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.     

Role of exercise stress testing in healthy subjects and patients with coronary heart disease. Controversies in cardiology--I.

The value of the exercise stress test in the evaluation of clinically healthy subjects and patients with coronary heart disease is not limited to the isolated interpretation of abnormalities of the S-T segment. Other measurable parameters which are of diagnostic and prognostic importance include: (1) a decrease in systolic blood pressure during exercise; (2) the appearance of complex ventricular arrhythmias of low exercise heart rates; (3) the appearance of inverted U waves during or after exercise; (4) the patient's maximal exercise capacity; and (5) new auscultatory findings postexercise. The reliability of the exercise test as a diagnostic tool is futher enhanced by proper patient selection and careful attention to exercise techniques. Subjects with labile ST-T wave changes during standing hyperventilation, fixed ST-T changes at rest, and intraventricular conduction defects are not ideal candidates for "diagnostic" stress testing and the examining physician must rely more heavily on nonelectrocardiographic findings. The criteria used to define an abnormal S-T response will vary according to the lead system used. However, in both symptomatic and asymptomatic subjects the appearance of marked degrees of S-T depression at low exercise heart rates significantly increases the probability of finding advanced coronary disease, particularly if the S-T depression is seen in multiple monitoring leads and is of prolonged duration postexercise.     

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.     

Septal Q wave in exercise testing: Angiographic correlation

A study of septal Q wave response in lead CM₅ was carried out to evaluate its usefulness in predicting coronary artery disease. Q wave amplitude was measured in 50 patients with coronary artery disease and 50 normal subjects before and immediately after exercise. In the 100 patients evaluated with coronary angiography, the septal Q wave in lead CM₅ was smaller in patients with coronary artery disease than in normal subjects at rest (probability [p]<0.001) and immediately after exercise (p<0.001). An embryonic (0.5 mm) or absent Q wave in lead CM₅ was significantly more frequent in patients with coronary artery disease than in normal subjects both at rest (76 versus 48 percent) and after exercise (82 versus 16 percent).The sensitivity for S-T depression was 52 percent, the specificity 74 percent and the predictive value 70 percent. The respective values for the Q wave were 82,88 and 87 percent. These differences were not significant (p <0.05). When either a positive S-T or Q wave response was used, the sensitivity increased to 92 percent (p <0.05), and the specificity and predictive values remained unchanged (p <0.01). An Increase in Q wave amplitude with exercise identified a false positive S-T segment response to stress in 75 percent of cases. Absence of the Q wave in lead CM₅ with S-T depression after exercise identified a true positive response in 100 percent of cases.These findings suggest that low Q wave voltage and its failure to increase after exercise imply abnormal septal activation, reflecting loss of contraction associated with ischemia. This finding may be a useful marker for ischemia; the increase in the septal Q wave with exercise may be of value in identifying a false positive S-T segment response.     

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.     

Epidemiologic study of asymptomatic men screened by maximal treadmill testing for latent coronary artery disease

A group of 1,390 asymptomatic men screened for latent coronary artery disease by maximal treadmill testing and double Master two-step test were followed up for a mean of 6.3 years. Angina, sudden death or acute myocardial infarction was used as the end point for coronary heart disease. There were differences in testing sensitivity and specificity among age and subject groups, but maximal treadmill testing out-performed the double Master test as a screening technique. Maximal treadmill testing demonstrated a 60.9 percent sensitivity, 92 percent specificity and a 20 percent probability that coronary artery disease would develop in a subject with an abnormal response. A risk ratio of 14.3 was obtained and demonstrated that maximal treadmill testing was a valuable screening technique for latent coronary artery disease. However, limitations of the sensitivity and specificity of the functional S-T segment response were apparent. The abnormal S-T segment response to exercise testing did not absolutely predict the future presentation of coronary artery disease, and a normal response to maximal treadmill testing did not rule out this possibility. Because premature ventricular contractions demonstrated a very low sensitivity, predictive value and risk ratio they were not a practical indicator of increased risk for latent coronary artery disease except when associated with an abnormal S-T segment response.     

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.     

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.     

Comparison of exercise radionuclide angiocardiography and thallium-201 myocardial perfusion imaging in coronary artery disease

First pass radionuclide angiocardiography and thallium-201 myocardial perfusion imaging were performed at rest and during exercise in 48 patients with chest pain: 39 with angiographically documented coronary artery disease and 9 with normal coronary arteries. Maximal graded upright bicycle exercise was used for both studies to assure identical exercise conditions. All nine patients without coronary artery disease had normal exercise thallium images, normal exercise regional wall motion and at least a 5 percent absolute increase in left ventricular ejection fraction during exercise (normal exercise left ventricular reserve). Ischemic S-T segment depression was demonstrated in 17 (44 percent) of the 39 patients with coronary artery disease. Findings on the two exercise tests were concordant in all cases. New or augmented thallium perfusion defects were detected in 24 (62 percent) of the 39 patients, whereas abnormal exercise left ventricular reserve was present in 33 (85 percent) (p <0.05). There was a close concordance between exercise-induced perfusion defects and regional wall motion abnormalities. The magnitude of change in ejection fraction from rest to exercise was significantly greater in patients with an abnormal exercise thallium study than in those with a normal study (−8 ± 2 percent versus −1 ± 1 percent, p <0.05). Both radionuclide studies were abnormal In 21 (54 percent) of the 39 patients, whereas both were normal only in 3 patients, all of whom had single vessel disease. Abnormal exercise left ventricular reserve was present in 12 patients with normal exercise thallium studies.     

Merits of stress thallium-201 myocardial perfusion imaging in patients with inconclusive exercise electrocardiograms: Correlation with coronary arteriograms

Stress thallium-201 myocardial perfusion images were obtained in 65 patients with an inconclusive exercise electrocardiogram. All 65 patients underwent coronary angiographic studies. The exercise electrocardiogram was judged inconclusive in 35 patients (54 percent) because submaximal exercise had been performed and in 30 patients (46 percent) who manifested ST-T segment abnormalities at rest. Exercise thallium-201 myocardial perfusion images were abnormal in 20 patients and normal in 45. Nineteen (95 percent) of the 20 patients with abnormal exercise images had severe disease of one or more major coronary arteries. Thirty-seven (82 percent) of the 45 patients with normal exercise images had no significant coronary artery disease; the remaining 8 patients had coronary artery disease. Therefore, 19 of 27 patients with coronary artery disease had abnormal exercise images (sensitivity 70 percent), and 37 of 38 patients without coronary artery disease had normal exercise images (specificity 97 percent). Thallium-201 imaging predicted the correct diagnosis in 56 patients (86 percent). Thus, exercise myocardial imaging with thallium-201 appears to be a useful diagnostic aid in patients with an inconclusive exercise electrocardiogram.     

Exercise-induced increase in diastolic pressure: indicator of severe coronary artery disease.

The diastolic blood pressure response to treadmill exercise testing was analyzed in 281 patients. Diastolic blood pressure was measured at rest, during each stage of exercise, immediately on recovery, and 1, 3 and 5 minutes into the recovery period. No change or a decrease in diastolic blood pressure was considered a normal response. An increase in diastolic blood pressure of more than 15 mm Hg on at least two determinations, comparing values at rest with those on exercise, was considered an abnormal response. Only patients showing a normal increase in systolic blood pressure during exercise were included. Two hundred and nine patients had a normal and 72 patients an abnormal diastolic blood pressure response. In a subgroup of 41 patients who underwent coronary arteriography, 50 percent of patients with a normal diastolic pressure response had normal coronary arteries, compared with 17 percent of those with an abnormal response (P < 0.03). Only 11 percent of patients with a normal diastolic pressure response had triple vessel or left main coronary artery disease, compared with 44 percent of patients with an abnormal response (P < 0.03). Blood pressure at rest ($\text{132}\text{84}\text{mm Hg}$) and peak heart rate (mean 155 beats/min) were similar in each group. There was no significant difference between exercise-induced ischemic S-T segment changes in the two groups (13 percent for patients with a normal diastolic pressure response versus 15 percent for those with an abnormal diastolic pressure response). In conclusion, an abnormal diastolic pressure response to treadmill testing may be a good indicator of coronary artery disease even in the absence of S-T segment changes.     

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.     

Natural history of S-T segment elevation after acute myocardial infarction

Clinical, electrocardiographic and cineventriculographic data in two patient groups were analyzed to define the natural history of S-T segment elevation after myocardial infarction. In sixteen of 22 patients (73 percent) with acute inferior myocardial infarction, S-T segment elevation was present on hospital admission, persisting in 1 (5 percent) by the 2nd week. S-T segment elevation was present on admission in 18 of 23 patients (78 percent) with acute anterior myocardial infarction and persisted in 13 after 1 week and in 9 of 14 (64 percent) during a follow-up period of 1 to 6 months. S-T segment elevation lasting more than 2 weeks after myocardial infarction did not resolve. Compared with patients with inferior myocardial infarction or anterior infarction without persistent S-T segment elevation, patients with anterior infarction and persistent S-T segment elevation had a higher level of mean maximal serum creatine phosphokinase (CPK), more severe left ventricular decompensation and a greater frequency of death in the early follow-up period. In a separate series of 95 patients with cineangiographically documented coronary artery disease, 40 of 65 patients (62 percent) with advanced anterior and apical asynergy had persistent S-T segment elevation. By contrast, only 1 of 30 (3 percent) with coronary disease and normal ventriculograms had persistent S-T segment elevation.We concluded that (1) the natural history of S-T segment elevation after myocardial infarction is resolution within 2 weeks in 95 percent of inferior but in only 40 percent of anterior infarctions; (2) S-T segment elevation persisting more than 2 weeks after myocardial infarction does not resolve; (3) persistent S-T segment elevation is associated with clinically more severe myocardial infarction; and (4) in patients with coronary artery disease, persistent S-T segment elevation after myocardial infarction is a specific but insensitive index of advanced asynergy.     

Pseudoischemic “false positive” S-T segment changes induced by hyperventilation in patients with mitral valve prolapse

Hyperventilation-induced S-T segment changes that simulate myocardial ischemia have previously been noted, but the origin of this electrocardiographic finding has never been defined. To investigate further the basis for this response, the records were reviewed of 1,678 consecutive patients who underwent forced hyperventilation for 90 seconds and treadmill exercise testing. Twenty-eight patients (1.7 percent) were identified in whom hyperventilation resulted in ischemic-appearing S-T segment changes, and follow-up was possible in 21 (17 women, 4 men). Of the 21 patients, 16 (76 percent), including 15 (88 percent) of the 17 women, had evidence of mitral valve prolapse, 6 on auscultation alone, 2 on echocardiography alone and 6 with a combination of studies. Ten of the 21 patients had a negative exercise test; of the 11 patients who had a positive exercise test, only 1 had angiographic evidence of coronary arterial narrowing. The finding of ischemic-appearing S-T segment changes in response to forced hyperventilation has a high predictive value for the presence of mitral valve prolapse, particularly in women. The possible association of autonomic factors and mitral valve prolapse in the patho-genesis of an abnormal response to hyperventilation is discussed.     

Correlation of computer-quantitated treadmill exercise electrocardiogram with arteriographic location of coronary artery disease

Graded treadmill exercise testing and coronary cinearteriographic studies were carried out on 86 patients with angina pectoris. At rest, all patients demonstrated a normal S-T segment on the modified bipolar lead V₅ recording used. The computer-quantitated S-T segment response to exercise was correlated with the location and extent of obstructive coronary artery disease. The coronary cineartertograms were reviewed by 3 physicians and stenosis of 75 percent or greater was considered significant. All patients showed at least this degree of stenosis in 1 or more major coronary arteries, and 83 of 86 exhibited 90 percent or greater stenosis in at least 1 artery. Thirty-one patients had stenosis in a single artery, 43 had stenosis in 2 arteries and 12 had significant lesions in all 3 major arteries. In 70 of the 86 (82 percent) patients, a positive S-T segment response developed during or immediately after exercise. In 12 of the 16 with a negative response, disease was limited to a single artery. In 11 of the 12 the disease was restricted to the right coronary or left circumflex arteries. Of the 12 patients with an isolated stenosis of the left anterior descending artery, 11 (92 percent) had a positive S-T segment response. Of 55 patients with 2- or 3-vessel disease, 51 (93 percent) demonstrated a positive S-T response. Graded treadmill exercise testing in 80 patients with chest pain, normal coronary art eriograms and normal left ventricular function revealed 4 (5 percent) with a false positive S-T segment response.     

Exercise testing early after myocardial infarction: Predictive value for subsequent unstable angina and death

Recently, modified treadmill exercise testing before hospital discharge has been reported to be safe in patients after uncomplicated myocardial infarction. Accordingly, the frequency of treadmill exercise-induced abnormalities and their prognostic value were evaluated in 130 patients with uncomplicated myocardlal infarction. Seventy-eight patients (60 percent) had one or more treadmill exercise-induced abnormalities; 42 had S-T segment depression, 35 had angina and 17 had an inadequate blood pressure response. During the mean follow-up period of 11 months, 27 patients experienced unstable angina, 12 had a recurrent myocardlal infarction and 10 died of cardiac causes. Compared with patients with no exercise-induced abnormality, patients with S-T segment depression, angina pectoris or an inadequate blood pressure response had a significantly greater (p < 0.001) incidence of all cardiac events during the follow-up period. Furthermore, unstable angina pectoris was significantly more frequent (p <0.005) in patients with S-T segment depression or angina pectoris. Finally, when the patients with ischemic treadmill abnormalities were combined with the patients exhibiting an inadequate blood pressure response, they had a statistically greater (p < 0.005) incidence of cardiac death than that of patients with no treadmill abnormalities. Therefore, these three abnormalities during modified treadmill exercise testing before hospital discharge identify patients with uncomplicated myocardial infarction who are at risk for a future cardiac event.     

Idiopathic hypertrophic subaortic stenosis: evaluation of anginal symptoms with thallium-201 myocardial imaging.

The evaluation of angina pectoris in patients with idiopathic hypertrophic subaortic stenosis is difficult in those in the age group prone to coronary artery disease. Ten patients with angina pectoris, normal coronary angiograms and idiopathic hypertrophic subaortic stenosis were studied with thallium-201 myocardial imaging performed in conjunction with submaximal treadmill exercise testing. The resting electrocardiogram demonstrated left ventricular hypertrophy with S-T segment abnormalities in seven patients, thereby vitiating the further increase in S-T segment abnormalities that developed in these patients during exercise or in the postexercise period. Of the three patients with a normal resting electrocardiogram, one had significant exercise-induced S-T segment depression. Thallium-201 myocardial imaging revealed no significant perfusion defects in 9 of the 10 patients (90 percent). In one patient with severe left ventricular hypertrophy significant perfusion defects developed after exercise that were not present at rest. Stress thallium-201 myocardial perfusion imaging is a useful noninvasive technique that assists in ruling out the presence of significant coronary artery disease in patients with idiopathic hypertrophic subaortic stenosis.     

Abnormal electrocardiographic responses to exercise in patients referred for noninvasive evaluation of occlusive peripheral arterial disease.

Fifty consecutive patients were referred to the noninvasive laboratory for evaluation of suspected peripheral vascular disease. There were 30 men and 20 women aged 27 to 88 years (mean 63). Measurement of cardiovascular risk factors revealed the following distributions: cigarette smoking 90 percent, hypertension 28 percent, diabetes mellitus 22 percent and hyperlipidemia 6 percent. Eight patients had a history of angina pectoris, 7 a prior myocardial infarction, 5 a cerebrovascular accident and 11 prior peripheral arterial revascularizatlon surgery. Evaluation detected 32 patients (64 percent) with occlusive arterial disease of the lower limbs. Lead II of the electrocardiogram was monitored during and 1, 2, 3, 4, and 5 minutes after treadmill exercise with a limiting grade of 10 percent at 2.5 miles/hour. The mean resting and maximal heart rates for the study group were, respectively, 78 and 106 beats/min. The average treadmill speed attained was 1.9 miles/hour at a mean duration of 3.8 minutes. Thirty-seven subjects (74 percent) had normal electrocardiographic responses to exercise. Of 13 patients (26 percent) with an abnormal exercise electrocardiogram, 7 had possible ischemic S-T segment responses. Six subjects manifested frequent premature ventricular complexes during exercise. Four other patients had abnormal S-T segments in the resting electrocardiogram (two had a pattern of left bundle branch block, and two a pattern of left ventricular hypertrophy and strain).A survey of 60 peripheral vascular laboratories in the United States revealed that only 29 percent of the responding 34 centers routinely performed electrocardiographic monitoring during exercise testing. It is concluded that (1) electrocardiographic monitoring during exercise in the peripheral vascular laboratory can provide useful information regarding S-T segment responses, (2) abnormal S-T segment responses in patients with suspected peripheral vascular disease are frequently manifested at low levels of work load, and (3) such routine monitoring should be performed for patient safety.     

S-T segment elevation during exercise: Electrocardiographic and arteriographic correlation in 38 patients

The clinical significance and underlying mechanisms of S-T segment elevation during exercise were evaluated by correlating the exercise-induced S-T elevation with the coronary arteriograms and left ventriculogram in 38 patients. Of these, 37 (97 percent) showed significant coronary artery disease; 71 percent of these had proximal lesions. Of 27 patients with old myocardial infarction manifested in the electrocardiogram at rest, 25 had significant coronary artery disease and a ventricular aneurysm. All 11 patients with no previous myocardial infarction in the electrocardiogram at rest had significant coronary artery disease but only 2 (18 percent) had a ventricular aneurysm. One patient had a ventricular aneurysm without coronary artery disease. The sites of S-T elevation correctly localized the area of ventricular aneurysm of 30 (91 percent) of 33 instances and the area of the compatible diseased vessels in 38 (95 percent) of 40 instances.Our data suggest that (1) S-T elevation during exercise in the absence of a pattern of previous myocardial infarction in the electrocardiogram at rest indicates significant proximal coronary artery disease without ventricular aneurysm, whereas in the presence of such a pattern it is indicative of both ventricular aneurysm and significant proximal coronary artery disease; (2) the sites of S-T elevation accurately identify the location of ventricular aneurysm and the compatible diseased vessels; and (3) ischemia and abnormal wall motion may independently or additively underlie the mechanism for S-T elevation during exercise.     

Electrocardiographic mapping after exercise for evaluation of coronary bypass graft surgery

Electrocardiographic mapping after exercise adds an extra dimension to the routine exercise test because a measure can be made of the area and severity of electrocardiographic changes that occur after exercise. The value of this technique in assessing coronary bypass graft surgery was investigated in 50 patients who had postoperative coronary angiography after undergoing such surgery. The patients were classified into three groups: The 35 patients in Group 1 were free of pain at follow-up and had no new precordial Q waves. Among these, 24 patients had patent grafts and no precordial area of S-T segment change after exercise. The remaining 11 patients had areas of exercise-induced S-T segment change postoperatively; 10 of the 11 had at least one blocked graft and 1 had a patent although poorly functioning graft. The 10 patients in Group 2 continued to have chest pain after operation. Eight of the 10 had an area of S-T segment change that persisted after exercise and at least one blocked graft; the 2 patients without precordial S-T segment changes after exercise had patent grafts. The five patients in Group 3 were in poorer condition after operation; three had greater areas of S-T segment change after exercise, and the remaining two had new areas of Q waves. All patients had at least one occluded graft.

In 8 (16 percent) of the 50 patients studied before operation precordial areas of S-T segment change after exercise that were identified with electrocardiographic mapping were not identified using a modified 12 lead system. After operation, mapping revealed precordial areas of ischemia in 24 patients; In 4 (17 percent). These areas were not detected with the modified 12 lead electrocardiogram. Electrocardiographic mapping after exercise is a simple noninvasive test that objectively describes the effects of coronary bypass surgery on myocardial ischemia and aids in interpretation of a patient's report of a change in the frequency of angina. Because it provides more information than a modified 12 lead system it may reduce the need for postoperative angiocardiography.