L. Thomas Sheffield

Natural history of angina pectoris

Abstract An understanding of the natural history of angina pectoris is crucial to decision making in the management of patients with this disease. Early investigations suggested a highly variable annual mortality rate, ranging from 2.5 to 9 percent. These studies clearly pointed to the association of certain electrocardiographic changes, hypertension, cardiac enlargement and congestive heart failure with increased mortality. Several recent studies based on findings at coronary arteriography indicate a high degree of correlation between the extent of coronary atherosclerotic occlusive disease and the likelihood of early death. A combination of data from several laboratories indicates that if only one of the three major coronary arterial branches (left anterior descending, left circumflex or right) is significantly stenosed, the annual mortality rate will be approximately 2 percent of the cohort. If two of the three major arteries are stenosed, the rate will be approximately 7 percent, and if all three arteries are stenosed, it will be approximately 11 percent. Some data suggest that these mortality figures based on the extent of atherosclerotic occlusive disease are importantly modulated by the extent of ventricular myocardial impairment as reflected by cardiac enlargement or symptoms of congestive heart failure.

Relation Between Mural Force and Pressure in the Left Ventricle of the Dog

An investigation of the relationship in the dog between left ventricular pressure, left ventricular size, and total longitudinal force developed by the wall of the left ventricle is reported. This study required the development of a method for recording the force needed to keep together the two edges of a slit in the ventricle. Such a method is described, and samples of the force curves are shown, the general features of which are consistent with predictions from the physiology of muscle strips. The net force which the muscle fibers develop perpendicular to a given plane through the ventricle is almost identical to the product of the intracavitary pressure and the area of the cavity included in the plane. This relationship holds true regardless of the thickness of the wall or the shape of the ventricle.

Relation of graded exercise test findings after myocardial infarction to extent of coronary artery disease and left ventricular dysfunction

Abstract To evaluate the effectiveness of the graded exercise test in predicting the extent of coronary artery disease and the degree of left ventricular dysfunction in patients with prior myocardial infarction, 100 consecutive patients underwent both graded exercise testing and coronary and left ventricular angiography at a median of 4 months after infarction. The studies caused no complications. An equal number of patients had anterior and inferior infarction. Coronary artery disease, defined as 70 percent or greater stenosis of luminal diameter, was present in three vessels in 31 patients, in two vessels in 35 patients, in one vessel in 33 patients and in no vessel in one patient. With “diagnostic” electrocardiographic criteria of 1 mm or greater J point depression plus a flat or downsloping S-T segment, 31 patients had an electrocardiographically positive exercise test; 27 of these (87 percent) had two or three vessel coronary artery disease. Of the 21 patients with a negative exercise test, 62 percent had coronary artery disease in no more than one vessel, 33 percent in two vessels and 5 percent in three vessels. Fourteen patients had S-T segment elevation during exercise; these patients had a lower ejection fraction and larger angiographic scar size than the remaining 86 patients. Patients terminating exercise because of symptoms of left ventricular dysfunction (fatigue or dyspnea) showed correlation between duration of exercise and ejection fraction ( r = 0.65) and between duration of exercise and angiographic scar size ( r = −0.62). Thus, several months after infarction, the graded exercise test can be performed safely and can be utilized to predict the extent of coronary artery disease and left ventricular dysfunction in selected groups of patients.

Enhanced evaluation of treadmill tests by means of scoring based on multivariate analysis and its clinical application: a study of 608 patients.

Six hundred eight patients being evaluated for chest pain who did not have valvular disease, cardiomyopathy, left ventricular hypertrophy or bundle branch block, and were not receiving digitalis, had treadmill tests and coronary angiograms. In 351, various exercise variables were correlated by multivariate analysis to coronary artery disease (CAD). In men, significant variables were: (1) maximal heart rate achieved less than 80% of maximal predicted heart rate (Mx PHR), (2) ST-T change greater than or equal to 1 mm, (3) age greater than or equal to 55 years and (4) treadmill time (TT) less than 8 minutes. These variables rated diagnostic scores of 9, 6, 5, and 3, respectively. A score of greater than or equal to 7 was considered diagnostic of CAD. In a test group of 192 men in which ST-T change was compared with treadmill score, sensitivity was 65 versus 85%, specificity 79 versus 74% and accuracy 69 versus 83%. In women, maximal heart rate less than 90% of Mx PHR and TT of less than 6 minutes were significant, with an accuracy of 75%. Moreover, 89% of incomplete tests and 70% of tests in patients with previous myocardial infarction were also correctly diagnosed. This method allows convenient use of significant exercise variables for clinical purposes with improved results.

Isometric effects on treadmill exercise response in healthy young men

Abstract This study evaluated the hypothesis that the isometric stress of load carrying augments the dynamic exercise response seen on the treadmill, and estimated the magnitude of this effect on heart rate and blood pressure for several methods of carrying the same load. Thirteen healthy subjects carried 40 lb in the right hand (H), 40 lb on the back (B), 20 lb in each hand (D) and no weight (N) while walking for 3 minutes on the treadmill at a grade of 0 at 1.7 miles/ hour. A statistically significant increase in the rate of rise and peak levels of systolic blood pressure, heart rate, estimated mean blood pressure, the product of estimated mean blood pressure and heart rate and systolic blood pressure-heart rate product was shown when task H was compared with tasks B, D and N. Values for tasks D and B did not differ significantly. The effects of isometric and dynamic exercise combined were greater than those of dynamic exercise alone. An effective technique of load distribution reduced the rate of increase in blood pressure, heart rate and the peak attained during dynamic exercise, thereby suggesting a lower level of myocardial oxygen consumption for a given weight-carrying task. These results can be applied to evaluation of patients with heart disease and estimation of their exercise tolerance.

Myocardial infarction after exercise-induced electrocardiographic changes in a patient with variant angina pectoris

Abstract The electrocardiographic response to stress testing varies considerably in patients with variant angina pectoris: no change in the S-T segment as well as S-T segment depression and elevation have been observed. This report describes a patient with a resting ST-T abnormality that reverted to normal appearance with exercise. However, the patient experienced severe chest pain shortly after discontinuing exercise testing, and an electrocardiogram showed evidence of acute anterolateral infarction. The possible implications of such electrocardiographic changes are discussed.

Thermographic Patterns of Angina Pectoris

Liquid crystals, encapsulated onto black Mylar tapes, were used as cutaneous temperature sensors in 50 male patients, who had thermographic examinations while they were being exercised on the treadmill, in an attempt to induce angina pectoris. Twenty-eight of the group remained free of pain and the exercise thoracic thermogram was essentially unchanged from the control or resting state. Twenty-two patients developed angina pectoris during exercise, of whom 21 had associated ST depression in the electrocardiogram, and 17 thermographic abnormalities. When the pain was unilateral (nine patients), skin coolness was invariable and was within the distribution of the pain. When the pain was central (13 patients), skin coolness was present in some of the patients (eight of 13) and was not always within the area of pain. When present, the skin coolness was transient and settled within minutes of relief of pain.