William C. Elliott

An Electrocardiographic, Anatomic, and Metabolic Study of Zonal Myocardial Ischemia in Coronary Heart Disease

An integrated approach, utilizing cine coronary angiography, the standard 12-lead and post-exercise electrocardiograms, and regional myocardial lactate metabolism, is presented for detection of regional myocardial ischemia in patients with coronary heart disease. The normal electrocardiogram was of no predictive value and was present with extensive coronary disease and myocardial production of lactate. The abnormal electrocardiogram gave an accurate indication of a portion, but not all zones of ischemia. Multiple electrocardiographic abnormalities were invariably associated with severe coronary artery disease, although in most patients many more coronary lesions were present than electrocardiographic abnormalities. The regional lactate pattern was very helpful in localizing myocardial ischemia and significant coronary artery lesions. Regional lactate abnormalities may have a great practical value in the selection of patients for myocardial revascularization surgery and in their postoperative evaluation.

Mechanisms of Angina in Aortic Stenosis

The pathophysiology of cardiac pain in pure aortic stenosis has primarily been ascribed to an augmented left ventricular demand outstripping energy supply. This report provides evidence that not only is the energy demand increased but the supply in terms of coronary vascular reserve may be impaired, particularly in response to stress. Hemodynamic and coronary circulatory changes were studied in 18 patients with aortic stenosis during standard isoproterenol infusion. It was not possible to differentiate any patient with or without angina pectoris or patients with or without coronary artery disease on a basis of change in any measure of left ventricular dynamics. On the other hand, differences did occur in the mechanisms of energy delivery during isoproterenol stress: (1) In group A (aortic stenosis without angina or coronary artery disease), coronary flow increased normally, myocardial oxygen extraction decreased, and myocardial lactate production occurred in only one of seven patients. This suggested that energy supply was, generally, adequate to demand. (2) In group B (critical aortic stenosis with angina but no coronary disease), coronary flow rose insignificantly, myocardial oxygen extraction actually increased in three of five patients, and abnormal glycolysis occurred in all patients. This suggested that little or no reserve for increased coronary flow existed and that compensatory mechanisms had to be summoned. (3) In group C (aortic stenosis with angina and coronary artery disease), coronary flow rose normally, myocardial oxygen extraction decreased normally, but abnormal lactate metabolism occurred in most patients. This suggested adequate overall coronary reserve but evidence of regional ischemia.

Diagnostic Accuracy of Selective Coronary Cinearteriography

The premortem selective coronary cinearteriograms of 29 patients who subsequently died of their underlying disease have been compared to findings at postmortem examination. Only three errors of functional significance were found. Possible sources of these errors were analyzed. The most important single factor in determining the accuracy was the radiographic quality of the arteriogram. The data support the conclusion that selective coronary cinearteriography is a highly accurate means of evaluating the morphology of both normal and diseased coronary vessels, but high quality arteriograms and experienced interpreters are required.

Hemodynamic Studies during Angina Pectoris

Sixteen patients developed angina pectoris during cardiac catheterization.During an anginal attack, left ventricular end-diastolic pressure did not uniformly rise. When it did occur, it seemed to be more closely related to acute left ventricular hypertension.During a stress-induced anginal attack, the rise, if any, in systolic ejection rate of the left ventricle, was markedly decreased below that achieved in normal subjects or in subjects with coronary artery disease without angina. The impaired augmentation in systolic ejection rate was associated with subnormal increases in cardiac output as well as in stroke volume during the anginal state. Average heart rate and systolic ejection period were no different from the nonanginal patients.Myocardial excess lactate was found in the vast majority of cases during an anginal episode, and actual myocardial lactate production was seen in one half of the patients during angina.The abnormalities in left ventricular function may be related to abnormalities in oxygen supply to the myocardium.

Effect of Supine Exercise on Left Ventricular Volume and Oxygen Consumption in Man

RESPONSE to physical exercise in man has been studied extensively. For any given workload, a predictable change in blood pressure, heart rate, and cardiac output has been shown to occur. Rushmerl has pointed out that the response of stroke volume to exercise, however, may be variable both in experimental animals and in man. He has also demonstrated that not only the amount, but also the direction of change in cardiac dimensions may vary in the exercising dog, thus indicating that the pattern of response cannot be readily predicted. In a preliminary report using radiocardiography, Cournand and associates2 demonstrated that the heart emptied more completely during physical exercise. In a recent study measuring cardiac dimensions by means of silver clips sewn on the heart of four postoperative subjects, Braunwald and associates3 showed that these dimensions diminished on the average of 3 to 5 per cent during supine leg exercise. It is the purpose of this report to present data obtained in 20 human subjects with minimal heart disease on the change induced by supine leg exercise in left ventricular volume, in the degree and speed of ventricular emptying, and to describe the relationship of this mechanical activity to myocardial oxygen consumption.

Regional Myocardial Blood Flow

A method is described which measures the local effectiveness of the myocardial circulation, expressed as a clearance constant. Uniform clearance constants have been demonstrated in the normal canine and human myocardium. A distinct difference in clearance constants has been demonstrated between the normal canine myocardium and areas of naturally occurring disease. Heterogeneous clearance constants have been found in a majority of human subjects with coronary artery disease-the lowest rates being noted in areas of fibrous aneurysm.