Reduction of sympathetic inotropic response after ischemia in dogs. Contributor to stunned myocardium

Eight open chest dogs underwent 25 min of coronary occlusion to determine whether brief myocardial ischemia disrupts the normal myocardial inotropic response to sympathetic nervous stimulation. If so, this could represent a mechanism contributing to postischemic myocardial dysfunction. Myocardial segment shortening was measured using ultrasonic dimension crystals before and after coronary artery occlusion and reperfusion. Left ansa subclavia stimulation and systemic norepinephrine (NE) infusion were used to test the myocardial inotropic response to neural stimulation and direct exposure to the sympathetic mediator, respectively. Before coronary artery occlusion, base-line preischemic segment shortening (12.5 +/- 1.6%) (SEM) increased during both sympathetic stimulation (20.2 +/- 1.4%) and NE infusion (19.7 +/- 1.1%). The control segment responded similarly. After ischemia and reperfusion there was no significant change in heart rate, aortic or left ventricular pressures, nor changes in control segment shortening. In contrast, shortening in the postischemic segment was markedly reduced compared to baseline (4.1 +/- 2.4%), and no longer responded to sympathetic stimulation (2.4 +/- 2.8%), while responsiveness to systemic NE was maintained (12.9 +/- 2.0%), P less than 0.001, which suggested injury to the sympathetic-neural axis during the period of ischemia. This reduced response to neural stimulation was persistent for up to 2 h after reperfusion. Left atrial or intracoronary infusion of bretylium tosylate, which releases norepinephrine from nerve terminals, resulted in an immediate inotropic response in the postischemic segment, which indicated that total depletion of NE from nerve terminals during the ischemic period had not occurred. Disruption of sympathetic neural responsiveness is likely a component of the mechanism of postischemic myocardial dysfunction whenever there is appreciable sympathetic drive to the heart.

Variables predictive of successful medical therapy in patients with unstable angina: selection by multivariate analysis from clinical, electrocardiographic, and angiographic evaluations

Although unstable angina can be initially controlled with medical therapy in most patients, there is a high incidence of subsequent death, myocardial infarction, or need for coronary bypass surgery to control symptoms. Identification at the time of presentation of the patient likely to do poorly on continued medical therapy would be useful in advising consideration of surgical therapy. Since coronary arterial spasm may have a significant role in the pathophysiology of unstable angina in some patients, the recently developed calcium channel antagonists may therefore be of particular benefit in the medical therapy of unstable angina. One hundred thirty-eight patients were entered into a randomized double-blind study of the efficacy of adding nifedipine to conventional treatment of unstable angina (nitrates and beta-blockers) and were followed for 18 months. Of these patients, 104 underwent coronary arteriography. A multivariate Cox's hazard function analysis was applied to variables selected from the history, electrocardiographic (ECG) changes during chest pain, and from scintigraphic and coronary arteriographic data to determine those variables most predictive of response to medical therapy. The percentage of the left ventricular myocardium supplied by vessels with 70% or greater luminal stenosis was the most significant variable in influencing failure of medical therapy defined as sudden death, myocardial infarction, or need for bypass surgery. Whether or not the patient received nifedipine was the second most powerful variable, with the use of nifedipine reducing by half the relative risk of failing medical therapy. These were followed by cigarette smoking and presence of global ST segment changes during ischemia. After 18 months the nifedipine group had fewer patients failing medical therapy (p = .02), with fewer patients undergoing coronary bypass surgery (p less than .01). However, nifedipine did not appear to have a preventive effect against myocardial infarction or death. Kaplan-Meier actuarial curves confirmed that medical therapy was significantly less successful in the presence of increasing numbers of significantly stenotic vessels (p = .03). However, nifedipine provided a significant beneficial effect in patients with two or more stenotic vessels (p less than .01) and in whom 50% or more of the myocardium was supplied by vessels with 70% or greater stenosis (p = .01). Thus, although patients with advanced obstructive coronary disease have the greatest likelihood of unfavorable outcomes, the addition of nifedipine is of significant benefit.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute nifedipine withdrawal: consequences of preoperative and late cessation of therapy in patients with prior unstable angina

Reports of acute ischemic events after withdrawal of calcium antagonist therapy in outpatients and during bypass surgery in patients with prior angina at rest prompted the examination of the effect of nifedipine withdrawal in 81 patients who had completed a prospective, double-blind randomized trial of nifedipine versus placebo for rest angina. Thirty-nine patients underwent bypass surgery for uncontrolled angina or left main coronary artery disease. No significant difference between patients withdrawn from nifedipine or placebo was seen in the incidence of perioperative myocardial infarction, hypotension requiring intraaortic balloon counterpulsation, vasopressor or vasodilator requirements or incidence of significant arrhythmias. An additional 42 patients had completed 2 years on a protocol consisting of nitrates and propranolol in addition to nifedipine or placebo. During a mean of 66 hours of continuous monitoring after withdrawal of nifedipine or placebo, heart rate and blood pressure were unchanged. A worsening of previously present angina at rest occurred in five patients who had continued to experience rest angina before drug withdrawal, four of whom were withdrawn from nifedipine. No patient with class I to III angina experienced new onset of rest angina during drug withdrawal. No patient experienced myocardial infarction. There was no significant difference between patients withdrawn from nifedipine or placebo in the duration or frequency of ischemic ST changes on continuous electrocardiographic monitoring, or in duration or positive results of serial exercise treadmill testing. Thus, no early adverse effects of acute nifedipine withdrawal were found in patients with prior rest angina at the time of bypass surgery or in stable patients receiving long-term medical therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracavitary thrombi in the right heart associated with multiple pulmonary emboli. Report of two patients

Two-dimensional echocardiography identified intracavitary masses in the right heart in two patients presenting with extensive pulmonary embolism. In one, a right ventricular mass was identified which was confirmed at subsequent autopsy to be an organizing thromboembolus. In the second patient, a right atrial mass was identified; it disappeared with thrombolytic therapy which was accompanied by clinical improvement. We demonstrate that intracardiac thrombi associated with pulmonary embolism may be identified noninvasively by two-dimensional echocardiography. We suggest the presence of thrombi may represent a large intravascular thrombus. This recognition may influence therapeutic decisions.

Reciprocal ST change in acute myocardial infarction: assessment by electrocardiography and echocardiography

To evaluate the incidence, time course and significance of reciprocal change, 25 consecutive patients admitted with their first acute transmural myocardial infarction were studied with serial electrocardiography and two-dimensional echocardiography. Reciprocal change was noted in all patients with inferior infarction (mean maximal ST segment depression 3.53 +/- 1.97 mm) and 70% of patients with anterior infarction (mean maximal ST depression 1.45 +/- 0.8 mm, p = 0.001). When initially present, reciprocal change had resolved within 24 hours in 59% of patients. The sum of reciprocal ST depression correlated with the sum of ST elevation in anterior (r = 0.92, p less than 0.001) and inferior (r = 0.55, p = 0.035) infarction, and this relation persisted when maximal ST depression and elevation were considered. Echocardiographic evidence of contraction abnormalities in areas of the left ventricle remote from the infarction was seen in 45% of patients. However, its presence did not correlate with the presence of reciprocal change. Although reciprocal change progressively diminished on serial electrocardiograms (maximal ST depression 2.73 +/- 1.77 mm at 19 hours after onset of symptoms; 1.0 +/- 0.92 mm at 2 to 3 days; and 0.22 +/- 0.26 mm at 7 to 10 days; p less than 0.05), the corresponding serial echocardiograms showed no change in the function of the remote wall (remote wall motion index 1.87 +/- 0.65, 1.81 +/- 0.62, 1.86 +/- 0.47, respectively, p = NS). These data, therefore, do not support the hypothesis that reciprocal ST depressions during early acute transmural myocardial infarction reflect remote ischemia. Rather, these changes are influenced by factors determining the degree of acute ST elevation, previously shown to include infarct size, shape, location, transmurality and duration.

Nifedipine in unstable angina: a double-blind, randomized trial

We assessed the efficacy of adding nifedipine to the conventional treatment of unstable angina in 138 patients in a prospective, double-blind, randomized, placebo-controlled trial. There was no difference between the two groups in the dose of conventional antianginal medication or in age, prior myocardial infarction, ejection fraction, or other risk factors. Failure of medical treatment (defined as sudden death, myocardial infarction, or bypass surgery within four months) occurred in 43 of 70 patients given placebo and in 30 of 68 given nifedipine. Kaplan-Meier survival-curve analysis of the number and time dependence of treatment failures demonstrated a benefit of nifedipine over placebo (P = 0.03). The benefit was particularly marked in patients with ST-segment elevation during angina (P = 0.02). Side effects (transient hypotension or diarrhea) required withdrawal of the drug from four patients given nifedipine and from one given placebo. We conclude that the addition of nifedipine to conventional therapy is safe and effective in unstable angina.

Ischemic ventricular fibrillation: the importance of being spontaneous

Although the energy level required to defibrillate normal myocardium is low and constant, as determined from studies of induced ventricular fibrillation, little is known of the specific energy requirements in regionally ischemic hearts for spontaneous or induced ventricular fibrillation. In this study the lowest energy threshold for defibrillation was determined in 10 open chest dogs with reversible 10 minute coronary occlusions at various sites for each of 44 events of ventricular fibrillation, using apical and superior vena caval electrodes with a generator providing variable output of 1 to 30 watt seconds. The ischemic mass, quantitated from postmortem angiographic and planimetric data, was 52 +/- 9 percent (mean +/- standard deviation) of the left ventricle in dogs with induced ventricular fibrillation (Group I), 52 +/- 12 percent in dogs with spontaneous ventricular fibrillation after occlusion (Group II) and 54 +/- 9 percent in dogs with spontaneous ventricular fibrillation after reperfusion (Group III). Defibrillation thresholds in watt seconds were 9 +/- 7 in Group I (n = 12), 19 +/- 10 in Group II (n = 13) and 18 +/- 10 in Group II (n = 19). (Group I versus Groups II and III, probability [p] less than 0.025). In nonischemic hearts, the defibrillation threshold was 3 +/- 2 (n = 32) (p less than 0.001 compared with values in Group I, II or III). Thus, despite similar masses of ischemia, twice as much energy was required for defibrillation of spontaneous ventricular fibrillation (whether after occlusion or reperfusion) as for induced ventricular fibrillation, suggesting that these conditions are caused by different metabolic or pathologic derangements. Such differences should be considered in assessing interventions such as drug therapy designed to inhibit the repetitive ventricular response and in design of implantable defibrillators.