Unreliability of exercise-induced R wave changes as indexes of coronary artery disease

Evaluation of the QRS score for diagnosing coronary artery disease in women: A Finnish cardiovascular study

Background

Exercise electrocardiography is a widely used diagnostic modality for diagnosing coronary artery disease. This method has been used for both sexes; however, its diagnostic accuracy in women is limited.

Methods

The study analyzed 332 women participating in the Finnish Cardiovascular Study. Among 332 women, 125 with angiographically proven coronary artery disease (mean age 62.1 ± 9.5 years), 91 with a low likelihood of coronary artery disease (mean age 47.3 ± 13.5 years), and 116 without angiographically proven coronary artery disease (mean age 56.3 ± 9.9 years) were analyzed. The Q, R, S, and ST‐segment changes and QRS score were determined by subtracting the Q, R, S, and ST‐segment amplitudes immediately after the maximal exercise changes from their rest values (Δ). Receiver operating characteristic curve analysis was performed to evaluate the overall diagnostic performance of the parameters for predicting coronary artery disease.

Results

The areas under the receiver operating characteristic curve between coronary artery disease and low likelihood of coronary artery disease groups for the QRS score and ΔSTV5, ΔQaVF, and ΔRaVF were 0.75, 0.73, 0.71, and 0.71, respectively. These areas were lower (0.62, 0.57, 0.60, and 0.60, respectively) between the groups with and without angiographically proven coronary artery disease. QRS score demonstrated the highest sensitivity at 80% specificity (61.5%) and the highest specificity at 80% sensitivity (57.6%).

Conclusions

This study suggests that the QRS and ST‐segment depression have a moderate diagnostic ability to predict coronary artery disease in women. Q and R waves in lead aVF showed good diagnostic ability.

Detection of multivessel disease post myocardial infarction using an exercise-induced QRS score

OBJECTIVE

The aim of this study was to investigate the ability of Athens QRS score values to detect stenoses in other coronary arteries than the obstructed ones (which caused the myocardial infarction [MI]) in patients with a history of MI.

METHODS

We studied 125 patients (93 males and 32 females, mean age 54 +/- 7 years [range 45-68 years]) with a history of MI (46 patients with anterior MI, 54 patients with inferior MI, 25 patients with lateral MI). All patients underwent treadmill exercise testing and coronary arteriography.

RESULTS

Athens QRS score values were inversely related to the extent of CAD: -0.5 +/- 0.3 mm for patients with 1-VD (obstructed vessel), -3.4 +/- 2.2 mm for patients with 2-VD (obstructed vessel and stenosis in another vessel), and -5 +/- 1.8 mm for patients with 3-VD (obstructed vessel and stenoses in two more vessels). The ROC curves for the detection of multivessel disease showed that the area under the curve for QRS score values < -3 mm is significantly higher than the curve for ST-segment depression > or = 1 mm (0.948 vs 0.792, P < 0.001).

CONCLUSIONS

Values of the Athens QRS score less than -3 may distinguish single- from multivessel coronary artery disease in patients with a history of MI.

Significance of ST-segment depression with R-wave amplitude decrease on exercise testing

A retrospective evaluation was performed of patients who underwent exercise tests and angiography and 50 ambulatory normal subjects who underwent only exercise testing. We found that when deltaST depression of 0.5 mm was combined with deltaR-wave decrease of 1 mm, the sensitivity and specificity were improved.

Transient disappearance of Q waves of previous myocardial infarction due to exercise-induced ischemia of the contralateral noninfarcted myocardium

The electrocardiogram (ECG) of a 40-year-old woman with an old inferolateral myocardial infarction revealed, in the course of an exercise treadmill/thallium test, gradual disappearance of infarctional Q waves, which reappeared gradually during recovery from exercise. The patient had evidence of exercise-induced myocardial ischemia both by the ECG and by thallium-201 perfusion scintigraphy involving several myocardial regions. The temporal association of transient disappearance of Q waves with the occurrence of reversible ischemia suggested that the latter was instrumental in producing this phenomenon, through a transient failure of the ischemic anterior wall to shift the initial depolarization forces away from the infarcted inferolateral territory. Further evidence for this concept was provided by the case of another patient, a 49-year-old man who also had an old inferolateral myocardial infarction and whose ECG in the course of an exercise treadmill/thallium test did not reveal any changes in the infarctional Q waves. In this patient, thallium images showed mild, reversible inferolateral myocardial ischemia but a well perfused anterior wall, which provided for early depolarization forces (thus Q waves) directed opposite to the region of infarcted myocardium.

Changes in the QRS segment during exercise: effects of acute beta-blockade with propranolol

Changes in the QRS complex during exercise may provide information with respect to ischaemic heart disease. The intention with present investigation was to shed light on mechanisms behind QRS changes and to study the possibly confounding effects of beta-blockade on such alterations with exercise. Placebo or propranolol respectively was infused in randomized and double-blinded order in seven young healthy men before a maximum exercise test. Advanced computerized vectorcardiography and impedance cardiography was recorded continuously together with blood pressures and blood samples. The Y-lead magnitude increased significantly with propranolol infusion (P < 0.05), but it tended to decrease in the Z-lead (P < 0.07). While the serum potassium concentrations increased (P < 0.0005), the spatial QRS magnitude tended to decrease irrespective of treatment (P < 0.07). These changes correlated with changes in QR-duration (adj r2 > 0.58). With exercise, the mean spatial QRS magnitude decreased with similar amounts irrespective of treatment. However, propranolol made the magnitude decrease earlier (P < 0.01). No effect of treatment was detected on the decrease in QRS-duration. Immediately after exercise, the QRS complex continued to change as during exercise in the placebo investigations, but did not with propranolol (P < 0.05). These different patterns were most obvious in the first half of the QRS complex in the Y-lead. It is concluded that acute beta-blockade modifies QRS alterations both during and after exercise in healthy subjects. This indicates that such drugs may have confounding effects in evaluations of the diagnostic value of QRS alterations.

Prognostic value of changes in R-wave amplitude during exercise testing after a first acute myocardial infarction

To investigate the prognostic value of exercise-induced changes in R-wave amplitude and their relation to other exercise and angiographic variables, 303 consecutive patients who underwent maximal exercise testing and coronary angiography within 2 months of a first acute myocardial infarction were studied. R-wave amplitude at peak exercise increased or was unchanged in 159 patients (57.4%) and decreased in 118 (42.6%). Increased R-wave amplitude was significantly related to underlying 3-vessel disease (p = 0.0001), the extent of ST-segment depression on exercise (p = 0.0001), and the time to 1 mm ST depression (p less than 0.05). Follow-up information was available in 285 patients (86.4%) at a mean of 4 +/- 1.8 years. Death from cardiac causes occurred in 25 patients (9%); 18 (6.5%) developed recurrent myocardial infarction, and 32 (11.6%) developed angina. Variables with a predictive value for cardiac death were maximal exercise heart rate (p = 0.0005), occurrence of exercise-related supraventricular arrythmia (p = 0.02), and number of diseased vessels (p = 0.02). R-wave changes had no predictive value. No variable had a predictive value for recurrent infarction. Maximal exercise heart rate (p = 0.02) and increased R-wave amplitude (p = 0.0001) were significantly related to the occurrence of angina at follow up. Exercise-related R-wave increases were associated with the presence of angina at follow-up, but had no predictive value for cardiac death or recurrent infarction; their association with subsequent angina appears to reflect an association with more severe underlying coronary disease.

Value of exercise vectorcardiography and exercise radionuclide ventriculography in identification of coronary arterial disease in patients with left bundle branch block

Twelve patients (8 male and 4 female, age ranged 39-60 years) with suspected coronary arterial disease with left bundle branch block were evaluated for ischemia by simultaneous exercise vectorcardiography and radionuclide-ventriculography. Selective coronary angiography revealed normal coronary arteries in 5 and significant coronary arterial disease in 7 patients. Radionuclide ventriculography revealed no significant difference in resting left ventricular ejection fraction in patients with normal coronary arteries (44.0 +/- 13.9%) and coronary arterial disease (45.7 +/- 11.9%). Exercise radionuclide ventriculography showed positive response suggestive of ischemia in 11 patients (11/12), including all 5 with normal coronary arteries and 6/7 with coronary arterial disease. The magnitude of spatial 'R' maximum cardiac vector in both groups at rest (normal coronary arteries: 1.61 +/- 0.22 mV, coronary arterial disease: 1.63 +/- 0.35 mV) did not show any significant difference. On exercise, the magnitude of spatial 'R' maximum cardiac vector uniformly increased in patients with normal coronary arteries (1.61 +/- 0.22 to 1.75 +/- 0.25 mV, P less than 0.01) and decreased in 6 and remained unchanged in 1 patient with coronary arterial disease (1.63 +/- 0.35 to 1.34 +/- 0.46 mV, P less than 0.01). There was no change in rotational characteristics of QRS and T loops at end exercise in either group. Our preliminary observations indicate that exercise induced alteration of the magnitude of the maximal spatial 'R' cardiac vector appears to be an useful parameter to diagnose underlying coronary arterial disease in patients with left bundle branch block. Having a high false positive response, exercise radionuclide ventriculography appears to be of limited value in these patients.

New coronary artery disease index based on exercise-induced QRS changes

Exercise-induced changes in Q, R, and S wave amplitudes have been reported to detect coronary artery disease but with low specificity, low sensitivity, or both; it was hypothesized that their incorporation into a composite index (Athens QRS score) might improve specificity and sensitivity. For this purpose 246 patients were analyzed retrospectively and 160 prospectively. All patients underwent maximal exercise testing with a standard Bruce protocol and coronary arteriography as part of the diagnostic evaluation for possible or definite coronary artery disease. The Athens QRS score was decreased as the number of obstructed coronary arteries increased (normal coronary arteries = 7.85 +/- 5.23 mm, one-vessel disease = 5.2 +/- 5.3 mm, two-vessel disease = -0.85 +/- 5.4 mm, three-vessel disease = -3.5 +/- 5.8 mm; p less than 0.0001); the score was unrelated to exercise-induced ST segment depression, and negative (less than 0) scores were always associated with coronary artery disease. An Athens QRS score of 5 mm predicted coronary artery disease with sensitivity ranging from 75% to 86% and a specificity ranging from 73% to 79%, values higher than those of the Q wave (75% and 50%, respectively), R wave (65% and 55%), and S wave (70% and 10%) and of the ST segment depression (62% and 70%). It is concluded that exercise-induced changes in the QRS complex provide a useful index not only for the diagnosis but also for the assessment of severity of coronary artery disease.

R- and S-wave amplitude changes with acute anterior transmural myocardial ischemia. Correlations with left ventricular filling pressures

The value of R- and S-wave amplitude changes as electrocardiographic (ECG) markers of myocardial ischemia and dysfunction was evaluated using coronary angioplasty as a model of acute transmural ischemia and ST segment elevation. Hemodynamic data and 12-lead ECGs were recorded at baseline and during coronary occlusion in 34 patients with left anterior descending artery angioplasty. In the precordial leads V1 through V4, the sum of R-wave amplitude increased in 17 patients, was unchanged in ten, and decreased in seven; the sum of S-wave amplitude decreased in 33 patients (including two patients with complete loss of S wave) and increased in one. Mean R-wave change was 2.7 +/- 6.2 mm, mean S-wave change was -12.9 +/- 9.0 mm, and mean precordial ST elevation was 12.5 +/- 8.7 mm. Absolute R-wave change correlated directly with ST elevations (p = .013), while S-wave change correlated inversely (p less than .007). Only ST elevations correlated with changes in pulmonary capillary wedge pressure (PW) (p less than .007). In the precordial lead with maximum ST elevations, only R-wave changes correlated with ST elevations (p = .002), and both R-wave changes and ST elevations correlated with changes in PW (R:p = .027; ST:p = .007). The presence of large increases in R waves or decreases in S wave, or of high-magnitude ST elevations identified patients with the highest elevations in PW. In conclusion, decreases in S waves and, less commonly, increases in R waves are seen with diagnostic ST elevations and may have some limited clinical value. The correlation between magnitude of acute anterior ST elevations and changes in left ventricular filling pressures may have important clinical consequence.

Evaluation of spatial R maximum cardiac vector changes in exercise testing: pre-exercise versus post-exercise measurements

R wave amplitude changes during exercise have been a controversial issue as both increase and decrease in amplitude have been reported in patients with coronary arterial disease. This variability in response is attributed to change in position and heart axis on exercise. In view of this limitation, this study evaluated the change in spatial R maximum amplitude on exercise, which should not be affected by the above factors. Twenty patients with ischaemic heart disease (male 20, age 38-61 years) and 9 control subjects (male 9, age 32-65 years) were studied. Orthogonal leads, X, Y, Z were recorded using corrected Frank lead system on a stereokinematic vectorcardiograph (Tonnies). The magnitude of spatial R maximum cardiac vector increased from 0.1 to 0.6 mV in 8/9 control subjects and decreased or showed no change in 18 of the 20 patients with coronary arterial disease. In the control group, the mean value at the end of exercise (0.98 +/- 0.34 mV) was significantly less (P less than 0.01) as compared to pre-exercise value (1.09 +/- 0.2 mV). Our preliminary observations thus indicate that, with exercise, the magnitude of spatial R maximum cardiac vector decreases or shows no alteration in height in patients with coronary arterial disease whereas it increases in normal subjects.

R wave amplitude changes during stress testing in ischemic patients with normal epicardial coronary arteries

R wave amplitude changes during stress testing were validated in 12 ischemic patients with normal coronary angiograms. The data were compared with findings obtained from 10 patients with clinical and angiographic evidence of coronary arterial disease and 10 normal controls. An abnormal R wave amplitude response occurred in 83.3% of the group with normal coronary angiography, in 80% of the group of patients with clinical and angiographic evidence of coronary arterial disease, and in only 10% of the control group. The similarity of R wave amplitude changes in the first two group suggests that these changes are related to ischemia. If so, then R wave amplitude response to exercise could be of value in the electrocardiographic diagnosis of ischemia in patients with angiographically normal coronary arteries.

Quantitative grading of exercise stress test for patients with coronary artery disease using multivariate discriminant analysis

A group of 111 male patients who had undergone maximal or symptom-limited maximal exercise stress testing for evaluation of coronary artery disease (CAD) were subjected to coronary angiography. Group I comprised 33 patients with normal or single-vessel disease (SVD), while 78 patients with double-vessel disease (DVD) or triple-vessel disease (TVD) formed Group II. On univariate analysis of the exercise test, the following variables were found to be of significance in discriminating between the two groups: age, exercise duration, double product (heart rate X systolic blood pressure) at peak exercise, duration of ST-segment depression, number of leads showing ST depression, ST depression of 1 mm or more, configuration of the depressed ST segment, and diastolic blood pressure response to exercise. Multivariate analysis however revealed that only the following five variables had significant discriminant power: number of leads showing ST depression, exercise duration, double product, diastolic pressure response, and ST-segment configuration. On the basis of their relative importance, a regression equation was developed to give a quantitative score to individual patients. A score of less than zero detected multivessel disease (MVD) with high specificity (94%) and sensitivity (70%), while a score of 15 or more almost excluded MVD (sensitivity 87%). The scoring system as reported here improved the exercise stress test interpretation when compared with the conventional reporting system.

Local conduction delay causes R-wave amplitude increase in patients with effort angina

Eighty-seven unipolar electrocardiograms distributed over the entire thorax were simulataneously recorded before and after treadmill exercise in 43 patients. Exercise-induced R-wave amplitude change (delta R) and peak R time (time from the onset of QRS to the peak of R wave), were calculated for each lead. The maximal delta R of 87 leads was designated as the max delta R. After exercise, regional delay of peak R time (greater than or equal to 10 msec) on the chest was observed in 13 patients. These patients had significantly higher max delta R than those without such regional peak R time delay (0.71 +/- 0.31mV vs. 0.33 +/- 0.20mV, p less than 0.01). In each case, the site of peak R time delay was almost the same as the site of max delta R. There was no significant difference in the peak heart rate, rise of the systolic blood pressure (delta BPs) during exercise or extent of ischemic ST depression between patients with and without peak R time delay. We concluded that ventricular condition delay plays an important role in the increase of R-wave amplitude after exercise in patients with effort angina pectoris.

R-wave amplitude changes during exercise stress testing: patients with dilative cardiomyopathy compared to patients with coronary artery disease

R-wave amplitude (RWA) depends to a large extent on the left ventricular filling volume. Changes of RWA are attributed to the Brody-effect. Exercise has been shown to induce a decrease of RWA in a healthy population and an increase in patients with coronary artery disease (CAD). No clear data exist for cardiomyopathy (CMP). Controls (n = 12), patients with CMP (n = 32) and CAD (n = 58) were compared. Alterations of RWA (Wilson lead V5) were correlated with parameters of a bicycle exercise test including resting and exercise hemodynamics and parameters of LV-function including EF, LVEDV and LVEDP. CMP compared to CAD had smaller RWA at rest (0.78 +/- 0.47 vs 1.32 +/- 0.72 mV, P less than 0.01). During comparable levels of exercise CMP (EF 35 +/- 14%) showed no significant changes of RWA. CAD (EF 57 +/- 16%) presented an increase of RWA by +0.11 +/- 0.23 mV (P less than 0.01), while controls showed a straight decline of RWA (-0.31 +/- 0.24 mV). In patients with CAD delta RWA (RWA max exercise - RWA rest) was a more sensitive parameter for detection of disease (assuming delta RWA greater than or equal to +0.1 mV, 36/58 patients) than maximal ST-segment changes (ST-segment-depression in lead V5 greater than or equal to 0.2 mV at 0.08 sec after J-point, 22/58 patients). Precordial leads V2, V4, V5 and V6 showed similar changes. This paper supports the theory that changes of wall thickness or changes in the amount of air respective to the amount of fluid in the lungs are responsible for RWA changes. These changes are clearly dependent on the severity of the disease and on left ventricular function. Therefore measurement of RWA changes during exercise may offer additional information in patients with CAD as well as in patients with CMP.

The changing role of the exercise electrocardiogram as a diagnostic and prognostic test for chronic ischemic heart disease

The exercise electrocardiogram has been the subject of intense research over the last 50 years, as both a diagnostic and prognostic method to assess patients with chronic ischemic heart disease. In 1986, the strengths and limitations of the technique to predict coronary and multivessel disease in clinical patient subsets are understood. The diagnostic accuracy of the test is improved by consideration of Bayesian theory, multivariate models and new non-ST segment criteria. Post-test coronary disease risk estimates are best reported in terms of a conditional probability, rather than statements of "positive" or "negative." The value of exercise testing in prognostic risk stratification is considerably enhanced by recent reports of long-term follow-up data in asymptomatic and symptomatic patients. Powerful prognostic information can be obtained when the clinical, electrocardiographic and physiologic data from the exercise test are used to formulate the post-test risk of a cardiac event, even in patients whose coronary anatomy is known. The changing role of the exercise electrocardiogram as a diagnostic and prognostic test is reviewed, with emphasis on the strengths and limitations of the procedure.

Effort angina pectoris without electrocardiographic changes in coronary disease patients: correlations between scintigraphic and coronary angiographic findings

The absence of electrocardiographic changes during angina is an unusual occurrence. In 15 male patients with exercise-induced angina, the electrocardiogram failed to show the usual ischemic ST-T changes. The exercise thallium-201 myocardial imaging was employed as indicator of the ischemia and the results were correlated with coronary angiographic findings. The exercise thallium-201 myocardial imaging showed an exercise-induced reversible defect in 14 patients and a fixed defect in the remaining 1. Out of 15 patients, 13 had defects involving the infero-apical, posterior and postero-lateral segments. The coronary angiography, performed in all patients but 2, showed single-vessel coronary artery disease in 8 patients and double-vessel disease in 5. A significant circumflex or right coronary artery stenosis was found in all cases except 1; 2 patients had a coexistent left anterior descending coronary artery stenosis and 1 an isolated stenosis of this vessel. It is concluded that the myocardial scintigraphy is useful to assess the ischemic myocardial origin of chest pain in the absence of ST-T changes. The silence of the electrocardiogram might be due to the production of ischemia in not well explored areas, such as the inferior and posterior myocardial segments, and possibly to a smaller extension of ischemia.

Spatial R wave amplitude changes during exercise: relation with left ventricular ischemia and function

Thirty patients who exhibited increased and 65 patients decreased spatial R wave amplitude during exercise testing were compared for left ventricular function and ischemic variables. Spatial R wave amplitude was derived from the three-dimensional Frank X, Y, Z leads using computerized methods. All patients had stable coronary artery disease and they were classified into two groups: one that attained a higher (n = 48) and one a lower (n = 47) median value of maximal heart rate during exercise (161 beats/min). Within these two groups, patients with increasing or decreasing spatial R wave amplitude during exercise were analyzed for differences in oxygen consumption, exercise-induced changes in spatial R wave amplitude, ST segment depression laterally (ST60, lead X), ST displacement spatially, left ventricular ejection fraction at rest, change in left ventricular ejection fraction with exercise and thallium-201 ischemia during exercise. Significant differences were demonstrated only in exercise-induced spatial R wave amplitude changes (p less than 0.0001). There was no significant correlation between exercise-induced change in heart rate and change in spatial R wave amplitude in either the group with increasing or the group with decreasing spatial R wave amplitude. It is concluded that changes in spatial R wave amplitude during exercise are not related to ischemic electrocardiographic or thallium-201 imaging changes or to left ventricular ejection fraction determined at rest or during exercise.

Predictive value of changes in R-wave amplitude after exercise in coronary heart disease

To assess the predictive value of coronary events reflected by changes in R-wave amplitude after exercise, 146 patients with angiographically documented coronary heart disease were studied. All patients were followed up for 6 years, during which time myocardial infarction and death of cardiovascular origin were considered endpoints. The incidence of events in patients in whom R-wave amplitude decreased (normal response) and in those in whom R-wave amplitude did not change or increase (abnormal response) were compared. The incidence of coronary events in patients with a normal response was 23% and in those with an abnormal response, 45.8% (p less than 0.01). Correlating the results with several noninvasive and angiographic variables, an abnormal R-wave response showed a significantly higher rate of events in the subsets of patients with prior myocardial infarction, absence of cardiomegaly, maximal functional capacity lower than 4 METs, maximal heart rate higher than 140 beats/min and abnormal left ventricular function. Thus, the changes in R-wave amplitude after exercise is a variable that should be taken into account when assessing the risk of future events in patients with coronary heart disease.

Directional variability in the R wave response during serial exercise testing in patients with coronary artery disease

The reproducibility of the direction of R wave amplitude response to exercise was analyzed in patients with coronary artery disease. Forty-three serial exercise tests were performed by 10 patients with exertional angina pectoris and documented coronary artery disease (CAD). Seventeen tests (37%) resulted in no change or an increase in R wave amplitude (abnormal response). Twenty-six tests (63%) resulted in a decrease in R wave amplitude. The direction of the R wave amplitude response was variable in at least one exercise test in 7 of 10 patients with CAD, all of whom had reproducible ischemic ST segment responses during serial testing. The inconsistent R wave response in these patients was unrelated to heart rate, workload, or duration of exercise. Because of the variability in the directional R wave response during serial exercise testing in CAD patients, we conclude that the R wave response during exercise is unreliable for the detection of CAD or ischemia-related myocardial dysfunction.

On the clinical value of conventional and new exercise electrocardiographic criteria: a comparative study

We have evaluated the clinical value of new electrocardiographic criteria in exercise testing. In this study, we compared both ST-segment and R-wave amplitude criteria, separately and in combination with the findings from coronary arteriography in 122 patients. In these selected patients application of conventional ST-segment criteria gave a sensitivity of 31% and a specificity of 100%; with application of the slow upsloping ST-segment criteria the sensitivity was 51% and the specificity 82%. Analysis of R-wave amplitude changes alone led to a sensitivity of 50% and a specificity of 61%. In combined interpretation of ST-segment and R-wave amplitude changes the sensitivity was 51% and the specificity 93%. We conclude that slow upsloping ST-segment criteria constitute the most important recent improvement in interpreting exercise test results and that the value of R-wave amplitude changes during exercise in diagnosing significant coronary artery disease is rather low in the individual patient. R-wave amplitude changes, however, may have value in patients with a previous myocardial infarction and in reducing false-negative and false-positive responses according to ST-segment criteria. Combined interpretation of ST-segment and R-wave amplitude criteria is useful but not very efficient.

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.

Electrocardiographic effects of myocardial ischemia induced by atrial pacing in dogs with coronary stenosis. II. Comparison of S-T segment and QRS changes in dogs with left circumflex arterial narrowing

The effects of tachycardia on the QRS complex in the absence and in the presence of coronary arterial constriction are of possible clinical significance. To study the spatial and temporal distributions of these effects, a canine model simulating progressive coronary occlusion was studied. Tachycardia was induced by atrial pacing, coronary narrowing was produced by implantation of an ameroid constrictor about the left circumflex coronary artery and electrocardiographic effects were studied by isopotential mapping techniques at rates of up to 250 beats per minute, one to three weeks after constrictor implant. In five dogs. pacing without coronary constriction demonstrated the spatial and temporal dependence of QRS changes; tachycardia-induced changes varied from one torso site to another at any instant, and from one moment to another at any one torso location. Patterns in ten dogs with constrictors were dependent upon time after ameroid placement. Resting QRS and S-T segment distributions remained unchanged. One week after surgery, QRS and S-T segment patterns during pacing were as in controls. Two weeks after surgery, QRS patterns were as in controls but flat S-T segment depression resulted at high rates. After three weeks, QRS patterns during pacing were abnormal and S-T segment depression was observed. At each of the later times, the QRS response was similar at rates which did and which did not cause S-T depression. Thus, the effects of tachycardia on excitation and recovery forces in the presence of restricted coronary flow are independent of one another. This suggests that the two responses to ischemia may be due to different basic mechanisms and, hence, that their detection may reflect different myocardial abnormalities.

R-wave amplitude responses to rapid atrial pacing: a marker for myocardial ischemia

Atrial pacing-induced changes in the sum of R-wave amplitude were measured in leads V5, X, Y, and Z at rates of 100 bpm (phase I), 150 bpm (phase II), and immediately after pacing (phase III) in 33 patients undergoing cardiac catheterization for evaluation of chest pain. Seventeen (51%) patients showed evidence of ischemia during atrial pacing (typical anginal pain and/or at least a 1 mm ST-segment depression) and 16 (49%) showed no evidence of ischemia. Mean R-wave amplitude changes from baseline in the ischemic patients were: phase I: -8% (p = not significant), phase II: +3% (p = not significant), and phase III: +13% (p less than 0.01); and in nonischemic patients: phase I: -11% (p less than 0.02), phase II: -18% (p less than 0.01), and phase III: +2% (p = not significant). These two distinct patterns of R-wave amplitude changes were highly sensitive (85%), specific (92%), and predictive (92%) for identifying patients with myocardial ischemia but did not correlate (p = not significant) with either the angiographically determined extent of coronary artery obstructive disease (CAD), resting left ventricular function, or the dynamic, atrial pacing-induced changes in left ventricular dimensions determined by M-mode and two-dimensional echocardiography. Thus, R-wave amplitude changes induced by atrial pacing can be used to identify patients with myocardial ischemia independent of coronary anatomy or resting left ventricular function.(ABSTRACT TRUNCATED AT 250 WORDS)

Improving diagnostic accuracy of the exercise test by combining R-wave changes with duration of ST segment depression in a simplified index

To enhance the reliability of the exercise test in diagnosing both overall coronary artery disease and multivessel coronary artery disease, a discriminant function was obtained by means of stepwise linear discriminant analysis. Both electrocardiographic and nonelectrocardiographic factors were used to derive the discriminant function in a retrospective group of 231 patients, 168 of whom had angiographically defined coronary artery disease. The discriminant function converted into a simple exercise index or score was then applied to a retrospective group of 120 patients, 98 of whom had coronary artery disease. This index, combining R-wave changes with duration of ST segment depression and patient's sex, proved highly accurate in diagnosing coronary artery disease in male patients and in diagnosing the absence of coronary artery disease in female patients. When compared to standard ST segment criteria, the sensitivity and predictive value of the exercise index was significantly higher.

Factors influencing R wave amplitude in patients with ischaemic heart disease

R wave amplitude changes during exercise have been ascribed to alteration in left ventricular volume and their measurement advocated for the improved diagnosis of coronary disease. The reproducibility of exercise QRS changes and their relation to ST segment depression, respiratory pattern, and left ventricular volume during ischaemia were studied in 10 patients with angina and coronary disease. QRS amplitude was measured in a 16 lead precordial map during three identical exercise tests in each patient and left ventricular volume assessed continuously using gated blood pool imaging with a single scintillation probe during manoeuvres to provoke ischaemia. During exercise, QRS amplitude increased or remained unchanged in four patients and fell in six patients in a consistent manner for each patient. R wave amplitude was not affected by changes in respiratory pattern. R wave amplitude did not alter in 33 of 39 episodes of left ventricular volume increase (mean 32%) or decrease (mean 36%) in end-diastolic counts. These findings suggest that precordial R wave changes during ischaemia are not determined primarily by alteration in left ventricular volume or the respiratory pattern. Though reproducible in each patient and following a definite relation to ST segment depression, the variable directional response during exercise suggest that R wave amplitude changes have little diagnostic value.

Disappearance of exercise-induced ST-segment depression associated with transient left anterior hemiblock

To our knowledge, this is the first case reported of total disappearance of exercise-induced ST-segment depression in the presence of transient left anterior hemiblock at peak exercise. An unusual paradoxic increase in T-wave amplitude was also noticed. The significant ST-segment displacement reappeared when the transient left anterior hemiblock disappeared during the recovery phase. Based on current review, the presence of transient left anterior hemiblock during exercise seems to correlate well with the proximal left anterior descending coronary artery disease. Therefore, the presence of transient left anterior hemiblock during exercise with either normalization of exercise-induced ST-segment depression or paradoxic increase in T-wavse amplitude at peak level may be a useful end-point to stop the test for patients who do not reach 2 mm ST-segment depression or who remain asymptomatic.

Influence of R wave analysis upon diagnostic accuracy of exercise testing in women

Exercise electrocardiography in women with chest pain is associated with a high incidence of false positive ST segment depression. The recent observation that changes in R wave amplitude during exercise can also be used diagnostically may improve the value of stress testing in women. The results of 12 lead treadmill exercise and coronary angiography were reviewed in 62 women, mean age 51 years, presenting with "angina" without previous myocardial infarction. These were compared with exercise results in 14 healthy asymptomatic volunteers with a mean age of 26 years. In addition to conventional ST analysis, R wave amplitude changes during exercise, measured in leads II, III, a VF, and V4 to 6, were examined. While the sensitivity and specificity of ST and R wave changes were similar at about 67%, their combined interpretation was helpful. If both ST and R wave criteria were negative the predictive accuracy for normal coronary angiography was 94% (17/18). Alternatively, in tests showing both ST depression and an abnormal R wave response, coronary angiography was always abnormal (13/13). None of the normal volunteers developed ST segment depression and 93% (13/14) had a normal R wave response. If both were positive, however, coronary angiography was always abnormal (13/13). Although stress test interpretation in women is difficult, R wave analysis is a useful adjunct to ST change and can improve the predictive accuracy of the test in a significant number of patients.

Inability of exercise-induced R wave changes to predict coronary artery disease

To determine the value of exercise-induced R wave changes in diagnosing coronary disease 200 patients undergoing coronary angiography were studied with 16 lead precordial exercise mapping. R wave amplitude was calculated before and immediately after exercise as the sum of R in all 16 leads, the sum of the R waves in the left plus the S waves in the right precordial leads, as well as the sum of the R waves only in those leads that manifested S-T depression. Coronary artery disease was found in 154 patients, S-T depression developed in 122 (sensitivity 79 percent); the sum of R increased or remained unchanged in 61 and decreased in 93 (sensitivity 40 percent). Forty-six patients did not have coronary artery disease; S-T depression developed in 5 (specificity 89 percent); the sum of R increased or was unchanged in 30 and decreased in 16 (specificity 35 percent). Similar results were obtained using the other criteria for calculating R wave amplitude. Exercise-induced S-T depression was identified in 5. 1 +/- 2.6 (mean +/- standard deviation) of the 16 precordial leads and in 2.0 +/- 1. 1 of the chest leads of the standard electrocardiogram (p less than 0.01). Thus, electrocardiographic alterations found in the standard chest leads represent only a small variable proportion of the total projection. When the whole precordial area was analyzed, R wave changes were so unpredictable that they could not be used in the diagnosis of coronary disease.

Relationship of resting ejection fraction and extent of coronary arterial disease with changes of QRS amplitude during exercise stress testing

To further elucidate the value of the R wave criteria during the exercise stress test (EST), we studied the direction and magnitude of the changes of the QRS amplitude (delta R) as well as the extent of ST segment depression in 75 patients with coronary artery disease (CAD) and 26 normal subjects (NLS). Results were analyzed in relation to severity of the disease (number of vessels involved) and left ventricular EF. In NLS, there was an average decrease of the QRS amplitude of --1.9 +/- 0.6 mm (mean +/- SE) compared to an average increase of 0.6 +/- 0.35 mm for CAD patients. Mean delta R for 1VD was --0.28 +/- 0.75 mm; for 2VD, it was 0.27 +/- 0.54 mm, and for 3VD, it was 1.37 +/- 0.55 mm. Mean delta R for NLS was significantly different (Duncan's multiple range test, p less than 0.05) from 2VD and 3VD but not from 1VD. Although there was no statistically significant difference of mean delta R among CAD groups, a significant linear trend was observed (p less than 0.008). Resting EF did not correlate either with extent of ST segment depression or with the direction or magnitude of delta R induced by exercise. We conclude that the direction of changes in delta R during exercise is related to the presence or absence of CAD. The magnitude of delta R appears to correlate with the severity of coronary arterial involvement. We did not detect any relationship between R wave changes and left ventricular function. The use of R wave criteria may slightly improve the sensitivity of EST but detracts from specificity.

Radionuclide angiographic correlation of the R wave, ejection fraction, and volume responses to upright bicycle exercise

The change in the R wave and the response of the ejection fraction to upright bicycle stress testing with radionuclide angiographic studies were determined for 18 control subjects and 29 patients with coronary arterial disease (70 percent stenosis or more). In the control group, all had an increase in the ejection fraction from 64.8 +/- 7.7 to 75.7 +/- 9.4 percent with stress (P less than 0.01). All control subjects had a decrease in the R wave with exercise. In the group with coronary arterial disease, most patients had a decrease in the ejection fraction averaging from 63.5 +/- 10.9 to 58.6 +/- 12.8 percent (P less than 0.01). An appropriate response of the R wave and ejection fraction (decrease in R wave and increase in ejection fraction or increase in R wave and decrease in ejection fraction) occurred in 23 (79 percent) of 29 subjects (P less than 0.005). The sensitivity, specificity, and predictive value for the response of the ejection fraction were as follows: 83 percent (24/29); 100 percent (18/18); and 100 percent (24/24). Of the patients with coronary arterial disease and an increase in the R wave, 17 (94 percent) had multivessel disease, while six (55 percent) of 11 with a decrease in the R wave had multivessel disease (P less than 0.05). The systolic volume decreased in all control subjects by -15.9 +/- 8.6 units (P less than 0.01) and increased in most of the group with coronary arterial disease by 13.7 +/- 17.8 units (P less than 0.01) in response to stress. There were 20 of 29 patients (P less than 0.05) with an appropriate response of the R wave and systolic volume to stress (increase in R wave and systolic volume or decrease in both). The change in the R wave did not correlate with the change in the diastolic volume with stress (P greater than 0.05). Changes in the R wave with exercise correlate with the change in the ejection fraction (and hence ventricular function) and with the changes in systolic volume, which may be one of the mechanisms of the response of the R wave, suggesting that the change in the R wave is related to changes in contractility. Increase in the R wave with stress suggests multivessel coronary arterial disease.

Effects of nitrates on R-wave variations after exercise in coronary heart disease: differences in patients with and without angina pectoris

With the purpose of investigating the pathophysiology of changes in the R wave after exercise and its relationship with left ventricular function, we studied 44 patients with coronary heart disease. They were classified into the following three groups: group A, 11 patients with angina pectoris and no prior myocardial infarction; group B, 18 patients with angina pectoris and prior myocardial infarction; and group C, 15 patients with prior myocardial infarction but no angina. All patients performed two exercise tests; one was a control test, and the other was performed after the sublingual administration of 5 mg of isosorbide dinitrate. In group A, variations in the R-wave voltage in control test and in the test after isosorbide dinitrate were 1.5 +/- 0.8 mm and -1.2 +/- 0.9 mm (P less than 0.05), respectively. In group B, results were 1.2 +/- 0.7 mm on the control test and -0.7 +/- 0.6 mm after isosorbide dinitrate (P less than 0.002), and in group C were -1.6 +/- 1.2 mm on the control test and -0.7 +/- 0.7 mm after isosorbide dinitrate (not significant). Thus, the two groups of patients with angina showed an increase of the R-wave after exercise in the control test but a decrease after the administration of nitrates, whereas the patients without angina showed a reduced R-wave after exercise both before and after the administration of nitrates (like normal subjects). This study suggests that ischemic ventricular dysfunction with exercise results in an increase in the R-wave, while exercise after nitrates results in a decrease in the R-wave consistent with less or no ventricular dysfunction due to nitrate therapy.

Comparative sensitivity and specificity of exercise electrocardiographic lead systems

A comparison of current exercise electrocardiographic lead systems reveals differences in the sensitivity and specificity of S-T segment shifts diagnostic of obstructive coronary artery disease. The differences are explained in part by differences in population samples, lead systems and criteria for positivity. Multiple electrocardiographic lead recording in symptomatic patients during and after exercise improves sensitivity in detecting S-T segment shifts with only a small decrease in specificity. A review of population screening studies in asymptomatic subjects shows a wide selection of different exercise electrocardiographic lead systems and criteria for a positive test. Few screening studies have compared the prevalence of different S-T segment configurations in individual leads of a simultaneously recorded multiple lead system during or after exercise. Data from animal studies of myocardial ischemia suggest why 100 percent sensitivity in detecting obstructive coronary disease is unlikely to be obtained with surface electrocardiographic recordings. Additional research is required to identify the optimal set of diagnostic exercise electrocardiographic leads and criteria for positivity so that maximal predictive accuracy can be obtained for different patient subsets.

Body surface distribution of exercise-induced QRS changes in normal subjects

Previously reported clinical studies have suggested an important diagnostic role for exercise-induced QRS changes. To explore the spatial features of such alterations, anterior thoracic isopotential distributions were examined at rest and at 85 percent of maximal heart rate in 30 normal male volunteers. Results demonstrated that exercise caused a reduction in positive forces and an augmentation of negative voltages at most anterior thoracic sites. However, the locations of map extrema were not significantly altered. Difference maps, computed by subtracting time-aligned distributions at rest and during exercise, suggested that exercise generated an electrical field characterized by a central anterior minimum bordered superiorly by positive potentials. The minimum reached a peak magnitude in the middle portion of the QRS pattern, then declined in intensity. Although difference patterns during inscription of the QRS complex were similar to those computed during the P-R and S-T segments, time-intensity curves were discontinuous with marked and abrupt early increases and late decreases in strength in the QRS complex. These results suggest that two commonly considered mechanisms (effects of changes in intracavitary blood mass and of atrial repolarization) cannot be solely responsible for the observed effects.

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.