Prevalence and magnitude of S-T segment and T wave abnormalities in normal men during continuous ambulatory electrocardiography

Fifty asymptomatic normal male volunteers, mean age 44.6 years (range 35 to 59), were prospectively studied to ascertain the prevalence and magnitude of S-T segment and T wave changes detected during continuous ambulatory electrocardiographic monitoring. Transient S-T segment depression of 1.0 mm or more was recorded in 15 (30 percent) of the subjects, and labile T wave inversion of up to 3 mm occurred in an additional 18 (36 percent). The presence of ST-T changes during monitoring did not correlate with age, daily activity status or heart rate. There was also no correlation with the S-T segment response or work performance during treadmill exercise testing. It is concluded that S-T segment depression and T wave inversions are commonly observed during ambulatory electrocardiographic monitoring of normal men. Therefore, similar changes observed in patients with coronary artery disease should be interpreted with caution.     

Evaluation of abnormal exercise electrocardiogram in apparently healthy subjects: Labile repolarization (ST-T) abnormalities as a cause of false positive responses

Long-term follow-up studies were carried out in 121 apparently healthy men with an abnormal S-T segment response to exercise—49 Indiana State policemen and 72 subjects from a large occupational health center. The mean follow-up periods were 66 months and 43 months, respectively, for the two groups of subjects. A tendency toward labile S-T or T wave abnormalities were documented during standing rest or with hyperventilation in 61 of these 121 subjects and there was only one new coronary event in this subgroup. The labile ST-T wave changes and the abnormal S-T segment responses to exercise were not consistently reproducible in these subjects, and it was not unusual to see an abnormal S-T segment response at a time when the labile repolarization changes could not be demonstrated. Many of the subjects exhibited labile ST-T wave changes only after oral glucose loading. Significant coronary artery disease was documented in 34 (57 percent) of the remaining 60 subjects during the follow-up period.Coronary cineangiographic studies, obtained in 21 of the 35 subjects from the health center who had had no evidence of labile ST-T wave abnormalities, revealed coronary arterial stenoses of 75 percent or greater in 19. A statistical analysis was carried out in the 35 subjects without labile ST-T abnormalities to determine if there were exercise test variables that would differentiate the true positive from the false positive responses. A set of criteria were identified that yielded a specificity of 92 percent, a sensitivity of 82 percent and a predictive value of 95 percent. The entire group of 72 from the health center subjects had undergone an average of 3.8 exercise tests before their referral to the authors' laboratory. A review of these records revealed that a serial conversion from a normal to an abnormal S-T segment response was not more predictive of underlying coronary artery disease than an initially abnormal test result.     

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

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

Transient asymptomatic S-T segment depression during daily activity.

The significance of asymptomatic episodes of ischemic type S-T segment depression was studied in 20 patients with coronary heart disease. Continuous 10 hour electrocardiographic recordings accompanied by detailed daily diaries of activity and symptoms were obtained periodically during a mean time of 16 months. All patients had ischemic type S-T depression associated with angina pectoris during treadmill exercise. Measurements of heart rate, S-T depression and exercise level at the onset of angina obtained during repeated controlled exercise tests at the start of each study period were compared with the measurements recorded during daily activity. After 2,826 hours of recording, 411 transient epidsodes of ischemic type S-T depression were noted during usual daily activity. Only 101 (25 percent) of these episodes were associated with angina. The remaining episodes were unrelated to other symptoms or to posture. All occurred at heart rates significantly lower than those observed at the onset of angina during exercise testing. Of these episodes of asymptomatic S-T depression, 72 percent occurred only at rest or during very light activity such as slow walking or sitting. Nitroglycerin administered hourly significantly reduced the frequency of these episodes, thus supporting the concept that they represent painless ischemia. Because the episodes of asymptomatic ischemic type S-T depression occurred more frequently than angina during usual daily activity and were evident at heart rates and activity levels well below those expected to evoke ischemia, they may be caused by factors other than those that cause angina.     

Upsloping S-T segments in exercise stress testing. Six year follow-up study of 438 patients and correlation with 248 angiograms.

A 6 year follow-up study of 438 patients who underwent maximal treadmill stress testing revealed the following annual incidence rate of coronary events (death, myocardial infarction or onset or progression of angina pectoris): 13 percent in 84 subjects whose stress test produced 2 mm downsloping S-T segment depression, 9 percent in 230 subjects with 2 mm horizontal S-T depression and 9 percent in 124 subjects who had an upsloping S-T segment with 2 mm S-T depression measured 0.08 second from the J point. Coronary angiograms were obtained in another group of 248 subjects who underwent maximal treadmill stress testing. They revealed major (greater than 50 percent) obstruction of two or three vessels in 67 percent of 62 subjects with a downsloping S-T pattern on the stress test, in 60 percent of 116 subjects with horizontal S-T depression and in 57 percent of 70 subjects with upsloping S-T depression. Patients with an upsloping pattern of S-T depression during stress testing had the same incidence of coronary events as those with a horizontal pattern of S-T depression. Upsloping S-T depression should not be confused with isolated J point depression. Subjects with an upsloping segment also had the same incidence of major two or three vessel disease as those with horizontal depression. Subjects with a downsloping pattern has a slightly greater incidence of coronary events and major two or three vessel disease.     

The influence of lead strength on the S-T changes with exercise electrocardiography (correlative study with coronary arteriography)

The contribution of relative lead strength to S-T segment depression amplitude during exercise was evaluated in 98 patients who had both a treadmill stress test and a coronary arteriogram. This was accomplished by constructing an exercise S-T depression to R wave ratio (S-T/R) and then relating these ratios to the extent of coronary disease found with arteriography. The additional criterion of 1 mm S-T depression for the bipolar V5 and 0.5 mm for the late unipolar V5 was also reviewed. These criteria were then compared to the sensitivity and specificity of the usual 1 mm S-T depression criterion. The S-T/R ratio of 0.04 improved the detection of significant coronary disease over the usual criteria. The ratio of 0.1 was effective in avoiding false positive tests but lacked sensitivity. This would suggest that strong lead systems may give false positive S-T changes with exercise. The use of 0.5 mm depression as abnormal for the post-exercise unipolar V5 improved sensitivity without loss of specificity over the usual criteria of 1 mm S-T depression criteria. This may be a reflection of the voltage differences between the bipolar lead and the unipolar lead in these two lead systems. It is concluded that lead strength must be considered when evaluating the S-T response to exercise.     

Exercise-Induced S-T segment elevation in variant angina

Five patients with known ischemic heart disease had an unusual pattern of S-T segment depression during treadmill exercise testing followed by S-T segment elevation and chest pain in the postexercise period. Thallium-201 scintigraphy revealed reversible exercise-induced myocardial ischemia, in areas supplied by severely narrowed coronary arteries as documented by coronary arteriography. Ambulatory electrocardiographic recording for S-T segment shift using a frequency-modulated system showed S-T segment depressions and elevations at rest in the same leads that showed similar shifts during exercise tests. Three of the five patients had a myocardial infarction within 8 weeks of diagnosis, and two died. This syndrome may be associated with severe coronary artery disease and may have a very poor prognosis.     

The predictive value of a strongly positive stress test in patients with minimal symptoms

The ability of a strongly positive stress test to predict left main coronary artery disease in people with suspected coronary artery disease but with minimal or no angina was investigated in 40 such patients. Nine had a history of myocardial infarction but no angina. Thirty-one had mild angina or a history of mild angina. The stress electrocardiograms were analyzed according to criteria known to be associated with left main coronary artery disease in moderately or severely symptomatic patients; (1) early S-T segment changes (stage I or II of exercise), (2) 2 mm or more S-T segment depression, (3) downsloping S-T segments, (4) associated exercise-induced hypotension, (5) prolonged S-T segment changes after the test (≥8 minutes) and (6) anterior and inferior S-T segment depression. The prevalence of left main coronary artery disease was 35 percent and that of any severe coronary artery disease 75 percent. The criterion of anterior and inferior electrocardiographic changes with exercise was most predictive of left main coronary artery disease (P < 0.01 by χ²). Exercise electrocardiography is useful in the prediction of left main or other severe coronary artery disease even when performed in patients who have minimal angina or in those who are asymptomatic after myocardial infarction.     

Myocardial infarction after exercise-induced electrocardiographic changes in a patient with variant angina pectoris

The electrocardiographic response to stress testing varies considerably in patients with variant angina pectoris: no change in the S-T segment as well as S-T segment depression and elevation have been observed. This report describes a patient with a resting ST-T abnormality that reverted to normal appearance with exercise. However, the patient experienced severe chest pain shortly after discontinuing exercise testing, and an electrocardiogram showed evidence of acute anterolateral infarction. The possible implications of such electrocardiographic changes are discussed.     

Predictive accuracy of Q-X/Q-T ratio, Q-Tc interval, S-T depression and R wave amplitude during stress testing.

The sensitivity, specificity and predictive value for $\text{Q-X}\text{Q-T}$ ratio, Q-Tc interval, S-T segment depression, R wave change and various combinations of these criteria were compared in 50 healthy, normal persons and 50 persons with angiographic coronary artery disease defined as 70 percent or greater stenosis of one or more major coronary vessels. Use of a positive S-T segment response and an increase or no change in R wave amplitude as criteria for coronary artery disease resulted in 84 percent sensitivity and 96 percent specificity levels and a 95 percent predictive value. The $\text{Q-X}\text{Q-T}$ and Q-Tc criteria offered no improvement in sensitivity, specificity or predictive value over S-T segment depression.When the study group was limited to 74 persons, 36 without and 38 with angiographically significant coronary artery disease, a Q-Tc interval of 1.08 or more in combination with either slowly or rapidly upsloping S-T depression after exercise predicted coronary disease at a sensitivity level of 76 percent compared with 50 percent with use of the S-T segment alone (P < 0.05). Specificity was not significantly reduced (89 percent for the S-T segment alone, 79 percent with the addition of the Q-Tc interval) (P > 0.05).Use of the R wave response with the presence of upsloping S-T segment depression of 1.5 mm or more 80 msec from the J point improved the sensitivity level from 50 percent for S-T depression alone to 76 percent (P < 0.05); specificity and predictive value were not significantly reduced (81 percent for each [P > 0.05]). The $\text{Q-X}\text{Q-T}$ ratio could be measured in only 55 patients (74 percent) and offered no improvement over S-T segment depression.Upsloping S-T segment depression of 1.5 mm or more 80 msec from the J point in the immediate postexercise period is most likely a positive test for ischemia. An increase or no change in R wave amplitude in response to exercise in these patients regardless of the degree of S-T segment depression is probably indicative of coronary artery disease. In patients with upsloping S-T segment depression, a Q-Tc interval of 1.08 or more in the immediate postexercise period is a useful measurement in predicting coronary artery disease.     

The quiz electrocardiogram: a new diagnostic and research technique for evaluating the relation between emotional stress and ischemic heart disease.

To evaluate possible cardiovascular effects of emotional stress, a specially designed 12 minute tape-recorded stress quiz was administered to 43 subjects while blood pressure and the electrocardiogram were monitored. For the entire group, the heart rate and blood pressure rose from respective control levels of 76 beats/min and 136/87 mm Hg to a mean during the quiz of 87 beats/min and 158/94 mm Hg. This difference was highly significant. Of the 43 subjects, 33 were classified as executives and 10 as nonexecutives. There were three groups of executives: control and angina with and without a history of hypertension. Both groups of executives with angina responded with a significantly higher heart rate than that of the executive control group. Blood pressure response was significantly greater in executives with angina and hypertension than in the other groups. Heart rate and systolic blood pressure responses to the quiz were lower in nonexecutives with angina than in executives with angina. During the quiz, 10 of 14 executives with angina had S-T segment depression greater than 0.5 mm; of these, 7 evidenced greater than 1.0 mm depression, andin 3 of these the depression was greater than 1.5 mm and in 2 greater than or equal to 2.0 mm. None of the executive control subjects had S-T depression greater than 0.5 mm Among nonexecutives, 2 had S-T depression greater than 0.5 mm but none greater than 1.0 mm S-T depression. Seventeen of the patients also were given a bicycle exercise tolerance test. There was a significant correlation between S-T depression in response to exercise and to the quiz (r = 0.63; P less than 0.01). The quiz electrocardiogram is presented as a new research technique and diagnostic test for evaluating the relation of emotional stress to ischemic heart disease.     

Comparison of ambulatory electrocardiography and exercise testing

Ambulatory electrocardiography and exercise testing are two noninvasive diagnostic procedures widely employed to evaluate patients for cardiac arrhythmias and S-T segment changes. This review addresses the differences and similarities of the two techniques, and examines the relative diagnostic and prognostic merit of the arrhythmia and S-T segment changes detected with each method.

Ambulatory electrocardiography is more sensitive than exercise testing in detecting cardiac arrhythmias. The recording of ventricular arrhythmia is of value in predicting sudden death in survivors of myocardial infarction, whereas exercise-induced ventricular arrhythmia has limited predictive value. Nevertheless, exercise-induced S-T depression is of great prognostic value in predicting mortaliy and sudden death in patients wlth acute and chronic coronary heart disease.     

Exercise-induced angina provoked by aspirin administration in patients with variant angina

The effects of aspirin (4.0 g/day) given orally to eight patients with variant angina were observed. An exercise stress test performed in the morning was positive in two of seven patients during placebo administration, whereas a test performed in the afternoon at the same exercise work load resulted in negative findings. During aspirin administration, the afternoon exercise test repeatedly provoked anginal attacks associated with electrocardiographic changes (S-T segment elevation in five and S-T depression in two). Rate-pressure product at the end of the exercise test during aspirin administration was significantly lower than that during placebo administration (p <0.01). During aspirin administration, the frequency of angina increased markedly, and the attacks occurred not only during the night or early morning but also in the daytime in six of the eight patients. Our observations suggest that aspirin, in this large dose, reduces the capacity for exercise and provokes exercise-induced coronary arterial spasm in patients with variant angina.     

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

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

Significance of chest pain during treadmill exercise: correlation with coronary events

A follow-up study of 1,402 patients with a positive maximal treadmill stress test was made to evaluate the significance of angina during the test. Life tables were constructed and evaluated for significance of age, sex and work load at onset of angina. Coronary events (myocardial infarction, progression of angina and coronary death) were twice as frequent in subjects with angina and S-T segment depression as in those without angina. The increased incidence in 4 years held for all coronary events and was still doubled at 7 years for progression of angina and coronary death. The incidence of coronary events was more than twice as great when the angina was induced by a light work load (4 metabolic equivalents = METS) as when it was induced by a heavy work load (8 to 9 METS). Men aged 41 to 50 years having angina during exercise testing had a 3-fold greater incidence of coronary events and a 4-fold greater incidence of myocardial infarction compared with their counterparts who had S-T segment depression alone. In this study, angina during exercise testing identified 85% of true positive tests for coronary artery disease, whereas S-T depression alone identified only 64% of such tests. Thus, angina during exercise testing increases the sensitivity of the test and identifies cohorts of subjects at high risk for subsequent coronary events.     

Comparison of the two-step and maximal exercise tests in patients with coronary artery disease

This study has investigated the claim that the electrocardiographic response to the maximal exercise test provides a more accurate method of assessing the presence and severity of coronary artery disease than the electrocardiographic response to the two-step test. One hundred and one men with a chest pain syndrome underwent the two-step test, maximal exercise test and coronary angiography during the same admission. There was a preponderance of men who performed the maximal exercise test as a result of a negative two-step test. A positive two-step test was defined as horizontal or downsloping S-T segment depression of 0.5 mm or more, whereas a positive maximal exercise test was defined as similar S-T segment depression of 1.0 mm or more. Of the 17 men with no or insignificant coronary artery disease, 5 had a positive two-step test and 6 a positive maximal exercise test. Of the 84 men with coronary artery disease, 33 had a positive two-step test and 38 a positive maximal exercise test. Thus, the specificity of the two-step test for coronary artery disease was 87 percent and that of the maximal exercise test was 86 percent; the respective sensitivity rates were 39 and 45 percent. The percentage of positive results of both exercise tests increased similarly with the severity of coronary artery disease.Nine patients, eight of whom had coronary artery disease, had a positive maximal exercise test but a negative two-step test; in these patients the maximal heart rate was significantly higher during the maximal exercise test than during the two-step test. Five patients, all with coronary artery disease, had a positive two-step test but a negative maximal exercise test. One patient manifested 0.5 mm S-T segment depression in both tests and was thus judged to have a positive two-step test and a negative maximal exercise test. In another patient results were positive in lead V₄ of the two-step test, a lead not recorded in the maximal exercise test. The other three patients had had positive results in a second maximal exercise test recorded in the supine position, thus demonstrating that in certain cases the effects of augmented venous return in the supine position may be as important a factor in eliciting ischemia as the achieved heart rate.     

Exercise cross-sectional echocardiographic diagnosis of coronary artery disease

To test the feasibility of detecting transient left ventricular regional wall motion abnormalities during exercise-induced myocardial ischemia, 55 patients undergoing diagnostic coronary arteriography were studied in a prospective blinded manner with wide angle cross-sectional echocardiography. The ultrasonic studies were obtained with the patients at rest and during exercise in the supine position using a bicycle ergometer. Cross-sectional echocardiographic studies during exercise were adequate for analysis in 43 (78 percent) of the 55 patients. Forty-one of the 43 manifested either a new regional wall motion abnormality during exercise (20 subjects) or wall motion that remained entirely normal during exercise (21 subjects); In two subjects an abnormal wall motion abnormality at rest did not change with exercise. Nineteen of the 20 patients with a new regional wall motion abnormality had significant coronary artery disease and 15 of these 19 had S-T segment depression during bicycle ergometry. The one patient with a normal coronary arteriogram had an early cardiomyopathy. Ten of the 21 subjects with normal wall motion at rest and during exercise had a normal coronary arteriogram, whereas 11 had evidence of important anatomic coronary artery disease and thus had a false negative echocardlographic findings. Six of these 11 patients had S-T segment depression during exercise. The usefulness of exercise echocardlography to predict coronary artery disease was not altered even when only 26 patients without previous myocardial infarction and with a normal cross-sectional echocardiogram at rest were considered. Thus, new regional wall motion abnormalities during exercise as identified with cross-sectional echocardiography represent a specific finding for the presence of coronary artery disease. However, normal regional wall motion during exercise does not exclude the presence of important anatomic coronary artery disease.     

The false positive stress test : Multivariate analysis of 215 subjects with hemodynamic,angiographic and clinical data

Factors causing the false positive stress test and the ability of the computer to improve test classification were studied in 95 patients with a positive stress test and normal coronary angiograms and 125 patients with a true positive stress test. Multivariate analysis revealed that in men the following clinical findings other than S-T depression were useful in correct stress test classification: (1) maximal heart rate, (2) maximal systolic blood pressure, (3) contour of S-T segment, (4) age, (5) history of chest pain, (6) T waves in resting record, (7) chest pain during test, (8) S-T and T changes with hyperventilation, (9) resting electrocardiogram, (10) time of onset of S-T depression, and (11) increase in P wave negativity in lead V₁ with exercise. These variables, presented in order of importance, had a different ranking in women.     

Incidence and significance of decreases in systolic blood pressure during graded treadmill exercise testing.

The incidence of decreases in peak systolic blood pressure during treadmill exercise was investigated in 460 patients with definite or suspected coronary heart disease. All patients were studied with coronary cineangiography. Exercise was continued to one of the following end points: chest pain, 85 to 90 percent of the patient's age-predicted maximal heart rate, ventricular tachycardia or a sustained decrease of 10 mm Hg or more below the peak level of systolic blood pressure. Twenty-two patients with 75 percent or greater stenosis of one or more major coronary arteries manifested a decrease in systolic pressure 10 mm Hg or more during exercise. These included 15 (17 percent) of 88 patients with three vessel, 7 (7 percent) of 101 with two vessel and 0 of 90 with single vessel disease. The decrease in pressure was reproducible in the seven patients who underwent a second exercise test before alteration of therapy; this decrease was abolished in the six patients who exercised again after coronary bypass graft surgery.A decrease in systolic pressure of 10 mm Hg or more also occurred during exercise testing in 3 of 23 patients with noncoronary organic heart disease; all 3 had an obstructive cardlomyopathy that had not been suspected clinically. Only 1 of 158 subjects with chest pain and no demonstrable heart disease had a decrease in systolic blood pressure with exercise. Declines in blood pressure were not observed during 650 maximal exercise tests performed on 560 clinically normal men.In conclusion, if one excludes subjects with cardiomyopathy or significant heart valve disease, a sustained exercise-induced decrease in peak systolic blood pressure of 10 mm Hg or more is a highly specific sign of multiple vessel coronary artery disease. This phenomenon is best explained by acute left ventricular pump failure secondary to extensive myocardial ischemia.     

Use of heart rate responses to standing and hyperventilation at rest to detect coronary artery disease: Correlation with the S-T response to exercise

The heart rate responses to standing and to hyperventilation, expressed as a percent change over the sitting heart rate value, were measured in 48 patients with angiographic coronary artery disease (≥70 percent luminal narrowing) and 50 young, healthy asymptomatic individuals.When an abnormal response suggesting coronary artery disease was defined as an increase in the standing heart rate of <15% over the sitting value and <20% increase in the heart rate to hyperventilation relative to the sitting value, the sensitivity of such a criterion was 56%, the specificity was 92% and the predictive value was 87%. These values were not significantly different (P>0.05) from those for the S-T response to exercise, which were 77%, 98%, and 97% respectively.When either a positive S-T response to exercise or a positive response for control heart rate changes to standing and hyperventilation were used as criteria for a positive test, the sensitivity significantly increased to 98% (P<0.01), while specificity and predictive value remained significantly unchanged (P>0.05) at 90% for each.The use of the heart rate response to standing and hyperventilation may be a useful test in detecting coronary artery disease in patients unable to undergo stress testing. The use of such heart rate responses in addition to S-T depression with exercise results in a highly sensitive and specific test with great predictive value.