Radionuclide angiographic assessment of global and segmental left ventricular function at rest and during exercise after coronary artery bypass graft surgery

Prediction by postexercise fluoro-18 deoxyglucose positron emission tomography of improvement in exercise capacity after revascularization

The extent of ischemic and hibernating myocardium, which may be detected by increased postexercise uptake of fluoro-18 deoxyglucose (FDG) using positron emission tomography, may determine the degree of functional benefit after revascularization. This study examined the influence of the amount of this FDG-avid myocardium on changes in left ventricular function and exercise parameters after revascularization. Echocardiography and exercise testing were performed before and after intervention in 23 patients who had undergone positron emission tomography for the evaluation of myocardial perfusion (using rubidium-82), and postexercise FDG imaging in the fasting state. Follow-up echocardiography (22 +/- 14 weeks after revascularization) was compared with preoperative FDG activity in 7 myocardial regions per patient. Systolic function improved after intervention in 19 of 26 malperfused, dysfunctional FDG-avid regions (73%), and did not improve in 35 of 47 dysfunctional regions without increased FDG uptake (74%). The influence of the amount of FDG-avid tissue on changes in functional state was examined by comparing 9 patients with multiple (greater than or equal to 2) FDG-avid regions with the remainder. Those with multiple FDG-avid regions demonstrated improvement in peak rate-pressure product (20 +/- 4 to 26 +/- 4 x 10(3), p less than 0.02), and percentage of maximal heart rate achieved at peak (84 +/- 10% to 93 +/- 6%, p = 0.04), neither of which changed significantly in the remaining patients. Exercise capacity increased from 5.6 +/- 2.7 to 7.5 +/- 1.7 METS in the group with multiple FDG-avid regions; this increase of 55 +/- 18% exceeded the increase of 13 +/- 10% in the remainder (p = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Upright bicycle exercise echocardiography after coronary artery bypass grafting

Upright bicycle exercise echocardiography and coronary angiography were performed in 42 patients from 1 month to 15 years (mean 6.3 years) after coronary artery bypass grafting (CABG) to determine if exercise-induced wall motion abnormalities could be correlated with the presence and location of nonrevascularized vessels. Nonrevascularized vessels were defined as obstructed vessels without grafts, obstructed grafts or native vessels obstructed distal to bypass graft insertion. Adequate quality echocardiograms were recorded at rest, peak exercise and after exercise in 38 patients (90%). Rest and postexercise echocardiograms were adequate in 3 others. Only 1 patient was excluded from analysis for inadequate peak and postexercise echocardiograms. Exercise-induced wall motion abnormalities were present in 33 of 35 patients (94%) who had 1 or more nonrevascularized vessels and these abnormalities were absent in 5 of 6 (83%) who had all vessels revascularized. Wall motion abnormalities were localized to the territory of the left anterior descending (LAD) artery or to a combined right (R) coronary-left circumflex (LC) region of circulation. Exercise-induced wall motion abnormalities were present in 24 of 27 LAD artery regions (89%) and 23 of 26 R-LC regions (88%) that had nonrevascularized vessels. These abnormalities were absent in 13 of 14 LAD regions (93%) and in 12 of 15 R-LC regions (80%) that had only revascularized vessels. Upright bicycle exercise echocardiography was successfully performed after CABG. The technique detected and accurately localized nonrevascularized and revascularized vessels.

Adjunct endarterectomy of the left anterior descending coronary artery

During a three-year period, complete revascularization of diffusely diseased left anterior descending (LAD) coronary arteries was accomplished by extensive endarterectomy in conjunction with bypass grafting in 37 patients in whom conventional bypass was not feasible. This group constituted 7.0% of all patients undergoing nonemergency coronary revascularization during this period. The left internal mammary artery was used to bypass the endarterectomized LAD artery in 22 patients. There was 1 (2.7%) operative death and 1 perioperative myocardial infarction. At follow-up, which was 100% with a mean of 41.4 months, all endarterectomy patients were in New York Heart Association Functional Class I or II. Twenty-four endarterectomy patients underwent first-pass radionuclide angiographic stress testing 20 months after operation. Twenty patients (83%) had excellent postoperative exercise tolerance, achieving 5 to 7 mets on treadmill testing. Left ventricular functional reserve was preserved, as evidenced by an increase of global ejection fraction from 48 +/- 15% at rest to 59 +/- 18% (p less than 0.005) with exercise. A similar increase was measured in the proximal and distal anterior wall segmental ejection fractions. No difference in response to exercise was found between the internal mammary artery and the vein graft groups. Thus, complete revascularization of the diffusely diseased LAD artery can be accomplished by adjunct endarterectomy without added morbidity or mortality and with excellent functional results.

Quantitative radionuclide angiocardiography

Quantitation of cardiac pump function using radionuclide angiocardiography provides objective information for the management of patients with heart disease. Left and right ventricular ejection fraction, stroke volume ratio, ejection rate, diastolic function, ventricular volume, parametric imaging, amplitude and phase analysis, and shunt quantification can be measured from the radionuclide angiocardiogram at rest, during exercise, and during pharmacologic interventions. This review describes these methods and discusses their reliability and their role in the clinical assessment of patients with cardiac disease.

Does coronary artery bypass surgery restore normal maximal coronary flow reserve? The effect of diffuse atherosclerosis and focal obstructive lesions

Aortocoronary vein bypass surgery might not restore normal maximal coronary flow reserve to bypassed coronary vessels because residual diffuse coronary atherosclerosis might limit maximal hyperemia. To investigate the effect of diffuse atherosclerosis and a focal stenosis at the graft-coronary anastomosis, we measured coronary flow reserve with an extensively validated subselective Doppler catheter in 24 patients with 35 bypass grafts perfusing angiographically normal coronary vessels. The Doppler catheter was positioned in the midportion of the graft, and coronary flow reserve was measured as the peak/resting velocity ratio after selective graft injection of a maximally vasodilating dose of papaverine. Luminal dimensions of the bypass graft, graft-coronary insertion, and bypassed coronary vessel were measured by quantitative coronary angiography (Brown/Dodge method). Measurements of coronary flow reserve and coronary dimensions of vein bypass grafts were compared with similar measurements obtained from 13 patients with normal coronary vessels and normal myocardium. Seventeen of the 35 bypass grafts perfused unobstructed coronary-vein graft anastomoses (less than 50% area stenosis) and normal myocardium. The coronary flow reserve of these 17 bypass grafts was normal (5.0 +/- 0.4, mean +/- SEM) and not significantly different from that measured in normal arteries (5.1 +/- 0.6), even though the cross-sectional area of the native coronary artery just distal to the bypass insertion was 40% smaller than in matched normal vessels. Bypass grafts perfusing hypertrophied (n = 2) or infarcted (n = 6) myocardium had significantly reduced coronary flow reserve compared with normal vessels (2.7 +/- 0.3; p less than .01), even when the infarcted wall had only minimal hypokinesis.(ABSTRACT TRUNCATED AT 250 WORDS)

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).

Effects of coronary artery revascularization and perioperative myocardial infarction on left ventricular wall motion

The effects of coronary artery revascularization and perioperative myocardial infarction on left ventricular wall motion are still controversial. In this study perioperative myocardial infarction was quantitatively estimated with the cumulative activity of the CK-MB isoenzyme in the perioperative period in a group of 77 consecutive patients undergoing coronary artery bypass surgery. After the operation (on average 9 +/- 1.8 months) all the patients were submitted to left ventricular and coronary angiography. Overall the global left ventricular ejection fraction was unchanged after the operation. The subgroup of patients with all patent grafts showed an improvement of both regional wall motion (P less than 0.05) and ejection fraction (from 58 +/- 13 to 64 +/- 13%, P less than 0.005); the number of angiographically abnormal left ventricular segments decreased from 28.5 to 16.6% (P less than 0.001). The cumulative activity of CK-MB enzyme was significantly correlated with the pre- and postoperative changes of ejection fraction (r = -0.51, P less than 0.01). Thus coronary artery bypass surgery can improve regional wall motion, but the likely benefit is observed in the absence of a perioperative myocardial ischemic damage.

The role of radionuclide cardiac imaging in coronary artery bypass surgery

The main applications of cardiac nuclear imaging in coronary artery bypass surgery include: patient selection, prediction of improvement in resting LV function after revascularization, diagnosis of perioperative myocardial infarction, assessment of the results of revascularization, evaluation of new or recurrent symptoms, and in risk stratification. Proper understanding of which test to be used, when, and why may be important to optimize patient management.

[Improved regional myocardial function after aortocoronary bypass surgery noninvasive studies using the first-pass technic]

50 patients after coronary artery bypass grafting were matched with 50 not-operated patients. After a follow-up period of four years they were investigated by first pass radionuclide angiography. Revascularized myocardial areas showed significantly higher regional ejection fraction during exercise and in territories with prior myocardial infarction. The results proved the hemodynamic benefits of coronary artery bypass grafting even in territories with poor myocardial function.

Value and limitation of biplane rest and exercise radionuclide angiography for assessing individual bypass grafts: a prospective study

This prospective study evaluated the ability of serial biplane rest and exercise radionuclide angiography to predict the status of individual coronary bypass grafts in 20 patients 2 to 6 months after surgery. The preoperative coronary angiogram was used to assign vessels to 10 regions of distribution on the radionuclide angiogram. Predictions of graft adequacy for individual vessels were based on a detailed assessment of rest and exercise wall motion in their regions of supply. Of 59 grafts, 38 were judged adequate (patent with less than 75% stenosis) and 21 inadequate by postoperative catheterization. Radionuclide prediction of graft status was possible for 32 of the 59 grafts, including 19 of 24 left anterior descending, 7 of 19 circumflex and 6 of 16 right coronary artery grafts. The status of the remaining 27 grafts could not be assessed because of normal wall motion in their region of supply both pre- and postoperatively (22 vessels) or because a region of supply was not represented on the biplane radionuclide angiogram (5 vessels). Of the 32 predictions made, 25 (78%) were correct, including 13 (93%) of 14 predictions of graft adequacy and 12 (67%) of 18 predictions of graft inadequacy. The single incorrect prediction of graft adequacy resulted from improved exercise wall motion in a region supplied by a graft judged as having a 75% anastomotic stenosis. Most incorrect predictions of graft inadequacy were due to new septal or other rest wall motion abnormalities postoperatively. The comparison of pre- and postoperative studies was essential to maintain the predictive ability of the test. Thus, a detailed analysis of regional wall motion by rest and exercise radionuclide angiography can be used to predict the status of individual coronary artery bypass grafts. Reliable predictions can be made for most successful anterior descending grafts, and may permit cardiac catheterization to be deferred in certain cases. However, the method is limited by the need to perform preoperative exercise studies, by the low number of right and circumflex coronary artery grafts that can be evaluated and by the poor specificity of predictions of graft failure.

Localization of exercise-induced myocardial ischemia with single view and biplanar radionuclide ventriculography: validation in single vessel coronary disease

The ability of single view and biplanar radionuclide ventriculography (RVG) to determine the location of myocardial ischemia during maximal graded supine bicycle exercise was assessed in 50 patients with chest pain, no prior myocardial infarction, and a single coronary stenosis of greater than or equal to 50% luminal diameter narrowing at coronary angiography. A biplane collimator was used so that both right anterior oblique (RAO) gated first-pass and left anterior oblique (LAO) equilibrium RVG could be performed at rest and exercise. Results were compared with those obtained using 4-view 201Tl myocardial scintigraphy in the same patients. Regional wall motion abnormalities (WMA) and 201Tl perfusion defects were detected and assigned to individual coronary vessels by agreement between at least two of three independent observers, who read all studies blinded along with those from control subjects with chest pain but no angiographically significant coronary artery disease. When scintigraphic abnormalities were detected, both biplanar RVG (36/39 = 92%) and 201Tl (25/25 = 100%) were more frequently correct in predicting the stenosed vessel than single view LAO RVG (24/32 = 75%) (P less than 0.05). At RVG only inferior WMA, in the RAO view, predicted right coronary stenosis. Only posterolateral WMA, in the LAO view, predicted left circumflex stenosis. Thus biplanar, but not single view, LAO exercise RVG is a reasonable alternative to exercise 201Tl for localizing exercise-induced ischemic abnormalities to individual coronary stenoses.

Effects of residual coronary artery disease on results of coronary artery bypass grafting

To assess the effects of residual coronary artery disease (non-revascularized coronary vessels) after coronary artery bypass grafting on symptoms and exercise left ventricular function, we categorized 77 patients into 3 groups according to the extent of residual coronary artery disease: group I (n = 17) had no residual coronary artery disease (residual score = 0); group II (n = 30) had light residual coronary artery disease (score of 1 to 9, mean 4.7); and group III (n = 30) had moderate residual coronary artery disease (score greater than or equal to 10, mean 23). Sixty patients were asymptomatic after coronary artery bypass grafting (14 in group I, 24 in group II, and 22 in group III), but the remaining patients had occasional angina pectoris. The resting left ventricular ejection fraction was significantly higher in group I than in the remaining 2 groups (56 +/- 18% in group I, 47 +/- 19% in group II, and 43 +/- 16% in group III, P less than 0.05). The exercise left ventricular ejection fraction was also significantly higher in group I (61 +/- 16% in group I, 51 +/- 18% in group II and 45 +/- 18% in group III, P less than 0.01). The ejection fraction response to exercise was abnormal in 5 patients in group I, 15 patients in group II, and 19 patients in group III. Thus, coronary artery bypass grafting results in symptomatic improvement, even in patients with residual coronary artery disease. The presence of residual coronary artery disease, however, may be a determinant of exercise left ventricular function in these patients.

Early and long-term results of coronary artery bypass grafting with severely depressed left ventricular performance

The effects of coronary artery bypass grafting (CABG) on ventricular performance and long-term clinical status were studied in 18 consecutive patients with disabling angina pectoris and severely depressed left ventricular (LV) performance (ejection fraction [EF] 27 +/- 9%). All patients survived CABG, although 1 patient had a perioperative myocardial infarction. There was no change in LVEF at rest, 29 +/- 12%, in the other 17 patients. However, LVEF during peak exercise increased from 22 +/- 7% to 27 +/- 14% (p less than 0.05). The 17 patients were separated into 2 groups: those who increased their peak exercise LVEF by at least 10% (group A, 8 patients) and those who increased it by less than 10% (group B, 9 patients). Preoperatively, patients in group A had a higher LVEF at rest (p less than 0.001) and smaller end-systolic and end-diastolic volumes at rest (p less than 0.001) and during exercise (p less than 0.005). Preoperatively, the LVEF in group A decreased with exercise, from 36 +/- 4% to 27 +/- 5% (p less than 0.01), but was unchanged in group B (19 +/- 3% vs 17 +/- 4%, difference not significant). After CABG, patients in group A had a smaller increase in end-systolic volume with exercise than those in group B (13 +/- 7 vs 34 +/- 22 ml/m2, p less than 0.05), but the changes in end-diastolic volume with exercise were not significantly different. At 27 +/- 5 months after CABG, 5 of 8 patients in group A were asymptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of coronary artery bypass grafting on left ventricular response to isometric exercise

The left ventricular (LV) response to isometric exercise was evaluated in 20 patients who performed handgrip exercise tests before and 3 months after coronary artery bypass grafting. Preoperative LV ejection fraction (EF) decreased during the handgrip test from 0.57 +/- 0.08 to 0.49 +/- 0.09 (p less than 0.001); the ratio between the LV peak systolic pressure (PSP) and end-systolic volume index (ESVI) did not change. In 12 patients with patent grafts, the LVEF after operation did not change (0.54 +/- 0.06 at rest and 0.56 +/- 0.06 during handgrip exercise) and PSP/ESVI ratio increased from 4.5 +/- 1.5 to 5.6 +/- 2.1 mm Hg/ml X m-2 (p less than 0.001) during exercise. In 8 patients with occluded grafts, the LVEF after operation decreased from 0.56 +/- 0.10 to 0.48 +/- 0.06 (p less than 0.02), whereas PSP/ESVI did not change during handgrip exercise. Thus, the LV response to isometric handgrip exercise appears to improve after coronary artery bypass grafting in patients with patent grafts, but not in patients with 1 or more occluded grafts.

Assessment of aortocoronary bypass grafting using exercise ST segment/heart rate relation

The maximal rate of progression of ST segment depression relative to increases in heart rate (maximal ST/HR slope) has recently been shown to be an accurate index of the presence and the severity of coronary heart disease in patients with angina. The value of this new exercise test was assessed in patients undergoing aortocoronary bypass. The maximal ST/HR slope and the results of coronary angiography were obtained in each of 46 patients before aortocoronary bypass surgery and in 26 of the 46 patients six months after the operation. At each stage of the investigation the maximal ST/HR slope detected without false results the absence and the number of significantly diseased vessels as shown by angiocardiography. As in previous findings the ranges of the maximal ST/HR slope showed no overlap between the four groups of patients: those with no significant disease and those with single, double, or triple vessel disease. In each of the 46 patients in whom the maximal ST/HR slope was determined before operation and three months afterwards the slope was lower after operation than before, indicating improvement. Follow up examinations showed that the maximal ST/HR slopes accurately detected the number of patent grafts used to bypass significantly diseased coronary arteries. Furthermore, the development of a significant narrowing or occlusion in any vein graft caused an increase in the maximal ST/HR slope which was equivalent to the value of single vessel disease. It is suggested that the maximal ST/HR slope may be used reliably in individual patients to indicate restoration of adequate blood supply to the myocardium after successfully aortorcoronary bypass surgery and the to detect in the period of six months after the operation the degree of severity of coronary heart disease whether it is caused by occlusion of the graft of significant disease of the coronary arteries.

Right and left ventricular function at rest and with exercise after the Mustard operation for transposition of the great arteries

Right and left ventricular function was assessed in 25 children (mean age at study 12.2 years and at operation 2.6 years) after a Mustard repair for transposition of the great arteries. Gated first pass and gated equilibrium radionuclide ventriculography was performed on all patients at rest and during supine bicycle exercise. The mean right ventricular ejection fraction did not increase with exercise by either technique. Individual results for right ventricular ejection fraction showed that with the gated equilibrium technique 71% had an abnormal exercise response (normal response being an increase in ejection fraction greater than 5%) and with the gated first pass technique 61% had abnormal results. Although the mean left ventricular ejection fraction increased significantly with exercise, 35% of patients had an abnormal exercise response with the equilibrium technique and 41% with the first pass technique. There was no evidence of a predictive relation between ventricular function and any clinical or haemodynamic variable examined. Covert right and left ventricular dysfunction can frequently be detected by exercise radionuclide ventriculography in long term survivors of repair for transposition of the great arteries. The prognostic consequences of these findings are unclear at present.

Incremental value of clinical assessment, supine exercise electrocardiography, and biplane exercise radionuclide ventriculography in the prediction of coronary artery disease in men with chest pain

The incremental value of clinical assessment, exercise electrocardiography (ECG) and biplane radionuclide ventriculography (RVG) in the prediction of coronary artery disease (CAD) was assessed in 105 men without myocardial infarction who were undergoing coronary angiography for investigation of chest pain. Independent clinical assessment of chest pain was made prospectively by 2 physicians. Graded supine bicycle exercise testing was symptom-limited. Right anterior oblique ECG-gated first-pass RVG and left anterior oblique ECG-gated equilibrium RVG were performed at rest and exercise. Regional wall motion abnormalities were defined by agreement of 2 of 3 blinded observers. A combined strongly positive exercise ECG response was defined as greater than or equal to 2 mm ST depression or 1.0 to 1.9 mm ST depression with exercise-induced chest pain. A multivariate logistic regression model for the preexercise prediction of CAD was derived from the clinical data and selected 2 variables: chest pain class and cholesterol level. A second model assessed the incremental value of the exercise test in prediction of CAD and found 2 exercise variables that improved prediction: RVG wall motion abnormalities, and a combined strongly positive ECG response. Applying the derived predictive models, 37 of the 58 patients (64%) with preexercise probabilities of 10 to 90% crossed either below the 10% probability threshold or above the 90% threshold and 28 (48%) also moved across the 5 and 95% thresholds. Supine exercise testing with ECG and biplane RVG together, but neither test alone, effectively adds to clinical prediction of CAD. It is most useful in men with atypical chest pain and when the ECG and RVG results are concordant.