Accuracy of treadmill testing in assessment of direct myocardial revascularization

Exercise technetium 99m sestamibi single-photon emission computed tomography late after coronary artery bypass surgery: long-term follow-up

BACKGROUND AND HYPOTHESIS

The prognostic value of exercise technetium 99m sestamibi single-photon emission computed tomography (SPECT) imaging in patients with previous bypass surgery is unknown. The aim of our study was to assess the prognostic information obtained with exercise scintigraphy performed for routine follow-up or reappearance of symptoms.

METHODS

We studied 75 patients referred to our Center at a mean of 38 +/- 53 months from the revascularization procedure and prospectively followed them for 38 +/- 24 months.

RESULTS

Fifteen patients (20%) had events at follow-up: there were 4 cardiac deaths, 3 nonfatal acute myocardial infarctions, 8 late revascularization procedures (4 percutaneous transluminal angioplasty and 4 repeat bypass surgery). Univariate analysis identified a history of typical angina (p = 0.001), a clinically positive ergometric test (p = 0.009), peak exercise heart rate (p = 0.0003), percentage of maximal predicted heart rate (p = 0.0001), peak exercise double product (p = 0.048), therapy during exercise (p = 0.003), scintigraphic summed reversibility score (i.e., the summation of the segmental differences between stress and rest) (p = 0.014), as significant predictors of events. Three multivariate models were built, with clinical variables (Model 1, chi square 15.97), ergometric variables (Model 2, chi square 19.66), and with scintigraphic variables added to clinical/ergometric variables (Model 3, chi square 31.13). The scintigraphic variable selected in the model as significant predictor of events was the summed reversibility score (p = 0.008).

CONCLUSIONS

Exercise sestamibi SPECT scintigraphy provides optimal prognostic information after clinical and ergometric parameters in patients with previous bypass surgery.

Exercise stress testing before and after successful multivessel percutaneous transluminal coronary angioplasty

Controversy exists regarding the diagnostic accuracy, optimal technique, and timing of exercise testing after percutaneous coronary intervention. The objectives of the present study were to analyze variables and the power of exercise testing to predict restenosis or a new lesion, 6 months after the procedure. Eight-four coronary multi-artery diseased patients with preserved ventricular function were studied (66 males, mean age of all patients: 59 +/- 10 years). All underwent coronary angiography and exercise testing with the Bruce protocol, before and 6 months after percutaneous coronary intervention. The following parameters were measured: heart rate, blood pressure, rate-pressure product (heart rate x systolic blood pressure), presence of angina, maximal ST-segment depression, and exercise duration. On average, 2.33 lesions/patient were treated and restenosis or progression of disease occurred in 46 (55%) patients. Significant increases in systolic blood pressure (P = 0.022), rate-pressure product (P = 0.045) and exercise duration (P = 0.003) were detected after the procedure. Twenty-seven (32%) patients presented angina during the exercise test before the procedure and 16 (19%) after the procedure. The exercise test for the detection of restenosis or new lesion presented 61% sensitivity, 63% specificity, 62% accuracy, and 67 and 57% positive and negative predictive values, respectively. In patients without restenosis, the exercise duration after percutaneous coronary intervention was significantly longer (460 +/- 154 vs 381 +/- 145 s, P = 0.008). Only the exercise duration permitted us to identify patients with and without restenosis or a new lesion.

Stress Recovery Index for Risk Stratification of Asymptomatic Patients Following Coronary Bypass Surgery

OBJECTIVE

To prospectively assess the prognostic value of the stress recovery index (SRI) following coronary bypass surgery.

DESIGN AND PATIENTS

Two hundred seventy-eight patients who had undergone coronary bypass surgery and participated in a secondary prevention program were exercise tested and prospectively followed up for a median of 36 months. Cardiac death, nonfatal infarction, and need for further revascularization were target end points. SRI, defined as the difference in absolute values between the area of heart rate-adjusted ST-segment depression during exercise and recovery, was derived in all. Clinical data, resting ejection fraction, and exercise testing data of patients were entered into a sequential Cox model; SRI was entered last. Model validation was performed by bootstrap adjusted by the degree of optimism in estimates. Survival curves were set up using Kaplan-Meier method and compared by the log-rank test.

RESULTS

SRI was the only significant and independent prognostic indicator (hazard ratio, 0.68; 95% confidence interval, 0.53 to 0.89) and increased the prognostic power of the model on top of clinical and exercise testing variables, as demonstrated by the significant (p = 0.01) increase of the area under the receiver operating characteristic curve of the risk function. Survival analysis showed ascending SRI quartiles to identify a significant (p = 0.001) increase in event-free survival.

CONCLUSIONS

SRI is of value in predicting outcome after coronary bypass surgery and provides additional prognostic information over clinical and exercise testing data.

[Nuclear cardiology: technical bases and clinical applications]

Although the role of nuclear cardiology is currently well consolidated, the addition of new radiotracers and modern techniques makes it necessary to continuously update the requirements, equipment and clinical applications of these isotopic tests. The characteristics of the radioisotopic drugs and examinations presently used are explained in the first part of this text. In the second, the indications of them in diagnostic and prognostic evaluation of the different coronary diseases are presented.

Significance of graft occlusion and coronary atherosclerosis 5 years after coronary artery bypass grafting. A quantitative angiographic study with serial exercise testing

OBJECTIVE

To evaluate the relative importance of graft occlusions and progression of atherosclerosis in coronary arteries as causes of the occurrence of angina pectoris and impairment of physical performance 5 years after coronary artery bypass surgery.

DESIGN

A 5-year follow-up study.

SETTING

University hospital in south-western Finland.

SUBJECTS

Altogether, 174 consecutive electively operated bypass patients.

MAIN OUTCOME MEASURES

Serial clinical evaluation and bicycle exercise tests (pre-operatively, at 6 months, and at 1 and 5 years). Quantitative coronary angiography pre-operatively and 5 years after the surgery.

RESULTS

Subjects with patent grafts had fewer angina pectoris symptoms at the 5-year follow-up (24 vs. 52%, P = 0.001) and were treated less frequently with long-acting nitrates (3 vs. 15%, P = 0.037) than subjects with graft occlusions. Fewer of them were in classes II-III of the functional classification of the Canadian Cardiovascular Society (39 vs. 74%, P = 0.001). The exercise test was interrupted less often because of chest pain (23 vs. 41%, P = 0.03) and improvement in exercise test variables during the follow-up period was significantly greater in subjects with patent grafts (P<0.002). Amongst patients without graft occlusions, those with new > or =50% diameter stenoses in coronary arteries were more often in functional classes II-III (59 vs. 32%, P = 0.03) than those without new stenoses, but the groups were similar with respect to angina pectoris and exercise tests variables. In patients with graft occlusions, those with and without new > or =50% diameter stenoses were similar with respect to functional class, angina pectoris and exercise test variables.

CONCLUSIONS

Angina pectoris and impairment of physical capacity 5 years after coronary artery bypass grafting are mainly due to occlusion of bypass grafts and not to progression of atherosclerosis in coronary arteries.

[Role of noninvasive examinations in the management of ischemic cardiopathy. V. Noninvasive examinations in the management of patients with chronic ischemic cardiopathy]

In the last few years the has been an enormous development in noninvasive testing in the field of clinical cardiology. In fact, excellent monographs on each one of these techniques have been published elsewhere, but fewer publications exist that treat the topic of their indications and use in an integrated way, except for in the most common clinical situations. In this paper, the treatment of patients who present chest pain, stable and unstable angina is discussed, including the study of postinfarction patients. Furthermore, the role of noninvasive tests in the detection of coronary heart disease in women and in patients with left bundle branch block is thoroughly analyzed; as well as their usefulness after surgical or percutaneous coronary revascularization and in patients with peripheral vascular disease.

Asymptomatic Cardiac Ischemia Pilot (ACIP) study: impact of anti-ischemia therapy on 12-week rest electrocardiogram and exercise test outcomes. The ACIP Investigators

OBJECTIVES

This report from the Asymptomatic Cardiac Ischemia Pilot (ACIP) study examines differences in the magnitude of reduction of myocardial ischemia as determined by exercise treadmill testing in patients randomized to three different treatment strategies: angina-guided medical therapy, ischemia-guided medical therapy and coronary revascularization.

BACKGROUND

No prospective randomized clinical trials in patients with exercise electrocardiographic (ECG) abnormalities and asymptomatic cardiac ischemia on ambulatory ECG monitoring have compared the impact of different treatment strategies, including coronary revascularization, in terms of reducing myocardial ischemia.

METHODS

The ACIP exercise protocol was used. Exercise variables measured included final exercise stage; presence of exercise-induced angina or ischemia; time to angina; time to 1-mm ST segment depression; number of exercise ECG leads with abnormalities; maximal depth of ST segment depression in any lead; sum of ST segment depression; ST/HR index; and rate-pressure product at time to angina, at time to 1-mm ST segment depression and at peak exertion.

RESULTS

Peak exercise time was increased by 0.5, 0.7 and 1.6 min in patients assigned to the angina-guided, ischemia-guided and coronary revascularization strategies, respectively, from the qualifying visit to the 12-week visit (p < 0.001). At the qualifying visit, the sum of exercise-induced ST segment depression was 9.4 +/- 5.0 (mean +/- SD), 9.6 +/- 4.7 and 9.9 +/- 5.5 mm (p = NS) in the three treatment strategies, respectively. At the 12-week visit, the sum of exercise-induced ST segment depression was 7.4 +/- 5.7, 6.8 +/- 5.3 and 5.6 +/- 5.6 mm (p = 0.02) in the three treatment strategies, respectively. Each treatment strategy resulted in a significant reduction in all exercise-induced variables of myocardial ischemia measured at 12 weeks.

CONCLUSIONS

Coronary revascularization significantly reduced the extent and frequency of exercise-induced myocardial ischemia compared with either medical strategy. The prognostic impact of these observations should be evaluated in a large-scale multicenter clinical trial.

Value and limitations of exercise stress testing to predict the functional results of coronary artery bypass grafting

To assess the value of exercise stress testing to predict the functional result of revascularization, 90 patients were evaluated by coronary angiography and exercise testing pre and postoperatively. Patients were classified on the basis of the postoperative angiogram in a group with successful surgery and a group with unsuccessful surgery. The predictive accuracy positive of ST segment depression to detect unsuccessful surgery was 67% The predictive accuracy negative was 61%. The best predictor of unsuccessful surgery was residual angina pectoris after revascularization with predictive value positive and negative of 85% and 60%, respectively. Thus exercise stress testing has limited value to accurately predict the degree of revascularization.

Clinical assessment following coronary revascularization

There remains a need to establish adequate protocols for investigating the short- and long-term follow-up of revascularization procedures. For coronary angioplasty the most reliable basis for decision-making in managing patients is the symptomatology of the patient. For bypass surgery a protocol should be established to evaluate patients late, at 5 to 10 years following bypass surgery, in particular those with saphenous vein grafting, as graft and patient survival begins to fall after this period. Investigation after this may be too late for many patients who may already have several occluded grafts and poor left ventricular function, two of the most important prognostic factors post bypass surgery. The improvement and refinement of non-invasive investigations has led to a better understanding of the value and limitations of many of these tests, but it is particularly important that the limitations of many investigation are fully appreciated when they are used to influence clinical decisions. In this regard, a study comparing and integrating the predictive value of the persistence or return to symptoms, a positive non-invasive test, and a positive invasive test would surely prove invaluable.

Significance of silent myocardial ischemia after coronary artery bypass surgery

The prevalence and prognostic significance of transient myocardial ischemia after coronary artery bypass grafting (CABG) were evaluated. In 3 studies, ischemia was found in an average of 24% of patients by ambulatory electrocardiographic monitoring at 3-12 months after CABG. An average of 36% of patients in 3 other studies experienced ischemic ST-segment depression during exercise testing at 4-50 months after CABG. Of the ischemic episodes, 77% were silent during exercise testing. In the Coronary Artery Surgery Study (CASS) randomized patient subsets, survival at 12 years was significantly lower for patients who had either silent or symptomatic ischemia during exercise testing at 6 months after CABG compared with those who had no ischemia.

Usefulness of a postoperative exercise test for predicting cardiac events after coronary artery bypass grafting

The predictive value of a postoperative exercise test in terms of cardiac events after coronary artery bypass grafting (CABG) was prospectively studied in 231 consecutive patients. During a 5-year follow-up there were 28 cardiac events (12%), of which 15 were cardiac deaths (13 sudden), and 13 were nonfatal myocardial infarctions. There was no difference in the rate of graft patency between groups with and without cardiac events, but ejection fraction was lower in patients with than without events (51 +/- 16% vs 58 +/- 10%; p less than 0.05). Duration of the exercise test was shorter, and maximal work load was lower in patients with cardiac events (p less than 0.05 for both). The prevalence of greater than or equal to 1 mm ST-segment depression was 22% (symptomatic in 25%, and silent in 75%) and did not differ between groups with and without cardiac events. After adjustment for prognostic variables using the proportional hazards method, diuretic treatment (p = 0.007) and a low postoperative ejection fraction (p = 0.04) remained significant for predicting the risk of cardiac events within 5 years of CABG, but exercise duration and work load did not have any significant predictive value. Thus, the predictive value of a postoperative exercise test is limited, and signs of impaired left ventricular function are of greater significance for the 5-year prognosis after CABG than are those of myocardial ischemia.

Prevalence and prognostic significance of silent and symptomatic ischemia after coronary bypass surgery: a report from the Coronary Artery Surgery Study (CASS) randomized population

The prevalence and prognostic significance of postoperative myocardial ischemia, as detected by exercise testing, were prospectively assessed in 174 patients from the Coronary Artery Surgery Study (CASS) randomized surgical population who had exercise testing before and 6 months after coronary artery bypass graft surgery. Whereas the prevalence of symptomatic ischemia significantly decreased postoperatively (52% vs. 6%, p less than 0.001), the frequency of silent myocardial ischemia did not change (30% vs. 29%). Survival at 12 years after bypass surgery based on the 6-month postoperative exercise test results was significantly better for the 112 patients with no ischemia (80%) than for the 51 patients with silent ischemia (68%) or the 11 patients with symptomatic ischemia (45%). These data show that coronary artery bypass graft surgery diminishes the overall prevalence of symptomatic but not silent ischemia and that both silent and symptomatic ischemia adversely affect the postoperative prognosis of these patients.

Use of the exercise test to predict prognosis after coronary artery bypass grafting

The objective of this study was to predict the prognosis of patients who become symptomatic after having undergone coronary artery bypass grafting (CABG) using clinical and exercise test responses. A retrospective analysis was performed of all veterans referred for clinical indications to a Veterans Administration Medical Center for a treadmill test after having undergone CABG. Of 2,044 patients who were exercise tested from April 1984 to May 1987, 296 had previously undergone CABG. Clinical data considered included age, sex, medication and symptom status, history of myocardial infarction, type of myocardial infarction and time from CABG. The exercise test responses considered were MET level, maximal heart rate, maximal systolic blood pressure, chest pain pattern and ST-segment response. During a 2-year follow-up after exercise testing, there were 15 deaths, 11 nonfatal myocardial infarctions, 6 repeat CABGs and 3 percutaneous transluminal coronary angioplasties. Although MET level and maximal heart rate were significantly related to prognosis and no patient who exceeded 8 METs died, the predictive power of these exercise test responses was low and ST-segment depression was not predictive at all. The inability of the exercise electrocardiogram to predict cardiac events in patients after CABG requires the use of other methods of testing to identify those who need invasive studies and intervention.

Exercise radionuclide assessment of left ventricular function before and after coronary bypass surgery

The effects of elective saphenous vein coronary artery bypass surgery on left ventricular ejection fraction were assessed by using exercise first-pass radionuclide angiography in 66 consecutive patients. All patients with left main coronary artery or concomitant valvular disease were eliminated from the study. Before surgery, 7 patients had normal postexercise left ventricular function (Group 1), 33 had normal resting left ventricular function with an abnormal response to exercise (Group 2), and 26 had an abnormal resting left ventricular ejection fraction with an abnormal response to exercise (Group 3). Following surgery, patients in all three groups had no change in mean resting left ventricular ejection fraction; however, patients in Groups 2 and 3 had significant improvement in mean postexercise left ventricular ejection fraction (p less than 0.0001 and p less than 0.0054 respectively), whereas patients in Group 1 did not. Previous studies reported improvement in postexercise ejection fraction in patients with reduced resting left ventricular function and with an ischemic response to exercise (Group 3). But this is the first study to confirm improvement in postexercise function in patients with normal resting function and an ischemic response to exercise (Group 2).

Computer-derived treadmill exercise score quantifies the degree of revascularization and improved exercise performance after coronary artery bypass surgery

A computer-derived treadmill exercise score (TES) that quantifies the severity of the ischemic ST response to exercise was used to detect noninvasively graft occlusion or the progression of new lesions after coronary artery bypass surgery. Three months after surgery TES completely normalized in 68% of patients and improved by more than 70% in another 18% of patients, thus reflecting excellent improvement in exercise-induced ischemia in 87% of patients. Surgical results correlated well with completeness of revascularization as shown by repeat coronary angiography. When TES, done serially up to 4 years after surgery, remained unchanged, grafts were patent and no new critical lesions had occurred. Deterioration in TES always predicted either late graft occlusion or appearance of new, high-grade lesions in the native vessels. Thus TES provides a new, accurate method that quantifies the ischemic response to exercise and detects graft occlusion or new obstructive lesions in the native coronary arteries.

Clinical indications for thallium-201 myocardial perfusion scanning

Thallium -201 myocardial perfusion scanning can assess regional myocardial perfusion noninvasively. As it is both time-consuming and expensive its use should be restricted to specific diagnostic problems. The clinical indications in known or suspected coronary artery disease are reviewed. In suspected coronary artery disease thallium scanning is most useful in patients with chest pain when the exercise ECG is uninterpretable, in men with probable angina but a negative exercise ECG, or conversely a positive exercise ECG without typical angina, and in women with probable angina and either a positive or a negative exercise ECG. In known coronary artery disease, thallium scanning may help determine the functional significance of a coronary obstruction found at angiography and may determine the site of myocardial ischaemia when multiple obstructions are present.

Evaluation of aortocoronary bypass graft status by computed tomography

The efficacy of contrast-enhanced computed tomography to define graft patency status was studied in 42 patients with 100 aortocoronary vein grafts. The status of each graft had been determined earlier by angiography. A rotary fan beam whole body scanner with a 2 second scan duration was used. Initial scans determined the optimal level for study of the graft; patency was assessed by computed tomographic enhancement of the graft after intravenous bolus injection of 30 ml meglumine and sodium diatriazoate. The computed tomographic studies were evaluated without knowledge of the angiographic findings; graft status by computed tomography was interpreted as patent, occluded or equivocal. Overall, computed tomography correctly defined graft patency status in 79 of the 100 grafts and incorrectly identified it in 9; in 12 grafts, the computed tomographic diagnosis was equivocal. Computed tomography correctly identified 61 of 74 patent grafts and 18 of 26 occluded grafts. Patency status was correctly defined by computed tomography in 35 of 37 grafts to the left anterior descending artery, 23 of 30 grafts to circumflex branches and 19 of 31 grafts to the right coronary artery. These data indicate that computed tomography is a promising noninvasive method of determining patency of aortocoronary bypass grafts, especially of grafts to the left anterior descending artery.

Serial exercise testing after coronary artery bypass surgery

To determine the duration of functional benefit from coronary bypass surgery, 111 patients with angina pectoris were serially evaluated by standard exercise testing prior to and for up to 4 years after surgery. Exercise testing 6 to 18 months after surgery showed greater heart rate-blood pressure product at peak work load, improved work capacity, and less symptomatic and electrocardiographic evidence of ischemia than was demonstrated preoperatively. Twenty patients were tested 37 to 48 months postoperatively and showed improved exercise performance in comparison with preoperative results, but the frequency of positive tests during this period no longer differed. Thus, improved exercise performance appears to persist for at least 4 years after coronary bypass surgery.

Clinical significance and characteristics of exercise-induced ventricular tachycardia

Forty-seven patients (0.08%) from a total of 5,730 consecutive patients undergoing treadmill stress tests developed one or more episodes of ventricular tachycardia. Forty patients had heart disease, coronary artery disease being the leading cause. Rest ECG was normal in 12 patients and showed long QTc (greater than 440 msec) in 16 patients. Ventricular tachycardia was brief and self-terminating, requiring D/C cardioversion in only one patient. "Exertional hypotension" preceded ventricular tachycardia in 16 of 34 patients. There was poor correlation (r = 0.16) between the rate of ventricular tachycardia (VT) and the underlying heart rate. Only four episodes of VT were initiated by R on T premature ventricular beats. In summary, exercise-induced ventricular tachycardia 1) is a rare complication of treadmill stress test and occurs in patients with heart disease; 2) is frequently preceded by "exertional hypotension," and 3) is not related to the R on T phenomenon. The high incidence of prolonged QT may indicate a role for the automatic nervous system in its pathogenesis.

Reversal of exertional hypotension after coronary bypass grafting

A decrease in systolic blood pressure that occurs with treadmill exercise testing may be a sign of reversible ischemic left ventricular dysfunction. To test this hypothesis, we examined retrospectively the postoperative treadmill responses of 37 patients who had exertional hypotension (end exercise systolic blood pressure less than or equal to initial preexercise levels) before coronary arterial bypass grafting. This group of 37 patients was characterized preoperatively by an abnormal exercise electrocardiogram (36 patients), multiple vessel occlusive disease (36 patients) and a normal ejection fraction at rest (32 patients). Postoperative exercise tests showed improvement in hemodynamic and electrocardiographic changes with reversal of exertional hypotension (33 patients), and conversion to a normal exercise electrocardiogram (29 patients). Coronary bypass surgery can be expected to reverse exertional hypotension in patients with symptomatic angina pectoris and evidence of ischemia in the exercise electrocardiogram.

Thallium-201 myocardial perfusion scintigraphy to evaluate patients after coronary bypass surgery

To determine the utility of thallium-201 stress scintigraphy in assessing the results of coronary bypass surgery, chest pain, stress electrocardiograms and scintigrams were evaluated in 27 patients postoperatively. These findings were compared with coronary angiographic data in which a significant postoperative lesion was defined as 75 percent or more stenosis in a graft, its distal vessel or in an ungrafted native vessel. As an indicator of postoperative coronary lesions, chest pain lacked sensitivity (60 percent) and was nonspecific (20 percent). The stress electrocardiogram had poor sensitivity (60 percent) and good specificity (86 percent) but was not helpful in six patients who had equivocal or suboptimal tests. The scintigram had good sensitivity (77 percent) and was highly specific for the diagnosis of coronary stenosis. It was significantly more specific than chest pain (P less than 0.01), gave excellent localizing information and added to the accuracy of both conclusive and inconclusive stress tests. In nine patients with preoperative stress scintigrams, comparison of pre- and postoperative studies reflected the éffects of bypass surgery on coronary perfusion. Scintigraphy is a useful technique for the noninvasive evaluation of the patient after coronary bypass surgery, and postoperative scintigraphy alone is of great value in documenting surgical results.