The purpose of this study was the determination of whether hemodynamic and pharmacologic factors influence the extent and severity of myocardial necrosis produced by coronary occlusion. In 48 dogs, 10 to 14 epicardial leads were recorded on the anterior surface of the left ventricle in the distribution and vicinity of the site of occlusion of a branch of the left anterior descending coronary artery. The average S-T segment elevation for each animal was determined at 5-min intervals after occlusion. This elevation was used as an index of the presence and severity of myocardial ischemic injury. The number of sites showing this elevation provided an additional measure of the size of the injured area. Occlusion alone raised the average S-T segment elevation from 0.22 ± 0.04 to 3.32 ± 0.37 mv (SEM). Isoproterenol, ouabain, glucagon, bretylium, and tachycardia given prior to a repeated occlusion increased the severity and extent of ischemic injury, while propranolol decreased it. Elevation of arterial pressure ...

Factors Influencing Infarct Size Following Experimental Coronary Artery Occlusions

Ten patients aged 22 to 80 years (median 57) with severe left ventricular (LV) dysfunction and atrial fibrillation (AF) with rapid ventricular response were evaluated after therapy. Because most patients were unaware of their arrhythmia, duration was usually unknown. All patients had heart failure symptoms; 9 presented with New York Heart Association class III or IV disability, and 1 with class II disability. Initial LV ejection fraction ranged from 12 to 30% (median 25). No patient had symptomatic coronary artery disease (4 underwent angiography). Myocarditis and infiltrative processes were excluded by biopsy in 5 patients. All patients were considered initially to have idiopathic dilated cardiomyopathy with secondary AF. Ventricular rate was controlled in all patients, with sinus rhythm restored in 5. At follow-up (median 30 months, range 3 to 56), all patients were asymptomatic. LV ejection fraction after treatment ranged from 40 to 64% (median 52). It is concluded that in some patients initially considered to have idiopathic dilated cardiomyopathy, AF with rapid ventricular response may be the primary cause rather than the consequence of severe LV dysfunction. LV dysfunction may be completely reversible with ventricular rate control.

Left ventricular dysfunction due to atrial fibrillation in patients initially believed to have idiopathic dilated cardiomyopathy.

Disturbances of rate, rhythm and conduction in acute myocardial infarction: A prospective study of 100 consecutive unselected patients with the aid of electrocardiographic monitoring

Acute phase of myocardial infarction.

In each of 11 necropsied patients with myocardial infarction and atrial arrhythmias, a coronary occlusion was found proximal to the origin of the sinus node artery and there was infarction of the sinus node. The multiple factors influencing the onset of atrial arrhythmias during acute myocardial infarction are discussed. Infarction of the sinus node is only one of these factors. Other important ones are ischemia of the AV node, vagal and vagomimetic reflexes, atrial distention, and circulating chronotropic substances. By combination of a knowledge of the anatomy and pathology of the human coronary arteries with the observation of atrial arrhythmias during acute myocardial infarction, an accurate diagnosis of the point of coronary occlusion can often be made.

Myocardial Infarction and Atrial Arrhythmias

Excerpt This study will consider the hemodynamic disturbances of the coronary flow which occur during cardiac arrhythmias. It has been shown that fast cardiac arrhythmias can precipitate severe dis...

Effect of the cardiac arrhythmias on the coronary circulations

Effect of systemic blood pressure and vasopressor drugs on coronary blood flow and the electrocardiogram.

Comparison of the antegrade and retrograde (collateal) coronary free flows showed that the retrograde flow was less than 10 per cent of the antegrade flow in 48 per cent of animals and above 20 per cent in 11 per cent of animals.

Lauro B. De Vera

Papers

Effect of the cardiac arrhythmias on the coronary circulations

Effect of systemic blood pressure and vasopressor drugs on coronary blood flow and the electrocardiogram.

Simultaneous Comparison of Antegrade and Collateral Coronary Blood Flows