Effect on myocardial perfusion of simultaneous delivery of cardioplegic solution through a single coronary artery and the coronary sinus.

OBJECTIVE: This study was to determine whether simultaneous antegrade-retrograde cardioplegia through a single coronary artery and the coronary sinus provides sufficient and homogeneous perfusion to the heart. METHODS: Simultaneous antegrade-retrograde cardioplegia was conducted in 7 isolated pig hearts through the coronary sinus in conjunction with the left anterior descending artery, the left circumflex artery, and the right coronary artery, respectively. The efficacy of simultaneous antegrade-retrograde cardioplegia for myocardial perfusion was assessed by monitoring the distribution of magnetic resonance contrast agent and measuring the effluent from the venting coronary arteries. RESULTS: Injection of contrast agent into a perfusing artery during simultaneous antegrade-retrograde cardioplegia resulted in increased image signal intensity not only in the territory of the perfusing artery but also in the areas normally served by the other 2 venting arteries (including the right ventricular wall). The myocardium in the territories of the 2 venting arteries was lightened with contrast agent given into the coronary sinus during simultaneous antegrade-retrograde cardioplegia. Myocardium in the perfusing artery territory and right ventricular wall remained dark. Moreover, a significant amount of effluent was collected from the venting arteries during simultaneous antegrade-retrograde cardioplegia: 4.7 to 7.8 mL/min from the right coronary artery; 10.5 to 17.7 mL/min from the left anterior descending artery; and 9.7 to 15.2 mL/min from the left circumflex coronary artery. CONCLUSIONS: Simultaneous antegrade-retrograde cardioplegia through a single coronary artery and the coronary sinus provides homogeneous perfusion to the entire heart. During simultaneous antegrade-retrograde cardioplegia, arterial flow supports its own designated myocardium, as well as adjacent myocardium normally served by the venting arteries; the arterial route also supports the right ventricular free wall when the right coronary artery is vented. Venous perfusion of simultaneous antegrade-retrograde cardioplegia mainly supports myocardium in the territories of the venting arteries and does not perfuse the right ventricular free wall. Blood flow delivered to myocardium normally supported by the venting arteries is believed to be sufficient to prevent ischemic injury.

Simultaneous antegrade/retrograde cardioplegia protects myocardium distal to a coronary occlusion: a study in isolated pig hearts.

This study was designed to assess the effects of simultaneous antegrade/retrograde cardioplegia (SARC) on myocardial perfusion and energy metabolism in the region supported by the occluded left anterior descending artery (LAD) in isolated pig hearts. It was found that injection of Gd-DTPA into the aorta during antegrade cardioplegia (AC) did not result in signal increase in the LAD region on T(1)-weighted images. During SARC, however, Gd-DTPA was detected in the LAD region with the contrast agent injected into the aorta and the coronary sinus (CS), respectively. This suggests that SARC delivered blood cardioplegia to the jeopardized myocardium through both arterial and venous perfusion routes. Moreover, localized (31)P spectra showed that occlusion of the LAD during AC resulted in severe ischemic changes in the LAD myocardium and the abnormal metabolic changes were completely abolished by use of SARC. Finally, recovery of myocardial contractile function during reperfusion in the hearts subjected to SARC was significantly better compared to those arrested with AC alone. It was concluded that the myocardium distal to a coronary occlusion can be fully protected by use of SARC.

Contrast agent distribution in microvascular damage of infarcted pig myocardium.

PURPOSE: We determined whether reperfusion damage was sufficient to allow extravasation of a large molecular weight contrast agent into infarcted pig myocardium. MATERIAL AND METHODS: Five pig hearts were subjected to in situ occlusion of the left anterior descending coronary artery (2 h) followed by reperfusion (1 h). The hearts were excised and perfused in the Langendorff mode for ex vivo MR imaging. Polylysine-Gd-DTPA (50,000 Da) and Gd-DTPA (500-700 Da) were injected into the aorta (alternately) and followed by measurements of T1 relaxation and mean transit time (MTT). RESULTS: In the normal myocardium, MTT of Gd-DTPA (56.8+/-23.2 s) was significantly (p=0.02) longer than that of polylysine-Gd-DTPA (29.0+/-7 s). However, both normal and infarcted myocardium showed similar MTT (29.0+/-7.0 vs. 28.0+/-5.0 s, p>0.05) when using polylysine-Gd-DTPA. CONCLUSION: The results indicate that the permeability of capillaries to polylysine-Gd-DTPA was not significantly higher in infarcted regions of the myocardium compared to normal tissue. However, infarcted myocardium displayed an increased permeability to the small molecular weight Gd-DTPA. We conclude that microvascular damage may not be sufficient to allow the extravasation of polylysine-Gd-DTPA in infarcted myocardium.

Safety and efficacy of fast track in patients undergoing coronary artery bypass surgery.

BACKGROUND: The incidence of coronary artery bypass surgery has been increasing annually with increasing pressure on the health care system. Fast track has been proposed as a means to increase efficiency and volume, without an increase in hospital resources. To date this approach has not been critically assessed in Canada. METHODS: We examined 617 consecutive patients undergoing isolated CABG surgery. The patients were divided into (1) fast track (FT) recovery (n = 219), without admission to an ICU, and (2) non-fast track (NFT) recovery (n = 398) with direct admission to the ICU. There were no differences in age, gender, timing of surgery, left main stenosis, preoperative myocardial infarction, renal failure, diabetes, peripheral vascular disease, or in the incidence of chronic obstructive pulmonary disease between the two groups. The NFT group had a higher proportion of patients with NYHA Class III/IV symptoms preoperatively (65.7% vs. 57.3%, p = 0.048), in patients with an ejection fraction < 40% (42.5% vs. 30.6%, p = 0.004), or in the number of individuals with an IABP inserted before surgery (13 vs. 1, p < 0.001). RESULTS: In the FT group the average period of aortic occlusion (40.7 +/- 15.2 min vs. 71.8 +/- 26.5 min, p < 0.001) and perfusion time (67.8 +/- 24.5 min vs. 117.5 +/- 40.2 min, p < 0.001) were significantly less than in the NFT group. The number of grafts per patient was 3.3 +/- 1.0 vs. 3.2 +/- 1.0, respectively (p = 0.38). Operative mortality was 0.9% in the FT group and 1.3% in the NFT group (p = 1.0). Significant differences were seen in the proportion of patients that suffered from postoperative ventilatory failure (3.2% in FT vs. 12.1% in NFT, p < 0.001), and the proportion of patients that suffered any postoperative complication was significantly higher in the NFT group (21.4%) than in the FT group (9.1%, p < 0.001). The differences in postoperative complications resulted in a shorter length of stay (LOS) in FT patients (5.6 +/- 4.1 days vs. 9.7 +/- 9.4 days NFT, p < 0.001). Only 4.1% of patients that entered the FT group failed and required admission to the ICU. Multivariate stepwise logistic regression analysis identified non-fast track recovery as an independent predictor of morbidity in CABG surgery patients. CONCLUSIONS: The data indicate it is possible to perform isolated CABG surgery, in a large proportion of the population, without the need for admission to an ICU for postoperative care.

The effects of retrograde cardioplegia technique on myocardial perfusion and energy metabolism: a magnetic resonance imaging and localized phosphorus 31 spectroscopy study in isolated pig hearts.

OBJECTIVE: The present work was designed to study the myocardial perfusion and energy metabolism during retrograde cardioplegia performed with different methods, including deep coronary sinus cardioplegia, coronary sinus orifice cardioplegia, and right atrial cardioplegia. METHODS: Isolated pig hearts were subjected to antegrade cardioplegia, right atrial cardioplegia, deep coronary sinus cardioplegia, and coronary sinus orifice cardioplegia in a random order. Cardioplegic distribution was assessed by T1-weighted magnetic resonance imaging in 1 group of hearts (n = 8). The flow dynamics of cardioplegia were assessed by T2*-weighted imaging in a second group of hearts (n = 8). RESULTS: T1-weighted images revealed an apparent perfusion defect in the posterior wall of the left ventricle, the posterior portion of the interventricular septum, and the right ventricular free wall during deep coronary sinus cardioplegia. The perfusion defect observed in the first 2 regions with deep coronary sinus cardioplegia resolved with coronary sinus orifice cardioplegia. Right atrial cardioplegia provided the most homogeneous perfusion to all regions of the myocardium relative to the other 2 retrograde cardioplegia modalities. T2*-weighted images showed that the 3 retrograde cardioplegia modalities provided similar cardioplegic flow velocities. Localized phosphorus 31 spectroscopy showed that the levels of adenosine triphosphate and phosphocreatine were significantly lower in the posterior wall (adenosine triphosphate, 42.86% +/- 5.91% of its initial value; phosphocreatine, 11.43% +/- 11.3%) than the anterior wall (adenosine triphosphate, 89.19% +/- 8.83%; phosphocreatine, 59.54% +/- 12.58%) of the left ventricle during 70 minutes of normothermic deep coronary sinus cardioplegia. CONCLUSIONS: Deep coronary sinus cardioplegia results in myocardial ischemia in the posterior wall of the left ventricle and the posterior portion of the interventricular septum, as well as in the right ventricular free wall. Coronary sinus orifice cardioplegia improves cardioplegic distribution in these regions. Relative to deep coronary sinus cardioplegia and coronary sinus orifice cardioplegia, right atrial cardioplegia provides the most homogeneous perfusion.

Effects of retrograde cardioplegia on myocardial perfusion and energy metabolism in immature porcine myocardium.

OBJECTIVES: Retrograde cardioplegia has been widely used for the protection of adult hearts during cardiac operations. Its efficacy to protect immature myocardium is still unclear. This study was designed to assess the effects of retrograde cardioplegia on myocardial perfusion and energy metabolism in immature hearts. METHODS: Piglet hearts were divided into 3 groups. Hearts in group 1 were used to assess myocardial perfusion of retrograde cardioplegia by means of magnetic resonance imaging. Hearts in groups 2 and 3 were used to assess the effects of retrograde cardioplegia on myocardial energy metabolism by use of phosphorus 31 magnetic resonance spectroscopy. RESULTS: Magnetic resonance images showed that perfusion with retrograde cardioplegic solution was heterogeneous. A perfusion defect was noted during retrograde cardioplegia in the right ventricular wall and in a portion of the posterior wall of the left ventricle in 4 of 6 hearts. Phosphorus 31 spectra showed that at the end of 45-minute retrograde cardioplegia, myocardial intracellular pH was 6.83 +/- 0.17 and phosphocreatine was 53.5% +/- 27% of its prearrest value. The adenosine triphosphate level, however, remained normal throughout the retrograde cardioplegia period. Last, the hearts subjected to retrograde cardioplegia or antegrade cardioplegia showed similar and complete metabolic and functional recovery during reperfusion. CONCLUSIONS: Retrograde cardioplegia provides heterogeneous perfusion. Its ability to protect the right ventricular myocardium is poor and varies between individuals. Myocardial perfusion provided by retrograde cardioplegia is slightly less than that needed to sustain normal myocardial energy metabolism under normothermic conditions.

Ten-year follow-up study of patients who had double valve replacement with the St. Jude Medical prosthesis.

Records of 100 consecutive patients who had received double valve replacement were reviewed (41 men, 59 women, mean age, 60.86 +/- 13.0 years). The early death rate was 6% (six patients). A completed follow-up rate of 93% was accomplished in these 94 patients who left the hospital (mean, 309.8 patient-years). Twenty-three of these patients died. The late death rate was 26.4%. Four patients experienced thromboembolic episodes (one transient and three permanent; all were minor). One patient had a paravalvular leak (mitral), and another had thrombosis of the tricuspid valve. There was no clinical evidence of hemolysis, infective endocarditis, or structural failure or anticoagulant-related bleeding. One of those 23 patients who died was the patient who had thrombosis of the tricuspid valve. Another three patients died of sudden and unknown causes, 15 of cardiac-related problems and four of noncardiac problems. Of those patients who survived, New York Heart Association functional class improved significantly (from 66% class III before to 85% class I after). Linearized rates for thromboembolism and thrombosis were 1.29 +/- 0.65 and 0.32 +/- 0.32 per 100 patient-years, respectively. The actuarial estimates of incidence free of all complications and valve-related deaths were 77.9% +/- 10.6%. Despite the advanced heart disease involving two native valves, the patients who had double valve replacement with the St. Jude Medical prosthesis had very good results over a 10-year period.

Ten years' experience with the St. Jude Medical valve prosthesis.

Records of 1,298 consecutive patients who had received the St. Jude Medical prosthesis were reviewed (713 male and 585 female patients; mean age, 61.79 +/- 13.4 years). Early mortality was 5.7% (74 patients). Ninety-three percent complete follow-up was accomplished for the 1,224 patients who left the hospital (4,306.50 patient-years). One hundred ninety-two of these patients died, a late mortality of 16.9%. Sixty-four patients experienced thromboembolic episodes (17 major and 35 permanent). Twenty-four patients had anticoagulant-related bleeding, 4 had valve thrombosis, 7 had prosthetic valve endocarditis, 9 had paravalvular leak, and 10 underwent reoperation. There was no structural valve failure in this series. Twenty-two of the 118 patients who had valve-related complications died; another 15 patients died of sudden and unknown causes. Therefore, the total number of valve-related deaths was 37. Of those patients who survived, New York Heart Association functional class improved significantly (98% in classes II and III preoperatively and 96% in classes I and II postoperatively). Linearized rates for thromboembolism, valve thrombosis, and anticoagulant-related bleeding were 1.49% +/- 0.19%, 0.09% +/- 0.05%, and 0.56% +/- 0.11%/100 patient-years, respectively. The actuarial estimate of incidence free from all complications, operative death, and valve-related death was 66.9% +/- 8.2% at the end of 9 years. In spite of old age and advanced heart disease, the patients who received the St. Jude Medical prosthesis had very good results over a 10-year period.

The comparative influence of prophylactic antibiotics on the prothrombin response to warfarin in the postoperative prosthetic cardiac valve patient. Cefamandole, cefazolin, vancomycin.

A prospective randomized trial was conducted comparing the effect of three antibiotics: cefamandole (CM), cefazolin (CZ), and vancomycin (V), used as prophylaxis for prosthetic valve surgery, on the prothrombin (PT) response to warfarin (W) on the third day of anticoagulant therapy. Twenty patients, with normal preoperative PTs, were randomized to each antibiotic. Their PTs were not significantly different at 2 hours after operation and the morning before W was begun. The three groups received similar W doses for 2 days, and the PT, as percentage of activity, on the morning of the third day demonstrated that V (51 +/- 18%) was significantly greater (p less than 0.005) than CM (29 +/- 14%) or CZ (38 +/- 18%). CM had a significantly greater percentage of change in PT (64 +/- 14%, p less than 0.0001) from the first to third day than either CZ (51.1 +/- 18%) or V (44.6 +/- 19%). CM also had a greater number of patients (6) with PTs greater than or equal to 30 seconds on day 3 than either CZ (1) or V (1). The antibiotic influence on the PT response to W in this study is ranked as CM greater than CZ greater than V.

St. Jude Medical prosthesis: valve-related deaths and complications.

Despite the hemodynamic improvement in cardiac valve prostheses, valve-related deaths and complications have remained a substantial source of morbidity and mortality. This follow-up study was carried out in April, 1986, in a group of 816 patients who received 876 St. Jude Medical prostheses between October, 1977, and October, 1984. One hundred fifty-five patients (37%) of the 422 having aortic valve replacement (AVR) and 88 (29%) of the 300 having mitral valve replacement (MVR) had concomitant coronary artery bypass grafting, and 94 patients (12%) had miscellaneous procedures performed in addition to valve replacement. Sixty-three patients died within the operative period, an operative mortality of 7.7%. Follow-up was complete for 98% of the patients; the mean follow-up was 42 months. At that time, 87 more patients had died, a late mortality of 11.9%. There were 13 valve-related deaths (4 in the AVR group, 7 in the MVR group, and 2 in the miscellaneous group); the causes of death were thromboembolism (7), anticoagulant-related hemorrhage (2), valve thrombosis (2), prosthetic valve endocarditis (1), and perivalvular leak (1). There were 37 thromboembolic episodes (1.78/100 patient-years) and 67 anticoagulant-related hemorrhages (3.22/100 patient-years), 46% of which necessitated transfusion. The incidence of valve thrombosis was 0.6% (4 patients). Perivalvular leak and prosthetic valve endocarditis occurred in 7 patients (1.0%) and 5 patients (0.7%), respectively. Reoperation was carried out in 6 patients (0.8%), but only for perivalvular leak. There were no deaths, no complications, and no clinical evidence of malfunction of the prosthetic valve.(ABSTRACT TRUNCATED AT 250 WORDS)

Six years of experience with the St. Jude Medical valvular prosthesis.

The cases of 680 consecutive patients who underwent valve replacement with the St. Jude Medical prostheses by one group of surgeons from October 1977 through October 1983 were reviewed. The operative mortality for the entire group was 6.6% (3.7% for aortic valve replacement [AVR], 1.6% for AVR and coronary artery bypass [CAB], 14.3% for AVR and miscellaneous procedures; 7.9% for mitral valve replacement [MVR], 15.5% for MVR and CAB, 33% for MVR and miscellaneous procedures; 5% for double valve replacement [DVR], 8.3% for DVR and CAB, and 0% for DVR and miscellaneous procedures). Warfarin (Coumadin) anticoagulation was recommended for all the patients. The mean follow-up of 24 months was completed in 95% of the patients (14,737 patient-months). The overall late mortality was 7.7% (6.2% for AVR, 6.3% for AVR and CAB, 8.3% for AVR and miscellaneous procedures; 7.9% for MVR, 6.7% for MVR and CAB, 33% for MVR and miscellaneous procedures; 15.8% for DVR, 18.2% for DVR and CAB, and 0% for DVR and miscellaneous procedures). There were no cases of mechanical prosthetic failure. Clinically significant hemolysis occurred in only five patients (less than 1%) with paravalvular leak after MVR. Only three patients (less than 0.5%) experienced prosthetic infection. Incidence of embolization was 0.7 per 100 patient-years in the patients who underwent AVR and 2.2 per 100 patient-years in those who underwent MVR.(ABSTRACT TRUNCATED AT 250 WORDS)

Should valve replacement and related procedures be performed in elderly patients?

The cases of 135 consecutive elderly patients 70 years old or older who had valve replacement and related surgical procedures from October, 1977, through April, 1982, were reviewed. There were 75 men and 60 women. The mean left ventricular ejection fraction was 50.16 +/- 5%. The overall operative mortality was 8% (11 patients). The early operative deaths were related mainly to cardiac failure, low cardiac output, sepsis, and renal and multiorgan failure. To assess the operative risk, these 135 patients were compared with 312 younger patients (less than 70 years old) who had undergone similar procedures during the same period. The operative mortality in this group was 5.2% (16). In-hospital complications included arrhythmia (13%), psychosis (7.4%), respiratory failure (6.7%), renal failure (6.7%), cerebrovascular accident (5.2%), myocardial infarction (4.4%), and reoperation for bleeding (2.2%). Wound dehiscence occurred in 1.5% of the patients, and pulmonary emboli and sepsis developed in 0.7%. Of these complications, only the incidence of cerebrovascular accident appeared to be more common in the elderly group (5.2% versus 2.8%), but it had no statistical significance (p = 0.18). A follow-up of 3,892 patient-months was completed in 98.4% of the survivors. There were 8 late deaths (6.4%). Six were related to the valve or to ongoing cardiovascular disease. Thirty-four patients subsequently required medical attention: 4 had bleeding because of the anticoagulant; 3 required a blood transfusion; and 27 were hospitalized. Six were admitted for related cardiac conditions and 7, for observation of other conditions; 14 underwent surgical procedures not related to the cardiovascular system.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of prophylactic antibiotics on the warfarin anticoagulation response in the postoperative prosthetic cardiac valve patient. Cefamandole versus vancomycin.

The influence of cefamandole and vancomycin used for prophylaxis on the warfarin anticoagulation response in 60 cardiac valve replacement patients during the postoperative period is presented. Patients were divided into two groups, hyper-responders prothrombin time (PT) greater than or equal to 32 sec, 48 hr after the initial warfarin dose (GrIHR), or normal responders PT less than 32 sec (GrIINR). Fifteen patients (25%) were in GrIHR (PT 44.3 +/- 10.5) and 45 in GrIINR (21 +/- 5). Fourteen of the 15 GrIHR patients received cefamandole and 1 of the 15 GrIHR patients received vancomycin p less than 0.05, as prophylaxis. Warfarin sensitivity was assessed using a warfarin dose index (WDI) calculated in the initial postoperative period (WDIINT) and at discharge (WDIDIS). GrIHR patients had greater WDIINT and WDIDIS compared to GrIINR p less than 0.001. Baseline prothrombin time measured 8 hours prior to start of warfarin therapy (PTBL), was linearly correlated to the WDIINT with r = 0.8, p less than 0.001 in cefamandole patients only. The data suggests that cefamandole increases warfarin sensitivity early in the postoperative course of oral anticoagulation therapy, which may lead to excessively high prothrombin times with the possibility for serious bleeding.

Effect of sodium nitroprusside during the payback period of cardiopulmonary bypass on the incidence of postoperative arrhythmias.

This study was designed to determine whether a sodium nitropruside infusion during the reperfusion (payback) period of cardiopulmonary bypass would minimize arrhythmias during the early postoperative period of coronary artery bypass surgery. A double-blind randomized study was carried out in 38 patients with no previous history of ventricular arrhythmias. Seventeen received 5% dextrose in water (D5W) and 21 received sodium nitroprusside at the rate of 2 microgram per kilogram per minute during the payback period. The pump flow was kept constant at 2.2 liters per square meter per minute, and mean pressure was maintained at greater than 50 mm Hg. There was a statistically significant difference between the two groups in the number of patients who developed ventricular arrhythmias (13 of 17, or 76%, in the D5W group versus 6 of 21, or 29%, in the sodium nitroprusside group; p less than 0.005). Twelve of the 13 patients in the D5W group experienced arrhythmias (6 ventricular tachycardia and 6 ventricular premature depolarization) within the first 24 hours, compared to 5 of 12 patients in the nitroprusside group (3 ventricular tachycardia and 2 ventricular premature depolarization). Only 1 patient in each group developed ventricular arrhythmia after the first postoperative day. One patient in each group experienced atrial arrhythmia during the first 24 hours. After 24 hours, atrial arrhythmias developed in 5 patients in the D5W group (35%) and 3 patients in the sodium nitroprusside group (17%) (p greater than 0.05). The arterial pH ranged from 7.35 to 7.55, with a Po2 greater than 70 torr and a serum potassium of 3.7 +/- 0.36 mEq per liter in the D5W group and 3.4 +/- 0.34 mEq per liter in the nitroprusside group during the period of arrhythmias. Sodium nitroprusside given during the payback period of cardiopulmonary bypass appears to minimize ventricular arrhythmias in the early postoperative period of coronary artery bypass surgery.

Clinical and hemodynamic results with the St. Jude Medical cardiac valve prosthesis. A three-year experience.

Two hundred thirty-two consecutive patients (October 3, 1977, through December, 31, 1980) underwent aortic (AVR), mitral (MVR), or double (DVR) valve replacement with the St. Jude Medical (SJM) prosthesis. Operative mortality for the entire group was 7.3%. There was 100% follow-up. Warfarin (Coumadin) anticoagulation was recommended for all patients. There were no cases of mechanical failure. The incidence of thromboembolism was 0.6/1,000 patient-months for those with AVR, 3/1,000 patient-months for those with MVR, and 0% for those with DVR. Thrombosis of a prosthesis occurred in two patients with DVR. Clinically significant hemolysis occurred in three patients with paravalvar leaks following MVR. Late postoperative prosthetic infection has not occurred. Postoperative catheterization studies in 33 patients revealed no transvalvular gradient at rest in 21 patients. The remainder of the patients catheterizd had low transvalvular gradients. There was a minimal increase in transvalvular gradient with exercise. The SJM cardiac valve is a viable alternative in the surgical therapy of valvular heart disease.

Influence of aspirin and dipyridamole on patency of coronary artery bypass grafts.

A prospective randomized trial was performed to determine if the administration of inhibitors of platelet function would improve the patency of coronary artery bypass grafts. Patients were operated on for intractable angina with angiographically demonstrable lesions. The left internal mammary artery (IMA) was used for bypass of lesions of the left anterior descending coronary artery (LAD). Saphenous vein grafts were used for the LAD if the IMA was inadequate and for all other vessels. Treated patients received 1,300 mg of aspirin and 100 mg of dipyridamole (Persantine) orally each day. Control patients received neither drug. Patients returned 3 to 6 months after operation for repeat angiography. Results were analyzed by chi-square. One hundred seventy-four patients entered the study from June, 1973, through December, 1975, and 113 were analyzed. In the control group, 66 patients had 27 IMA-LAD grafts and 93 saphenous vein grafts. In the treatment group, 47 patients underwent 18 IMA-LAD grafts and 75 saphenous vein grafts. Ninety-eight of the 120 grafts (82%) were patent in the control group, and 87 of 93 grafts (94%) were patent in the treatment group (x2 = 6.34, p less than 0.02). Of the 45 IMA-LAD grafts in both groups, only 1 was occluded, a patency of 98%. In the control group, 72 of 93 saphenous vein grafts (77%) were patent. In the treatment group, 69 of 75 (92%) were patent (x2 = 6.54, p less than 0.02). The results of the study show a 15% difference between the two groups in the early patency of saphenous vein grafts. We continue to use aspirin and dipyridamole to improve the patency of saphenous vein bypass grafts.

Effect of cardiopulmonary bypass on cefazolin disposition.

Cefazolin kinetics was studied in 8 patients the day before (PREOP), during (SURG), and the day after (POSTOP) cardiopulmonary bypass (CPB) surgery. PREOP (48.6 ml/min) and POSTOP (46.6 ml/min) total body clearances were of the same order and both were greater than the SURG (27.4 ml/min) total body clearance. Since cefazolin is almost entirely eliminated by the kidney, the lower SURG clearance is a result of reduced renal elimination, as confirmed by measuring cefazolin SURG (28.7 ml/min) and POSTOP (52.9 ml/min) renal clearance. The reduction in cefazolin renal elimination was the same throughout the surgical procedure, including the period of extracorporeal circulation. Cefazolin distribution was altered by the operative procedure as evidence by a higher SURG steady-state volume of distribution. This increase in apparent cefazolin distribution volume brought about by surgery was not seen with cephalothin, which was investigated by us in a similar group of patients. The different effect of CPB surgery on cefazolin and cephalothin distribution may be due to differences in plasma protein binding.