Guy P. Curtis

Limitations and advantages of the ejection fraction for defining high risk after acute myocardial infarction

Left ventricular (LV) ejection fraction (EF) is known to be related to prognosis after acute myocardial infarction (AMI), but its role alone and in combination with other factors in the definition of a high-risk group has not been adequately specified. Several recent multicenter studies emphasize that LVEF together with features of ventricular ectopic activity during ambulatory electrocardiography define a group at high risk for death for up to 3 years. However, these high-risk groups comprised only a small fraction of the population (less than 7.5%) and failed to include 75% or more (less than 25% specificity) of observed events. In our study, LVEF was determined close to the time of hospital discharge in 750 patients with AMI enrolled in a collaborative study. Used alone, an LVEF of less than 0.45 best defined a high-risk group (39% of the population) yielding 62% sensitivity and 64% specificity for total cardiac mortality by 1 year; it was 77% sensitive for sudden death alone. In a multivariate analysis together with other factors, LVEF was an independent predictor, but other markers of LV dysfunction entered before LVEF with similar sensitivity for total cardiac deaths, but with increased specificity (75%). When an LVEF of less than 0.45 was used together with the presence of complex arrhythmias to define a high-risk group (19% of the population), sensitivity decreased to 39% and specificity increased to 84%. Thus, LVEF is a simple and effective alternative to multivariate analysis for risk assessment after AMI.(ABSTRACT TRUNCATED AT 250 WORDS)

A simplified model for heterotopic rat heart transplantation.

A technique for simplified heterotopic rat heart transplantation having only aorto-aortic anastomosis is presented. The heterotopic rat heart survives and functions well when one lung lobe is attached to the transplantation and functions as a reservoir. Iso- and allotransplants are compared by electrocardiogram (ECG) determination and histological examination. Isotransplants exhibited normal heart and lung throughout the 6-month observation period. Allotransplants ceased to function by the 16th postoperative day, with the cessation of palpable heart beat over the abdominal wall by the 10th postoperative day. This simplified heterotopic rat heart transplantation model can be operated by nonsurgeons in an unhurried manner with minimal training in microvascular surgery, and can be applied to various transplantation immunological studies.

Effect of sublingual nitroglycerin on left ventricular function at rest and during spontaneous angina pectoris: Assessment with a radionuclide approach

Abstract Left ventricular function and size were assessed with equilibrium radionuclide angiography at rest and after administration of 0.6 mg of sublingual nitroglycerin in 12 patients with a history of previous myocardial infarction. Spontaneous angina developed in five patients and seven patients had no pain at the time of study. Sequential ejection fractions and end-diastolic and end-systolic volumes were developed by summing multiple R-R intervals to produce a composite time-activity curve. Volumes were calculated with a nongeometric method that utilizes counts at end-diastole and end-systole and is corrected for total heartbeats and plasma radioactivity. In the patients without acute ischemia, peak increase in ejection fraction occurred 6 to 8 minutes after ingestion of nitroglycerin and was associated with an equal decrease in end-diastolic and end-systolic volumes with no change in stroke volume. End-diastolic and end-systolic volumes, stroke volume, heart rate and systolic blood pressure all returned to baseline levels by 1 hour after nitroglycerin. In the patients with spontaneous angina, ejection fraction and stroke volume decreased before pain occurred. End-diastolic volume increased slightly (7 percent), but end-systolic volume increased markedly (38 percent), thus explaining the decrease in stroke volume. After nitroglycerin, end-diastolic volume and end-systolic volume and systolic blood pressure decreased and stroke volume and ejection fraction increased. Improvement in function occurred before relief of pain. It is concluded that the action of nitroglycerin on the left ventricle in patients without acute ischemia is to increase ejection fraction by an equal decrease in end-diastolic and end-systolic volumes with little change in stroke volume. A reduction in left ventricular function during acute ischemia precedes complaints of pain and is associated with an increase in end-systolic and end-diastolic volumes and a decrease in ejection fraction and stroke volume. In these patients, nitroglycerin appeared to contribute to relief of pain by decreasing end-diastolic volume and systolic blood pressure.

Effects of equiblocking doses of nadolol and propranolol on left ventricular performance

Nadolol, a recently developed noncardioselective β‐adrenergic blocker, has the potential advantages of a longer oral half‐life (t½) than propranolol and, in animal studies, markedly fewer direct myocardial depressant effects. Neither the relative intravenous potency of nadolol and propranolol nor the comparative effects of the 2 drugs on left ventricular performance has been studied in man. We compared equiblocking intravenous doses of nadolol and propranolol in 10 subjects with ischemic wall‐motion disorders. Nadolol was on the average 6.2 times as potent on a milligram‐for‐milligram basis. Both drugs decreased resting heart rate (p < 0.02) and produced small rises in both mean pulmonary artery (p < 0.03) and mean pulmonary artery wedge (p < 0.03) pressures without significantly reducing the cardiac output. Both drugs also produced depression of the radionuclide ejection fraction (p < 0.002). There were no significant differences between the effects of the 2 drugs on any of the aforementioned variables. Thus, the effects of nadolol on left ventricular performances are similar to those of propranolol. Because of its long oral t½, nadolol may prove to be a clinically useful drug.

Immediate Effects of Physostigmine on Amitriptyline-Induced QRS Prolongation

Prior studies have suggested that physostigmine may be useful in reversing QRS prolongation due to amitriptyline toxicity. To investigate this question, we devised a pharmacologic model in rabbits utilizing an initial intravenous bolus of amitriptyline (4-6 mg) followed by a constant amitriptyline infusion (0.2-0.4 mg/min) empirically titered to maintain the QRS at 50% or more of control value for at least 5 min. Intravenous physostigmine (2 mg) sufficient to produce muscle fasciculations and significant (P less than 0.01) slowing of sinus rate was then administered to six animals. No significant change in QRS duration was noted at 1, 3, and 5 min intervals following physostigmine. Although no immediate antidotal effect of physostigmine on amitriptyline-induced QRS prolongation could be demonstrated, these results do not exclude a possible interaction between the membrane effects of the tricyclic antidepressants (and related agents) and the vagal branch of the autonomic nervous system.

Reduction of Pacemaker Pressure Symptoms Using Nonantigenic Preserved Human Dermis Grafts

Skin pressure symptoms can occur in thin patients with pacemakers, with erosion through the skin surface a possibility. To correct this problem without device removal, two patients had nonantigenic preserved human dermis grafts placed over their pacemakers. This acellular nonantigenic human dermal substitute provided significant thickness over the devices and improvement in pressure symptoms.

Patient activated asynchronous ventricular pacing at normal rates for termination of ventricular tachycardia

Ventricular pacing has been used to prevent or convert ventricular tachycardia. We report the use of patient-activated asynchronous mode ventricular pacing at normal rates for conversion of ventricular tachycardia by competitive pacing impulses. Following electrophysiologic studies, a specially constructed pacemaker was inserted. Routine function mode resulted in no output but activation of the reed switch resulted in V00 (asynchronous) pacing at 80/min. Patient-initiated conversion of ventricular tachycardia was documented by ambulatory electrocardiographic monitoring. The patient reports an average of two episodes per month converted over a four year period.