bluuebunny/crossref_metadata_2025 huggingface dataset:
Lack of beta-adrenoreceptor hypersensitivity after abrupt withdrawal of long-term therapy with oxprenolol.
Authors: Bolli P , Bühler F R , Raeder E A , Amann F W , Meier M , Rogg H , Burckhardt D
Published: June 2011

The possibility of beta-adrenoreceptor hypersensitivity after abrupt withdrawal of long-term therapy (8-18 months) with the slow-release (SR) formulation of oxprenolol (160-320 mg/day) was assessed in six patients with uncomplicated essential hypertension. The chronotropic dose 25 of isoproterenol (the dose that increases the resting heart rate by 25 beats/min), plasma concentration of catecholamines, triiodothyronin and thyroxin, plasma renin activity and aldosterone, hemoglobin, hematocrit and oxyhemoglobin dissociation were measured on the last day of oxprenolol SR intake and 1, 2, 3, 6 and 13 days after abrupt replacement by identical placebo tablets. The chronotropic dose 25 of isoproterenol (microgram/m2), which was greater than 25.6 in all patients on the last day of oxprenolol SR, fell to 4.83 +/- 2.03 on the second day and to 3.50 on the third day after its abrupt withdrawal and reached a minimal value on the thirteenth day (2.78 +/- 0.30). Throughout the study, plasma concentrations of catecholamines, triiodothyronin and thyroxin and oxyhemoglobin dissociation remained unchanged. Plasma renin activity and plasma aldosterone, which were suppressed during oxprenolol administration, rose significantly during placebo, coinciding with a significant fall in hematocrit and hemoglobin. No major subjective symptoms were reported by the patients. Thus, hypersensitivity of beta-adrenoreceptor-mediated responses was not demonstrated after sudden withdrawal of oxprenolol SR.
Hemodynamic effects of atrial pacing and prenalterol infusion in patients taking beta-adrenergic blocking drugs.
Authors: Shiu M F , Ireland M A , Littler W A
Published: June 2011

Prenalterol, a beta-adrenergic agonist, was given to nine patients with angiographically proved coronary artery disease. Subjects were studied during chronic beta-adrenergic blockade. The adequacy of blockade was assessed by the exercise heart rate response and by plasma concentrations of blocking agents. After incremental doses of 2.5 mg, 5.0 mg and 7.5 mg of prenalterol, heart rate was increased by 20%, 24% and 38%, respectively, and left ventricular dP/dt max by 55%, 73% and 61%, respectively. Systolic and diastolic blood pressures did not change significantly; pulmonary artery wedge pressure fell from 10 +/- 0.5 mm Hg to 7.1 +/- 0.9 and 6.7 +/- 0.7 mm Hg after 2.5 mg and 5.0 mg, respectively (p less than 0.01 for both). The net inotropic response to prenalterol was assessed, independent of the chronotropic response, using incremental atrial pacing before and after drug infusion. At identical heart rates, left ventricular dP/dt max increased by 40%, 49% and 48% after 2.5 mg, 5.0 mg and 7.5 mg, respectively. Left ventricular cineangiography before and after infusion showed an increase in ejection fraction from 0.73 +/- 0.02 to 0.83 +/- 0.03 (p less than 0.001). Plasma prenalterol concentration estimations demonstrated a clear, dose-related inotropic response, the level of response in each patient being largely determined by the degree of beta-adrenergic blockade at the time of the study.
Recurrence of ventricular fibrillation in acute ischemic heart disease.
Authors: Logan K R , McIlwaine W J , Adgey A A , Pantridge J F
Published: June 2011

We assessed factors during an initial episode of ventricular fibrillation that may be predictive of recurrence. Of 141 consecutive patients with acute ischemic heart disease who survived an initial episode of ventricular fibrillation, 41 (29%) had recurrent ventricular fibrillation during hospitalization. The incidence of recurrent ventricular fibrillation was lower among those with an acute myocardial infarction than among those with acute ischemic episode. Recurrent ventricular fibrillation occurred more frequently among patients with secondary ventricular fibrillation complicating an acute myocardial infarction than among those with primary ventricular fibrillation. Primary ventricular fibrillation than occurred within 2 hours of the onset of symptoms was no more likely to be recurrent than when it occurred later. Age, sex, site of infarction, place of arrest, adequacy of initial resuscitation, interval onset of symptoms to the initial episode of ventricular fibrillation, onset of symptoms to intensive care and delay before initial attempted defibrillation were not significantly related to the recurrence of ventricular fibrillation.
Intermediate-density lipoprotein and cholesterol-rich very low density lipoprotein in angiographically determined coronary artery disease.
Authors: Tatami R , Mabuchi H , Ueda K , Ueda R , Haba T , Kametani T , Ito S , Koizumi J , Ohta M , Miyamoto S , Nakayama A , Kanaya H , Oiwake H , Genda A , Takeda R
Published: June 2011

The relationship between the concentrations of intermediate-density lipoprotein (IDL) and other lipoproteins and the extent of coronary artery disease (CAD) was studied in 182 consecutive patients evaluated by selective coronary cineangiography. On univariate analysis, the extent of CAD correlated significantly and positively with very low density lipoprotein (VLDL) cholesterol, IDL cholesterol and low-density lipoprotein (LDL) cholesterol, and negatively with high-density lipoprotein (HDL) cholesterol. Analysis of four subgroups divided by IDL cholesterol and LDL cholesterol levels indicated that moderately increased levels of IDL cholesterol were closely associated with a high frequency of CAD. Moreover, multi-variate regression analysis demonstrated that IDL cholesterol for men, LDL cholesterol for men and women and HDL cholesterol for men were significant variables of use in the final weighting procedure. IDL cholesterol was closely associated with cholesterol-rich VLDL. This study shows that IDL and cholesterol-rich VLDL combine to contribute to the development of CAD.
Ultrasonic duplex scanning for disease of the carotid artery.
Authors: Fell G , Phillips D J , Chikos P M , Harley J D , Thiele B L , Strandness D E
Published: June 2011

The duplex ultrasonic scanner combines real-time B-mode imaging with a single-gate, variable-range pulsed Doppler. The detection and categorization of the severity of carotid artery atherosclerosis is achieved by performing spectral analysis of the pulsed Doppler velocity signal obtained from vessels of interest. Using this technique, 750 patients with suspected extracranial carotid artery disease were evaluated between January 1978 and January 1980. One hundred thirty-five of these 750 patients (18%) underwent cerebral arteriography performed with biplanar views of the carotid bifurcation. The degree of stenosis was measured independently in these patients and was available for comparison with the results of duplex scanning and spectral analysis. Duplex scanning correctly detected the presence of disease in 252 of 259 carotid arteries studied (97%). The extent of involvement varied from plaques that produced less than 10% diameter reduction to those that resulted in a total occlusion. The technique was less accurate with lesions that produced less than 10% diameter reduction.
Hemodynamic determinants of pulmonary valve motion during systole in experimental pulmonary hypertension.
Authors: Tahara M , Tanaka H , Nakao S , Yoshimura H , Sakurai S , Tei C , Kashima T
Published: June 2011

To clarify the determinants of pulmonary valve (PV) motion in pulmonary hypertension, we examined the correlations among PV echo patterns, the pulmonary artery (PA) flow curve just above the PA orifice and the pulmonary artery-right ventricle (PA-RV) pressure gradient. By constricting the PA, we could produce a variety of PV echo patterns, including midsystolic semiclosure in open-chest dogs. Throughout the experiments, the PV echo pattern and PA flow curve were similar in pattern and timing. When the PV echo showed midsystolic semiclosure with reopening. The PA flow curve showed a transient decrease followed by a transient increase during midsystole. The PA-RV pressure gradient became transiently positive (PA pressure greater than RV pressure) and then negative in midsystole only when the PV echo showed midsystolic semiclosure with reopening. In conclusion, PV motion during systole may be instantaneously determined by PA flow change and the PA-RV pressure gradient during the cardiac cycle in experimental pulmonary hypertension.
Two-dimensional echocardiographic features of right ventricular infarction.
Authors: D'Arcy B , Nanda N C
Published: June 2011

Real-time, two-dimensional echocardiographic studies were performed in 10 patients with acute myocardial infarction who had clinical features suggestive of right ventricular involvement. All patients showed right ventricular wall motion abnormalities. In the four-chamber view, seven patients showed akinesis of the entire right ventricular diaphragmatic wall and three showed akinesis of segments of the diaphragmatic wall. Segmental dyskinetic areas involving the right ventricular free wall were identified in four patients. One patient showed a large right ventricular apical aneurysm. Other echocardiographic features included enlargement of the right ventricle in eight cases, paradoxical ventricular septal motion in seven cases, tricuspid incompetence in eight cases, dilatation of the stomach in four cases and localized pericardial effusion in two cases. Right ventricular infarction was confirmed by radionuclide in seven patients, at surgery in one patient and at autopsy in two patients.
Ruptured atheromatous plaques in saphenous vein coronary artery bypass grafts: a mechanism of acute, thrombotic, late graft occlusion.
Authors: Walts A E , Fishbein M C , Sustaita H , Matloff J M
Published: June 2011

Although early occlusion of saphenous vein coronary artery bypass grafts is usually thrombotic, late occlusion is most often a result of progressive intimal fibromuscular proliferation or atheroma formation in the implanted vain. We describe another mechanism of late graft occlusion: atheromatous plaque rupture with superimposed occlusive thrombosis. Four men, ages 48-67 years underwent repeat bypass surgery for recurrent angina. Six of eight vein grafts excised 5-8 years after original bypass showed complete luminal occlusion by recent thrombus superimposed on ruptured atheromatous plaques. Similar findings were present at autopsy in two of three vein grafts from a 66-year-old man who died 7 years after bypass. These lesions are indistinguishable from those that occur in native coronary arteries of many patients with acute myocardial infarction. Unlike previously described graft occlusions, the present lesion represents a mechanism of acute, thrombotic, late graft occlusion. If recognized early, it may be amenable to nonsurgical intervention by angioplasty or thrombolysis.
Mechanism of supraventricular parasystole.
Authors: Kinoshita S , Nakagawa K , Kato N , Nishino T , Tanabe Y
Published: June 2011

Two patients with supraventricular parasystole (one atrioventricular and one auricular) are reported. In both patients, reentrant extrasystoles appeared to occur as the result of Mobitz type I second-degree entrance block. We believe that when a sinus impulse fell soon after the absolute refractory period of the pathway containing the parasytolic focus, it reached and discharged the focus after marked delay, and thereafter became a reentrant extrasystole. In interectopic intervals containing more than one sinus beat, the number of intervening sinus beats was always even, suggesting the presence of concealed reentrant extrasystolic bigeminy. The observations in the present report and in our previous patients with ventricular parasystole strongly suggest that most cases of parasystole, whether ventricular or supraventricular, or whether intermittent or "continuous," may be governed by second-degree entrance block.
Adrenergic responsiveness in prehypertensive subjects.
Authors: Kotchen T A , Guthrie G P , McKean H , Kotchen J M
Published: June 2011

To determine if alterations in adrenergic activity precede hypertension, we evaluated the pressor effect of an alpha agonist (phenylephrine) and the chronotropic effect of a beta agonist (isoproterenol) in prehypertensive young men. The subjects were selected from a 5-year follow-up of individuals in the upper ("high") and lower ("low") deciles of the blood pressure distribution in a high school population. At follow-up, the blood pressure differences between groups were maintained. The baroreflex slopes of the high (n = 13) and low (n = 10) blood pressure groups did not differ. The dose of phenylephrine required to increase systolic blood pressure by 20 mm Hg (PD20) was greater in the high blood pressure group than in the low blood pressure group (250 +/- 38 micrograms vs 167 +/- 35 micrograms, p less than 0.05). The dose of isoproterenol required to increase the heart rate by 25 beats/min (CD25) was also greater in the high than in the low blood pressure group (1.9 +/- 0.5 micrograms vs 0.9 +/- 0.2 micrograms, p less than 0.05). The increase in plasma renin activity in response to treadmill exercise was less in the high than in the low blood pressure group (1.8 +/- 0.6 ng/ml/hr vs 3.4 +/- 0.7 ng/ml/hr, p less than 0.03). Overall, systolic blood pressure correlated with PD20 (r = 0.52, p less than 0.01) and CD25 (r = 0.62, p less than 0.001). Plasma norepinephrine correlated with systolic blood pressure (r = 0.44, p less than 0.04) and with PD20 (r = 0.63, p less than 0.001). We conclude that baroreflex sensitivity is not altered in young men with relatively high blood pressure. Insensitivity to alpha and beta agonists may be related to the positive correlation of systolic blood pressure with plasma norepinephrine concentration.
Sequelae of the initial attack of acute rheumatic fever in children from north India. A prospective 5-year follow-up study.
Authors: Sanyal S K , Berry A M , Duggal S , Hooja V , Ghosh S
Published: June 2011

We determined the outcome of acute rheumatic fever in 85 children from North India who had received regular antistreptococcal prophylaxis after their first attack. By the end of the 5-year follow-up, 33 patients had rheumatic heart disease. Mitral insufficiency, the most common valvular lesion, appeared in 91% of the patients, whereas mitral stenosis developed in only 18%. Initial carditis, congestive heart failure, cardiomegaly or moderate-to-severe mitral insufficiency significantly increased the risk of rheumatic heart disease (p less than 0.001). The recurrence rate of acute rheumatic fever in children who received continuous prophylaxis was 0.006 per patient-year. Most recurrence (92%) mimicked the first attack and produced further cardiac damage in five patients with carditis and in one patient with chorea. Cardiac status during the first attack of rheumatic fever and the continuity of prophylaxis were the major determinants of outcome. Statistical comparisons disclosed that with continuous prophylaxis, the prevalence rate, evolution and clinical spectrum of the sequelae of acute rheumatic fever in children from India do not differ significantly from those in the West.
Action of intracoronary nitroglycerin in refractory coronary artery spasm.
Authors: Pepine C J , Feldman R L , Conti C R
Published: June 2011

Coronary artery spasm usually responds to sublingual nitroglycerin. This report describes four patients with variant angina and one patient with rest angina who had coronary spasm that was refractory to sublingual or i.v. nitroglycerin. In four patients, spasm occurred spontaneous and in one patient after 0.05 mg of ergonovine. In each case, 25-100 micrograms of intracoronary nitroglycerin promptly (30-45 seconds) resulted in reopacification of the vessel involved in spasm and resolution of evidence for ischemia. Thus, intracoronary nitroglycerin can reverse coronary artery spasm that does not respond to systemic nitroglycerin administration.
The effect of high lung conductivity on electrocardiographic potentials. Results from human subjects undergoing bronchopulmonary lavage.
Authors: Rudy Y , Wood R , Plonsey R , Liebman J
Published: June 2011

The effect of increased lung conductivity on ECG potentials was studied in human subjects undergoing pulmonary lavage of a whole lung. In this procedure, the air in the lung is replaced by physiologic saline solution, which is a highly conductive fluid. The same situation was simulated theoretically with an eccentric spherical model of the heart and torso. Both the experimental results and theoretical simulations show a decrease in body-surface potentials as the lung conductivity increases. In particular, a large decrease was observed in the posterior vector and the scalar Z lead both experimentally and theoretically. The model simulation shows that the scalar Z lead is maximal at a conductivity value that is very close to the typical normal lung conductivity, so that low voltages are predicted for low lung conductivities as well.
Modification of abnormal left ventricular diastolic properties by nifedipine in patients with hypertrophic cardiomyopathy.
Authors: Lorell B H , Paulus W J , Grossman W , Wynne J , Cohn P F
Published: June 2011

The effect of nifedipine on left ventricular isovolumic relaxation and diastolic filling properties and systemic and left ventricular hemodynamics was studied in 15 patients with hypertrophic cardiomyopathy. After nidefipine (10 mg sublingually), the prolonged left ventricular isovolumic relaxation time assessed by echocardiography decreased from 112 +/- 26 to 83 +/- 23 msec (p less than 0.0001), and the left ventricular pressure decay as measured by time constant T improved from 63 +/- 20 to 49 +/- 11 msec (p less than 0.05). Left ventricular filling dynamics also improved as assessed by a return toward normal in the depressed peak rate of left ventricular diastolic filling (dimension change 72 +/- 37 to 101 +/- 39 mm/sec, p less than 0.01) and the peak rate of posterior wall thinning (47 +/- 31 to 68 +/- 36 mm/sec, p less than 0.001). These changes were accompanied by hemodynamic evidence of improved diastolic function shown as a decrease in left ventricular end-diastolic pressure and a downward shift in the left ventricular diastolic pressure-dimension relationship, suggesting improved left ventricular distensibility. After nifedipine, there was a slight increase in heart rate and a decrease in systemic ventricular distensibility. After nifedipine, there was a slight increase in heart rate and a decrease in systemic arterial blood pressure, and no depression of the left ventricular percent fractional shortening or cardiac index. These data indicate that abnormal left ventricular relaxation and diastolic filling rates in hypertrophic cardiomyopathy are dynamic and favorably modified by nifedipine, and that this effect is not related to a depression of left ventricular systolic function.
Effects of hydralazine on coronary blood flow and myocardial energetics in congestive heart failure.
Authors: Magorien R D , Brown G P , Unverferth D V , Nelson S , Boudoulas H , Bambach D , Leier C V
Published: June 2011

The acute effects of oral hydralazine, 1 mg/kg, on coronary vascular resistance, coronary blood flow (estimated using the coronary sinus thermodilution technique), and myocardial oxygen consumption were evaluated in 10 patients with chronic (New York Heart Association class III and IV) nonischemic congestive heart failure. Central hemodynamic responses demonstrated a modest decrease in mean arterial pressure, pulmonary capillary wedge pressure and systemic vascular resistance (12%, 15% and 29%, respectively), while the cardiac index increased from 2.3 +/- 0.1 to 3.1 +/- 0.3 and left ventricular stroke work index from 24 +/- 3.7 to 28 +/- 3.4 (p less than 0.01). Heart rate and diastolic filling time did not change. Coronary blood flow increased approximately 50%, from 144 +/- 17 to 218 +/- 30 ml/min, and coronary vascular resistance decreased from 0.55 +/- 0.09 to 0.36 +/- 0.08 mm Hg/ml/min (both p less than 0.01). Oral hydralazine increased myocardial oxygen consumption by 33%, from 15 +/- 1.6 to 20 +/- 2.7 ml/min. Despite this moderate augmentation in myocardial oxygen consumption, the arterial-coronary sinus oxygen difference decreased from 104 +/- 6.2 to 94 +/- 7.5 and the myocardial oxygen extraction ratio decreased from 71% to 64% (both p less than 0.05). The ratio of coronary vascular resistance to systemic vascular resistance decreased with hydralazine therapy, while coronary blood flow increased from 3.5% to 4.3 % of total cardiac output. In this group of patients with nonischemic cardiomyopathy, hydralazine had a favorable effect on the coronary circulation and improved the critical myocardial oxygen supply-demand ratio.
Detection of cardiac transplant rejection with radiolabeled lymphocytes.
Authors: Bergmann S R , Lerch R A , Carlson E M , Saffitz J E , Sobel B E
Published: June 2011

To determine whether rejections of cardiac transplants could be detected specifically and non-invasively by lymphocytes labeled with indium-111 (111In), we studied 36 allogeneic and 14 isogeneic heterotopic cardiac transplants in rats. Allogeneic grafts accumulated autologous 111In-lymphocytes, detectable scintigraphically 24 hours after i.v. injection of the labeled cells. At the time of peak histologic rejection, the allogeneic grafts accumulated 92. +/- 4.8 times more activity than the native hearts (determined by well counting). The tissue-to-blood ratio in the rejecting transplants was 3.7 +/- 2.2; total uptake by the graft was 2.9 +/- 2.1% of the injected dose. Autoradiography confirmed that graft radioactivity was associated with labeled lymphocytes. In contrast, isogeneic grafts showed no signs of rejection and did not accumulate radioactivity. Because conventionally isolated and labeled lymphocytes are often contaminated with platelets, we prepared both 111In-platelets and purified 111In-lymphocytes for use in additional experiments. Allogeneic grafts accumulated platelets and purified lymphocytes independently. Thus, deposition of immunologically active cells in the rejecting graft representing specific pathophysiologic events can be detected. The results suggest that rejection of cardiac transplants can be detected noninvasively, potentially facilitating objective early clinical detection of rejection and titration of antirejection therapy.
Reversal of exercise-induced hemodynamic and electrocardiographic abnormalities after coronary artery bypass surgery.
Authors: Sarma R J , Sanmarco M E
Published: June 2011

Forty patients (35 men and five women) who experienced hypotension during maximal symptom-limited exercise test were retested after a 12 +/- 4-month interval. Mean age was 53.5 years. All patients had multiple-vessel disease. Seventeen patients underwent coronary artery bypass surgery because of disabling angina, and 23 patients without disabling angina continued under medical management. At entry, there were no significant differences in age, left ventricular function or exercise performance between the medical and surgical groups. At follow-up, the surgical group showed an average increase in the exercise duration of 2.2 +/- 1.7 minutes (p less than 0.001), maximal heart rate of 17 +/- 15 beats/min (p less than 0.001), maximal systolic blood pressure of 26 +/- 23 mm Hg (p less than 0.001) and maximal rate-pressure product of 60 +/- 41 (p less than 0.001). These measurements did not change significantly in the medically managed group. Exercise-induced hypotension is apparently caused by ischemic left ventricular dysfunction, since in the majority of patients, it is reversible after successful revascularization. This observation is supported by the lack of improvement in a comparable group of patients managed without surgery.
Intravenous isosorbide dinitrate in patients with refractory pump failure and acute myocardial infarction.
Authors: Rabinowitz B , Tamari I , Elazar E , Neufeld H N
Published: June 2011

We studied the hemodynamic effects of isosorbide dinitrate administered by continuous i.v. infusion to 22 patients with chronic refractory pump failure and 18 with pump failure due to acute myocardial infarction. In patients with severe pump failure, i.v. ISDN markedly decreased pulmonary capillary wedge pressure (p less than 0.001), moderately increased cardiac output (p less than 0.01), and decreased systemic vascular resistance (SVR) (p less than 0.001). There were no deleterious effects on arterial pressure and heart rate. The effects obtained in acute and chronic left ventricular failure were similar. Patients with initial SVR levels lower than 1500 dyn-sec-cm-5 did not significantly increase their cardiac output (p less than 0.005). Cardiac output increased more than 25% only in patients with initial high SVR levels (greater than 2000 dyn-sec-cm(-)5). Positive correlations were found between high SVR and elevated plasma catecholamines (r = 0.53, p less than 0.05) and between the initial SVR and initial heart rate (r = 0.70, p less than 0.01). The i.v. administration of isosorbide dinitrate appears to be an efficient therapy, particularly in selected patients with ischemic pump failure.
A comparative study of serum lipids between Belgium and Korea.
Authors: Kesteloot H , Lee C S , Park H M , Kegels C , Geboers J , Claes J H , Joossens J V
Published: June 2011

Serum cholesterol values are markedly lower in Korea than in Belgium in both males and females. This is attributed to the much lower consumption of saturated fat in Korea. A mean population serum cholesterol value of about 160 mg/dl appears to be compatible with excellent general health and with the absence of ischemic heart disease or other atheromatous diseases. The influence of age, height and weight on cholesterol between Belgium and Korea is qualitatively similar but quantitatively different. High-density lipoprotein cholesterol values are lower in Korea than in Belgium, particularly in females. Differences in the HDL cholesterol level thus cannot explain the low prevalence of ischemic heart disease in Korea.
Determinants of ventricular tachycardia in patients with ventricular aneurysms: results of intraoperative epicardial and endocardial mapping.
Authors: Wiener I , Mindich B , Pitchon R
Published: June 2011

We performed epicardial and endocardial mapping in 11 patients with ventricular aneurysms; six had chronic, recurrent ventricular tachycardia and five had no ventricular arrhythmias more severe than isolated ventricular premature complexes. Forty to 66 epicardial and 16-40 endocardial points were recorded during stable sinus rhythm in each patient. Local electrograms were evaluated as to timing and presence of fragmentation (duration greater than 50 msec, amplitude less than 1 mV, absence of discrete intrinsicoid deflection). Activation of the epicardial surface of the aneurysm was abnormal in all patients, and extended beyond completion of the QRS in three patients in the arrhythmia group and two in the nonarrhythmia group (NS). Activation of the epicardial border zone was normal in all patients. Electrograms from the endocardial surface of the aneurysm were abnormally fragmented in all patients and the mean duration of activation was not different between patients with and without arrhythmias (85.5 +/- 14.1 vs 96.2 +/- 13.8 msec, NS). However, in patients with ventricular tachycardia, electrograms from 33-58.3% (mean 45.5 +/- 8.8%) of the endocardial border zone showed fragmentation, compared with 0-16.7% (mean 4.9 +/- 7.4%) of the endocardial border zone in patients without arrhythmias (p less than 0.05). Fragmentation was always along the septal border of the aneurysm. The mean duration of the most prolonged endocardial border zone electrogram was 97.5 +/- 17.0 msec in ventricular tachycardia patients and 67.0 +/- 27.1 msec in patients without arrhythmia (p less than 0.05). Five of six ventricular tachycardia patients had electrical activity in the endocardial border zone extending beyond the end of the QRS, compared with one of five patients without ventricular tachycardia (p less than 0.05). We conclude that fragmented electrical activity is present in all patients with ventricular aneurysms, but the extent and severity of fragmentation in the endocardial border zone is greatest in patients with recurrent ventricular tachycardia.
Cycle length alternation in circus movement tachycardia using an atrioventricular accessory pathway. A study of the role of the atrioventricular node using a computer model of tachycardia.
Authors: Ross D L , Dassen W R , Vanagt E J , Brugada P , Bär F W , Wellens H J
Published: June 2011

The possible role of the atrioventricular nodal (AVN) function curve during tachycardia as a cause of cycle length alternation was investigated using a computer model of circus movement tachycardia utilizing an atrioventricular accessory pathway. Two types of AVN function curves during tachycardia were entered into the computer: straight lines of various gradients and representative examples of patient-based AVN function curves obtained during clinical electrophysiologic studies. Perturbations of the tachycardia model were induced by introducing a short cycle, by suddenly prolonging a conduction interval, or by moving the AVN function curve relative to that in stable tachycardia. Using the straight line AVN function curves, stable, sustained cycle length alternation could be induced by perturbation of the tachycardia cycle if the gradient of the line was -1 (slope = 45 degrees). If the gradient was more than -1 (slope less than 45 degrees), the perturbation was damped. If the gradient was less than -1 (slope greater than 45 degrees), the perturbation was amplified, leading to termination of tachycardia by block in the AVN. Similar but more complex responses to perturbation of tachycardia were found using patient-based AVN function curves. Thus, sustained cycle length alternation and amplification or damping of perturbation could be produced. Using physiologic AVN function curves, the response to perturbation of tachycardia depended on the interrelationship of the shape of the AVN function curve, the location of the cycle length of tachycardia on the curve, the magnitude and direction of the perturbation, and the AVN effective refractory period. We conclude that cycle length alternation during tachycardia may be explained by the characteristics of a single antegrade AVN function curve without postulating the presence of additional AVN pathways. The stability of circus movement tachycardias depends on the interaction of several variables.
The effects of a cardioselective (metoprolol) and a nonselective (propranolol) beta-adrenergic blocker on the response to dynamic exercise in normal men.
Authors: Sklar J , Johnston G D , Overlie P , Gerber J G , Brammell H L , Gal J , Nies A S
Published: June 2011

We compared the effects of a cardioselective beta-adrenergic blocking drug, metoprolol, with a nonselective beta-adrenergic blocker, propranolol, on the response of 10 normal men to dynamic treadmill exercise. The volunteers underwent a standard graded exercise test to exhaustion while receiving placebo; propranolol, 40 mg every 6 hours; propranolol, 80 mg every 6 hours; metoprolol, 50 mg every 6 hours; or metoprolol, 100 mg every 6 hours. The drugs were given in a double-blind fashion for 48 hours before exercise. Five days were allowed between successive drug administrations and the order of drug administration was randomized. Heart rate, arterial pressure, oxygen consumption, minute ventilation and CO2 production were monitored. Plasma drug concentrations were measured at the time of exercise. Judged by plasma levels, propranolol was about three times more potent than metoprolol in attenuating heart rate. Both drugs produced a wide variation in plasma levels after a given oral dose, and both drugs attenuated the systolic blood pressure response to exercise. Neither drug affected diastolic blood pressure or maximum oxygen consumption, maximum minute ventilation or the anaerobic threshold. We conclude that there is no evidence that the cardioselective drug metoprolol is superior to propranolol in terms of the ability to perform or respond to short-term maximal exercise. In addition, the fact that maximal oxygen consumption and the anaerobic threshold were unaffected implies that fatigue during exercise while on beta-adrenergic blocking drugs is not due to an effect of these drugs in limiting blood flow to the exercising extremities.
Preoperative secundum atrial septal defect with coexisting sinus node and atrioventricular node dysfunction.
Authors: Clark E B , Kugler J D
Published: June 2011

Sinus node dysfunction in patients after repair of the secundum atrial septal defect has been ascribed to surgical damage. We studied 15 consecutive patients with secundum atrial septal defect before operative intervention. Noninvasive testing included 34-hour electrocardiographic monitoring and a standard 13-lead ECG. Intracardiac electrophysiologic techniques included corrected sinus node recovery time, sinoatrial conduction time, His bundle recording to measure AH and HV intervals, the atrial pacing rate at which atrioventricular node Wenckebach occurred, and atrioventricular nodal refractory period. The ECG revealed an ectopic atrial rhythm in two patients. Intracardiac electrophysiology showed an abnormal corrected sinus node recovery time (range -40 to 800 msec) in 10 patients. Five patients had evidence of atrioventricular nodal dysfunction with prolonged AH interval or abnormal atrial pacing rate at which atrioventricular Wenckebach occurred. These data indicate that sinus node dysfunction or atrioventricular node dysfunction were present before surgical intervention.
Angiographic findings 1 month after myocardial infarction: a prospective study of 259 survivors.
Authors: Betriu A , Castañer A , Sanz G A , Pare J C , Roig E , Coll S , Magriña J , Navarro-Lopez F
Published: June 2011

Coronary anatomy as it relates to left ventricular function was assessed prospectively in patients who survived acute myocardial infarction. The study population included 259 consecutive male patients age 60 years or younger who underwent catheterization 30 days after the acute event. Coronary artery obstructive lesions (greater than 50% reduction in luminal diameter) were found in 241 patients (93%), 118 (45%) of whom had total and 76 (29%) subtotal (greater than 90%) stenosis) occlusion of at least one coronary artery. Normal coronary vessels were seen in eight patients (3%) and nonobstructive lesions in 10 (4%). One-, two- and three-vessel disease were present in 89, 86 and 66 patients, respectively. Patients with normal coronary arteries or nonobstructive lesions had higher ejection fractions than those with obstructive lesions in one, two or three vessels (p less than 0.05). Ejection fraction was lower (p less than .001) and the percentage of akinetic segments higher (p less than 0.001) in patients with total or subtotal lesions and no collaterals. Adequate collaterals, seen in 29 patients (11%), significantly improved regional wall motion (p less than 0.05) and decreased the percentage of akinetic segments (p less than 0.001). Thus, in a substantial number of patients (32% in our series), the infarcted area is spontaneously reperfused by collaterals or through the involved artery. Both mechanisms ameliorate wall motion in corresponding areas.
Acebutolol therapy for ventricular arrhythmia. A randomized placebo-controlled double-blind multicenter study.
Authors: De Soyza N , Shapiro W , Chandraratna P A , Aronow W S , Laddu A R , Thompson C H
Published: June 2011

The safety and efficacy of acebutolol in suppressing ventricular ectopy was evaluated in 60 males (average 59 years) using 24-hour Holter recordings and a double-blind, randomized, crossover protocol. Acebutolol, 200 mg and 400 mg thrice daily, was compared with placebo. Only patients who had a mean of at least 30 ventricular premature complexes (VPCs) per hour on three 24-hour control Holter recordings were included. Analysis of Holter recordings revealed greater than 70% reduction in VPCs/hour from control levels during acebutolol therapy in over 50% of the 60 patients; dose-related reduction in the mean number of single and paired VPCs and ventricular tachycardia episodes (p less than 0.05) by acebutolol; and significant, asymptomatic reduction in resting heart rate and blood pressure. All side effects were transient. Acebutolol was discontinued because of side effects in one patient only.
Surgery for ventricular tachycardia: efficacy of left ventricular aneurysm resection compared with operation guided by electrical activation mapping.
Authors: Mason J W , Stinson E B , Winkle R A , Griffin J C , Oyer P E , Ross D L , Derby G
Published: June 2011

Sixty-five patients underwent surgery for recurrent ventricular tachyarrhythmias. The 32 patients in group 1 underwent simple left ventricular aneurysm resection. The 33 patients in group 2 underwent myocardial resection or incision guided by intraoperative mapping of the electrical activation sequence. The clinical, hemodynamic and angiographic characteristics of the two groups were similar. Although actuarial survival in the two groups was similar through 24 months, late attrition in group 1 patients has left only 21 +/- 13% (+/- SEM) alive by life-table analysis at 94 months. Arrhythmia recurrence has been greater in group 1 than in group 2. In group 1, 50 +/- 9% of patients at risk at 3 months had recurrences by actuarial analysis. In group 2, only 13 +/- 6% at 1 month, 17 +/- 7% at 3 months and 29 +/- 9% at 24 months relapsed. Death was caused by ventricular tachyarrhythmias in 12 of the 17 patients (71%) who died in group 1, but only three of 12 (25%) who died in group 2. We conclude that surgery of the left ventricle, guided and modified by intraoperative mapping of the electrical activation sequence, frequently eliminates ventricular tachyarrhythmias and may be more effective than blind resection of left ventricular aneurysm.
Effects of prazosin on coronary and left ventricular dynamics in conscious dogs.
Authors: Macho P , Vatner S F
Published: June 2011

The left ventricular (LV) and coronary vascular effects of prazosin, a drug that reduces peripheral vascular resistance by blocking postsynaptic alpha receptors, were examined in conscious dogs. Prazosin, 0.07 mg/kg/min i.v. for 7 minutes, induced sustained hypotensive effects for more than 12 hours. The peak effects occurred 30-45 minutes after administration. Prazosin increased heart rate by 28 +/- 9%, did not change mean coronary blood flow significantly, decreased mean arterial pressure by 15 +/- 4%, LV end-diastolic diameter by 10 +/- 2%, LV end-systolic diameter by 8 +/- 2%, late diastolic coronary resistance by 22 +/- 7%, and LV dP/dt by 9 +/- 4%. These effects of prazosin were not altered substantially by maintaining heart rate constant with electrical pacing or by pretreatment with beta-adrenergic blockade. However, after chronic reserpine treatment, prazosin did not reduce either mean arterial pressure or late diastolic coronary resistance. The alpha-blocking properties of the drug were established when prazosin attenuated pressure responses to phenylephrine, norepinephrine and bilateral carotid occlusion. Thus, in conscious dogs with heart rate constant, prazosin, by blocking alpha-adrenergic receptors, induces prolonged coronary vasodilation associated with reductions in the major determinants of myocardial oxygen consumption, e.g., arterial and LV pressures, LV end-diastolic diameter and LV dP/dt. However, the coronary vasodilation was not intense enough to increase coronary blood flow above control levels.
Evolution of QRS and ST-T-wave body surface potential distributions during the first year of life.
Authors: Benson D W , Spach M S
Published: June 2011

Using a system for obtaining body surface potential distributions from 150 sites on the anterior and posterior torso, 43 body surface maps were evaluated in 31 normal infants, ages 15 hours to 10 months. Serial maps were obtained at 0.6-msec intervals during QRS and at 2.4-4-msec intervals throughout the ST-T wave. We found an orderly evolution of both QRS and ST-T wave maps during the first year of life. In the newborn, the patterns during the latter half of QRS were consistent with early completion of depolarization of the left ventricle and prolonged depolarization of the right ventricle. The patterns changed gradually such that by 5-6 months of age, the maps demonstrated simultaneous effects of both right and left ventricles during the latter half of QRS. By 9 months, the QRS patterns were similar to those of older children and adults. The changes in the ST-T-wave maps were consistent with the idea that age-related changes in the sequence of ventricular activation.
Hemodynamic and radionuclide effects of acute captopril therapy for heart failure: changes in left and right ventricular volumes and function at rest and during exercise.
Authors: Massie B , Kramer B L , Topic N , Henderson S G
Published: June 2011

Although the resting hemodynamic effects of captopril in congestive heart failure are known, little information is available about the hemodynamic response to captopril during exercise or about changes in noninvasive measurements of the size and function of both ventricles. In this study, 14 stable New York Heart Association class III patients were given 25 mg or oral captopril. Rest and exercise hemodynamic measurements and blood pool scintigrams were performed simultaneously before and 90 minutes after captopril. The radionuclide studies were analyzed for left and right ventricular end-diastolic volumes, end-systolic volumes, ejection fractions and pulmonary blood volume. The primary beneficial responses at rest were decreases in left and right ventricular end-diastolic volumes from 388 +/- 81 to 350 +/- 77 ml (p less than 0.01) and from 52 +/- 26 to 43 +/- 20 volume units (p less than 0.01), respectively, and in their corresponding filling pressures, from 24 +/- 10 to 17 +/- 9 mm Hg and 10 +/- 5 to 6 +/- 5 mm Hg (both p less than 0.001). Although stroke volume did not increase significantly, both left and right ventricular ejection fractions increased slightly, from 19 +/- 6% to 22 +/- 5% and from 25 +/- 9% to 29 +/- 11%, respectively (both p less than 0.01). During exercise, similar changes were noted in both hemodynamic and radionuclide indexes. Thus, in patients with moderate symptomatic limitation from chronic heart failure, captopril predominantly reduces ventricular volume and filling pressure, with a less significant effect on cardiac output. These effects persist during exercise, when systemic vascular resistance is already very low. Radionuclide techniques are valuable in assessing the drug effect in these subjects, particularly when ventricular volumes are also measured.
Sudden death in hypertrophic cardiomyopathy: a profile of 78 patients.
Authors: Maron B J , Roberts W C , Epstein S E
Published: June 2011

The clinical profile of 78 patients with hypertrophic cardiomyopathy who died suddenly (or experienced cardiac arrest and survived) was analyzed. At the time of cardiac catastrophe, 71% of the patients were younger than 30 years of age, 54% were without functional limitation and 61% were performing sedentary or minimal physical activity. Nineteen of the 78 patients (24%) were taking propranolol in apparently adequate dosages, indicating that this drug does not provide absolute protection against sudden death. No clinical or morphologic variable was particularly reliable in identifying patients at risk for sudden death. Forty-eight of 62 patients (77%) who died suddenly had a markedly increased ventricular septal thickness of 20 mm or more; however, mean septal thickness was similar in patients who died suddenly (25.2 +/- 0.9 mm) and in age- and sex-matched control patients with hypertrophic cardiomyopathy who have survived (23.6 +/- 0.8 mm). An abnormal ECG was present as often in patients who died suddenly as in control patients who have survived, (51 or 53, 96%). In addition, no particular cardiac symptom or hemodynamic variable (such as the magnitude of left ventricular outflow tract obstruction under basal conditions or left ventricular end-diastolic pressure) was characteristic of the patients with hypertrophic cardiomyopathy who died suddenly.
Prognostic implications of diagnostic Q waves after myocardial infarction.
Authors: Wasserman A G , Bren G B , Ross A M , Richardson D W , Hutchinson R G , Rios J C
Published: June 2011

The long-term prognostic implications of the electrocardiographic location of a myocardial infarction and the subsequent retention or disappearance of diagnostic Q waves were examined in patients enrolled in the Aspirin Myocardial Infarction Study (AMIS). The 4524 participants, ages 30-69 years, had sustained a myocardial infarction 8 weeks to 60 months before randomization to aspirin and placebo groups. Subjects were followed for at least 3 years (average 38.2 months). Using the Minnesota Code, myocardial infarctions were classified according to three electrocardiographic locations: lateral, inferior and anterior, with further subdivision into major, moderate and minor criteria based on Q-wave duration and Q/R rations. Total mortality was not significantly different among patients with single infarct sites: lateral 11.8%, inferior 8.0% and anterior 9.4%. Patients with multiple electrocardiographic infarct locations had a significantly higher mortality (14.6%, p less than 0.0002). Participants with Minnesota Code major criteria of infarction also had a significantly higher mortality (10.6%) than those with moderate (7.2%) or minor (7.4%) criteria (p less than 0.01). Loss of a previously documented diagnostic Q wave occurred in 14.2% of participants. Mortality among patients who lost Q waves (6.5%) was not significantly different from that among those with persistent Q waves in a single infarct location (8.7%). No long-term prognostic significance can be attributed to the site of infarction or loss of Q wave on the resting ECG. However, major Q-wave criteria and extent of infarction based on multiple coded sites are associated with a higher 3-year mortality.
Enhanced atrioventricular conduction in patients without preexcitation syndrome: relation to heart rate in paroxysmal reciprocating tachycardia.
Authors: Benditt D G , Epstein M L , Arentzen C E , Kriett J M , Klein G J
Published: June 2011

We studied the electrophysiologic characteristics of atrioventricular (AV) nodal conduction in patients with reciprocating tachycardia (RT) without ventricular preexcitation, and the relation of these characteristics to RT cycle length (CL). Thirty-five symptomatic patients who had a normal PR interval (0.13-0.20 second) during sinus rhythm underwent detailed intracardiac electrophysiologic study during which ventricular preexcitation was excluded, and the RT mechanism was determined. RT was due to reentry using an accessory AV pathway capable of conduction only in the retrograde direction (concealed AP) in 13 patients (37%) and to reentry within the AV node in 22 (63%). Dynamic properties of AV conduction (assessed by degree of AH prolongation during progressive increase in atrial pacing rate) were normally distributed (p less then 0.005); 12 patients (34%) fulfilled the criteria for enhanced AV conduction (EAVC). The patients with EAVC had a shorter RT CL than did patients without EAVC (294 +/- 43.3 msec vs 360 +/- 68.1 msec, p less than 0.01). However, CL differences were primarily due to the influence of EAVC in the subgroup of patients with RT using a concealed AP (EAVC CL, 274 +/- 35.1 msec; without EAVC, 326 +/- 15.7 msec, p less than 0.005). The RT CL in patients with reentry within AV node was not measureable influenced by concomitant EAVC (EAVC, 314 +/- 43.8 msec; without EAVC, 376 +/- 76.8 msec) (NS). This study suggests that despite the presence of a normal PR interval during sinus rhythm, dynamic AV conduction responses can vary widely in patients with RT. In patients with RT using a concealed AP, but not in those with reentry within the AV node, coexisting diminished physiologic AV conduction slowing may be associated with more rapid tachycardia rates.