Analysis of exercise-induced changes in R wave amplitude in asymptomatic men with electrocardiographic ST-T changes at rest

Fifty asymptomatic men, 44 (88 percent) of whom were pilots or allied aviation personnel, were referred because of resting ST-T electrocardiographic changes indistinguishable from those of myocardial ischemia. Because of the nature of their occupations, cardiac catheterization was performed to establish the presence or absence of coronary artery disease. Exercise tests were performed and analyzed retrospectively with respect to exercise-induced changes in the S-T segment and R wave amplitude. The results were correlated with coronary angiographic and echocardiographic findings.The 50 subjects were classified into two groups: Group I, 5 men with angiographically proved coronary artery disease, and Group II, 45 men without significant coronary arterial obstruction. Analysis of the S-T segment changes at peak exercise showed 21 subjects (42 percent) with a positive exercise test and 29 (58 percent) with a negative test. All subjects in Group I had a positive test. Sixteen subjects (35 percent) in Group II had a false positive result. Analysis of exercise-induced changes in R wave amplitude revealed that six subjects had a positive R wave response on the basis of sum of the changes in voltage in the leads measured (Δ∑R). Four of the six subjects had coronary artery disease and the other two were thought to have a cardiomyopathy. One subject with coronary artery disease had a negative R wave response. Echocardiography revealed five subjects with asymmetric septal hypertrophy; two of these had a positive exercise test and three a negative test on the basis of S-T segment criteria.Thus, symptom-limited treadmill exercise testing of asymptomatic men with resting ST-T electrocardiographic changes produced a high incidence rate of false positive results when S-T segment criteria were used, whereas analysis of changes in R wave amplitude yielded only two false positive results, both in men who had evidence of other heart disease.     

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.     

Is the treadmill exercise test useful for evaluating coronary artery disease in patients with complete left bundle branch block?

To aid in the study of coronary artery disease, 57 patients with complete left bundle branch block underwent clinical evaluation, treadmill exercise testing and cardiac catheterization. The patients were classified into two groups according to coronary anglographic findings: 30 patients with significant stenosis (70 percent or greater luminal narrowing) of at least one major vessel and 27 with no significant coronary artery disease. There was no difference in age, presenting symptoms or previous medical treatment between the two groups. There were more men in the group with coronary artery disease. Exercise-induced S-T changes were similar in the two groups; the sensitivity and specificity of these changes for the diagnosis of coronary artery disease were unacceptable irrespective of the criterion chosen. With additional S-T depression of either 1 or 2 mm below the baseline value, the predictive accuracy was only 53 percent. Combined exertional chest pain and 1 mm S-T depression increased the predictive accuracy of exercise testing to 71 percent. These data indicate that exercise-induced electrocardiographic changes do not facilitate detection of coronary artery disease in patients with complete left bundle branch block.     

Exercise-induced S-wave prolongation in left anterior descending coronary artery stenosis.

Myocardial ischemia may decrease conduction velocity and produce QRS prolongation in the surface electrocardiogram. In cases with normal intraventricular conduction, areas of the myocardium contributing to the development of the S wave receive blood from all 3 major coronary arteries, whereas in left anterior hemiblock or right bundle branch block, most of the blood supply to the areas of the myocardium contributing to the development of the S wave is from the left anterior descending (LAD) coronary artery. To test the hypothesis that the S wave will be prolonged with exercise only in patients with LAD coronary artery stenosis and left anterior hemiblock or right bundle branch block, 88 patients with normal intraventricular conduction, 66 with left anterior hemiblock and 36 with right bundle branch block were studied. Sixty-four, 32 and 21 patients had LAD, right and left circumflex coronary artery stenoses, respectively. In patients with normal coronary arteries, S-wave duration decreased with exercise regardless of the status of ventricular conduction. In patients with coronary artery disease and normal intraventricular conduction, the S wave was prolonged slightly with exercise, but in those with left anterior hemiblock and right bundle branch block, it was prolonged significantly (12.5 +/- 6 and 10.4 ms, respectively) only in those with LAD, but not in those with circumflex or right coronary artery stenosis. S-wave prolongation in patients with LAD coronary artery stenosis and left anterior hemiblock or right bundle branch block most likely is related to exercise-induced ischemia in the areas of the myocardium contributing to the development of the S wave.     

Comparative features of newly acquired left and right bundle branch block in the general population: the Framingham study

Cardiovascular abnormalities were prospectively identified in all 55 persons who acquired left bundle branch block and all 70 persons who acquired right bundle branch block during 18 years of follow-up of the Framingham Study cohort. Those with left and right bundle branch block did not differ from each other in the overall prevalence of either hypertension, clinical coronary disease or diabetes. In men, but not in women, left bundle branch block was associated with a significantly greater prevalence of cardiac enlargement and congestive failure than was right bundle branch block. A trend suggesting a higher mortality rate from cardiovascular disease in those with left than in those with right bundle branch block was more apparent in men than in women. It is concluded that in the general adult population, men who acquire left bundle branch block are more likely to have or subsequently acquire advanced cardiovascular abnormalities than are men who acquire right bundle branch block. In women, however, the clinical correlates of the two conduction abnormalities are similar.     

Diagnostic value of exercise-induced S-T segment depression in patients with right bundle branch block

The sensitivity of submaximal exercise testing in detecting coronary artery disease in patients with right bundle branch block is not known. Thirty patients were identified who had right bundle branch block, submaximal treadmill exercise tests and selective coronary angiography. Eighteen of these patients were found to have significant coronary artery disease. Treadmill exercise testing was associated with S-T segment depression limited to leads V₁ to V₃ in three patients with coronary artery disease, whereas S-T segment depression was noted in leads V₄ to V₆ in eight patients, all of whom had multivessel coronary artery disease. Among patients without significant coronary artery disease, six had S-T segment depression limited to leads V₁ to V₃ during exercise testing.In this patient population, composed predominantly of men with symptoms of ischemic heart disease, the 12 lead submaximal treadmill exercise test had a sensitivity rate of 69 percent and a specificity rate of 45 percent in detecting coronary artery disease in the presence of right bundle branch block. The specificity of the treadmill test appears to be greater if S-T depression is recorded in leads V₄ to V₆. S-T segment depression limited to leads V₁ to V₃ often represents a false positive exercise test.     

Superior QRS axis of ventricular premature complexes: An additional criterion to enhance the sensitivity of exercise stress testing

The presence or frequency of ventricular premature complexes during exercise is not highly predictive for identifying patients with coronary artery disease. To determine whether the morphologic features or axis of exercise-induced ventricular premature complexes may increase this predictability, a study was made of 63 symptomatic patients with coronary artery disease (electrocardiographic evidence of infarction or occlusive lesions seen on coronary angiography, or both) and 10 control patients with normal coronary arteriograms. In 48 of the 63 patients with coronary artery disease the exercise-induced ventricular premature complexes had a superior frontal plane QRS axis between ?30 ° and ?120 °; in 12 the axis was between ?30 ° and +150 °, and in 2 the axis was indeterminate, between +150 ° and ?120 °. In all 10 control subjects without coronary artery disease the QRS axis of the exercise-induced ventricular premature complexes was in the normal range, between ?30 ° and +150 °. If the standard criterion of 1 mm S-T segment depression were used to predict coronary artery disease during exercise stress testing, 25 of the 63 patients with coronary artery disease would have had a normal or borderline exercise test. However, in 21 of these 25 patients the exercise-induced ventricular premature complexes had a superior axis, a criterion that would enhance the predictive sensitivity of the exercise test from 60 to 94 percent. A left bundle branch block pattern of ventricular premature complexes was not helpful in detecting patients with coronary artery disease, although a right bundle branch block pattern was infrequent in the control subjects. The occurrence of ventricular premature complexes with a superior axis during exercise testing can enhance the exercise test's sensitivity for detecting the presence of coronary artery disease, particularly when this criterion is used in patients with a nondiagnostic S-T segment response to exercise.     

Bundle branch block in patients with chronic coronary artery disease: angiographic correlates and prognostic significance

The onset of bundle branch block during acute myocardial infarction is indicative of ischemia in the distribution of the left anterior descending coronary artery. However, whether patients with chronic coronary artery disease and bundle branch block have a predominance of left anterior descending artery lesions is not known. Similarly, the prognostic implications of bundle branch block have been studied primarily in the setting of acute myocardial infarction, and the independent prognostic implications of bundle branch block in patients with chronic coronary artery disease are not known. The electrocardiograms (ECGs) of 15,609 patients with chronic coronary artery disease who underwent coronary and left ventricular angiography as part of the Coronary Artery Surgery Study (CASS) were reviewed, and 522 patients with bundle branch block were identified. Patients with bundle branch block had both more extensive coronary artery disease and worse left ventricular function than did patients without bundle branch block. However, no particular location of coronary artery stenosis or left ventricular wall motion abnormality predominated in patients with bundle branch block. During a follow-up period of 4.9 +/- 1.3 years, 2,386 patients died. Actuarial probability of mortality at 2 years in patients with left bundle branch block was more than five times that in patients without bundle branch block (p less than 0.0001), and in patients with right bundle branch block the mortality rate was approximately twice that in patients without bundle branch block (p less than 0.0001). Stepwise Cox regression analysis showed that left bundle branch block, but not right bundle branch block, was a strong predictor of mortality, independent of degree of heart failure, extent of coronary disease and other variables (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Left ventricular performance during exercise in patients with left bundle branch block: evaluation by gated radionuclide ventriculography

To investigate changes in left ventricular (LV) function during exercise in patients with left bundle branch block (LBBB), 22 patients without a history or physical findings of previous myocardial infarction or LV dysfunction were studied by gated radionuclide ventriculography (GRNV) at rest and during bicycle exercise. Coronary arteriography demonstrated greater than 75% diameter narrowing of at least one coronary artery in nine patients. Of the remaining 13 patients, GRNV demonstrated wall motion abnormalities in seven patients either at rest or with exercise. During exercise, mean ejection fraction (EF) did not increase in patients without coronary artery disease (CAD). Patients with CAD had a 12-point fall in mean EF with exercise. We conclude that LV reserve, as demonstrated by ability to increase EF with exercise, is impaired in patients with LBBB even in the absence of CAD or other underlying cardiac disease and that standard GRNV criteria to exclude the presence of CAD (a greater than five-point increase in EF with exercise and normal wall motion) are not strictly applicable in screening patients with LBBB.     

Diagnostic value of exercise tomoscintigraphy with thallium 201 in patients with complete left branch block

Eighteen patients with rate-dependent (n = 5) or chronic (n = 13) left bundle branch block underwent thallium 201 exercise SPECT and selective coronary arteriography. 15 patients showed significant septal or anteroseptal perfusion defects on the exercise scintigrams, but in only 4 of them did the coronary disease involve the left anterior descending artery (LAD) (n = 3) or the left main coronary artery (n = 1). Among patients with normal scintigrams, one had right coronary artery stenosis. Test performance in detecting individual coronary artery stenosis greater than 70 p. 100 was: sensitivity 80 p. 100 (4/5) and specificity 15 p. 100. In patients with left bundle branch block, T1 201 SPECT was indeterminate for LAD disease due to reversible septal perfusion defect. We conclude that the usefulness of stress thallium 201 SPECT in patients with left bundle branch block is very limited.     

Left bundle branch block: angiographic segmental wall motion abnormalities.

Ventricular wall motion as studied with contrast ventriculography has been judged normal in the few previously reported cases of patients with left bundle branch block who have neither coronary artery disease nor diffuse cardiomyopathy. However, recent echocardiographic studies have demonstrated a high frequency of segmental asynergy of the septal wall in such patients. In this study left ventricular wall motion was analyzed in 15 patients with left bundle branch block and without significant coronary artery disease or diffuse cardiomyopathy. Biplane cineangiograms from these patients were compared with those from 100 consecutive patients with normal intraventricular conduction and without coronary artery disease or cardiomyopathy using two techniques: qualitative visual inspection and a computer-assisted quantitative method. By qualitative review, 6 of 15 patients with left bundle branch block had regional akinesia or dyskinesia as compared with none of 100 patients with normal intraventricular conduction (chi square = 42.3; P less than 0.001). By quantitative review, 10 of 12 patients with left bundle branch block had abnormal wall motion along at least one hemiaxis. It is concluded that angiographic regional wall motion abnormalities are common in patients with left bundle branch block, even in the absence of coronary artery disease or diffuse cardiomyopathy. The abnormalities may result from the abnormal sequence of ventricular activation rather than from myocardial fibrosis.     

Noninvasive myocardial imaging with potassium-43 and rubidium-81 in patients with left bundle branch block

Noninvasive myocardial imaging with potassium-43 and rubidium-81 has been used successfully to identify areas of infarction and exercise-induced ischemia as regions of decreased radioactivity. The image defects observed are believed to be due to a decreased radionuclide uptake in regions of myocardial scar or to heterogeneous myocardial accumulation of tracer as a result of regional ischemia. Of 27 patients with left bundle branch block studied with noninvasive imaging at rest and during exercise, 25 manifested at rest reduced radioactivity in the region of the interventricular septum. This pattern is similar to that seen in patients with anteroseptal myocardial infarction. Sixteen of the 27 patients underwent diagnostic coronary arteriography and left ventriculography. Only five of these patients had evidence of either previous infarction or significant obstructive coronary artery disease as assessed with clinical or anglographic criteria, or both. Although the image defect was routinely demonstrated at rest in patients with left bundle branch block, this defect was generally normalized or less distinct with exercise in patients with no anatomic heart disease. In contrast, a larger, more distinct or new image defect with exercise correctly identified the presence of significant obstructive coronary artery disease in patients with left bundle branch block. In the clinical application of noninvasive myocardial imaging, these image defects observed at rest can lead to the false positive radionuclide interpretation of anteroseptal myocardial infarction.     

Epicardial activation in human left anterior fascicular block.

Four patients with coronary artery disease and chronic marked left axis deviation, defined as a frontal QRS axis more negative than -45 degrees, were studied with epicardial mapping during coronary bypass surgery. All patients had normal right ventricular and inferior left ventricular epicardial breakthrough sites and activation sequence. Normal breakthrough in the basal anterolateral left ventricular epicardium was absent in all four patients. Two patients had breakthrough in the apical region of the anterolateral left ventricle. In the other two this region was activated from wave fronts emerging in the right ventricle and inferior left ventricle. The latest site of left ventricular activation was the basal segment of the anterolateral wall, a site never found to be the latest activated in our previously studied patients without conduction defects. This site was activated during or slightly after the terminal portion of the QRS complex. It is concluded that marked left axis deviation in patients with coronary artery disease reflects delayed activation of the basal anterolateral left ventricle, and is consistent with the presence of block or delay in the anterior "fascicle" of the left bundle branch.     

R wave amplitude during exercise. Relation to left ventricular function and coronary artery disease.

Change in R wave amplitude (mean delta R) was measured sequentially during and after 12 lead maximal treadmill exercise tests in 14 subjects with normal coronary arteries and 62 patients with coronary artery disease. In normal subjects mean delta R decreased maximally one minute after exercise and returned to control levels within three minutes. In contrast, mean delta R increased in patients with coronary artery disease, the greatest change occurring in patients with either triple vessel or left main disease or those with an akinetic region on the left ventriculogram. R wave amplitude returned to resting levels in five minutes. Increase in R wave amplitude was not directly related to changes in the ST segment. Changes in R wave amplitude during maximal treadmill exercise may improve the discrimination between patients with and without coronary artery disease and may help to identify those patients with abnormal left ventricular function.     

Comparison of exercise radionuclide angiocardiography and thallium-201 myocardial perfusion imaging in coronary artery disease

First pass radionuclide angiocardiography and thallium-201 myocardial perfusion imaging were performed at rest and during exercise in 48 patients with chest pain: 39 with angiographically documented coronary artery disease and 9 with normal coronary arteries. Maximal graded upright bicycle exercise was used for both studies to assure identical exercise conditions. All nine patients without coronary artery disease had normal exercise thallium images, normal exercise regional wall motion and at least a 5 percent absolute increase in left ventricular ejection fraction during exercise (normal exercise left ventricular reserve). Ischemic S-T segment depression was demonstrated in 17 (44 percent) of the 39 patients with coronary artery disease. Findings on the two exercise tests were concordant in all cases. New or augmented thallium perfusion defects were detected in 24 (62 percent) of the 39 patients, whereas abnormal exercise left ventricular reserve was present in 33 (85 percent) (p <0.05). There was a close concordance between exercise-induced perfusion defects and regional wall motion abnormalities. The magnitude of change in ejection fraction from rest to exercise was significantly greater in patients with an abnormal exercise thallium study than in those with a normal study (−8 ± 2 percent versus −1 ± 1 percent, p <0.05). Both radionuclide studies were abnormal In 21 (54 percent) of the 39 patients, whereas both were normal only in 3 patients, all of whom had single vessel disease. Abnormal exercise left ventricular reserve was present in 12 patients with normal exercise thallium studies.     

What is the value of myocardial perfusion studies with isotopes in patients with complete left bundle branch block?]

The prognosis of left bundle branch block is determined by associated cardiovascular disease. Exercise electrocardiography is not helpful in detecting ischemia in these patients. Exercise thallium-201 scintigraphy has been widely accepted for that purpose. The authors made an overview of several studies suggesting that exercise thallium-201 scintigraphy has low specificity regarding left anterior descending coronary artery disease. They also review the mechanisms of perfusion defects in patients with left bundle branch block without coronary artery disease. One important question to be clarified is weather small defects are unrelated to coronary artery disease. Finally the authors analyse a few methods to increase diagnostic accuracy of perfusion scintigraphy in left bundle branch block. First the employment of a new criterium that requires the apex to be abnormal to indicate left anterior descendent artery disease. Second Pharmacological Stress with Dipyridamole or Adenosine. Third imaging with Tc-99m-MIBI.     

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.     

The electrocardiogram in systemic sclerosis (scleroderma). Study of 102 consecutive cases with functional correlations and review of the literature

The electrocardiographic findings in 102 consecutive patients with scleroderma were reviewed to determine the frequency and nature of the electrocardiographic abnormalities associated with this disease. Septal infarction pattern unassociated with QRS prolongation was present in 10 percent, compared with none of 96 control subjects (p less than 0.001). Ventricular conduction abnormalities were present in 17 percent. A normal electrocardiogram was obtained in 49 percent. A subset of 48 patients underwent detailed cardiopulmonary evaluation including exercise thallium scintigraphy, rest and exercise radionuclide ventriculography, pulmonary function tests, and chest roentgenography. Functional correlations of the electrocardiographic findings were examined in this subset. Septal infarction pattern (five of 48) and ventricular conduction abnormalities (10 of 48) were both associated with septal or anteroseptal thallium perfusion abnormalities (10 of 15 versus six of 33 of the remainder, p less than 0.005), which were present despite normal coronary angiographic results. Thallium defect scores were greater in patients with septal infarction pattern or ventricular conduction abnormalities compared with the remainder (defect scores 3.0 +/- 2.6 versus 1.4 +/- 2.2, respectively, p less than 0.025). In patients with ventricular conduction abnormalities, both left bundle branch block and right bundle branch block with left anterior fascicular block were associated with abnormal left ventricular function, whereas isolated right bundle branch block or left anterior fascicular block was associated with normal left ventricular function. A normal electrocardiographic finding (19 of 48) was associated with normal left ventricular function at rest (19 of 19). However, 11 of 19 (58 percent) had thallium perfusion defects and four of 19 (21 percent) had an abnormal response to exercise, although in none was the peak ejection fraction less than 50 percent. It is concluded that both septal infarction pattern and ventricular conduction abnormalities are electrocardiographic abnormalities associated with scleroderma heart disease; they appear to be a result of myocardial fibrosis. Some degree of myocardial fibrosis may be present with a normal electrocardiographic result, but significant left ventricular dysfunction is unlikely. Septal infarction pattern and ventricular conduction abnormalities, when present, are indicators of more advanced fibrosis.     

Exercise electrocardiography: recognition of the ischemic response, false positive and negative patterns

The ischemic electrocardiographic response is characterized by S-T segment depression in the left ventricular leads. When this response is elicited by exercise and is accompanied by anginal discomfort, it constitutes powerful diagnostic evidence of the presence of coronary arterial obstructive disease. The amount of exercise required to elicit the response is closely related to the extent of the obstruction. S-T segment elevation provoked by exercise rarely occurs with proximal severe stenosis in the left anterior descending coronary artery or in leads exploring the region of healed myocardial infarcts. Depression of the J point may be an ischemic manifestation reversible by administration of nitroglycerin.The ischemic electrocardiographic response may be obscured by conduction defects as in bundle branch block and healed myocardial infarcts. False positive ischemic responses may be encountered in patients taking digitalis glycosides or potassium-depleting drugs, or in patients with hyperadrenergic states, pectus excavatum or short P-R Intervals.     

Complete bundle branch block during exercise test. Clinical and coronary angiographic data

Thirty-two complete bundle branch blocks were observed during 16,500 exercise stress tests between 1973 and 1988: there were 7 right bundle branch blocks and 25 left bundle branch blocks. Exercise stress testing was indicated in 15 cases for stable angina, in 15 cases for different functional disturbances and in 2 cases as a systematic investigation. All patients underwent coronary angiography and selective left ventriculography. Right bundle branch block occurring at a heart rate of 105 +/- 25/mn were associated with typical anginal pain at the time of apparition in 5 patients. Coronary angiography showed triple vessel disease in 3 cases, double vessel disease in 2 cases and an isolated proximal lesion of the left anterior descending artery in 2 cases. Left bundle branch block occurring at a heart rate of 125 +/- 12/mn was associated with normal coronary angiography in 7 cases. Eighteen patients had pathological coronary angiogrammes with severe lesions of the left anterior descending artery. Two women suffered from chest pain when the block developed and coronary angiography was normal in one of them. During follow-up (average 62 months), 16 coronary events were observed including 2 infarcts, and 6 patients developed cardiac failure. In conclusion, complete right bundle branch block appearing during exercise stress testing was constantly associated with atherosclerotic coronary artery disease. The predictive value of complete left bundle branch block on effort was 72%. Complete left bundle branch block occurring at heart rates of less than 120/mn was frequently associated with a proximal stenosis of the left anterior descending artery.