Perioperative myocardial infarction and changes in left ventricular performance related to coronary artery bypass graft surgery

Myocardial indium-111 antimyosin uptake after uncomplicated coronary artery bypass surgery

The prevalence of myocardial damage after coronary artery bypass grafting is related to the criteria of its evaluation. Indium-111 monoclonal antimyosin antibody scintigraphy has been shown to be highly sensitive and specific for even small areas of myocardial necrosis or injury like those of myocarditis or transplant rejection. Our purpose was to evaluate, by using this method, myocardial damage after uncomplicated coronary artery bypass grafting. Uptake of this radio tracer was evaluated after coronary artery bypass grafting in 14 informed and consenting consecutive patients without previous myocardial infarction, with no post-surgical complications and a favorable postoperative course, following coronary artery bypass grafting for stable angina pectoris. Monoclonal antimyosin antibody indium-111 74 MBq (Myoscint Centocor) was injected on the third postoperative day; planar images in the anterior, left anterior oblique 45 degrees and 70 degrees projections were obtained 24 and 48 h later and analyzed for myocardial uptake. Indium-111 antimyosin uptake was present in 10 out of 14 patients (71.4%); it was diffuse in 6 and localized in 4. The ratio of the maximal counts in the myocardium to the counts in the adjacent lung background was measured and found elevated: 1.94 +/- 0.23, higher than the normal values reported in the literature. Indium-111 antimyosin uptake was clear in a group of patients after uncomplicated coronary artery bypass grafting. No correlation was observed between indium-111 antimyosin uptake or heart to lung ratio and creatine kinase, creatine kinase isoenzyme MB, glutamic oxalacetic transferase levels, duration of cardiopulmonary bypass or aortic cross-clamp time, while elevated serum beta myosin heavy chain fragments (IRMA Pasteur) were observed (1378 +/- 238 microU/l). This study suggests that some degree of myocardial damage, though silent, is common after coronary artery bypass grafting.

Perioperative myocardial cell damage assessed by immunoradiometric assay of beta-myosin heavy chain serum levels in patients undergoing coronary bypass surgery

In order to investigate myocardial cell damage in patients undergoing coronary bypass surgery, serum levels of cardiac myosin fragments, using monoclonal antibodies to myosin beta heavy chains, were measured in serial blood samples of 85 patients, 79 male and 6 female, 43-66 years old, after a total of 86 internal mammary artery and 137 saphenous vein graft implants. Eight patients had perioperative acute myocardial infarction (MI), detected by abnormal Q waves and a rise of CK-MB levels. After surgery, beta-myosin levels increased from post-operative day 3 and reached peak values on day 5 in patients without and in day 7 in patients with perioperative MI, in these 8 patients, myosin peak levels were greater as compared to 77 patients without perioperative MI (3452 +/- 1596 vs. 761 +/- 494; P < 0.01). There was a correlation between myosin peak levels and creatine kinase (CK) (r = 0.71; P < 0.05) and CK-MB peak levels (r = 0.74; P < 0.05) only in the patients with perioperative MI, but not in the patients without MI. There was no correlation between myosin peak levels and the times of aortic cross clamping or cardiopulmonary bypass. Peak myosin levels over 75% confidence limits of the mean were found in 23 patients; post-operative low output syndrome occurred in 10 of these 23 patients and in 7 out of 62 patients with peak myosin levels within 75% of the mean (P < 0.005). The increase in beta-myosin heavy chain serum levels observed in almost all patients undergoing coronary surgery suggests lesser perioperative damage of the contractile apparatus, which could be detected by the usual enzyme and ECG criteria. The higher prevalence of low output syndrome in patients with higher increases in myosin levels suggests more pronounced damage to the contractile apparatus in these patients. The higher myosin levels clearly indicate the presence of perioperative MI.

Heat shock protein (HSP 72) expression in patients undergoing cardiac operations

The major mammalian stress-inducible protein, heat shock protein 72, protects cells from certain stresses and rapidly accumulates in cells after ischemia. Heat shock protein 72 is rapidly synthesized in the myocardium of various species in response to ischemia, but it has not been investigated in human heart. To determine if heat shock protein 72 accumulated in the ischemic myocardium of patients undergoing cardiac operations, we obtained sequential right atrial biopsy specimens from 12 patients undergoing repair at three intervals: before bypass, after reperfusion, and after bypass. Immunoblot analysis for heat shock protein 72 demonstrated a high expression in the human heart compared with other mammalian hearts, p (Binomial) = 0.01. Compared with before bypass, heat shock protein 72 contents after reperfusion and after bypass were 98.2% +/- 8.9%, p (signed-rank) = 0.65, and 87.6% +/- 17.1%, p (signed-rank) = 0.28, respectively. Although heat shock protein 72 concentration was unchanged in hearts after reperfusion and after bypass, the initial prebypass level of heat shock protein 72 was high. The high heat shock protein 72 level detected in human hearts may reflect preoperative disease and drug therapy, or inherently high levels may be usual in the human myocardium. These findings indicate that the myocardium of patients undergoing cardiac operations contains relatively high concentrations of heat shock protein 72, which are not increased during the surgical procedure.

Myocardial damage following coronary bypass surgery: assessment with antimyosin antibody uptake

To assess the role of 111In antimyosin antibody (AbAm) in the delineation of myocardial damage following coronary bypass surgery, we studied 51 consecutive patients who underwent coronary surgery, 27 of whom had a history of prior myocardial infarction. All patients underwent a diagnostic protocol comprising: (1) 99Tcm pyrophosphate (PYP) and AbAm injection 48 h after surgery (AbAm imaging 24 and 48 h post-injection) (myocardial/background and myocardial/lung ratios were obtained respectively from the computer image); (2) Radioimmunoassay (RIA) serum CK-B levels from samples obtained immediately before surgery, and 24 and 48 h later; (3) clinical and ECG follow-up. Twenty-five patients showed positive AbAm studies, 10 had positive PYP images, and 21 had CK-B levels above normal limits at 24 h. One patient with abnormal AbAm, PYP and CK-B studies had new Q waves on the ECG after surgery. This patient was considered to have sustained a peri-operative myocardial infarction. The large number of positive AbAm studies probably reflects myocardial damage frequently associated with coronary bypass surgery.

Clinical experience of coenzyme Q10 to enhance intraoperative myocardial protection in coronary artery revascularization

Seventy-eight patients undergoing coronary artery bypass grafting (CABG) were compared retrospectively to evaluate whether pretreatment with coenzyme Q10 (CoQ) is effective in preventing left ventricular depression in early reperfusion following CABG. CoQ (5 mg/kg, intravenously) was given to 60 patients, 2 hours prior to the onset of cardiopulmonary bypass (CPB). CABG was performed using saphenous vein under CPB associated with cold cardioplegia in the standard fashion. Heart rate, mean arterial pressure, and cardiac index showed no significant difference between the CoQ and control groups. However, left ventricular stroke work index was significantly elevated at 6 and 10 hours of reperfusion following CABG in the CoQ-treated group compared with the controls. Serum MB-CK was lower at 0 and 6 hours of reperfusion in the CoQ group compared with the controls. These results suggest that pretreatment with intravenous CoQ is effective in preventing left ventricular depression in early reperfusion and in minimizing myocardial cellular injury during CABG followed by reperfusion.

Frequency of myocardial indium-111 antimyosin uptake after uncomplicated coronary artery bypass grafting

The reported incidence of myocardial damage after coronary artery bypass grafting (CABG) is highly related to the methods used. Since indium-111 monoclonal antimyosin antibody scintigraphy has been shown to be highly specific and sensitive for myocardial necrosis, even in small lesions, uptake of this radiotracer was evaluated after CABG. In 23 consecutive patients without previous myocardial infarction who underwent CABG for stable angina, 80 MBq indium-111 antimyosin was injected on the third postoperative day. Planar images were obtained 48 hours later and analyzed for myocardial uptake of indium-111 antimyosin. Scintigraphic results were related to creatine kinase MB levels, duration of both aortic cross-clamping and cardiopulmonary bypass, and electrocardiographic changes. In all patients surgical procedure and postoperative course was uncomplicated. Indium-111 antimyosin uptake was present in 19 of 23 patients (82%). It was diffused in 7 patients and localized in 12. No pathologic Q waves occurred postoperatively. Fourteen patients exhibited ST-segment changes. No good relation was found among indium-111 antimyosin uptake and creatine kinase MB levels, duration of cross-clamping or bypass, and ST-T changes. It is concluded that some degree of myocardial damage, though silent, is common after CABG.

Frequency and significance of complete atrioventricular block after coronary artery bypass grafting

Three hundred forty-eight consecutive patients were evaluated during 1985 and 1986 for the development of complete atrioventricular (AV) block after coronary artery bypass grafting. Cold (4 degrees) asanguineous potassium cardioplegia with temperature monitoring was used uniformly. AV block developed in 56 instances (16%). In 32 patients (group 1) the block was transient (less than 6 hours) and in 24 it was persistent (group 2). Left main coronary artery stenosis in conjunction with total obstruction of a dominant right coronary artery occurred more commonly in patients manifesting AV block (18 of 56, 32%) than in those without it (35 of 292, 12%) (p less than 0.05). Complete occlusion of a dominant right coronary artery was observed with equal frequency in patients with and without AV block. The presence of an ungraftable right coronary artery, however, was significantly more frequent in the AV block group: 16 of 37 (47%) vs 6 of 194 (3%) (p less than 0.01). Endarterectomy of the right coronary artery was performed in 8 of 24 patients (33%) with persistent AV block versus none in the patients with transient AV block (n = 32) or normal sinus rhythm postoperatively (n = 292) (p less than 0.0001). Persistent AV block (greater than 6 hours) was associated with myocardial infarction in 6 patients (25%) (p less than 0.05) and with low cardiac output in 18 patients (75%) (p less than 0.0001). In conclusion, AV block after myocardial revascularization was frequently associated with the presence of multivessel coronary disease and an ungraftable dominant right coronary artery. Persistent (greater than 6 hours) AV block was correlated with both perioperative myocardial infarction and low cardiac output.

Changes in serum CK-MB mass after coronary artery bypass surgery

We assessed the release of creatine kinase MB as both mass and activity during the postoperative period following cardiac surgery. CK-MB mass was determined by enzyme immunoassay using reagents obtained from Hybritech. CK-MB activity was determined both by agarose electrophoresis and by an immunochemical method. Fifty-five patients who underwent coronary artery bypass surgery and 52 control subjects who had orthopedic surgery were selected for study. Serial serum samples were collected following surgery and total LD, CK, AST, LD-1, CK-MB mass, and CK-MB activity determined. Results were compared to each other and to surgical parameters. All patients exhibited significant CK-MB mass and activity after surgery and peak serum levels were 6-94 micrograms/L and 12-84 U/L, respectively. CK-MB mass correlated with CK-MB activity on paired samples (r = 0.94). Total AST and CK activities correlated with CK-MB mass (r = 0.60, and 0.63, respectively). Peak levels of CK-MB mass correlated significantly with peak MB activity (r = 0.88), peak LD-1 (r = 0.62), peak AST (r = 0.71), and time on pump (r = 0.54). Similar correlations were also seen between peak CK-MB activity and these parameters. No relationship could be identified between extent of CK-MB mass release and number of grafts, degree of hypothermia, or minimum PaO2. The time course of CK-MB mass release exhibited 85% concordance with CK-MB activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Closed-heart technique for Wolff-Parkinson-White syndrome: further experience and potential limitations

We have described a closed-heart technique for division of atrioventricular (AV) pathways in Wolff-Parkinson-White (WPW) syndrome. The technique involves dissection and mobilization of the AV fat pad with exposure and cryoablation of the AV junction at the site of the AV pathways. One hundred five consecutive patients with WPW syndrome with left ventricular free wall (74), posterior septal (23), and right ventricular free wall AV pathways (11) were operated on between July, 1982, and September, 1985. Three patients had multiple accessory pathways, and 9 had associated cardiac disease. Electrophysiological testing to determine the presence and site of the AV pathway was performed before and after dissection of the fat pad and again after cryoablation of the AV junction. All AV pathways but 1 were successfully ablated. There were no deaths and no incident of AV block. One hundred four patients remain free from arrhythmia in the absence of drugs after a mean follow-up of 18 months (range, 2 to 42 months). Four patients required a second operation within the first few weeks for recurrence of AV pathway conduction, and 1 patient required a third operation. In 3 of these patients, AV pathway conduction persisted after extensive dissection and exposure of the AV junction and disappeared only after cryoablation. Recurrence of AV pathway conduction in the latter patients suggests the presence of a subendocardial pathway protected from cryoablation by the warm, circulating blood pool. The closed-heart technique appears safe and efficacious. A potential limitation may be the presence of subendocardial AV pathways, which may require an alternative surgical approach at the site of the pathway to attain uniform primary success.

Coronary artery bypass graft surgery: clinical comparison of cold blood potassium cardioplegia, warm cardioplegic induction, and secondary cardioplegia

An analysis of myocardial protection was performed in 45 low-risk patients undergoing coronary bypass procedures who were divided into three equal groups with similar preoperative ejection fractions and coronary artery obstructions. Group 1 (N = 15) received cold blood cardioplegia, Group 2 received cold blood cardioplegia and secondary cardioplegia, and Group 3 received cold blood cardioplegia plus warm cardioplegic induction. The aortic cross-clamp time and the number of bypass grafts were similar among the groups. The following variables were measured serially: electrocardiographic changes, serum myocardial-specific isoenzyme of creatine kinase, cardiac output, left ventricular filling pressure, ejection fraction, and left ventricular wall motion. The three methods evaluated were all effective in protecting the myocardium during global myocardial ischemia. Patients who received secondary cardioplegia (Group 2) were more likely to exhibit spontaneous defibrillation (12/15) than those in Group 1 (5/15) or Group 3 (6/15) (p less than 0.05). However, measurements of left ventricular performance and evidence of perioperative myocardial infarction were similar among all three groups. These data suggest that a standard technique of cold potassium cardioplegia alone should be the method of choice in elective, low-risk coronary bypass operations rather than this technique in combination with either of the other two more costly and complex methods evaluated in this study.

Perioperative ischemic injury after coronary bypass graft surgery

Two hundred twelve patients who underwent isolated coronary bypass graft surgery were prospectively evaluated for perioperative ischemic injury. All patients underwent preoperative and postoperative testing with technetium 99m pyrophosphate first-pass ventriculography combined with myocardial uptake scans, 12-lead electrocardiography, and serial creatinine phosphokinase MB determination. Fifteen percent of the patients had ischemic injury with at least two test results positive, but only 4 percent had positive results of all three tests. No single test proved adequate. Enzyme levels were highly sensitive and had value as a screening test. The electrocardiogram was specific but only moderately sensitive. The single best test was the radionuclide scan with good sensitivity and no false-positive results. All three tests are required to rigorously diagnose ischemic injury.

Coronary artery bypass graft surgery: relative efficacy of initial proximal versus distal anastomoses

Controversy exists concerning the most appropriate sequence of anastomoses in coronary artery bypass grafting (CABG) procedures. While the more commonly employed method of distal coronary anastomoses first has withstood a long clinical experience, a recent study and several cardiac surgical groups have suggested that construction of the proximal anastomoses first offers certain advantages. In 30 patients undergoing CABG, we performed a prospective, randomized trial comparing both techniques. Relative efficacy was assessed by hemodynamic, radionuclide, electrocardiographic, enzymatic, thermographic, and clinical evaluation. The length of cardiopulmonary bypass was longer in the group having the distal anastomoses done first. Myocardial temperature mapping was similar between groups. Hemodynamic changes, including cardiac output, ejection fraction, and regional wall motion, were nearly identical between the groups. The incidence of myocardial damage reflected by levels of myocardial-specific isoenzymes (serum CK-MB) and electrocardiographic changes was also similar. In conclusion, the sequence of anastomoses is not critical in routine CABG operations. However, we speculate that each technique may have certain advantages under different clinical circumstances found on occasion. Ideally, each method should be part of the coronary surgeon's armamentarium.

Blood cardioplegia delivery. Deleterious effects of potassium versus lidocaine

Delivery of cardioplegic (CP) solutions to all regions of the myocardium is critical for optimal myocardial protection during cardiac surgery. However, there are little data regarding the effects of CP agents upon coronary vascular resistance (CVR) and CP delivery. Accordingly, we evaluated blood CP (Hct 30) delivery and CVR during 75 minutes of multi-dose hypothermic blood CP arrest in an in vivo isolated dog heart preparation. Three groups of dogs were studied: K(K+ = 30 mEq/L; n = 6), L (Lidocaine = 400 mg/L; K+ = 4 mEq/L; n = 6), and KL (K+ = 30 mEq/L, Lidocaine 400 mg/L; n = 6) during total cardiopulmonary bypass and moderate systemic hypothermia (28 C). Basal CVR was calculated by measuring total coronary flow (HR 120/min; mean aortic pressure = 80 mmHg) in the empty beating heart. After aortic cross-clamping, the blood CP solution was infused into the aortic root at a constant pressure (80 mmHg) and constant temperature (16 +/- 2 C) for 60 seconds at 15 minute intervals for a total arrest time of 75 min. Total CP flow, CVR, O2 consumption, lactate extraction/production, and K+ balance during 75 minutes of arrest and 30 minutes of reperfusion were determined. The distribution of the CP solution in the left ventricle was measured with radioactive microspheres (9 +/- 1 mu). Biopsy specimens were taken to measure wet to dry ratios. Values are mean +/- SEM. Data were analyzed by BMDP-P2V. During the first CP infusion, after aortic cross-clamping, no differences in CVR or CP distribution were found among the three groups. However, CVR was increased significantly in the K group during the second CP infusion (O': 0.98 +/- 0.20 mmHg/ml/min/100 g; 15': 2.66 +/- 0.82; p less than 0.001). The CVR remained high for the remainder of the arrest period. Moreover, total, epi- and endocardial flow decreased significantly (54%, p less than 0.001). In groups L and KL, no significant changes in CVR were seen. Groups K and KL showed a significant K+ extraction during the first CP infusion. During the early reperfusion period, K+ washout occurred in these two groups, which was not seen in the L group. There was no significant difference between the three groups in myocardial O2 consumption, lactate metabolism, and water content during the arrest and the reperfusion period. In conclusion, high concentrations of K+ (30 mEq/L) can markedly increase CVR and impair blood CP delivery and distribution. These effects can be prevented by lidocaine. These findings warrant reassessment of the various additives to CP solutions and their effects on CVR and CP distribution during multi-dose hypothermic CP arrest.