Exercise testing in the diagnosis of coronary heart disease: a perspective.

The methods of assessing the diagnostic usefulness of exercise testing in detecting coronary obstructive disease are examined. The limitations of long-term clinical follow-up and coronary angiography as standards for the determination of disease are described as are the effects of test methodology, criteria for positivity, prevalence of disease in the study population, reliability of the standard and recognition of false positive and false negative results in determining reliability of such testing. High values were found for sensitivity and specificity for exercise testing of patients with coronary artery disease referred for consultation to medical center cardiology services. Maximal exercise testing and consideration of symptomatic and hemodynamic as well as electrocardiographic criteria for identification of myocardial ischemia are helpful in improving reliability. Diagnostic accuracy is greatly enhanced by recognition of known causes for false positive and false negative results.

Treadmill walking protocol for the diagnostic evaluation and exercise programming of cardiac patients.

This study (1) describes a treadmill walking protocol which has been used safely in over 40,000 tests since 1960, (2) presents normative data on oxygen consumption (VO2) so that it may be determined from work load without direct measurement, and (3) demonstrates simple techniques for early activity prescription or later therapeutic walking programs for patients after myocardial infarction (MI) based on this treadmill test. Normative data are presented on 131 subjects. There were no significant differences in VO2 values at the various work loads dependent on age, gender, fitness level, familiarity with the test procedure, clinical status, or the presence or absence of beta blockade. The protocol was then applied in cardiac rehabilitation of 25 patients. As a low level test, in 2 to 9 minutes patients attained 56 to 83% of age-predicted maximal heart rate. The translation of these data into early activity guidelines is shown. For a walking program, the maximal speed attained at 10% grade on the treadmill when walked on level ground put patients in the target heart rate zone for cardiovascular conditioning.

Effectiveness of isosorbide dinitrate and nitroglycerin in relieving angina pectoris during uninterrupted exercise.

Twenty patients with ischemic heart disease documented by coronary angiograms or ST segment depression in the ECG during treadmill walking, were administered sublingual nitroglycerin 0.3 to 0.6 mg on one occasion and a chewable form of isosorbide dinitrate 5 mg on another occasion during treadmill walking when anginal discomfort was definitely present at a mild degree of intensity. Despite continued walking at a constant speed and grade, angina was relieved in all patients, completely in most patients, partially in a few. The average time from administration of the medication to onset to relief was 74.7 seconds for nitroglycerin and 107.6 seconds for chewable isosorbide dinitrate. Average time to complete relief or maximal incomplete relief was 190.3 seconds for nitroglycerin and 315.1 seconds for chewable isosorbide dinitrate. Ischemic electrocardiographic changes were reverted toward normal by nitroglycerin in 13 subjects and by isosorbide dinitrate in 15. The differences in onset to complete relief were all statistically significant indicating that nitroglycerin is more rapid in its action than is chewable isosorbide dinitrate.

Comparison of placebo, nitroglycerin, and isosorbide dinitrate for effectiveness of relief of angina and duration of action.

Each of 13 patients with angina had either chewable isosorbide dinitrate, nitroglycerin (sublingual therapy), or placebo administered on each of three different days when mild anginal pain had been induced by walking on a treadmill. Both therapy with isosorbide dinitrate and therapy with nitroglycerin were effective in bringing about complete relief of the angina in less than ten minutes of uninterrupted continuous walking on the treadmill in 11 of the 13 subjects, while administration of placebo afforded complete relief in none. The duration of action of the drug was determined by following the first effort (during which the tested drug was given) by successive ten-minute walks at the same workload that first induced anginal pain. Half-hour resting periods separated the repeated periods of exercise, and the duration of action was taken to be the time from administration of the agent to the return of angina on one of the repetitive efforts. No prolonged protection was afforded by administration of the placebo. Nitroglycerin protected for slightly longer than one hour, while isosorbide dinitrate protected for 2 1/2 to 3 hours.

Hypoplasia of the right ventricular myocardium with ventricular tachycardia.

A 20-year-old woman died suddenly after having had recurrent ventricular tachycardia for five years. An ECG showed two distinct varieties of ventricular tachycardia, both characterized by left bundle-branch block. Pathologic examination showed what we considered to be a type of Uhl's anomaly. Most of the compact layer of the right ventricle was replaced by fat, with the trabeculated areas intact but showing severe fibrosis and chronic inflammation. Patches of such degeneration were also found in the septum and the left ventricle. The conduction system disclosed a septated bundle of His.

Prevention of heart disease in the normal subject with a positive exercise test.

The person who has asymptomatic myocardial ischemia is at high risk because he does not have the benefit of the warning signals afforded by the substernal pain that tells most patients with angina to stop what they are doing.

Treadmill exercise protocols to demonstrate effectiveness of nitrate drugs in relief of angina pectoris; duration of action and degree of functional enhancement.

During constant uninterrupted exercise with mild angina present, either placebo, nitroglycerin, isosorbide dinitrate or erythrityl trinitrate was given by buccal membrane absorption. Placebo produced no relief and exercise had to be stopped. Nitroglycerin produced rapid complete relief and the long-acting drugs effected relief more slowly but of long duration as shown on repetitive walks as long as 3 h after drug administration.

Adaptation to exercise in angina pectoris. The electrocardiogram during treadmill walking and coronary angiographic findings.

Twelve patients with angina pectoris manifested an ability to adapt to exercise during treadmill stress testing with electrocardiographic monitoring. Three patterns of adaptation were seen. Nine subjects had the ability to continue walking after the onset of angina with eventual disappearance or lessening of anginal pain and the associated ischemic ST-segment depression; anginal pain and ST depression began to diminish during a steady state of blood pressure and heart rate in those cases in which these factors were measured. Four subjects were able to continue walking for long periods of time during a state of angina and ischemic ST depression. Three subjects demonstrated an increase in exercise capacity after being warmed up by a preceding bout of exercise-induced angina; blood pressures and heart rates during the initial, "warming-up" effort tended to be higher than those during the early stages of the second effort. In three subjects more than one of these patterns of adaptation were demonstrated. Five of the subjects showed striking subjective and objective improvement in exercise tolerance while on a program of regular walking exercise. Selective coronary cineangiography was performed in eight of these patients and two patterns of coronary disease were seen: (1) occlusion of a major coronary vessel with good collateral channels circumventing the obstruction; (2) strategically placed, proximal, stenotic lesions in major coronary vessels without frank occlusion and without discernible collateral development. Some diagnostic and therapeutic implications of these findings are discussed.

Ischemic heart disease. Precarious coronary lesions and prognosis.

Coronary arteriograms in 113 patients whose cases were followed for 2 to 12 years were analyzed in an attempt to discover why in some patients with angina pectoris there are long stable clinical courses and in others the courses proceed rapidly to death. It was found that patients with completed coronary occlusions, usually with distal portions reconstituted by collateral, had favorable prognoses with prolonged longevity. Patients with multiple high grade narrowings of the coronary arteries, on the other hand, had poor prognoses with high attrition rates. The more stenotic lesions present in the coronary arteries, the higher the attrition rates. Completed coronary occlusions, therefore, have been classified as nonprecarious while local coronary stenoses greater than 50 percent of the lumen diameter have been classified as degrees of precariousness according to the number of lesions present. When compared with classification by number of diseased vessels and by arteriographic score of Friesinger, the nonprecarious cases had better prognoses than the precarious.

Effect on training on myocardial oxygen supply/demand balance.

In five well-trained and five sedentary control subjects potential subendocardial blood supply was estimated from the diastolic pressure time index (DPTI) and myocardial oxygen demands from the tension time index (TII) during a progressive near-maximal treadmill test. DPTI/TTi was used to assess the effects of training on myocardial oxygen supply/demand balance. DPTI/TTI was significantly higher in trained subjects at rest and comparable workloads. At 6.4 km/hr, 18% grade (maximum for the controls), TTI was significantly lower (4300 +/- 76 vs 4495 +/- 99 mm Hg-sec/min) and DPTI significantly higher (2534 +/- 86 vs 2295 +/- 91 mm Hg-sec/min) in the trained subjects; DPTI/TTI was significantly higher (0.59 +/- .02 vs 0.50 vs .03). At near-maximal heart rates both groups achieved the same supply/demand balance (0.50); however, the trained subjects were working at higher workloads. We conclude that endurance conditioning increases work capacity, reduces myocardial O2 demands, increases potential O2 supply and improves the supply/demand balance at any given submaximal workload which reduces the risk of ischemia.

Near-maximal ECG stress testing and coronary artery disease risk factor analysis in Los Angeles City fire fighters.

Near-maximal ECG stress testing and coronary artery disease risk factor analysis including blood pressure, serum cholesterol and smoking habits were conducted on a randomly selected group (N=90) of Los Angeles City Fire Fighters ranging in age from 40 to 59 yrs. The data obtained from the fire fighters were compared to data previously reported for a group of Los Angeles insurance underwriters of the same age range. Only 12% of the fire fighters had cholesterol values greater than 260 mg% while 18% of the insurance executives fell into this category. Only 2% of the fire fighters had blood pressure values greater than 160/90 mm Hg while 25% of the insurance executives were hypertensive. Thirty-two percent of the fire fighters were smokers at the time of testing as compared to 26% for the insurance executives. Only one fire fighter had all three risk factors elevated and only five had two risk factors elevated. Forty-seven of the fire fighters had no risk factors elevated. Ten percent of the fire fighters had ischemic stress tests as compared to 8% for the insurance executives. Of the nine fire fighters with ischemic stress tests one was hypertensive, one had elevated serum triglycerides, and three were smokers at the time of testing. Since the fire fighters are a medically-selected population with low risk factors for CHD, the observed incidence of ischemic stress tests is surprising and suggests that ischemic heart disease may be job associated.