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.     

心磁图对冠心病心肌缺血与高血压心室肥厚的诊断价值

目的 探讨心磁图（MCG）在诊断冠心病心肌缺血及高血压左心室肥厚中的作用.方法 ①冠状动脉造影（CAG）的104例患者,分为CAG阳性的冠心病组及CAG阴性的非冠心病对照组,对照观察MCG与核素心肌灌注显像（MPI）在诊断冠心病中的应用价值.②收集所有同时行超声心动图（UCG）、CAG及MCG检查患者共205例,以UCG检查为诊断标准将患者分为左心室肥厚组（93例,室壁厚度≥12 mm）和对照组（112例,CAG阴性,室壁厚度〈12 mm）.确定QRS波最大磁通量（R1）、QRS波最小磁通量（R2）、QRS波最大磁通量与QRS波最小磁通量的差值（R1-R2）在左心室肥厚的诊断标准,并观察MCG在诊断左心室肥厚中的作用.结果 ①以CAG作为诊断冠心病的金标准,MCG7项参数中任意2项以上阳性,诊断冠心病的敏感性为81.25%,特异性为59.72%,任意3项以上阳性,诊断冠心病的敏感性为65.63%,特异性为69.44%.MPI诊断冠心病的敏感性为75.00%,特异性为79.20%.②确定R1、R2及R1-R2诊断左室肥厚的标准为〉18.5pT,〈-10pT及〉28pT,三项参数诊断高血压左心室肥厚的敏感性分别为58.82%、55.88%、55.88%,特异性分别为68.75%、80.36%、71.43%.MCG 7项复极参数中任意3项以上阳性,诊断左心室肥厚的敏感性为64.71%,特异性为69.64%.结论 ①心磁图与核素心肌灌注显像相似,在冠心病心肌缺血的诊断中具有较好的临床应用价值,MCG绝对无创,更易于临床推广应用.②心磁图在高血压左心室肥厚的诊断中具有较好临床应用前景.     

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.     

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.     

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.     

Variable patterns of ST-T abnormalities in patients with left ventricular hypertrophy and normal coronary arteries.

BACKGROUND--Classically, the ST-T configuration in the electrocardiogram of patients with left ventricular hypertrophy is said to have a typical pattern of ST depression together with asymmetrical T wave inversion (the so-called left ventricular strain pattern). However, many patients with left ventricular hypertrophy may also have ischaemic heart disease. To revise the electrocardiographic criteria for left ventricular hypertrophy the ST-T configuration in patients with left ventricular hypertrophy documented by echocardiography and with normal coronary arteries was assessed. METHODS--24 patients were selected for this study. All had left ventricular hypertrophy documented by echocardiography, normal coronary arteries by cardiac catheterisation, and ST and/or T wave abnormalities in the lateral leads of their electrocardiogram. There were eight patients with aortic valve disease and 16 with hypertension who had coronary angiography as part of an investigation into the risk factors of sudden cardiac death caused by hypertensive left ventricular hypertrophy. No patient was receiving digitalis preparations or had electrolyte disturbances, and none had a previous myocardial infarction or ventricular conduction defect. RESULTS--Typical electrocardiographic evidence of left ventricular strain was found in approximately two thirds (63%) of patients and 95% of this subgroup had asymmetrical T wave inversion. Flat ST segment depression, with or without T wave inversion or isolated T wave inversion (symmetrical or asymmetrical) in the anterolateral leads, was seen in the remaining 37% of patients. CONCLUSIONS--These findings indicate that left ventricular hypertrophy without coronary artery disease can cause variable types of ST-T abnormalities in the anterolateral leads including the typical left ventricular strain pattern and non-specific ST-T changes. Non-specific abnormalities could not be distinguished from those of coronary artery disease and may adversely affect the accuracy of the electrocardiographic criteria for the diagnosis of left ventricular hypertrophy because they do not accord with the criteria for left ventricular strain.     

Negative U wave: A highly specific but poorly understood sign of heart disease

A negative U wave is highly specific for the presence of heart disease and is associated with other electrocardiographic abnormalities in more than 90 percent of patients. The three most common conditions associated with a negative U wave are systemic hypertension, aortic and mitral regurgi- tation and ischemic heart disease. The U wave vector is directed opposite to the QRS axis in the horizontal plane in patients with both left and right ventricular hypertrophy. In patients with ischemic heart disease, the U wave vector tends to be directed away from the site of the akinetic or dyskinetic region. The change from a negative to an upright U wave after a reduction in blood pressure, renal transplantation, insertion of a valve prosthesis or a coronary arterial bypass graft procedure is associated with a decrease in the QRS amplitude but with no consistent changes in T wave polarity. The timing of the U wave apex is dependent on the duration of ventricular repolarization but not on the duration of the QRS complex. This finding and other electrocardiographic observations are explained better by the ventricular relaxation than by the Purkinje fiber repolarization theory of U wave genesis.     

体表记录心室晚电位对冠心病室性心律失常临床意义

本文应用体表记录心室晚电位的方法,对220人(正常人78名);急性心肌梗塞92例;陈旧心肌梗塞50例;心绞痛10例进行了检测。正常人无一例晚电位阳性,而陈旧心肌梗塞合并室性心动过速(室速)者晚电位阳性率高达66.7%。心肌梗塞部位、室壁瘤及左室射血分数与晚电位缺乏相关性。体表记录心室晚电位对于冠心病室性心律失常的检测不失为一种有价值的非创伤性手段。     

Analysis of exercise-induced R wave amplitude changes in detection of coronary artery disease in asymptomatic men with left bundle branch block

The exercise electrocardiograms of 44 asymptomatic men with acquired left bundle branch block were analyzed for changes in R wave amplitude. Results were correlated with findings on selective coronary angiography. There were two subgroups: 7 men with significant angiographic coronary artery disease (Group I) and 37 with normal coronary angiograms (Group II). Exercise induced an increase in R wave amplitude in all seven men with coronary artery disease but in only 10 of the 37 men without significant coronary artery disease. This criterion thus had a sensitivity of 100 percent but a poor specificity of 73 percent, a predictive value of 41 percent and an accuracy rate of 77 percent for the diagnosis of coronary artery disease. The greater the increase in R wave amplitude the greater was the likelihood of some degree of left ventricular dysfunction as measured by wall motion abnormalities and elevated left ventricular end-diastolic pressure. The increase in R wave amplitude with exercise appears to be a sensitive test in identifying coronary artery disease in asymptomatic men with acquired left bundle branch block.     

Left ventricular hemodynamics in patients with coronary artery disease and in normal subjects: Correlations with the extent of coronary artery lesions and the electrocardiogram

Left ventricular hemodynamics were studied during supine leg exercise immediately prior to coronary arteriography in seventy-one patients with coronary artery disease and nineteen without evidence of heart disease. Patients were divided into six groups, based on the number of major coronary arteries (right coronary, left anterior descending, left anterior descending diagonal, left circumflex, left circumflex marginal) with greater than 75 per cent obstruction. Mean resting and exercise left ventricular end-diastolic pressure (LVEDP) and increase in LVEDP during supine exercise rose progressively with more extensive coronary artery disease. All patients without coronary artery disease or with disease confined to one coronary artery had LVEDP of less than 24 mm Hg during exercise. There was no significant difference between groups with coronary artery disease in regard to stroke volume, heart rate and systemic arterial pressure. There was no significant difference in LVEDP at rest or during exercise between patients with normal and those with abnormal resting electrocardiograms. However, in patients with abnormal electrocardiograms after exercise, the mean LVEDP was significantly higher than in those with normal electrocardiograms after exercise (P < 0.05). Other hemodynamic differences between patients with normal and those with abnormal electrocardiograms after exercise were insignificant.     

Anomalies of the T wave following treatment of complete chronic left branch block by massage of the carotid sinus or injection of adenosine triphosphate

We studied the T wave during normal conduction in 25 patients aged 42 to 81 years (average 62 +/- 5) during sinus rhythm and complete left bundle branch block which regressed transiently after carotid sinus massage (22 cases) or injection of adenosine triphosphate (5 cases). Six patients had angina pectoris; coronary arteriography in 3 of the other 19 patients was normal. The reversion to normal intraventricular conduction was obtained with a lengthening of the ventricular cycle in all patients. The T wave axis with narrow QRS complexes was between + 70 degrees and -140 degrees (normal T axis in 11/25 patients); in the horizontal plane, the T wave was negative in V2 in 4 patients, in V2-V4 in 12 patients, in V2-V6 in 7 patients and in V4 in 1 patient. The amplitude of inversion in V2 varied from 0.1 to 1.5 mV; there was no significant difference between the patients with angina (0.50 +/- 0.31) and the remainder (0.43 +/- 0.16). In normal conduction, the T wave changes were more common in the horizontal plane (24/25 patients: 96%) than in the frontal plane (14/25 patients, 56%). The high incidence of abnormalities of ventricular repolarisation after regression of complete left bundle branch block does not appear to be related to coronary artery disease. Another explanation is proposed because of the analogy with the changes observed after terminating right ventricular pacing and after regression of a Wolff-Parkinson-White syndrome. An abnormality of initial ventricular depolarisation--common to left bundle branch block, the Wolff syndrome and right ventricular pacing--could be responsible for these T wave changes during normal conduction.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

心电图QRS记分与左室功能及冠状动脉病变关系的探讨

对２１例做过左室和冠状动脉造影的首次发生Ｑ波型急性前壁或下壁心肌梗塞患者采用Ｗａｇｎｅｒ心电图记分法进行心电图ＱＲＳ记分。结果显示：ＱＲＳ记分分别与左室射血分数和左室壁运动记分呈显著负相关和正相关（ｒ值分别为－０．８７和０．８０，Ｐ均＜０．０１）；单支和多支血管病变者ＱＲＳ记分无显著性差异（５．７７±２．９５ｖｓ７．１２±３．６０，Ｐ＞０．０５）；ＱＲＳ记分与冠状动脉记分无相关性（ｒ＝０．０９，Ｐ＞０．０５）。提示简便的ＱＲＳ记分法可以较好地反映急性心肌梗塞患者的左室功能。     

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.     

QRS score improves diagnostic ability of treadmill exercise testing in women

OBJECTIVE: The accuracy of treadmill exercise testing to detect coronary artery disease is limited in women. This study was undertaken to evaluate whether QRS score can improve the accuracy of treadmill exercise testing in women. METHODS: The study population consisted of 114 women with angina-like symptoms, who underwent both treadmill exercise testing and coronary angiography. The impact of QRS score on the standard ST-segment based diagnostic ability of treadmill exercise testing to detect coronary artery disease was studied. RESULTS: Incorporation of QRS score in standard ST-segment diagnostic criteria significantly enhanced sensitivity (from 59 to 80%), specificity (from 40 to 94%) and diagnostic accuracy (from 50 to 87%) of treadmill exercise testing. The QRS score was shown to reduce significantly the false-positive results from 60 to 6%. Furthermore, QRS score accuracy was correlated with the extent of coronary artery disease. The diagnostic ability of QRS score was greater both among patients with normal and impaired systolic function of the left ventricle. CONCLUSIONS: QRS score can improve the limited diagnostic accuracy of treadmill exercise testing in women, by predominantly decreasing the high prevalence of false-positive results.     

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.     

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.     

Comparison of exercise QRS amplitude changes in patients with slow coronary flow versus significant coronary stenosis

Exercise Q, R, and S wave amplitude changes, called the QRS score, have been reported to be a marker of exercise-induced myocardial ischemia. Therefore, in this study, using the exercise QRS score, we sought to determine if slow coronary flow (SCF) phenomenon is associated with the exercise-induced myocardial ischemia. This retrospective study included 23 patients evaluated for suspected coronary artery disease and found to have SCF (group I) and 19 subjects with angiographically-defined significant coronary artery stenosis (group II). All study subjects underwent treadmill exercise testing using the modified Bruce protocol. For each subject the amplitude of the Q, R, and S waves in leads aVF and V5 was measured manually using calipers before and immediately after exercise. The QRS score was calculated by subtracting the Q, R, and S wave differences in leads aVF and V5. There was no difference between the two groups with respect to demographic properties. The peak heart rate achieved, baseline and peak systolic-diastolic blood pressure, exercise duration, and the metabolic equivalent values were similar in both groups. The maximum ST-segment depression ratio was significantly lower in patients with SCF than those of significant coronary stenosis (0.8 +/- 0.4 vs 1.3 +/- 0.5 P = 0.001, respectively). However, the exercise QRS score was found to be similar in both groups (3.3 +/- 2.3 vs 2.1 +/- 3.0 P = 0.2, respectively). The data suggest that SCF phenomenon may alone lead to myocardial ischemia even in the absence of obstructed major epicardial coronary arteries as detected by similar exercise QRS scores to those of significant coronary artery stenosis.     

QRS voltage of the electrocardiogram and Frank vectorcardiogram in relation to ventricular volume.

Left ventricular volumes were estimated in 59 patients, who were investigated by single plane ventriculography and coronary arteriography. The relation of the left ventricular end-diastolic volumes to the QRS voltage of the 12-lead electrocardiograms and Frank vectorcardiograms was examined. It was found that the maximum spatial QRS voltage and the R wave voltage of leads V5 and V6 in patients without left ventricular hypertrophy were inversely correlated with end-diastolic volume. This inverse relation of QRS voltage and left ventricular volume may explain loss of QRS voltage with dilatation of the heart. In patients with left ventricular hypertropy QRS voltage is usually positively correlated with the degree of hypertrophy, but there is no significant correlation in the presence of cardiac dilatation. If the results of this study are extrapolated to patients with left ventricular hypertrophy and cardiac dilatation, then the inverse correlation of volume and QRS voltage may reduce the diagnostic sensitivity of unipolar chest lead and vectorcardiographic criteria of left ventricular hypertrophy.     

QRS voltage of the electrocardiogram and Frank vectorcardiogram in relation to ventricular volume.

Left ventricular volumes were estimated in 59 patients, who were investigated by single plane ventriculography and coronary arteriography. The relation of the left ventricular end-diastolic volumes to the QRS voltage of the 12-lead electrocardiograms and Frank vectorcardiograms was examined. It was found that the maximum spatial QRS voltage and the R wave voltage of leads V5 and V6 in patients without left ventricular hypertrophy were inversely correlated with end-diastolic volume. This inverse relation of QRS voltage and left ventricular volume may explain loss of QRS voltage with dilatation of the heart. In patients with left ventricular hypertropy QRS voltage is usually positively correlated with the degree of hypertrophy, but there is no significant correlation in the presence of cardiac dilatation. If the results of this study are extrapolated to patients with left ventricular hypertrophy and cardiac dilatation, then the inverse correlation of volume and QRS voltage may reduce the diagnostic sensitivity of unipolar chest lead and vectorcardiographic criteria of left ventricular hypertrophy.