects of timolol on infarct size and late ventricular tachycardia in patients with acute myocardial infarction.
Authors: Roqué F , Amuchastegui L M , Lopez Morillos M A , Mon G A , Girotti A L , Drajer S , Fortunato M , Moreyra E , Tuero P , Solchaga J C
Published: June 2011

This investigation was undertaken to study the effects of beta-adrenergic blockade with timolol on infarct size and on the incidence of late ventricular tachycardia in patients with acute myocardial infarction of less than 6 hr of evolution. Patients were assigned randomly either to a placebo-treated group (98 patients) or to a timolol-treated group (102 patients). The patients were treated with 5.5 mg iv timolol (or matched placebo) as a bolus divided into four doses during the first 2 hr followed by 10 mg orally twice daily for 1 month. Cumulative total creatine kinase (CK) release, which reflects the amount of myocardial necrosis was 1677 +/- 132 IU/liter in the placebo group (n = 83) and 1274 +/- 73 IU/liter in the timolol group (n = 81, p less than .01), a 24% reduction. Cumulative release of CK-MB was 138 +/- 8 IU/liter in the placebo group and 106 +/- 8 IU/liter in the timolol group (p less than .01), a 23% reduction. Twenty-four hour Holter electrocardiograms were obtained on days 7, 14, 21, and 28 after the onset of the acute myocardial infarction in 80 patients in the placebo group and 82 patients in the timolol group. The incidence of ventricular tachycardia was lower in the timolol than in the placebo group (7 vs 16 patients, p = .05). We conclude that early administration of intravenous timolol followed by oral treatment in patients with acute myocardial infarction reduces infarct size as assessed by CK and CK-MB serum activity, and decreases the occurrence of late ventricular tachycardia.
Influence of a laminar steady-state fluid-imposed wall shear stress on the binding, internalization, and degradation of low-density lipoproteins by cultured arterial endothelium.
Authors: Sprague E A , Steinbach B L , Nerem R M , Schwartz C J
Published: June 2011

Fluid mechanical steady-state laminar wall shear stresses of 30 dyne/cm2 (high stress) and less than 1 dyne/cm2 (low stress) have been applied for varying times to confluent cultures of bovine aortic endothelial cells (BAECs) by means of two parallel plate channel flow chambers in series. BAEC cultures not exposed to shear or flow (no stress) were also studied. A shear stress of 30 dyne/cm2 resulted in cellular elongation and alignment, changes that were largely complete by 24 hr. In experiments in which BAECs were incubated with 125I-labeled low-density lipoprotein for 2 or 24 hr in the presence of shear stress levels, 125I-LDL internalization at 24 hr was increased (p less than .05) in response to high-stress conditions. This increased uptake of 125I-LDL was observed in BAECs prealigned for 24 hr under high stress and in BAECs undergoing alignment in the presence of circulating 125I-LDL. BAECs were also exposed to shear stress for 24 hr in the presence of a lipoprotein-deficient circulating medium to maximize LDL receptor expression. Receptor-mediated 125I-LDL internalization and degradation measured immediately after shear stress were both significantly enhanced (p less than .01) in BAECs exposed to high stress. Furthermore, 125I-LDL binding studies at 4 degrees C revealed a significant increase (p less than .01) in specific 125I-LDL binding to BAECs exposed to high stress relative to those exposed to low or no stress. Nonspecific 125I-LDL endocytosis was not influenced by shear stress levels.(ABSTRACT TRUNCATED AT 250 WORDS)
Left ventricular mechanics in the normal newborn.
Authors: Rein A J , Sanders S P , Colan S D , Parness I A , Epstein M
Published: June 2011

The transition from fetal to neonatal circulatory status is accompanied by marked alteration in relative right and left ventricular systolic and diastolic pressure. These alterations would be expected to influence both global and regional performance of the left ventricle. To address this issue, sequential two-dimensional echocardiographic studies were performed in normal newborns during the first days of life. Global and regional left ventricular wall motion were quantified by computer digitization with the use of an automated edge detection algorithm and a floating-center-of-mass model. Comparison was made with a control group of normal infants and young children and the sequential change over the first 5 days of life was assessed. Newborns were found to have a circular left ventricular configuration at end-diastole beginning on day 1. At end-systole, however, there was significant left ventricular distortion due to septal flattening, which persisted until day 3 and resolved entirely by day 5 of life. Regional wall motion analysis demonstrated a corresponding augmentation of septal and contralateral left ventricular free wall systolic movement during the first days of life, with a normal pattern attained by day 4. Due to the nonhomogeneity of the left ventricular wall motion in the first few days of life, standard single-dimension shortening fraction provided an unreliable measure of global left ventricular performance before day 4. Thus, systolic right ventricular hypertension at a level sufficient to distort the left ventricular configuration is present until day 4 or 5 of life, resulting in altered left ventricular regional wall motion. As a result, usual M mode echocardiographic assessment of left ventricular function is unreliable in this age group.(ABSTRACT TRUNCATED AT 250 WORDS)
Quantitative ultrasonic tissue characterization with real-time integrated backscatter imaging in normal human subjects and in patients with dilated cardiomyopathy.
Authors: Vered Z , Barzilai B , Mohr G A , Thomas L J , Genton R , Sobel B E , Shoup T A , Melton H E , Miller J G , Pérez J E
Published: June 2011

We have shown previously that the physical properties of myocardium in dogs can be characterized with quantitative ultrasonic integrated backscatter and that interrogation of the tissue with ultrasound can delineate cardiac cycle-dependent changes in ultrasonic backscatter in normal tissue that disappear with ischemia and reappear with reperfusion if functional integrity is restorable. To determine whether this approach can be applied to man, we implemented an automatic gain compensation and continuous data acquisition system to characterize myocardium with quantitative ultrasonic backscatter and to detect cardiac cycle-dependent changes in real time. We developed a two-dimensional echocardiographic system with quantitative integrated backscatter imaging capabilities for use in human subjects that can automatically differentiate ultrasonic signals from blood as opposed to those obtained from tissue and adjust the slope of the gain compensation appropriately. Real-time images were formed from a continuous signal proportional to the logarithm of the integrated backscatter along each A-line. In our initial investigation, 15 normal volunteers (ages 17 to 40 years, heart rates 44 to 88 beats/min) and five patients with dilated cardiomyopathy (ages 22 to 52, heart rates 82 to 120 beats/min) were studied with conventional parasternal long-axis echocardiographic views. Diastolic-to-systolic variation of integrated backscatter in the interventricular septum and left ventricular posterior wall was seen in each of the normal subjects averaging 4.6 +/- 1.4 dB (SD) and 5.3 +/- 1.5 dB (n = 127 sites), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Inconsistency of the slope and the volume intercept of the end-systolic pressure-volume relationship as individual indexes of inotropic state in conscious dogs: presentation of an index combining both variables.
Authors: Crottogini A J , Willshaw P , Barra J G , Armentano R , Cabrera Fischer E I , Pichel R H
Published: June 2011

We tested the ability of the slope (Emax) and the volume intercept (Vo) of the end-systolic pressure-volume relationship (ESPVR) to indicate contractility changes in conscious dogs instrumented with sonomicrometers measuring left ventricular diameter in three orthogonal axes and a left ventricular pressure microtransducer. ESPVRs were generated by inferior vena caval occlusion under control conditions (C1 and C2) and during enhanced (I+) and depressed (I-) inotropic states achieved by infusion of dobutamine and injection of propranolol, respectively. No significant difference between the first control (C1) and I+ or between the second control (C2) and I- were found for either Emax (C1, 5.31 +/- 1.68 mm Hg/ml, mean +/- SD; I+, 5.37 +/- 1.44; C2, 5.20 +/- 1.62; I-, 4.18 +/- 1.32) or Vo (C1, 10.3 +/- 9.6 ml; I+, 7.3 +/- 9.1; C2, 9.9 +/- 9.0; I-, 12.7 +/- 12.5), despite significant changes in other indexes of contractility. Comparison of changes in Emax in individual animals in response to I+ and I- revealed that 63% were nonsignificant, 28% were significant and expected, and 9% were significant and paradoxical. Within defined volume limits and irrespective of individual changes in Emax and Vo, in all animals I+ shifted the ESPVR above and to the left of C1 and I- shifted the ESPVR below and to the right of C2. We thus integrated the changes in Emax and Vo by measuring the area beneath each ESPVR between defined limits of end-systolic volume. The values for area were: C1, 612 +/- 150 mm Hg.ml; I+, 745 +/- 191 (p less than .001); C2, 520 +/- 198; I-, 420 +/- 139 (p less than .001). We conclude that (1) neither Emax nor Vo are individually reliable indexes of changed contractility, and (2) the area beneath the ESPVR between defined end-systolic volume limits is a consistent indicator of variations in inotropic state.
Effect of graded coronary flow reduction on ionic, electrical, and mechanical indexes of ischemia in the pig.
Authors: Watanabe I , Johnson T A , Buchanan J , Engle C L , Gettes L S
Published: June 2011

This study was performed to determine the relative sensitivities of ionic, electrical, and mechanical indexes of myocardial ischemia. We used ion-selective and bipolar plunge electrodes, epicardial unipolar electrodes, a suction electrode, and ultrasonic crystals to determine the changes in intramyocardial extracellular potassium ([K+]e) and extracellular pH (pHe), local activation, epicardial TQ-ST segment, monophasic action potential duration (MAPD), and regional contractility during graded coronary flow reduction in open-chest pigs. A carotid-to-coronary shunt was created to perfuse the left anterior descending coronary artery via a roller pump. The shunted coronary flow was reduced in a stepwise fashion at 5-min intervals. In 25 pigs, the approximate myocardial blood flow associated with the initial changes in each variable was as follows: midmyocardial [K+]e, pHe, and TQ-ST segment, 0.7 to 0.8 ml/min/g; subepicardial [K+]e and TQ-ST segment, 0.6 to 0.7 ml/min/g; segmental shortening, 0.5 to 0.6 ml/min/g; local activation and epicardial TQ-ST segment, 0.3 to 0.4 ml/min/g; epicardial MAPD, 0.15 to 0.2 ml/min/g. Our results indicate that changes in [K+]e, pHe, and TQ-ST segment provide the most sensitive means of detecting myocardial ischemia and of determining the effect of interventions capable of influencing the ischemic process.
Quantitative analysis of infarct size, contraction band necrosis, and coagulation necrosis in human autopsied hearts with acute myocardial infarction after treatment with selective intracoronary thrombolysis.
Authors: Matsuda M , Fujiwara H , Onodera T , Tanaka M , Wu D J , Fujiwara T , Hamashima Y , Kawai C
Published: June 2011

To assess the importance of contraction band necrosis (CBN) in patients with acute myocardial infarction (AMI) treated with selective intracoronary thrombolysis, CBN, coagulation necrosis, and infarct size (expressed as CBN + coagulation necrosis) were analyzed quantitatively in 16 autopsied hearts. Intracoronary thrombolysis was performed from 2 to 6 hr after the onset of AMI, and the time from the onset of AMI to death was 7 to 168 hr. Cineangiography revealed no evidence of good collateral circulation in any of the patients. The 16 patients were classified into three groups: six patients with successful thrombolysis (100% to 99% stenosis, group I), five patients with unsuccessful thrombolysis (100% to 100%, group II), and five patients with 99% stenosis before thrombolysis (group III). Among the three groups, there were no significant differences in the time from the onset of AMI to thrombolysis, the time from the onset of AMI to death, the cause of death, or the degree of collateral circulation. The percentage of the risk area involved by the infarct in group I (82 +/- 6%) was similar to that in group II (80 +/- 11%). Infarct size was not reduced in group I because collateral circulation was not good and because the degree of recanalization after thrombolysis was 1%. However, the percentage of the infarct area with CBN was significantly higher in group I (20 +/- 9%) then in group II (3 +/- 3%). This finding shows that diffuse CBN occurred after reperfusion in patients with AMI treated with thrombolysis.(ABSTRACT TRUNCATED AT 250 WORDS)
Electrical alternans and cardiac electrical instability.
Authors: Smith J M , Clancy E A , Valeri C R , Ruskin J N , Cohen R J
Published: June 2011

We investigated the relationship between electrical alternans and cardiac electrical stability in a series of 20 dog experiments and in a pilot clinical study. Electrical alternans was detected in both the QRS complex and the ST-T wave by use of a novel multidimensional spectral technique. The magnitude of the alteration was expressed as the alternating electrocardiographic morphology index (AEMI), expressed as parts per million of waveform energy. Electrical stability in the dog preparations was assessed via the ventricular fibrillation threshold measurement, and in the clinical studies via programmed stimulation. In 10 dog experiments, systemic hypothermia resulted in a 60% decrease in ventricular fibrillation threshold (VFT) (p less than .0001) and a significant increase in both AEMI(QRS) form 3.7 +/- 3.0 to 1448 +/- 548 (p less than .0001) and AEMI(ST-T) from 43.9 +/- 18.4 to 19,178 +/- 5579 (p less than .0001). In 10 dog experiments, transient coronary artery ligation also resulted in a 60% decrease in VFT (p less than .0001), an increase from 76.3 +/- 46.5 to 245 +/- 11 in AEMI(QRS) (p less than .05), and an increase from 842 +/- 505 to 1365 +/- 392 in AEMI(ST-T) (p less than .002). In 119 observations in 20 animal experiments, the rank correlation between VFT and AEMI(QRS) was -.30 (p less than .001), with that between VFT and AEMI(ST-T) being -.55 (p less than .0001). In a double-blind pilot clinical trial consisting of 23 studies in 19 patients, the result of electrophysiologic testing was used as an independent measure of cardiac electrical stability. Alternation in waveform morphology identified the inducible patient population with a sensitivity of 92%, a positive predictivity of 70%, and a specificity of 50% (p less than .05). We conclude that analysis of subtle beat-to-beat variability in electrocardiographic morphology may provide a noninvasive measure of cardiac electrical stability.
Implantation of balloon-expandable intravascular grafts by catheterization in pulmonary arteries and systemic veins.
Authors: Mullins C E , O'Laughlin M P , Vick G W , Mayer D C , Myers T J , Kearney D L , Schatz R A , Palmaz J C
Published: June 2011

The purpose of this investigation was to evaluate the efficacy and safety of implanting expandable intravascular stents in pulmonary arteries and systemic veins. Twenty-seven balloon-expandable grafts were placed in 13 mongrel dogs under anesthesia. A long sheath was introduced over a wire and catheter or dilator into the pulmonary artery or target vein. A collapsed stainless steel expandable mesh stent was placed over the balloon of an angioplasty catheter. The catheter with the mounted stent was advanced through the sheath. The stent expanded to the diameter of the balloon as the balloon was inflated, and remained expanded as the balloon was deflated. The stent was expanded further with a larger balloon in 11 instances. Eleven stents were placed successfully in pulmonary arteries (out of thirteen attempted), and 11 of 14 were installed in tributaries of the precava or postcava. Three inadvertent embolizations of the devices occurred. All three devices that embolized lodged in the pulmonary arteries and did not obstruct flow. Seven dogs were recatheterized at intervals ranging from 56 to 278 days. Twelve stents were patent and nonobstructive, and two were malpositioned, one of which was obstructed. Three animals were killed 2 months (two dogs) and 9 months (one dog) after the implantations. The stents (four in the pulmonary arteries and two in veins) were completely covered with neointima and were patent, without thrombosis. These stents hold promise for definitive dilation of congenital or postoperative vessel stenoses.
The antiarrhythmic efficacy of amiodarone and desethylamiodarone, alone and in combination, in dogs with acute myocardial infarction.
Authors: Nattel S , Davies M , Quantz M
Published: June 2011

Antiarrhythmic activity of amiodarone's desethyl metabolite, which accumulates during oral amiodarone therapy, has been postulated to explain the delayed onset of antiarrhythmic effects during long-term amiodarone therapy. To determine their relative antiarrhythmic efficacy, amiodarone and its desethyl metabolite, desethylamiodarone, were administered to mongrel dogs with ventricular tachycardia 24 hr after ligation of the left anterior descending coronary artery. Cumulative doses of amiodarone, desethylamiodarone, a combination of amiodarone and desethylamiodarone, or the vehicle for drug administration were given at 1 hr intervals. Both amiodarone and desethylamiodarone suppressed ventricular arrhythmias in a dose-dependent fashion. The metabolite, however, was more potent with a 50% effective concentration for suppression of premature ventricular complexes of 1.4 mg/liter compared with 4.6 mg/liter for the parent compound. Plasma and myocardial drug concentrations were similar to those measured during long-term amiodarone therapy in man, with desethylamiodarone producing greater myocardial concentrations than amiodarone for a given plasma concentration. Coadministration of the metabolite along with the parent drug resulted in suppression of arrhythmias at lower doses of amiodarone than when the latter was administered alone, and concentration-response analysis indicated an additive antiarrhythmic effect. These experiments suggest that the accumulation of desethylamiodarone that occurs with long-term oral amiodarone therapy contributes importantly to the antiarrhythmic effects of the drug, and may account for the gradual increase in antiarrhythmic action during the course of amiodarone therapy.
Arterial baroreflex control of sympathetic nerve activity during elevation of blood pressure in normal man: dominance of aortic baroreflexes.
Authors: Sanders J S , Ferguson D W , Mark A L
Published: June 2011

Arterial baroreceptors in the carotid sinus (CBR) and aortic arch (ABR) regions exert important control over heart rate and peripheral vascular responses to changes in arterial pressure. The relative roles of these two baroreflex pathways on control of sympathetic nerve activity during sustained elevation of arterial pressure in man is unknown. We therefore studied the relative contributions of the carotid versus the aortic baroreflexes on the control of muscle sympathetic nerve activity (MSNA) during elevation of arterial pressure in normal human subjects. In eight normal men (group I), we measured MSNA (microneurography) during sustained elevation of arterial pressure produced by intravenous infusion of phenylephrine (PE) alone (combined ABR and CBR activation) versus during PE infusion with superimposed application of sustained external neck pressure (NP). NP was applied during sustained PE infusion to eliminate the increase in transmural carotid sinus pressure and thus remove CBR activation, thereby causing ABR stimulation alone. Mean arterial pressure was measured directly, central venous pressure was held constant during PE infusion, and MSNA was measured as total activity (burst frequency X amplitude) and expressed as units. Infusion of PE (ABR and CBR activation) increased mean arterial pressure from 87.2 +/- 2.8 to 94.9 +/- 2.9 mm Hg (+/- SE, p less than .001). This was accompanied by a decrease in heart rate from 65.8 +/- 3.4 to 56.1 +/- 3.3 beats/min (p less than .001) and a decrease in MSNA from 236.2 +/- 47.5 to 84.5 +/- 19.3 units (p less than .001). During infusion of PE with superimposed NP (ABR activation alone), mean arterial pressure increased further to 101.2 +/- 2.9 mm Hg (p less than .001 versus control or PE alone), and heart rate returned to control levels of 62.9 +/- 2.0 beats/min (p = NS vs control; p less than .01 PE vs PE plus NP), but MSNA remained reduced at 48.6 +/- 9.2 units (p less than .01 vs control; p = NS vs PE alone). Thus, combined activation of ABR and CBR resulted in a 65 +/- 5% attenution of MSNA, while activation of ABR alone resulted in a 73 +/- 7% attenuation of MSNA. In a separate series of experiments in seven subjects (group II) we used sustained external neck suction alone to activate the CBR (leaving the ABR either unchanged or minimally deactivated) and studied the MSNA responses to this CBR activation.(ABSTRACT TRUNCATED AT 400 WORDS)
Incidence of restenosis after successful coronary angioplasty: a time-related phenomenon. A quantitative angiographic study in 342 consecutive patients at 1, 2, 3, and 4 months.
Authors: Serruys P W , Luijten H E , Beatt K J , Geuskens R , de Feyter P J , van den Brand M , Reiber J H , ten Katen H J , van Es G A , Hugenholtz P G
Published: June 2011

Data from experimental, clinical, and pathologic studies have suggested that the process of restenosis begins very early after coronary angioplasty. The present study was performed to determine prospectively the incidence of restenosis with use of the four National Heart, Lung, and Blood Institute and the 50% or greater diameter stenosis criteria, as well as a criterion based on a decrease of 0.72 mm or more in minimal luminal diameter. Patients were recatheterized at 30, 60, 90, or 120 days after successful percutaneous transluminal coronary angioplasty (PTCA). After PTCA all patients received 10 mg nifedipine three to six times a day and aspirin once a day until repeat angiography. Of 400 consecutive patients in whom PTCA was successful (less than 50% diameter stenosis), 342 underwent quantitative angiographic follow-up (86%) by use of an automated edge-detection technique. A wide variation in the incidence of restenosis was found dependent on the criterion applied. The incidence of restenosis proved to be progressive to at least the third month for all except NHLBI criterion II. At 4 months a further increase in the incidence of restenosis was observed when defined as a decrease of 0.72 mm or more in minimal luminal diameter, whereas the criteria based on percentage diameter stenosis showed a variable response. The lack of overlap between the different restenosis criteria applied affirms the arbitrary nature of angiographic definitions currently in use. Restenosis should be assessed by repeat angiography, and preferably ascertained according to the change in absolute quantitative measurements of the luminal diameter.
Mechanisms mediating the heart rate response to hypoxemia.
Authors: Kato H , Menon A S , Slutsky A S
Published: June 2011

We studied the effect of phasic pulmonary afferent information on heart rate (HR) during a progressive reduction in oxygen saturation (SaO2). The Hering-Breuer reflex was evaluated with the use of the ratio of apnea duration after lung inflation to the preceding expiratory time (dT). Phasic afferent activity was stopped in anesthetized, paralyzed dogs by constant-flow ventilation (CFV), a technique that removes cyclic changes in lung volume. During normocapnic (PaCO2 = 36.4 +/- 1.1 mm Hg) spontaneous breathing, there was a wide variability in HR response, with a mean delta HR/delta SaO2 (+/- SE) of 0.62 +/- 0.27 beats/min/% (values greater than 0 indicate a tachycardiac response). There was a good correlation between delta HR/delta SaO2 and dT (r = .79). Mean delta HR/delta SaO2 for the combined normocapnic and hypercapnic studies during CFV was lower (-1.32 +/- 0.19 bpm/%) than that during spontaneous breathing (0.23 +/- 0.19, p less than .0001). We suggest that the HR response to hypoxemia is strongly related to the strength of the Hering-Breuer reflex, which may explain the large interdog variability in HR responses.
Myocardial kinetics of technetium-99m-hexakis-2-methoxy-2-methylpropyl-isonitrile.
Authors: Okada R D , Glover D , Gaffney T , Williams S
Published: June 2011

To study the potential usefulness of technetium-99m hexakis-2-methoxy-2-methylpropyl-isonitrile (Tc-MIBI) as a cardiac perfusion imaging agent, the left circumflex coronary arteries of 12 dogs were partially occluded. Eight additional control dogs had no coronary artery stenosis. Myocardial Tc-MIBI activities in the left circumflex and left anterior descending zones were continuously monitored by miniature implantable radiation detectors for 4 hr after administration of the isotope. The dogs were then killed. Serial gamma camera images were also acquired during the study. Heart rate, arterial blood pressure, pressure distal to the stenosis, and cardiac output did not change significantly during the experiment. Microsphere-determined regional myocardial blood flow was significantly reduced in the left circumflex distribution in the 12 dogs with coronary artery stenoses. In the 12 dogs with left circumflex coronary artery stenoses, the 4 hr fractional Tc-MIBI clearances from the normal and ischemic zones were minimal and equivalent (0.15 +/- 0.05 vs 0.15 +/- 0.07). In the eight control dogs, 4 hr fractional Tc-MIBI clearances from the left anterior descending and left circumflex artery zones were minimal and equivalent (0.11 +/- 0.06 vs 0.10 +/- 0.07). Four hour fractional Tc-MIBI clearance from the blood was 0.98 +/- 0.03 for the dogs with stenosis and 0.97 +/- 0.02 for the dogs without stenosis. One additional dog had complete occlusion of the left circumflex coronary artery followed by administration of Tc-MIBI and scandium-46-labeled microspheres. This heart was immediately sectioned and counted to determine the relationship of regional blood flow to Tc-MIBI distribution (r = .92).(ABSTRACT TRUNCATED AT 250 WORDS)