Hemorrhagic complications of thrombolytic therapy.

Thrombolytic therapy salvages ischemic myocardium by rapidly reestablishing coronary artery patency in acute myocardial infarction. One of its major limitations is the complication of hemorrhage. A retrospective study of myocardial infarction patients who received thrombolytic therapy was performed to determine risk factors associated with a hemorrhagic event. Three hundred fifty patients were enrolled, and 20 (5.7%) had a bleeding complication, including four patients (1.1%) who had an intracranial hemorrhage. The factors associated with an increased risk for a significant hemorrhagic event were age (> 65 years) and female gender. Factors associated with an intracranial hemorrhage were age (> 65 years) and a history of hypertension.

Double cardiac valve replacement: a community hospital experience.

The morbidity and mortality of double cardiac valve replacement were assessed in a community hospital setting. Four hundred twenty-two cardiac patients undergoing valve replacement from 1977 to 1991 were analyzed. Forty-two patients underwent double valve replacement. The clinical variables associated with increased operative mortality (early and late) were determined. The overall operative mortality rate for valve replacement was 7.87% (29 of 422 patients). The mortality rate was 9.09% (3/33 patients) for double valve replacement and 11.11% (1/9 patients) for double valve replacement in conjunction with coronary bypass. The clinical variables associated with increased mortality were: significant reduction in preoperative left ventricular ejection fraction (< 35%); advanced age (> 60); presence of ischemic mitral valve disease; and preoperative functional class (New York Heart Association Functional Class IV). The results of this study suggest that strategies to diminish operative mortality should include assessment of risk preoperatively as well as anticipation of high mortality in selected subgroups.

State program tracks Schedule II drugs.

By implementing the multiple copy prescription program, Indiana demonstrates its concern with the problems of doctor shoppers and physicians involved with abuse. By trying to track illegal diversion of Schedule II drugs, states that have implemented tracking programs are trying to rid the streets of illicit drug use. When it is time to renew the law, the state should consider using modern computer technology. Indiana's program could be even more effective if it incorporated electronic data transfer.

Refractory swallowing-induced paroxysmal supraventricular tachycardia.

A 51-year-old female with a two-year history of palpitations associated with swallowing was evaluated by intracardiac electrophysiologic studies. Intracardiac recordings documented the presence of an ectopic left atrial focus induced by swallowing with no evidence of accessory pathway conduction. Gastrointestinal evaluation did not demonstrate any significant disorder. The tachycardia was refractory to all pharmacologic therapy including investigational therapy with mexiletine and amiodarone.

Acute left main coronary artery occlusion. Survival following emergent coronary bypass.

Emergent aortocoronary bypass surgery for acute myocardial infarction is controversial. We describe a patient with total occlusion of the left main coronary artery associated with acute anterior wall infarction and refractory cardiogenic shock. The patient underwent successful emergent coronary bypass surgery to manage refractory cardiogenic shock. He has subsequently experienced a prolonged survival (60 months postsurgery). This report suggests that emergent aortocoronary bypass surgery should be considered in patients with acute myocardial infarction with refractory cardiogenic shock in whom other forms of reperfusion are unsuccessful.

Alterations in ventricular excitability in conscious dogs during development of chronic heart failure.

Arrhythmias in patients with heart failure may result from altered electrophysiological properties of the myocardium. To examine changes in ventricular excitability during cardiac failure and to relate these changes to ventricular structural and neurochemical abnormalities, right ventricular failure was produced in dogs by pulmonary artery banding and by creating tricuspid regurgitation. Right and left ventricular excitability thresholds were tested biweekly in heart failure (HF) and sham-operated conscious dogs by means of strength-duration curves (1-40 ms) at basic cycle lengths (BCL) of 300-500 ms until time of death (21-188 days). Marked increases in the excitability threshold of the right ventricle occurred in HF (mean maximum % increase, 205 +/- 42 at BCL 500 ms). Smaller, though significant increases in the left ventricular excitability threshold in HF were also seen (mean maximum % increase 103 +/- 36 at BCL 500 ms). Increases in the excitability threshold of the left as well as the right ventricles occurred, even though ventricular dilation (2-D Echo) was confined to the right ventricle. The time course of changes in the excitability threshold was variable (maximum occurrence at 21 +/- 3 days right ventricle, 23 +/- 11 days left ventricle). Tyrosine hydroxylase activity and norepinephrine content of the right ventricle were markedly depleted at death, when the excitability threshold was high. Similar though nonsignificant trends in reductions of these sympathetic neurochemicals were seen in the left ventricle. Levels of choline acetyltransferase and QNB binding in both ventricles were unaffected.

ELectrophysiologic properties of bretylium tosylate on atrial myocardium.

The antifibrillatory property of bretylium tosylate was first observed in experimental atrial fibrillation, yet the cellular basis for this phenomenon has not been explored. The purpose of this study was to determine the electrophysiologic properties of bretylium tosylate on guinea pig atrial myocardium in the presence and absence of cholinergic influence. Bretylium (10(-6) M - 10(-4) M) produced a concentration-dependent prolongation of atrial action potential duration with a threshold concentration of 10(-5) M. This direct effect of bretylium was unaltered by blockade of beta-adrenergic receptors with propranolol (10(-6) M) or blockade of alpha-adrenergic receptors with phentolamine (10(-6) M). In a second series of experiments the muscarinic receptor blocking properties of bretylium were determined. Acetylcholine produced a concentration-dependent shortening of action potential duration in paced (200 ms) left atrial muscle strips. This well-recognized muscarinic effect was unaltered in the presence of bretylium (10(-6) M - 10(-3) M). These data indicate that bretylium tosylate physiologically exerts direct effects on the atrial myocardium to prolong action potential duration. This compound does not appear to physiologically antagonize the effects of acetylcholine and therefore its reported atrial antiarrhythmic properties cannot be explained by muscarinic receptor blockade.

Electrophysiological effects of the optical isomers of disopyramide and quinidine in the dog. Dependence on stereochemistry.

We studied the electrophysiological effects of the optical isomers of disopyramide and quinidine on canine cardiac Purkinje fibers. Conventional microelectrode techniques were employed to study the effects of racemic disopyramide, (+)-disopyramide, (-)-disopyramide, quinidine, and quinine. Racemic disopyramide, (+)-disopyramide, and quinidine prolonged action potential duration (APD) measured at 90% repolarization. In contrast, (-)-disopyramide and quinine shortened APD. These directionally opposite effects on repolarization were observed throughout 60 minutes exposure to drug and were concentration-dependent. All five components reduced dV/dt of phase 0, increased conduction time, and increased the current requirement for all-or-none depolarization. The effects of all five compounds on dV/dt, conduction time, and current requirements were time- and concentration-dependent. Our results indicate that the stereochemical configurations of disopyramide and quinidine determine their effects on repolarization of cardiac Purkinje fibers.

Anticholinergic effects of disopyramide and quinidine on guinea pig myocardium. Mediation by direct muscarinic receptor blockade.

We studied the interaction of disopyramide, quinidine, and procainamide with cardiac muscarinic receptors. In electrophysiological experiments, the effects of disopyramide, quinidine, procainamide, and atropine were determined on spontaneously depolarizing guinea pig right atria (GPRA) both in the presence and absence of pharmacologically induced (physostigmine) cholinergic stimulation. All four agents demonstrated a concentration-dependent antagonism of the negative chronotropic effects of physostigmine. The order of anticholinergic potency was atropine greater than disopyramide greater than quinidine greater than procainamide. The ability of disopyramide to antagonize the physostigmine induced slowing was stereoselective, (+)disopyramide greater than (-)disopyramide. In contrast, the ability of quinidine to antagonize the negative chronotropic effects of physostigmine was non-stereoselective, quinidine = quinine. In parallel experiments, we studied the ability of disopyramide, quinidine, procainamide, and atropine to compete with the radiolabeled muscarinic receptor antagonist [3H] quinuclidinyl benzilate ([3H]QNB) for binding to muscarinic receptors in crude homogenates of GPRA and membrane vesicles from canine ventricular myocardium. All four agents inhibited [3H]QNB binding to muscarinic receptors. The order of anticholinergic potency determined by the receptor binding studies was identical to that determined by the physiological studies. The interaction of disopyramide with muscarinic receptors was stereoselective, (+)disopyramide > (-)disopyramide. Quinidine was only slightly more potent than quinine in inhibiting [3H]QNB binding to muscarinic receptors. Interaction of antiarrhythmic drugs with muscarinic receptors satisfied criteria for a competitive interaction. The data from this study localize the anticholinergic effects of disopyramide and quinidine to the muscarinic receptor.

Dissociation between the electrophysiological properties and total tissue cyclic guanosine monophosphate content of guinea pig atria.

The purpose of this study was to investigate the role of cyclic guanosine monophosphate (cyclic GMP) in mediating the direct electrophysiological effects of acetylcholine in guinea pig atria. Acetylcholine significantly diminished spontaneous rate of right atria without increasing cyclic GMP content. Reductions in rate following acetylcholine were augmented by pretreatment with physostigmine, but cyclic GMP levels remained unchanged. In left atria, acetylcholine significantly shortened action potential duration within 5 seconds (both with and without physostigmine pretreatment), but cyclic GMP content was not significantly elevated. Cyclic GMP levels in right atria were significantly increased in response to acetylcholine when the Ca2+ content of the buffer was elevated from 1.25 mM TO 2.5 MM; however, reductions in automaticity in the right atria were not augmented in the high Ca2+ buffer. Marked increases in cyclic GMP content were produced by Na nitroprusside superfusion without changing automaticity of right atria or action potential duration of left atria. Finally, both right and left atria were superfused with cyclic GMP analogs (8-bromo cyclic GMP and dibutyryl cyclic GMP) at high concentrations (10(-4)) for 15 minutes without producing significant effects on spontaneous rate or action potential duration. These results failed to show a correlation between total tissue cyclic GMP content and the electrophysiological effects of acetylcholine on guinea pig atria. The reasons for this are either that cyclic GMP does not mediate directly the electrophysiological effects of acetylcholine, or that small changes in cyclic GMP concentrations, undetectable when total tissue nucleotide levels are measured, occur in discrete effector pools of the cardiac cell to mediate the intracellular effects of the choline ester.

Diastolic rumbles in normally functioning porcine mitral valves.

Fourteen of 22 patients (64%) with normally functioning porcine prosthetic valves in the mitral position had apical diastolic rumbles on phonocardiogram and by auscultation. Six (27%) had opening snaps. Factors necessary for the production of a diastolic rumble appear to include central flow, a flexible stent, and the presence of biologic material. Clinicians should be aware that diastolic murmurs and snaps occur in the normally functioning porcine valve.