Diagnostic incapacity of exercise-induced QRS wave amplitude changes to detect coronary artery disease and left ventricular dysfunction

To evaluate the diagnostic potential of exercise-induced QRSwave amplitude changes, we studied exercise test responses indifferent clinical subsets. The lead system used was a modified12-lead ECG, supplemented with CC5, CM5 and CL5. The potentialof QRS wave amplitude changes compared to conventional ST segmentchanges, to detect coronary artery disease was examined in patientswith no prior myocardial infarction, divided into those witha history of typical angina pectoris and those with atypicalangina pectoris. A similar analysis was undertaken to detectadditional coronary artery disease in patients with prior myocardialinfarction, divided into those with typical and atypical anginapectoris. Finally, the diagnostic ability of QRS wave amplitudechanges to detect left ventricular dysfunction was examinedin all the patients. It is concluded that QRS wave amplitude changes, induced byexercise, have no relevant diagnostic value in detecting (additional)coronary artery disease or left ventricular dysfuntion.     

The usefulness of exercise-induced QRS axis shift as a predictor of coronary artery disease

The QRS axis of 101 patients with coronary artery disease (CAD) and 57 normal subjects without CAD who underwent coronary arteriograms were measured before and after exercise testing. There was no improvement in the sensitivity of positive axis shifts (15 degrees or greater) for CAD (18%) when compared to the value of positive ST depression (61%). However, the specificity of positive axis shifts for CAD was significantly increased (98%) when compared to the value of positive ST depression (77%). In addition, 39% of those patients with CAD (39 of 101) showed false negative ST depression, but 18% of these patients (7 of 39) showed a positive axis shift. In normal subjects 21% (12 of 57) showed false positive ST depression, but all of the 21% (12 of 12) showed negative axis shift. There was no significant difference in the increments of heart rate between positive ST depression, positive axis shift, and negative ST depression, negative axis shift. No statistical differences in the sensitivity of ST depression and an axis shift for one-, two- and three-vessel diseases were noted. The specificity of left-axis shift for the left anterior descending artery lesion was 98% and the specificity of right-axis shift for the right coronary artery and/or left circumflex artery lesion was 91%. Therefore, the axis shift response is no more sensitive for the detection of CAD than ST depression. However, when a positive axis shift is observed, one can predict two things: the CAD and the localization of the coronary stenosis.     

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 segment 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 < 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.     

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

To investigate the diagnostic value of exercise-related QRS amplitude changes, the responses of 40 young normal subjects and 28 patients with chest pain and no significant coronary arterial obstruction were compared with those of 73 patients with coronary arterial narrowing of various degrees of severity. All underwent submaximal, multiple lead multistaged treadmill exercise testing. The combined normal group showed an average decrease in R wave amplitude between rest and exercise of 1.1 ± 2.8 mm (mean ± standard deviation) in lead V₅; those with coronary artery disease had an increase of 0.6 ± 3.4 mm (P = 0.001). Similar but less pronounced differences were observed in lead II (a decrease of 1.9 ± 2.3 mm in normal subjects versus a decrease of 0.5 ± 3.1 mm in those with coronary disease, P = 0.01). When derived R wave criteria were used, the test sensitivity averaged 52 percent and the specificity 63 percent; these values were inferior to the sensitivity of 88 percent and specificity of 72 percent of S-T segment criteria in the same group of patients. No significant relation was found between the extent of coronary artery disease and R wave changes, and an analysis of multiple variables suggested possible correlations with factors not directly related to ischemia. It is concluded that exercise-induced QRS amplitude changes are unreliable predictors of the presence, absence or severity of coronary artery disease.     

Useless diagnostic value of exercise-induced R wave changes in coronary artery disease

To investigate the usefulness of exercise-induced R wave changesin the diagnosis of coronary artery disease and detection ofleft ventricular contraction abnormalities, 105 patients werestudied. Among 64 patients who had significant coronary arterydisease ( 70% narrowing), 43 showed an increase or no changein the R wave amplitude and 55 showed ST segment depression(sensitivity 67 versus 86%). Among 41 patients without significantstenosis, 11 had decreased R wave amplitude and 36 had no changein ST segment (specificity 27 versus 88%). Twenty-five of 64coronary disease patients had left ventricular contraction abnormalities,and the R wave amplitude changes gave a sensitivity of 80%,specificity of 41% and a predictive value of 47%. There wereno differences in the variables of exercise intensity and ejectionfraction between patients who had decreased R wave amplitudeand those in whom it increased or did not change. We conclude that R wave amplitude change during exercise isnot a useful variable for the diagnosis or evaluation of patientswith coronary artery disease.     

lschaemic heart disease: The QRS score: a promising new exercise score for detecting coronary artery disease based on exercise-induced changes of Q-, R- and S-waves: a relationship with myocardial ischaemia

BACKGROUND: Recently, a new exercise test criterion diagnosing coronaryartery disease was proposed, based on a composite of changesin Q-, R- and S-waves: the QRS score. We compared this new criterionwith conventional ST-segment depression and other compositionsof Q-, R and S-wave changes in patients and normals and relatedthe QRS score to reversible thallium-201 scintigraphic defectsand ST-segment depression as markers for ischaemia. The influenceof beta-blockade on the QRS score was also studied. METHODS: The study population consisted of 155 persons with 53 normals(group I) and 102 patients with documented coronary artery disease(group II). Another 20 patients (group III) with proven coronaryartery disease and a positive exercise test by ST-segment criteriawere studied for the influence of beta-blockade on the QRS score.A symptom-limited exercise protocol according to the modifiedBruce protocol was used. For the QRS score, Q-, R- and S-waveamplitudes which could be recovered immediately were subtractedfrom pretest values: Q, R, S respectively. The score was calculatedby the formula: (R – Q –S)AVF+(R –Q–S)V5. RESULTS: Using a cut-off point of >5 as normal, the QRS score resultedin a sensitivity of 88·2%, a specificity of 84·8%and a predictive accuracy of 87·1%. For ST-segment depressionthese values were 54·9% 83% and 64·5% respectively(P<0·00l compared to the QRS score.) Predictive accuraciesof changes in Q-, R- and S-waves in leads AVF and VS separately,combinations of changes and combining the two leads, resulted—withthe exception of solitary S-wave changes—in predictiveaccuracies higher than those of ST-segment depression, but allwere lower than the QRS score. We found a significant correlationbetween the QRS score, the summed ST-segment depres sion (P<0004)and the extent of reversible thallium-201 defects (P<0·004Applying Bayes' theorem, the combination of an abnormal QRSscore and ST-segment depression resulted in the highest post-testrisk for coronary artery disease and a normal QRS score withoutST-segment depression in the lowest post-test risk. The QRSscore and the maximal ST-segment depression changed significantlyunder the influence of beta-blockade (P<0·02 and P<0·001respectively). CONCLUSION: Our data suggest that an abnormal QRS score reflects myocardialischaemia. Furthermore, for the interpretation of the exercisetest, the combined analysis of ST-segments and the QRS scoreis of value for the prediction of the presence or absence ofcoronary artery disease and its follow-up.     

Analysis of the exercise-induced orthogonal P wave changes in normal subjects and patients with coronary artery disease

Near-maximal treadmill exercise testing was performed on 26 normal individuals (NL) and 78 patients with coronary artery disease (CAD) using a modified Bruce's protocol. Exercise-induced changes in orthogonal P wave measurements were made automatically, using an averaging technique, immediately before and 30 sec after treadmill exercise to assess their diagnostic significance in evaluation of left ventricular (LV) function in CAD patients. The maximal inferior and posterior components of the P wave and the maximal P-vector magnitude in the frontal and left sagittal planes showed a statistically significant increase after treadmill exercise both in NL and CAD patients. These changes were considered to be physiological responses of the P wave to dynamic exercise. The percent changes of the maximal horizontal P-vector magnitude (%Hmax) were significantly higher after treadmill exercise in CAD patients than in NL. In patients with effort angina pectoris and without a previous myocardial infarction, the %Hmax showed a highly significant negative correlation with the percent changes of the LV ejection fraction (r = 0.66, p less than 0.01), measured by exercise RI angiography. These results suggest that the exercise-induced increase in %Hmax reflects transient impairment of LV function during exercise. It was concluded that a %Hmax of more than 120% provided a useful, noninvasive index for assessing LV function in treadmill exercise testing.     

Determinants of exercise-induced changes in mitral regurgitation in patients with coronary artery disease and left ventricular dysfunction

OBJECTIVES: We sought to examine the determinants of exercise-induced changes in ischemic mitral regurgitation (MR) in patients with left ventricular (LV) dysfunction. BACKGROUND: In the post-myocardial infarction (MI) phase, ischemic MR contributes to worsening of symptoms and of LV dysfunction. METHODS: In this study, 70 patients in the chronic, post-MI phase, with LV ejection fraction <45% and at least mild MR, underwent semi-supine exercise Doppler echocardiography. The effective regurgitant orifice (ERO) of MR was quantified at rest and during exercise. Exercise-induced changes in ERO were compared with changes in mitral deformation and in local and global LV remodeling. RESULTS: The wide range of exercise-induced ERO changes that were observed was unrelated to the degree of MR at rest (r = 0.20). Effective regurgitant orifice changes correlated best with changes in mitral deformation (i.e., differences in systolic mitral tenting area, systolic annular area, and coaptation height) (p < 0.0001). Posterior displacement of the papillary muscles was associated with larger changes in the ERO in both infarct groups. In patients with inferior MI, a decrease in the ERO was related to improvement in wall motion (r = 0.68). The independent predictors of ERO changes during exercise were changes in systolic annular area for all infarct categories, in tenting area and wall motion score in the global population and those with inferior infarction, and in apical displacement of mitral leaflets for patients with anterior MI. CONCLUSIONS: The degree of MR at rest is unrelated to exercise-induced changes in EROs, which are related to those in local LV remodeling and in mitral deformation but not those in global LV function.     

Clinical relevance of exercise-induced ventricular arrhythmias in suspected coronary artery disease

Because there is controversy regarding the clinical relevance of exercise-induced ventricular arrhythmias, we analyzed their significance in 383 patients who had undergone both exercise thallium-201 stress-testing and cardiac catheterization. Two-hundred twenty-one patients (58%) had no exercise-induced ventricular arrhythmias while 162 (42%) did. There was no difference between patients with and without exercise-induced ventricular arrhythmias in terms of previous myocardial infarction (p = 0.61), incidence of fixed thallium-201 defects (0.06), number of diseased vessels (p = 0.09) and resting left ventricular ejection fraction (p = 0.06). In contrast, evidence of provocable ischemia (redistribution on thallium-201 and ST-segment depression on the electrocardiogram) were more likely (p less than 0.02) to be seen in patients with exercise-induced ventricular arrhythmias. Discriminant function analysis revealed that these 2 variables best separated patients with and without exercise-induced ventricular arrhythmias. In a 4- to 8-year follow-up, 89 patients had adverse cardiac events. Of these 89, there were 41 deaths, 9 nonfatal myocardial infarctions and 39 coronary revascularization procedures performed later than 3 months after catheterization. Patients with exercise-induced ventricular arrhythmias were more likely (p = 0.01) to have these events than those without these arrhythmias. Moreover, these arrhythmias provided independent prognostic information beyond that provided by the thallium-201 stress test and coronary angiography. We conclude that exercise-induced ventricular arrhythmias are associated with exercise-induced ischemia and provide prognostic information which adds marginally to that provided by other noninvasive and invasive parameters in ambulatory patients being evaluated for chest pain.     

Significance of exercise-induced junctional S-T depression in evaluation of coronary artery disease

Isolated junctional S-T depression induced during treadmill exercise testing was correlated with coronary arteriographic findings in 230 patients. Of 75 patients with junctional depression of less than 1.5 mm, 10 had 50 percent or greater stenosis of at least one major coronary artery and 2 patients (3 percent) had multivessel disease. Of 42 with junctional depression of 1.5 mm or more and a rapid upsloping S-T segment, 23 had 50 percent or greater coronary stenosis and 12 of these had multivessel disease. Of 35 with an upsloping pattern (Junctional depression of more than 2 mm, upsloping S-T segment depressed 2 mm or more, 0.08 second after the J point), 33 (94 percent) had 50 percent or greater coronary stenosis compared with 46 (96 percent) and 30 (97 percent) with 2 mm or more junctional depression and a horizontal or downsloping S-T segment. In conclusion, multivessel disease is rare with isolated exercise-induced junctional depression of less than 1.5 mm but common when the J point is depressed 1.5 mm or more. Junctional depression of more than 2 mm is associated with the same incidence of coronary disease when the S-T segment is slowly ascending (upsloping pattern) as when it is horizontal.     

Relation between QRS changes and left ventricular function after coronary artery bypass grafting

Preoperative and serial postoperative electrocar-diograms (ECGs) were reviewed in 104 patients undergoing rest and exercise radionuclide angiocardiography before and 1 to 12 months after coronary artery bypass grafting (CABG). Five patient groups were defined by ECG findings before and after CABG: Group I—normal ECG before and no ECG change after CABG; Group II—prior myocardial infarction by ECG before but no QRS change after CABG; Group III—all patients with a minor QRS change (< 0.04-second Q wave, loss of R-wave amplitude) after CABG; Group IV—all patients with a major QRS change (≥ 0.04-second Q wave) after CABG; Group V—all patients without new Q waves or loss of R-wave amplitude but with a major QRS change (conduction disturbance) after CABG. Mean resting ejection fraction changed little after CABG in all groups, although the 0.03 increase in Group I was significant (p < 0.05). Group IV had the largest decrease in resting ejection fraction after CABG (0.04), but this was not statistically significant. Mean exercise ejection fraction increased significantly (p < 0.0001) in Groups I, II and III but not in Groups IV and V. QRS changes do not consistently reflect impairment of left ventricular (LV) function after CABG.