Paul S. Greenberg

Significance of Changes in R Wave Amplitude During Treadmill Stress Testing: Angiographic Correlation

Coronary angiograms and treadmill stress tests were reviewed in 89 patients. Changes in R wave amplitude were measured in the control and immediate postexercise periods. Of 45 patients with normal coronary arteries, 41 (91 percent) had a decrease in R wave amplitude (P less than 0.01); 3 (7 percent) had an increase in amplitude, including 2 with abnormal left ventriculograms. The remaining patient (2 percent) had abnormal wall motion but no change in R wave amplitude. Among the 44 patients with significant coronary artery disease (70 percent or greater luminal narrowing in one or more vessels), R wave amplitude increased after exercise in 26 (59 percent) with more severe coronary artery disease. R wave amplitude decreased in 18 patients (41 percent) with normal or minimally abnormal resting ventriculograms and less severe coronary artery disease (P less than 0.01). Changes in R wave amplitude reflect ventricular function, an increase in R wave amplitude reflecting more severe dysfunction and severe coronary narrowing. A decreased R wave amplitude indicates normal or minimal dysfunction and is strongly associated with normal coronary angiograms.

Comparison of S-T segment changes on exercise testing with angiographic findings in patients with prior myocardial infarction☆

Ninety-seven patients with a prior transmural myocardial infarction who underwent coronary angiography and treadmill stress testing were studied retrospectively to assess the reliability of the exercise electrocardiogram in detecting additional disease in patients with a prior infarction. In patients with a previous inferior wall infarction, the S-T response to the treadmill stress test had a high degree of sensitivity (87 percent) and specificity (90 percent) in detecting additional significant coronary artery disease. However, in patients with a previous anteroseptal wall infarction, the S-T response had much less sensitivity (52 percent), but the degree of specificity remained high (90 percent). In this group a positive test suggested the presence of ischemia in the lateral or inferoposterior region of the myocardium, or both. A negative S-T response was of little value in distinguishing among groups of patients with single or multiple vessel coronary artery disease. The presence of an anterior ventricular aneurysm is most likely responsible for this low sensitivity rate because it generates an opposing force to the ischemic vector, thereby cancelling the S-T segment changes and producing a false negative treadmill stress test. The resting surface electrocardiogram proved useful in predicting a false negative exercise test. The presence of Q waves in the precordial leads extending to lead V4 or beyond decreased the sensitivity rate of treadmill stress testing to 33 percent.

Stress testing: Clinical application and predictive capacity

T HIS article presents a conceptual review of the “state of the art” as pertains to the clinical application of exercise stress testing. We will provide data insofar as possible on the physiologic basis for the findings now utilized in the day-to-day application of this important diagnostic tool. It is of interest that a number of exercise tests designed to evaluate aerobic capacity were popular in the 1920s and 193Os, during which the heart rate and blood pressure were carefully recorded and compared to the normal response. After a number of workers demonstrated that ST segment changes correlated with ischemia, Master’ and those who followed his lead abandoned their interest in the total cardiovascular response to exercise and focused on the ischemic ST segment to the exclusion of all else. Only in the late 1950s following the lead of Bruce,’ were efforts again made to use the stress test as an attempt to evaluate as many exercise parameters as possible in order to derive an overall evaluation of the patient’s function. This treatise will emphasize this approach. It is our contention that the tendency to concentrate on ST changes to the exclusion of many other parameters now known to be of importance in the evaluation of patients during an exercise test should be abandoned. Many of the articles deprecating the value of exercise testing were written by authors with this type of tunnel vision.3 Much of the voluminous cardiovascular literature of the past few decades has been oriented towards assessment of cardiac function. Most of the early studies, though well conceived and well executed, involved making correlations and observations with the subjects at rest. It became obvious that such studies were insufficient in many instances, since the hemodynamics of exercise alter many parameters quite drastically. Consequently, observations made during rest were discovered to be not necessarily applicable during periods of physical activity. Despite certain limitations, exercise stress testing has become an invaluable tool for diagnosing the presence as well as extent of coronary artery disease. Although only electrocardiographic abberations have been extensively used in the past, it has become apparent that assessment of hemodynamic and symptomatic data may be equally as useful. The currently accepted indications and contraindications for stress testing are presented in Tables 1 and 2, respectively.

Septal Q wave in exercise testing: Angiographic correlation

A study of septal Q wave response in lead CM5 was carried out to evaluate its usefulness in predicting coronary artery disease. Q wave amplitude was measured in 50 patients with coronary artery disease and 50 normal subjects before and immediately after exercise. In the 100 patients evaluated with coronary angiography, the septal Q wave in lead, CM5 was smaller in patients with coronary artery disease than in normal subjects at rest (probability [p] less than 0.001) and immediately after exercise (p less than 0.001). An embryonic (0.5 mm) or absent Q wave in lead CM5 was significantly more frequent in patients with coronary artery disease than in normal subjects both at rest (76 versus 48 percent) and after exercise (82 versus 16 percent). The sensitivity for S-T depression was 52 percent, the specificity 74 percent and the predictive value 70 percent. The respective values for Q wave were 82, 88 and 87 percent. These differences were not significant (p less than 0.05). When either a positive S-T or Q wave response was used, the sensitivity increased to 92 percent (p less than 0.05), and the specificity and predictive values remained unchanged (p less than 0.01). An increase in Q wave amplitude with exercise identified a false positive S-T segment response to stress in 75 percent of cases. Absence of the Q wave in lead CM5 with S-T depression after identified a true positive response in 100 percent of cases. These findings suggest that low Q wave voltage and it failure to increase after exercise imply abnormal septal activation, reflecting loss of contraction associated with ischemia. This finding may be a useful marker for ischemia; the increase in the septal Q wave with exercise may be of value in identifying a false positive S-T segment response.

Permanent pacemaker implantation using the femoral vein: a preliminary report.

A permanent pacemaker was implanted through the femoral vein in 23 patients using the percutaneous puncture technique. The pulse generator was placed in the lower abdominal wall. The method is simple and reduces (he time necessary to accomplish implantation. Catheter extrusion in one patient was easily corrected. Another patient had late thrombophlebitis, possibly unrelated to the procedure. Catheter dislodgement occurred in four (4) patients and penetration of the right atrial appendage and right ventricular apex each occurred once. We believe these problems can be circumvented with more experience and expect the femoral approach to be a simple and practical method of permanent pacemaker implantation.

Comparison of the multivariate analysis and CADENZA systems for determination of the probability of coronary artery disease

The accuracy of 2 discriminate systems for diagnosis of coronary artery disease (CAD), multivariate analysis (MVA) and Bayesian analysis (CADENZA), was evaluated in 113 patients undergoing electrocardiographic stress testing and coronary angiography. MVA uses weighting factors (F values) generated from our patient data, whereas CADENZA uses probabilities gleaned from an extensive review of the American literature. Overall accuracy was similar. MVA had a higher sensitivity for 1-vessel CAD (75 versus 33%), but CADENZA was better for determining the severity of CAD. The 2 systems provided posterior probabilities for disease that were highly correlated (r = 0.56; p less than 0.001). Both systems suggest the need for further testing based on the probability generated; herein lies their major strength. The application of such systems should help the clinician reach a diagnosis or make a decision as to management in a cost-effective manner.

Predictive accuracy of Q-XQ-T ratio, Q-Tc interval, S-T depression and R wave amplitude during stress testing

Abstract The sensitivity, specificity and predictive value for Q-X Q-T ratio, Q-Tc interval, S-T segment depression, R wave change and various combinations of these criteria were compared in 50 healthy, normal persons and 50 persons with angiographic coronary artery disease defined as 70 percent or greater stenosis of one or more major coronary vessels. Use of a positive S-T segment response and an increase or no change in R wave amplitude as criteria for coronary artery disease resulted in 84 percent sensitivity and 96 percent specificity levels and a 95 percent predictive value. The Q-X Q-T and Q-Tc criteria offered no improvement in sensitivity, specificity or predictive value over S-T segment depression. When the study group was limited to 74 persons, 36 without and 38 with angiographically significant coronary artery disease, a Q-Tc interval of 1.08 or more in combination with either slowly or rapidly upsloping S-T depression after exercise predicted coronary disease at a sensitivity level of 76 percent compared with 50 percent with use of the S-T segment alone (P 0.05). Use of the R wave response with the presence of upsloping S-T segment depression of 1.5 mm or more 80 msec from the J point improved the sensitivity level from 50 percent for S-T depression alone to 76 percent (P 0.05]). The Q-X Q-T ratio could be measured in only 55 patients (74 percent) and offered no improvement over S-T segment depression. Upsloping S-T segment depression of 1.5 mm or more 80 msec from the J point in the immediate postexercise period is most likely a positive test for ischemia. An increase or no change in R wave amplitude in response to exercise in these patients regardless of the degree of S-T segment depression is probably indicative of coronary artery disease. In patients with upsloping S-T segment depression, a Q-Tc interval of 1.08 or more in the immediate postexercise period is a useful measurement in predicting coronary artery disease.

Predicting Coronary Artery Disease with Treadmill Stress Testing: Changes in R-Wave Amplitude Compared with ST Segment Depression

Coronary angiograms and treadmill stress tests were reviewed independently in 108 nonconsecutively selected cases. There were 16 patients (15%) with infarcts on ECG. Changes in R-wave amplitude and ST segments during exercise were evaluated to determine the sensitivity and specificity of each as a predictor of coronary artery disease (CAD). ST segment changes had a sensitivity of 49%, and a specificity of 74%. The sensitivity increased to 55% when infarcts were excluded. R-wave amplitude changes had a sensitivity of 68% and a specificity of 84%. The sensitivity increased to 78% when infarcts were excluded. An index formed by the sum of the change in R-wave amplitude and the magnitude of ST segment change yielded a sensitivity of 76% and specificity of 78%. The sensitivity increased to 84% when infarcts were excluded. There was no statistical difference between specificities for each criteria. Of those patients with an R-wave amplitude decrease, 69% had no coronary artery atherosclerosis, while 31% had significant lesions. Of those patients with no change or an increase in R-wave amplitude, 83% had coronary artery atherosclerosis, while 17% were normal. Of the 83% with coronary artery atherosclerosis, 81% had two and three vessel disease, while only 19% had single vessel disease. No change or an increase in R-wave amplitude during treadmill stress testing is a more reliable indicator of CAD in our laboratory than ST segment changes.

Prospective application of the multivariate approach toenhance the accuracy of the treadmill stress test

Thirty normal subjects and 84 patients with coronary artery disease were subjected to stress testing and the results assessed by multivariate analysis. Probabilities for the presence or absence of disease were determined based on the results of a previous retrospective study. The multivariate analysis approach significantly improved the sensitivity, from 73% to 88%, and correct classification rate, from 78% to 88%, when compared to the ST response (P less than 0.05). The specificity remained significantly unchanged at 93% and 87% respectively in comparison to the ST response. The predictive value of a positive and negative test were not significantly different from those values from the ST response. Although the probability of disease could separate normal from diseased subjects, it could not separate single vessel from multi-vessel disease. The correct classification rate remained the same for all probabilities greater than or equal to 50% suggesting that a higher probability was not more accurate in detecting disease. The multivariate approach did not improve the accuracy of the stress test over the ST response in women, but the females in this study were a small and highly select group. Multivariate analysis appears to be a valuable method in detecting disease and appears to improve diagnostic accuracy over the ST response alone. However, further studies are needed to determine the final role of such a system, particularly in female subjects.

Ability of the R-Wave Change During Stress Testing to Accurately Detect Coronary Disease in the Presence of Left Bundle Branch Block at Rest

The treadmill stress test and antiographic records of 18 patients with left bundle block on resting ECG were reviewed retrospectively. Thirteen of the patients had significant coronary artery disease defined as greater than or equal to 70% cross-sectional narrowing of one or more vessels, while 5 patients were hemodynamically and angiographically normal. The R-wave and ST-segment response to exercise were determined in each case and compared. A positive R-wave response was an exercise-induced increase or no change in amplitude over the baseline level, while a positive ST-segment response was greater than or equal to 2 mm of excerise-induced depression over the baseline level. The sensitivity for the R-wave response was 69% (9 of 13), the specificity was 100% (5 of 5), and the predictive value was 100% (9 of 9). For ST depression these values were 46% (6 of 13), 40% (2 of 5)8 and 67% (6 of 9). Although the number of patients in this study is small--a reflection of the fact that ST depression in the presence of left bundle branch block with exercise is associated with many false positive responses and hence less referral for stress testing--it appears that the R-wave response to exercise in the presence of left bundle branch block can accurately detect coronary artery disease.