Variations in normal electrocardiographic response to treadmill testing

Changes in the electrocardiographic response to exercise in healthy women

Changes in the P wave, QRS complex, ST segment, and T wave during and after maximal exercise were quantitatively analysed in 116 healthy women with a mean age of 39. The corrected orthogonal Frank lead electrocardiogram was continuously recorded and computer processed during bicycle ergometry. With exercise, maximal spatial P wave vectors shifted downward. The Q wave amplitude became more negative and the R wave amplitude diminished considerably in leads X and Y: the S wave amplitude decreased only slightly in these leads. The QRS vectors shifted towards right and posteriorly during exertion and a further shift in the same direction was seen in the recovery period. The ST segment amplitude 60 ms after the J point decreased with exertion and became negative at heart rates above 140 beats per minute, in particular in lead Y. ST segment depression increased with age. The T wave amplitude decreased during exercise and increased sharply in the recovery period. Though mean R wave amplitude in leads X and Y became more negative with exercise, this response was unpredictable in individual women. The exercise induced changes in QRS vectors in women resembled those described in men. Changes in the amplitude of the R wave should not be used for the diagnosis of coronary disease in women. ST segment depression was more pronounced in the inferiorly oriented lead Y than in lead X but it was unrelated to changes in the QRS vectors in these leads.

The role of esophageal leads in the detection of exercise-induced postero-basal ischemia

The effects of maximal hyperventilation and submaximal exercise were studied on the unipolar, esophageal electrocardiogram recorded at ventricular level in 25 'normal' persons and 15 patients having ischemic heart disease with a positive exercise stress test. In normal persons, hyperventilation decreased the amplitude of the R and T waves in 10 and 6 cases, respectively. Submaximal exercise increased the height of the P wave in 8 cases, decreased the amplitude of the R wave in 16 cases and increased the depth of the S wave in 10 cases. In patients with established ischemic heart disease, the esophageal lead could detect exercise-induced posterior ischemia in 8 cases when compared to lead V8, which could detect posterior ischemia in only 3 cases. It is inferred that the esophageal lead placed at the ventricular level is much more sensitive in detecting exercise-induced posterobasal ischemia. Lack of facilities for coronary angiographic and exercise thallium scintigraphic studies limited us from correlating this study and thereby establishing its independent usefulness.

ST-segment fluctuation during treadmill exercise in patients with angina pectoris

The level of the ST-segment fluctuates transiently during treadmill exercise in some patients with angina pectoris. In the present study, the incidence and clinical significance of ST-segment fluctuation were studied before and after propranolol in 52 patients with angina pectoris. A transient greater than 0.5-mm (0.05 mV) upward shift of the ST-segment during a graded treadmill test was considered a significant fluctuation in leads without signs of previous myocardial infarction. The fluctuation was observed in three of 30 patients with rest or rest and effort angina pectoris before propranolol and in 14 of them after propranolol, while only one of 22 patients with effort angina alone showed fluctuation after the drug. Coronary arteriography revealed that in 15 patients showing ST-segment fluctuation with propranolol, seven patients had no significant coronary stenosis, six had one-vessel disease and two had two-vessel disease. In 24 patients with documented coronary artery spasm, ST-segment fluctuation was induced in two (8%) before propranolol and in 13 (54%) after propranolol. Our results suggest that ST-segment fluctuation during graded treadmill exercise may be related to transient coronary vasospasms exacerbated by propranolol.

Discriminant value of clinical and exercise variables in detecting significant coronary artery disease in asymptomatic men

To determine whether clinical or exercise test variables could reliably detect coronary disease in asymptomatic men, several variables were compared with angiographic findings in 225 asymptomatic men. None of the individual clinical or rest electrocardiographic variables were able to detect coronary artery disease. The three individual exercise variables with a high likelihood ratio were: 1) at least 0.3 mV ST depression, 2) persistence of ST depression 6 minutes after exercise, and 3) total duration of exercise of less than 10 minutes. However, because of low sensitivity and predictive value, these single variables were not helpful in identifying individual patients with coronary disease. The combination of any single clinical risk factor and any two of these exercise risk predictors was highly predictive (89%) but relatively insensitive (37%) for detecting any coronary disease. These criteria have a sensitivity of 55% and a predictive value of 84% for the detection of two and three vessel coronary disease. The effectiveness of exercise testing for detecting asymptomatic coronary disease is improved when the group is first screened for the presence of risk factors and additional exercise variables other than ST segment criteria are evaluated.

Limitation of exercise-induced R wave amplitude changes in detecting coronary artery disease in asymptomatic men

The exercise electrocardiograms of 255 asymptomatic men were analyzed for changes in R wave amplitude and ST segments. The results were correlated with findings at cardiac catheterization. There were 65 men with coronary artery disease and 190 normal subjects. R wave amplitude changes were evaluated in bipolar leads X, Y and Z. The predictive value of an abnormal ST segment response for detecting disease was only 29%. This value was improved to 42% using R wave amplitude changes with a sensitivity of 28% and specificity of 87%. Exercise-induced R wave amplitude changes enhance the specificity of detecting coronary disease in asymptomatic men over ST segment criteria alone but the sensitivity is poor and the predictive value is not enhanced. Thus, these criteria are limited in adding to the diagnostic accuracy of stress testing.

Influence of heart rate on exercise-induced R-wave amplitude changes in coronary patients and normal subjects

In order to study whether different heart rates achieved at peak exercise by normal subjects and patients with coronary artery disease (CAD) affect the results of analysis of R-wave amplitude changes (delta R), we evaluated delta R at progressively increasing heart rate (HR) steps in 60 normal subjects with negative exercise tests (ET), in 130 patients with CAD, in 88 patients with true positive and 42 with false negative ET, and in 43 patients with no CAD and false positive ET. We found that the sensitivity and specificity of delta R were HR dependent, the former decreasing and the latter increasing with progressively increasing HR steps. Mean values of delta R did not discriminate among the four groups for HRs up to 150 bpm; significant differences were found between normal subjects and CAD patients, both with true positive and false negative stress tests, at HR greater than 150 bpm. False positive patients had mean delta R similar to those found in normal subjects. We hypothesize that quantitative delta R analysis could be useful in ECG diagnosis of false negative and false positive patients at HR greater than 150 bpm.