Changes in the electrocardiographic response to exercise in healthy women.

Changes in the P wave, QRS complex, ST segment, and T wave during and after maximal exercise were quantitatively analysed in 116 healthy women with a mean age of 39. The corrected orthogonal Frank lead electrocardiogram was continuously recorded and computer processed during bicycle ergometry. With exercise, maximal spatial P wave vectors shifted downward. The Q wave amplitude became more negative and the R wave amplitude diminished considerably in leads X and Y: the S wave amplitude decreased only slightly in these leads. The QRS vectors shifted towards right and posteriorly during exertion and a further shift in the same direction was seen in the recovery period. The ST segment amplitude 60 ms after the J point decreased with exertion and became negative at heart rates above 140 beats per minute, in particular in lead Y. ST segment depression increased with age. The T wave amplitude decreased during exercise and increased sharply in the recovery period. Though mean R wave amplitude in leads X and Y became more negative with exercise, this response was unpredictable in individual women. The exercise induced changes in QRS vectors in women resembled those described in men. Changes in the amplitude of the R wave should not be used for the diagnosis of coronary disease in women. ST segment depression was more pronounced in the inferiorly oriented lead Y than in lead X but it was unrelated to changes in the QRS vectors in these leads.     

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.     

Giant R wave, convex ST-segment elevation, and negative T wave during exercise treadmill test

The giant R wave syndrome is characterized by giant R wave accompanied by widening of the QRS complex, marked ST segment elevation, QRS axis deviation, and the formation of monophasic QRS-ST complex with obliteration of S wave in leads facing the ischemic zone. This report describes a 65-year-old-man with variant angina who had a transient giant R wave syndrome during an exercise treadmill test. Initially, at peak exercise, there was a convex ST segment elevation ending in a negative T wave in the same (inferior) leads which showed giant R waves. Later, in the recovery period and coinciding with an amelioration of myocardial ischemia, there was a less marked increase of R wave amplitude associated with concave ST segment elevation and positive T wave in the inferolateral leads. Subsequently, a ST segment depression in the inferolateral leads preceded the ECG normalization. The patient had also a concave ST segment elevation and positive T wave in inferolateral leads during a spontaneous episode of variant angina at rest. An emergency coronary arteriography showed a dominant right coronary artery with an 80% and a 75% diameter stenosis of the middle and distal segment, respectively; the other arteries and left ventriculogram were normal. The underlying mechanisms of the different shapes of ST segment elevation and T waveform in the setting of acute transmural myocardial ischemia are discussed.     

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.     

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.     

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.     

Relation of exercise-induced physiologic S-T segment depression to R wave amplitude in normal subjects

Exercise electrocardiography was performed in 100 asymptomatic male volunteers with a mean age of 42.6 years. The R wave and total RS amplitude and the magnitude of physiologic S-T segment depression at the J junction were quantitated for a modified bipolar CC₅ lead and a vertically oriented bipolar lead (VL) using computer-averaged groups of 25 consecutive QRS complexes from each of seven stages of rest and exercise. Computer-generated X-Y plots were used to examine the correlations between the magnitude of S-T depression and the R wave and total RS amplitudes. The magnitude of S-T depression and of the R wave amplitude were unrelated at standing rest but showed increasing correlation with progressive increases in exercise heart rate (correlation coefficient = 0.425, p <0.00001 at maximal exercise). The total RS amplitude was also related to the magnitude of S-T depression during exercise, but the correlations did not improve progressively with increases in exercise heart rate. The magnitude of S-T depression was more closely related to R wave amplitude and total RS amplitude in the vertically oriented lead than in the CC₅ lead.These data demonstrate a significant relation between the magnitude of R wave and total RS amplitudes and the magnitude of physiologic S-T segment depression in normal subjects during exercise. They suggest the need for evaluation of S-T depression corrected for R wave amplitude in an attempt to improve the diagnostic accuracy of the exercise electrocardiogram. The data also suggest that the criteria for abnormal S-T depression should take into consideration the different R wave voltages reflected by different types of recording leads.     

A randomized trail of the effects of 1 year of exercise training on computer-measured ST segment displacement in patients with coronary artery disease

As part of a randomized trial of the effects of 1 year of exercise training on patients with stable coronary artery disease, 48 patients who exercised and 59 control patients had computerized exercise electrocardiography performed initially and 1 year later. The patients who had exercise training as an intervention had a 9% increase in measured maximal oxygen consumption and significant decreases in heart rate at rest and during submaximal exercise. ST segment displacement was analyzed 60 ms after the end of the QRS complex in the three-dimensional X, Y and Z leads and utilizing the spatial amplitude derived from them. Statistical analysis by t testing yielded no significant differences between the groups except for less ST segment displacement at a matched work load, but this could be explained by a lowered heart rate. Analysis of variance yielded some minor differences within clinical subgroups, particularly in the spatial analysis. Obvious changes in exercise-induced ST segment depression could not be demonstrated in this heterogeneous group of selected volunteers with coronary artery disease secondary to an exercise program.     

ECG changes in exercise-induced asthma

Changes in ECG during and after exercise were analyzed in 17 patients with exercise-induced asthma (EIA) and in 12 control patients (asthmatic patients without exercise-induced bronchial obstruction). The changes in ECG were compared with those in peak expiratory flow (PEF) rate and in arterial PCO2, PO2 and pH. It was found that in EIA the amplitude of the P wave increased in the inferior leads and decreased in the aVL lead during and after exercise. In addition, the amplitude of the R wave diminished and the amplitude of the S wave increased in the anterior precordial leads during bronchoconstriction. The changes in the ECG of the control patients were small and were already beginning to return to normal 4 min after exercise, whereas the changes in EIA patients persisted for 4-10 min after exercise. In EIA, a significant negative correlation was found between the PEF rate and the amplitude of the P wave in leads II, III and aVF. In addition, the PEF rate and the amplitude of the S wave in the V3 lead showed significant negative correlation. Almost no changes were observed in PO2 or PCO2 in the EIA or in the control patients. The pH decreased significantly in both groups during exercise. The PEF rate did not correlate with arterial PO2, PCO2 or pH after exercise in EIA.     

QRS Changes During Percutaneous Transluminal Coronary Angioplasty and Their Possible Mechanisms

Objectives. The purpose of the study was to describe the configuration, and investigate the mechanisms, of QRS changes occurring during percutaneous transluminal coronary angioplasty (PTCA).Background. QRS changes during PTCA have been attributed to both a passive ST segment shift and conduction disturbances (peri-ischemic block). The direct relation between ST segment shift and QRS changes, however, has not been established, and the definition of conduction disturbances remains to be clarified.Methods. Twelve-lead electrocardiograms (ECGs) were recorded before PTCA, at the end of 2 min of PTCA and after return to baseline values in 29 patients (left anterior descending coronary artery [LAD] in 13 patients, right coronary artery [RCA] in 14 and left circumflex coronary artery in 2). Electrocardiographic complexes before and during PTCA were superimposed to determine the amplitudes of initial, terminal and total QRS deflection; the relations of QRS changes to baseline (TP segment) and ST segment shift; and the duration of QRS and corrected QT intervals.Results. 1) The direction of the initial QRS deflection was unchanged, but changes of its amplitude occurred. 2) Terminal QRS deflection changed in all patients with a ST segment shift >17% of the R amplitude, and the correlation between the decrease in the S amplitude and ST segment shift was significant (r = 0.9, p < 0.01) in patients with LAD PTCA. Correlation between changes in total QRS amplitude and ST segment shift in patients with RCA PTCA was weaker (r = 0.54, p = 0.056). 3) Transient conduction disturbance manifested by QRS widening in selected leads occurred in 2 of 29 patients.Conclusions. 1) Changes in terminal QRS deflection during PTCA are proportional to the magnitude of the ST segment shift. 2) Conduction disturbances manifested by increased QRS duration occurred infrequently. We suggest that the term peri-ischemic block be applied only to changes in QRS configuration associated with QRS widening.     

The giant R wave of acute myocardial infarction

The common clinical electrocardiographic criteria for diagnosis of acute transmural myocardial infarction include ST segment elevation and tall, upright T waves, but do not include changes in QRS morphology. The purpose of this study was to show that development of a 50% or greater increase in R wave amplitude, the giant R wave, in patients with acute transmural myocardial infarction occurs, and also to characterize changes in QRS morphology which may aid the ECG diagnosis of acute transmural myocardial infarction. Over the past 6 years, 36 patients with an increase in R wave amplitude during acute transmural myocardial infarction were identified at the Strong Memorial Hospital Coronary Care Unit. A significant increase in R wave height (0.33 +/- 0.10 to 0.97 +/- 0.08 mV, p less than 0.05), width (0.03 +/- 0.00 to 0.08 +/- 0.01, p less than 0.05) and area (0.01 +/- 0.00 to 0.05 +/- 0.01 mV-msec, p less than 0.05) appeared in the same ECG lead demonstrating ST segment elevation and tall T waves during the acute phase of transmural myocardial infarction. Patients with diaphragmatic myocardial infarction showed a significant (p less than 0.05) rightward QRS frontal plane axis shift and patients with anterior wall myocardial infarctions developed an anterior QRS axis shift in the horizontal plane during occurrence of the giant R wave. We conclude from this preliminary study that the giant R wave may be observed during acute transmural myocardial infarction and may in part be caused by local intramyocardial conduction delay in acutely ischemic tissue as supported by an increase in the R wave width along with shifts in the frontal and horizontal plane QRS axis toward the area of acute ischemia. The giant R wave occurs in conjunction with ST segment elevation and tall T waves and may aid the ECG diagnosis of acute transmural myocardial infarction.     

Gradual changes of ECG waveform during and after exercise in normal subjects.

The directions and magnitudes of time-normalized P, QRS, and ST vectors, and other ECG parameters were analyzed during and after multistage exercise in 56 ostensibly healthy men aged 23 to 62. By selective averaging with a digital computer system a single representative beat was obtained from each stage. Measurements were taken from this beat. During exercise, the interval between the spatial maximum of the P wave and the onset of the QRS complex decreased while the magnitude of the P wave increased. The direction of the P vectors did not change. This pattern corresponds to the electrocardiographic manifestations of predominant right atrial overload. No significant changes in the QRS duration were observed. Also the magnitude and spatial orientation of the maximum QRS vectors remained constant. The interval between the QRS onset and the maximum spatial magnitude of the T wave shortened. The terminal QRS vectors and the ST vectors gradually shifted toward the right, and superiorly. The T magnitude lessened during exercise. In the first minute of the recovery period the P and T magnitudes markedly increased. Afterward all measurements gradually returned to the resting level. Mechanisms which may explain the observed ECG changes during and after exercise are discussed, including changes in the blood conductivity and intracardiac blood volume. Age did not contribute to the variance of the ECG measurements, but a significant reduction of this variance could be otained in some ST-segment measurements by relating them to heart rate with linear regression equations (P less than or equal to 0.05). Therefore it is expected that the sensitivity of the exercise ECG for detection of ischemic heart disease would be increased when heart rate dependent normal limits for ST-segment measurements are used. Different criteria should be employed for the interpretation of the ECG during and after exercise.     

Normal limits of the electrocardiogram in a Chinese population

12-lead electrocardiograms (ECGs) from 503 healthy Chinese individuals were computer-analyzed to derive the normal limits of the ECG in a Chinese population. With respect to ECG amplitudes, there were highly significant differences between men and women. The mean S wave amplitude in V2 decreased with increasing age, but the mean R wave amplitude in V5, for example, remained remarkably constant throughout the age groups. The QRS duration was on average 7.6 msec shorter in women than in men. The mean frontal QRS axis shifted superiorly by 17 degrees with increasing age, resulting in an upward trend in R wave amplitude in leads I and aVL. It was concluded that ECG diagnostic criteria for Chinese individuals should be age- and sex-dependent.     

Respective diagnostic value of CM5 and V5 leads in exercise tests. Comparative study of 100 cases

The respective diagnostic values of CM5 and V5 leads in exercise tests were studied in 100 patients, 89 of whom had coronary disease. Mean maximum ST depression and mean R wave amplitude at rest and at peak exertion were very much greater with CM5 than with V5 (p less than 0.0001). These two parameters seemed to vary concurrently. The contribution of both leads to the diagnosis in terms of sensitivity is probably the same; the more severe the coronary disease, the more pronounced the ST depression on CM5 tracings as compared to V5 tracings. A significant ST depression (1 mm) also appears more rapidly on the bipolar MC5 lead.     

Influence of hemodialysis on electrocardiographic wave forms

Alterations in Frank lead electrocardiograms induced by hemodialysis were investigated in 19 patients with chronic renal failure. The most prominent findings after hemodialysis were marked increases in the magnitudes of the R wave in Leads X, Y, and Z, and of the maximal QRS vectors in the frontal, sagittal, and transverse planes. Echocardiographic and roentgenographic examinations revealed no evidence of pericardial effusion before and after hemodialysis.Although the true origin of these findings remains undetermined, it appears reasonable to speculate that the decreased intracavitary blood volume due to hemodialysis may cause an increase in the QRS voltage by a short-circuiting effect. It should be emphasized that a sudden increase in QRS amplitude after hemodialysis might lead to an erroneous diagnosis of left ventricular hypertrophy. The clinician should be aware of such voltage increases when examining the ECGs of patients who undergo hemodialysis.     

Diagnostic value of amplitude variations of the QRS complex during computerized exercise testing

Two hundred and fifteen patients were examined: 20 athletes, 40 subjects with radiologically normal coronary arteries (NCA) and 155 patients with one or more coronary artery stenoses (82 without, 73 with previous myocardial infarction). Exercise testing was by bicycle ergometry. The ECG recordings obtained by a computerised system had stable base lines and variations in QRS amplitude related to respiration were eliminated. The changes in amplitude of the R wave (delta R) and QRS complex (delta QRS) during exercise are interesting, especially in lead CM5. The amplitude decreases or remains the same in athletes (delta R = -1.3 +/- 3.2 mm; delta QRS = 0.7 +/- 3.4 mm) and in patients with NCA (delta R = -0.2 +/- 2.5 mm; delta QRS = 0.5 +/- 3.1 mm). This contrasted with the coronary group in whom these amplitudes increased significantly (delta R = 1.5 +/- 2.9 mm; delta QRS = 3.1 +/- 3.2 mm, p less than 0,001). These variations did not give indications of ischaemia of another region or of the presence of an aneurysm in patients with previous infarction. The greatest variations in amplitude were observed in patients with signs of previous inferior infarction. Can this method provide diagnostic information in patients without previous myocardial infarction? If positive delta R and delta QRS are defined as increases of at least 1 mm on exercise, the diagnostic value of these changes (sensitivity: delta R = 58.5%, delta QRS = 78%; specificity: delta R = 67.5%, delta QRS = 57.5%) is comparable with the classical signs of: pain (sensitivity: 63%; specificity: 75%) and ST depression of over 1 mm in CM5 (sensitivity: 72%; specificity: 62.5%). In conclusion, in patients without previous myocardial infarction, the reliability of exercise stress testing in diagnosing coronary artery disease can be increased when the following three parameters are taken into consideration: pain, ST segment, delta R or delta QRS or both. When all three signs are negative, the stress test can be considered negative (the 82 coronary patients had at least one positive sign). The positivity of one sign alone corresponds to a normal coronary circulation in the majority of cases. The presence of 2 or 3 positive signs is very much in favour of coronary artery disease.     

Electrocardiographic findings in acute right ventricular infarction: sensitivity and specificity of electrocardiographic alterations in right precordial leads V4R, V3R, V1, V2, and V3

To determine the sensitivity, specificity, predictive value and diagnostic efficiency of electrocardiographic alterations in the diagnosis of acute right ventricular infarction, 43 autopsy patients with acute myocardial infarction and an electrocardiogram including 12 leads plus leads V3R and V4R were studied. Group A included 21 patients with right ventricular infarction, of whom 14 (group AI) had posterior and 7 (group AII) had anterior right ventricular infarction. Group B included 22 patients without right ventricular infarction. Excluding group AII patients, the sensitivity of the presence of a Q wave reached 78.6% in lead V4R and decreased in leads V1 to V3; its specificity was low in all the leads. The sensitivity of ST segment elevation reached 100% in lead V4R and decreased in leads V1 to V3; its specificity was highest (68.2%) in leads V4R and V3R, its negative predictive value was 100% and its diagnostic efficiency was 80.6%. The criterion of ST segment elevation in lead V4R being higher than that in leads V1 to V3 was less sensitive (78.6%) than ST segment elevation in lead V4R alone, but its specificity reached 100%, its positive predictive value 100% and its diagnostic efficiency 91.7%. In conclusion, there are no electrocardiographic criteria to identify anterior right ventricular necrosis, but posterior right ventricular necrosis may be identified by the presence of a Q wave or ST segment elevation in the right precordial leads, reaching the highest sensitivity and specificity in lead V4R. The criterion of ST segment elevation in lead V4R being higher than that in leads V1 to V3 offers the highest specificity and efficiency in the diagnosis.     

Late potential-like deflections in the ST segment of normal subjects

Irregular high frequency deflections of low amplitude have been found within the ST segment immediately following the QRS complex and in the T wave of high resolution bipolar recordings (lead V4-V7) in single beats as well as in averages of 100 beats. The signals in the T wave, found in six out of 22 normal subjects, coincide with the apex of the T wave in standard lead II. Their amplitude depends on the phase of the respiratory cycle. They were most pronounced during expiration. The occurrence of these signals depends on the position of the electrodes relative to the position of the equivalent current dipole, which is determined from simultaneous magnetocardiographic measurements. When electrode V4 is systematically shifted these signals vanish or increase, respectively become measurable.     

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.     

Correlation between R wave amplitude, exercise ischemic electrocardiographic indices and thallium-201 imaging defects in patients with known coronary artery disease

We investigated the relation between R wave amplitude (RWA) and ST depression as well as the presence and extent of reversible ischemia in thallium-201 scanning in patients with known coronary artery disease (CAD) and found that RWA both at rest and during exercise testing (ET) correlates with the magnitude of ST depression in the same leads. Greater ST changes appear on leads with highest RWA. Thus lead selection strongly influences interpretation of ECG ischemic changes during ET in patients with CAD. An electrocardiographic result negative for ischemia in patients with low RWA should prompt the alternative use of echocardiography and scintigraphy.