The electrocardiographic response to maximal treadmill exercise of asymptomatic men with right bundle branch block

Overview of exercise stress testing

Exercise stress testing is a non-invasive, safe and affordable screening test for coronary artery disease (CAD), provided there is careful patient selection for better predictive value. Patients at moderate risk for CAD are best served with this kind of screening, with the exception of females during their reproductive period, when a high incidence of false positive results has been reported. Patients with a high pretest probability for CAD should undergo stress testing combined with cardiac imaging or cardiac catheterization directly. Data from the test, other than ECG changes, should be taken into consideration when interpreting the exercise stress test since it has a strong prognostic value, i.e. workload, heart rate rise and recovery and blood pressure changes. Only a low-level exercise stress test can be performed early post myocardial infarction (first week), and a full exercise test should be delayed 4 to 6 weeks post uncomplicated myocardial infarction. The ECG interpretation with myocardial perfusion imaging follows the same criteria, but the sensitivity is much lower and the specificity is high enough to overrule the imaging part.

Diagnostic value of exercise electrocardiography and dipyridamole stress echocardiography in hypertensive and normotensive chest pain patients with right bundle branch block

OBJECTIVES

Studies on the diagnostic value of exercise electrocardiography in right bundle branch block produced controversial results, and data on the accuracy of stress echo are still lacking. The aim of the study was to compare the diagnostic value of exercise electrocardiography and dipyridamole stress echo in chest pain patients with right bundle branch block, and to verify whether stress testing accuracy is affected by history of hypertension.

METHODS

The study group was made up of 71 patients (56 men, aged 63 +/- 8 years) with chest pain of unknown origin and complete right bundle branch block. Of them, 35 were hypertensives and 36 normotensives. Patients performed, on different days and in random order, exercise electrocardiography and dipyridamole stress echo and underwent coronary angiography.

RESULTS

Significant (> or = 70% diameter stenosis) coronary artery disease was found in 34 patients (17 hypertensives and 17 normotensives). Positive exercise electrocardiography (ST-segment shift > 1 mm at 80 ms after the J point in leads V5 and V6 or leads II and Vf) and dipyridamole stress echo (new wall motion abnormalities) were observed in 38 and 30 patients, respectively. The result of tests was concordant in 69% of hypertensives and 92% of normotensives. The two tests shared the same sensitivity in hypertensives (82%) and normotensives (71%). Of 37 patients without coronary artery disease, 12 had a false-positive result during exercise electrocardiography and four during stress echo. The specificity was lower for exercise electrocardiography than for stress echo in hypertensives (50 versus 89%, P = 0.0006), while no difference was evidenced in normotensives (84 versus 89%, P = 0.4). In hypertensives, the accuracy, positive, and negative predictive values were 66, 61, and 75% for exercise electrocardiography, and 86, 87, and 84% for stress echo. Corresponding figures in normotensives were 78, 80, and 76% for exercise electrocardiography, and 81, 86, and 77% for stress echo.

CONCLUSIONS

In chest-pain patients with right bundle branch block, dipyridamole stress echo was effective to diagnose coronary artery disease in both normotensives and hypertensives. Moreover, it exhibited superior diagnostic information than exercise electrocardiography in hypertensives, due to significantly higher specificity. However, the two tests had similar diagnostic value in normotensives.

Some common abnormal responses to exercise testing: what to do when you see them

This article reviews the role of exercise testing in the assessment of patients with suspected coronary disease. To accomplish this, four major topics are considered: the general concept of risk stratification; the estimation of outcomes using data from the initial evaluation of the patient; diagnostic assessment with the exercise test; and prognostic assessment with the exercise test. This review focuses on the standard treadmill exercise test.

Diagnostic and prognostic accuracy of the exercise electrocardiogram in patients with preexisting right bundle branch block

The value of exercise testing in patients with right bundle branch block (RBBB) is uncertain. A retrospective review of 3609 patients who underwent exercise testing identified 163 (4.5%) with preexisting RBBB. After excluding those with coronary artery bypass graft(s), 133 patients remained and 48 (36%) had a prior myocardial infarction. Angiograms were available for 30 (23%) patients. After a mean follow-up of 33 +/- 23 months, seven patients had a fatal or nonfatal myocardial infarction. Twenty five (19%) patients had > or = 1 mm of non-upsloping ST depression in leads V5 or V6. With angiographic disease or previous myocardial infarction used as endpoints of coronary artery disease, the exercise test had a sensitivity of 27% (15/56), a specificity of 87% (67/77), and a predictive accuracy of 62% (82/133), (chi 2 = 4.04, p = 0.04). There were 24 deaths, a 10% annual mortality rate. Univariate analysis of clinical, exercise, and angiographic data revealed that nonsurvivors had a lower peak systolic blood pressure, a lower exercise capacity in METS, and a higher prevalence of coronary artery disease (p = 0.0001, p = 0.02, p = 0.03, respectively). Left ventricular ejection fraction and the amount of additional ST depression during exercise did not differ significantly (p = NS). Receiver operating characteristic curve analysis revealed that systolic blood pressure (area = 0.741, z = 5.22, p < 0.001) and exercise capacity (area = 0.66, z = 3.12, p = 0.009) were predictive of mortality, whereas additional ST depression during exercise (area = 0.588, z = 0.70, p = 0.24) was not.(ABSTRACT TRUNCATED AT 250 WORDS)

Optimal interpretation of the supine exercise electrocardiogram in patients with right bundle branch block

A detailed analysis of the exercise ECG was performed in 82 patients with right bundle branch block who underwent supine exercise equilibrium radionuclide angiography. The sensitivity and specificity of each individual electrocardiographic lead for the detection of a positive radionuclide angiogram was determined. Leads V5 and V6 had a sensitivity of 58 percent and a specificity of 89 percent. The limb leads and lead V4 had a lower sensitivity, but an equivalent specificity. Leads V1 and V3 each had a clearly lower specificity that ranged from 56 to 67 percent. Receiver operating characteristic curve analysis demonstrated that the optimal interpretation of the exercise ECG included the limb leads and V4 to V6, but not V1 to V3. The results of coronary angiography in the subset of 16 patients who underwent this procedure confirmed these findings.

Exercise-induced ST segment depression in the diagnosis of multivessel coronary disease: a meta analysis

To evaluate the variability in the reported accuracy of the exercise electrocardiogram (ECG) for predicting severe coronary disease, meta analysis was applied to 60 consecutively published reports comparing exercise-induced ST depression with coronary angiographic findings. The 60 reports included 62 distinct study groups comprising 12,030 patients who underwent both tests. Both technical and methodologic factors were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity 81% [range 40% to 100%, SD 12%]; mean specificity 66% [range 17% to 100%, SD 16%]). All three variables found to be significantly and independently related to sensitivity were methodologic (the exclusion of patients with right bundle branch block, the comparison with another exercise test thought to be superior in accuracy and the exclusion of patients taking digitalis). Exclusion of patients with right bundle branch block and comparison with a "better" exercise test were both significantly associated with sensitivity for the prediction of triple vessel or left main coronary artery disease. Adjustment of exercise-induced ECG changes for changes in heart rate was strongly associated with the specificity for critical disease (partial R2 = 0.436, p = 0.0001).

Ischemia-associated intraventricular conduction disturbances during exercise testing as a predictor of proximal left anterior descending coronary artery disease

To determine the incidence and significance of transient intraventricular conduction abnormalities occurring in association with myocardial ischemia during exercise testing, the recordings of 2,200 consecutive exercise tests were reviewed. Ten patients (0.45%) were identified as having both ischemia and intraventricular conduction abnormalities that developed transiently during the exercise test. In all 10 patients both typical angina and electrocardiographic evidence of ischemia developed during exercise. Among the 10 patients, left anterior hemiblock developed in 4, left posterior hemiblock in 2, right bundle branch block (RBBB) in 2, RBBB with left axis deviation in 1, and left anterior hemiblock progressing to complete left bundle branch block (LBBB) in 1. All 10 patients had cardiac catheterization showing significant obstruction of the left anterior descending (LAD) coronary artery at or before the origin of the first septal branch. Eight patients were treated surgically and 2 medically, all with relief of ischemic symptoms. Nine of the 10 had repeat exercise stress testing without angina or electrocardiographic evidence of ischemia and without recurrence of the transient intraventricular conduction disturbance. It is concluded that the development of transient intraventricular conduction abnormalities associated with myocardial ischemia during exercise testing is an uncommon occurrence (0.45%). When such conduction disturbances do develop, the existence of significant disease in the proximal portion of the LAD coronary artery is strongly suggested. With control of myocardial ischemia, the transient conduction disturbances during exercise are ameliorated.

Right bundle branch block: long-term prognosis in apparently healthy men

The long-term cardiac prognosis of 24 clinically healthy men with complete right bundle branch block, identified from the 1,142 men constituting the population of the Baltimore Longitudinal Study on Aging, was assessed over a follow-up period averaging 8.4 years. When compared with a control group matched for age at which right bundle branch block appeared (mean +/- standard deviation 64.0 +/- 13.5 years), men with right bundle branch block showed no difference in the prevalence of antecedent coronary risk factors or obstructive lung disease. The incidence of angina pectoris, myocardial infarction, valvular heart disease, cardiomegaly, congestive heart failure, advanced heart block or cardiac death in these men did not differ from that of the control group over the observation period. Furthermore, at the latest follow-up study, maximal aerobic exercise tolerance and chronotropic response to maximal exercise were not impaired in men with right bundle branch block relative to control men (9.1 +/- 2.2 versus 7.3 +/- 3.0 minutes and 150.3 +/- 23.5 versus 147.7 +/- 20.7 beats/minute, respectively). However, axis deviation leftward of -30 degrees was present in 46% of men with right bundle branch block but in only 15% of control subjects at latest follow-up (probability [p] less than 0.01). Although the PR interval lengthened by 40 ms or more developed in only 6% of control subjects over the observation period, such prolongation occurred in 29% of men with right bundle branch block (p less than 0.05). These results support the concept that right bundle branch block in these asymptomatic men is a manifestation of a primary abnormality of the cardiac conduction system but has no demonstrable adverse effect on long-term cardiac morbidity or mortality.

Rest and exercise electrocardiograms and radionuclides in patients presenting for cardiac rehabilitation

The rest and exercise ECG, 201thallium myocardial scintigram (201T1), and radionuclide ventriculography are noninvasive procedures which can be used to evaluate myocardial damage and ischemia. To compare these procedures and to obtain baseline information, 85 male patients with coronary heart disease were evaluated prior to beginning an exercise program. Findings at rest included Q waves or bundle branch block in 54%; 47% had 201T1 redistribution defects and 33% an abnormal ejection fraction (EF). Of the 39 patients with normal ECGs, 31 had no 201T1 defects and only of these 31 (3%) had an abnormal EF. Abnormal EF or 201T1 redistribution defects did not occur in patients without a history of myocardial infarction. Abnormal resting EF occurred in 63% of patients with abnormal versus 7% of those with normal 201T1 redistribution scans. Exercise test results included an abnormal ST-segment response in 80%, an abnormal EF response in 65%, and a 201T1 ischemic defect in 37%. Twenty patients had exercise-induced ST elevation, and this phenomenon was more related to ventricular aneurysms than to ischemia. 201Thallium imaging, radionuclide ventriculography, and the ECG provide results regarding myocardial damage that agree by more than chance, while the exercise induced ST-segment changes did not agree with the radionuclide indications of exercise-induced ischemia.

Value of treadmill exercise testing in patients with complete bundle branch block

Exercise electrocardiography and selective coronary arteriography was performed in 24 consecutive patients with complete bundle branch block. The criteria for a positive exercise electrocardiogram (E-ECG) were a 1 mm depression or elevation in the J point from the control state, as well as in the ST-segment measured at 0.04 seconds from the J point. Eleven of 12 patients with complete left bundle branch block had a positive E-ECG. Nine of them had normal coronary arteriograms, except one with less than 50% lesions in two arteries. Two patients had severe three-vessel disease. Only one patient had a true negative exercise test. No patient had a false negative test. Nine of 12 patients with complete right bundle branch block had a positive E-ECG. One of these 9 had minimal nonobstructive disease, while the other 8 had severe two- or three-vessel coronary artery disease. Three of the 12 right bundle branch block patients had a negative E-ECG. Two of them had a true negative exercise test, and one a false negative test. Because of a high incidence of probably false positive results, E-ECG appears to be unreliable in detecting coronary artery disease in patients with complete left bundle branch block. But it can provide useful information in the noninvasive evaluation of coronary artery disease in patients with complete right bundle branch block.

Exercise testing for detection of myocardial ischemia in patients with abnormal electrocardiograms at rest

This review consists of two parts: (1) discussion of the electrophysiologic mechanisms that are believed to produce ventricular repolarization changes during the electrocardiographic stress test, and (2) clinical assessment of the electrocardiographic changes with stress in patients with an abnormal electrocardiogram at rest. In the first part, the mechanisms of S-T segment elevation, S-T segment depression, T wave changes and linked S-T and T wave changes are reviewed. In the second part, all electrocardiographic abnormalities at rest are grouped into four categories: (1) changes that mask the manifestations of ischemia, (2) changes that stimulate or exaggerate the manifestations of ischemia, (3) changes that have no important effect on the manifestations of ischemia, and (4) changes that reproduce the patterns of acute myocardial infarction after an apparent healing. The reported studies of electrocardiographic stress testing in patients who have abnormal electrocardiogram at rest are summarized.

The electrocardiographic response to maximal treadmill exercise of asymptomatic men with left bundle branch block

This study presents the results of maximal treadmill testing and coronary angiography in 31 asymptomatic USAF aircrewmen with acquired left bundle branch block. There were two subgroups: 26 men with normal coronary angiography and five men with significant angiographic coronary angiography and five men with significant angiographic coronary artery disease. The mean amount of maximal ST-segment depression induced by treadmill exercise was --0.5 mv. for both groups and the range in the normal subgroup was --0.3 to --1.0 mv. No significant differences were found between the groups. We concluded that apparently healthy, asymptomatic men with acquired left bundle branch block can have considerable ST-segment depression in response to maximal treadmill testing and that their ST-segment response cannot be used to make diagnostic decisions about them.