Editorial: Pitfalls in diagnostic and functional evaluation using exercise testing

Significance of exercise-induced junctional S-T depression in evaluation of coronary artery disease

Isolated junctional S-T depression induced during treadmill exercise testing was correlated with coronary arteriographic findings in 230 patients. Of 75 patients with junctional depression of less than 1.5 mm, 10 had 50% or greater stenosis of at least one major coronary artery and 2 patients (3%) had multivessel disease. Of 42 with junctional depression of 1.5 mm or more and a rapid upsloping S-T segment, 23 had 50% or greater coronary stenosis and 12 of these had multivessel disease. Of 35 with an upsloping pattern (junctional depression of more than 2 mm, upsloping S-T segment depressed 2 mm or more, 0.08 second after the J point), 33 (94%) had 50% or greater coronary stenosis compared with 46 (96%) and 30 (97%) with 2 mm or more junctional depression ahd a horizontal or downsloping S-T segment. In conclusion, multivessel disease is rare with isolated exercise-induced junctional depression of less than 1.5 mm but common when the J point is depressed 1.5 mm or more. Junctional depression of more than 2 mm is associated with the same incidence of coronary disease when the S-T segment is slowly ascending (upsloping pattern) as when it is horizontal.

Systolic time intervals utilizing ear densitography. Advantages and reliability for stress testing

Systolic time intervals were determined in 10 volunteer subjects at rest and during a variety of cardiocirculatory stresses to further evaluate the ear densitogram derivative as a replacement for the carotid pulse curve. There was close tracking of the two methods not only for left ventricular ejection time (r = +0.98), but also for pre-ejection period (r = +0.98). The results confirmed that this technically simple and remarkably stable wave form permits reliable measurement of the systolic time intervals both at rest and during the actual performance of stress.

Noninvasive measurement of cardiac function during exercise, using resaturation curves

The resaturation curve, a noninvasive indicator-dilution test using an ear oximeter to detect rates of change in arterial oxygen saturation during breathing of various concentrations of oxygen, was used to assess cardiac performance in normal subjects and in 108 patients with cardiac valvular disease. Measurements made during exercise included the time constant of resaturation (tau) and beat-to-beat changes in arterial oxygen saturation (the left heart clearance fraction). At maximum rates of voluntary work, patients had a significantly reduced clearance fraction and longer tau than normal subjects. Clearance fraction and tau improved in patients after aortic valve replacement; deterioration occurred in tau and clearance fraction over time in patients treated medically, as compared to normal subjects who showed little change during a ten-year period. Clearance fraction and tau correlated with hemodynamic data obtained during cardiac catheterization. The resaturation curve provides an objective measure of cardiac impairment that can be readily repeated during follow-up of patients with heart disease.

Evaluation of physical performance by rectangular-triangular bicycle ergometry and computer-assisted ergospirometry

A great deal of information about physical adjustment to work can be obtained from quantitative stress testing. Maximal stress limited by symptoms of exertional intolerance is the concept of the 2 min duration work increment test (rectangular-triangular exercise test). Compared to steady-state work tests strict observation of the standardized procedure- and computer assisted evaluation of ergospirometric parameters offer innovatory opportunities: (1) the test is of short duration (8-14 min), (2) the subjects recover rapidly, even from an exhausting test, (3) one is more likely to be able to observe plateauing of VO2, should determination of maximal VO2 be desired, (4) adaptation to increasing work rates and maximal work capacity is assessable, (5) computer technics provide on-line assessment of aerobic and anaerobic power in quantitative terms, (6) measurements proved to be highly reproducible, (7) the relationship between variables such as increments of heart rate and systolic blood pressure, respiratory minute volume, oxygen uptake during the early phase of the non-steady-state condition and the index of anaerobic power, and the influence of factors such as work load and work output, has been studied to derive standard values. Soft-ware programs have been designed to estimate deviation of parameters actually measured from standard values in terms of multiples of the standard deviation of the standard regression line. In particular, evaluating oxygen uptake during short time-intervals (0.5 min) provides information about adequate adaptational forces of the cardio-circulatory system. Energy that is not accounted for by reactions involving the VO2 measured is computed by substracting the caloric equivalent of oxygen uptake during work exceeding the steady-state level during rest from the energy demand to sustain a given work load aerobically. This index of anaerobic power is defined in kcal, cal/kg body wt., and as a percentage of the total amount of energy required (moderately trained athletes 350-500 cal/kg; sedentary people 200-300 cal/kg). A close relationship to parameters of metabolic acidosis (base excess) exists. It is concluded that the physical performance of sedentary people, athletes and patients with impaired cardio-pulmonary function can be more precisely qualified in quantitative terms by means of computer assisted rectangular-triangular ergospirometry. Results obtained in patients with diseased conditions must be carefully interpreted, their condition suggesting the use of more invasive investigations to reveal the pathophysiologic mechanism.

Maximum treadmill exercise electrocardiography in female patients

Exercise testing has become standardized for the diagnostic and functional evaluation of male patients but little data is available regarding its specificity and sensitivity in the female. Therefore, maximum treadmill exercise (Bruce protocol) was performed on 98 consecutive females and compared to coronary arteriography. Using 50% obstruction as indicating coronary artery disease and 1 mm ST-segment depression (horizontal or downsloping) as positive for ischemia, 24 patients had coronary artery disease with seven false-negative results (sensitivity = 71%) and 74 patients had no coronary artery disease with 16 false-positive responses (specificity = 78%).

Five of seven false-negative tests were in patients with single-vessel disease. Eleven of 16 false-positive responses were in patients on digitalis, diazepam, or methyldopa. In 39 patients on no drug therapy except for nitroglycerin there were no false negatives and only four false-positive tests. There were no false negatives and only two false-positive tests in 34 patients with normal resting electrocardiograms. Only one of 18 patients with both normal resting electrocardiograms and on no drug therapy had a false-positive test result. Eleven false-positive and seven false-negative results occurred in 40 patients with both an abnormal resting electrocardiogram and associated drug therapy.

The exercise electrocardiographic response in female patients is similar to the male when patients with resting electrocardiographic abnormalities and concomitant drug therapy are eliminated.