John A. Sullivan

Coronary Bypass Surgery Performed off Pump Does Not Result in Lower In-Hospital Morbidity Than Coronary Artery Bypass Grafting Performed on Pump

Background—There is increasing evidence that cardiopulmonary bypass (CPB) may be responsible for the morbidity associated with coronary artery bypass grafting (CABG) surgery. Recent developments in cardiac stabilization devices have made CABG without CPB feasible. However, there is conflicting evidence to date from published trials comparing outcomes between CABG performed with and without CPB, with some trials indicating an advantage to the avoidance of CPB and others showing little benefit. Methods and Results—In a single-center randomized trial, 300 patients requiring CABG surgery at a single institution were prospectively randomized to have the procedure performed with CPB (n=150) or on the beating heart (n=150). Exclusion criteria for the trial included emergency procedure, concomitant major cardiac procedures, ejection fraction <30%, and reoperation. In-hospital outcomes were analyzed on an intention-to-treat basis. A mean of 3.0±0.9 grafts were performed in the CPB group compared with 2.8±0.9 grafts in the beating-heart group (P =0.06). There were no significant differences between the CPB group and the beating-heart group in mortality (0.7% versus 1.3%; P =1.0), transfusion (8.7% versus 9.3%), perioperative myocardial infarction (0.7% versus 2.7%; P =0.37), permanent stroke (0% versus 1.3%; P =0.50), new atrial fibrillation (32% versus 25%; P =0.20), and deep sternal wound infection (0.7% versus 0%; P =1.0). The mean time to extubation was 4 hours, the mean stay in the intensive care unit was 22 hours, and the median length of hospitalization was 5 days in both groups (P =NS). Conclusions—In contrast to published trials, we were unable to demonstrate any advantage with CABG performed without CPB in terms of patient morbidity. Excellent results can be obtained with either surgical approach.

Preoperative prediction of prolonged mechanical ventilation following coronary artery bypass grafting

OBJECTIVE Few studies have attempted to evaluate who would require prolonged mechanical ventilation following heart surgery. The objectives of this study were to identify predictors of prolonged ventilation in a large group of coronary artery bypass grafting (CABG) patients from a single institution. METHODS One thousand, eight hundred and twenty-nine consecutive patients undergoing CABG were reviewed retrospectively and evaluated for preoperative predictors of prolonged ventilation which included: age, gender, ejection fraction (EF), renal function, diabetes, angina status, New York Heart Association Class, number of diseased vessels, urgency of the procedure, re-operation, chronic lung disease (COPD) and intraoperative variables such as IABP, inotropes, stroke and myocardial infarction. Prolonged ventilation was defined as > or = 24 h. Stepwise logistic regression analysis was performed. RESULTS Patients were on average 65.4+/-10.6 years of age, 30% were diabetic, 80% had triple vessel disease and 93% were of functional class III/IV. The mean ejection fraction was 60+/-16 percent. Overall peri-operative mortality was 2.7%. There were 157 patients that required prolonged ventilation with a peri-operative mortality of 18.5% (P < 0.001). Preoperative independent predictors of prolonged ventilation were found to be: unstable angina (OR 5.6), EF < 50 (OR 2.3), COPD (OR 2.0), preop. renal failure (OR 1.9), female gender (OR 1.8) and age > 70 (OR 1.7). Based on these predictors, a model was created to estimate of the risk of prolonged ventilation in individual patients following CABG with results ranging from < or = 3% in patients without any risk factors to > or = 32% in patients with five or more independent risk factors. Certain intraoperative variables were strong predictors of prolonged ventilation and included: stroke (OR 12.3), re-operation for bleeding (OR 6.9) and perioperative MI (OR 5.8). CONCLUSION We were able to create a stable model where several preoperative and intra-operative variables were shown to be predictive of prolonged ventilation after CABG surgery. The ability to identify patients at increased risk for prolonged ventilation may allow the development of pre-emptive strategies and more effective resource allocation.

Is it safe to train residents to perform cardiac surgery

BACKGROUND The impact of surgical training on patient outcomes in cardiac surgery is unknown. METHODS All cases performed by residents from 1998 to 2001 were compared to staff surgeon cases using prospectively collected data. Operative mortality and a composite morbidity of: reoperation for bleeding perioperative myocardial infarction, infection, stroke, or ventilation more than 24 hours were compared using multivariate analysis. RESULTS Four residents performed 584 cases. The cases were as follows: coronary artery bypass grafting (CABG), 366 cases; aortic valve replacement (AVR) with or without CABG (AVR +/- CABG), 86 cases; mitral valve replacement, 31 cases; mitral valve repair, 25 cases; thoracic aneurysm/dissection, 22 cases; aortic root, 20 cases; transplantations, 14 cases; and adult congenital defect repairs, 20 cases. There were 2,638 CABGs and 363 AVR +/- CABG performed by the staff during the same period. Crude operative mortality in CABG patients was 2.5% (resident) and 2.9% (staff) (p = 0.62). In multivariate analysis, resident was not associated with operative mortality odds ratio (OR) of 0.59 (p = 0.19). Resident cases had a higher incidence of the composite morbidity outcome for CABG cases (19.4% vs 13.6% for staff; p = 0.003). However, in multivariate analysis, resident was not associated with increased morbidity (OR = 1.23, p = 0.16). The AVR +/- CABG crude mortality was 3.6% (resident) and 2.8% (staff) (p = 0.69). Because of the small number of cases (n = 447), operative mortality was combined with the composite morbidity outcome for the AVR +/- CABG model. In all, 16.7% of resident cases and 19.8% of staff cases had the composite outcome or died (p = 0.51). In multivariate analysis resident was not associated with this outcome (OR = 0.74, p = 0.35). CONCLUSIONS In this analysis of our experience with residency training, the operative morbidity and mortality in CABG and AVR patients was similar for residents and staff. Training residents to perform cardiac surgery appears to be safe.

The Effects of Nitrous Oxide on Myocardial Metabolism and Hemodynamics during Fentanyl or Enflurane Anesthesia in Patients with Coronary Disease

Twenty patients about to have coronary artery bypass grafts were studied before and after 15 min of 50% nitrous oxide added to either fentanyl (75 μg/kg) or enflurane (0.5%) anesthesia. Arterial and central pressures and cardiac output were measured, plus coronary sinus blood flow and arterio-coronary sinus differences in oxygen, hemoglobin, and lactate contents. Fentanyl-N2O and enflurane-N2O both decreased systemic resistance, heart rate, cardiac output, and hence arterial pressure. Stroke work decreased significantly with little or no change in wedge pressure: ventricular function was impaired. Coronary flow and myocardial O2 consumption decreased with fentanyl-N2O. Oxygen extraction increased with enflurane-N2O, as did lactate contents of coronary sinus blood. Hemodynamic depression occurred from the combined effects of nitrous oxide and fentanyl or enflurane. The β-blocked myocardia of nonstimulated coronary patients were becoming ischemic globally on 50% oxygen, after significant hypotension. From this and other evidence, we conclude that nitrous oxide may not be benign in patients with coronary arterial disease.

Transmyocardial laser revascularization does not denervate the canine heart.

BACKGROUND Transmyocardial laser revascularization has been used as an indirect approach to improve myocardial perfusion in patients with refractory angina not amenable to conventional therapy. Three mechanisms have been proposed for its therapeutic effects: direct perfusion of the ischemic myocardium through patent channels; induction of angiogenesis; and regional denervation. We sought to determine whether transmyocardial laser revascularization modifies afferent and efferent axonal function within the affected myocardium. METHODS Studies were performed in 9 dogs that were artificially ventilated and underwent thoracotomy. Changes in ventricular dynamics and intrinsic cardiac neuronal activity were monitored before and after creating 20 transmural channels in the left ventricular ventral free wall with a holmium:yttrium-aluminum-garnet laser in response to three stimuli: application of veratridine or bradykinin to the epicardial sensory neurites of intrinsic cardiac afferent neurons; sympathetic or parasympathetic efferent neuronal activation either electrically (4 V, 10 Hz, 5 ms) or chemically (nicotine, 5 microg/kg intravenously), and direct cardiomyocyte beta-adrenergic receptor stimulation (isoproterenol hydrochloride, 5 microg intravenously). RESULTS Sensory neurites of right atrial afferent neurons in the studied epicardial region responded similarly to chemical stimulation before and after transmyocardial laser revascularization. Transmyocardial laser treatment did not reduce local ventricular contractile responses to direct activation of sympathetic or parasympathetic efferent neurons by electrical or chemical means, nor did it affect cardiomyocyte augmentor responses elicited by exogenous beta-adrenergic receptor challenge. CONCLUSIONS As transmyocardial laser revascularization does not affect afferent or efferent axonal function in the affected ventricle, the efficacy of this form of therapy cannot be ascribed to local denervation.

Light Versus Heavy Sedation After Cardiac Surgery: Myocardial Ischemia and the Stress Response

The influence of light versus heavy sedation after coronary artery bypass graft (CABG) surgery on the development of postoperative myocardial ischemia has not been described.After uncomplicated CABG surgery, 50 patients were randomly assigned to receive LOW (n = 24; target Ramsay Sedation Score [RSS] = 2) or HIGH (n = 26; target RSS = 4) sedation with propofol. Analgesia was provided to maintain a visual analog scale (VAS) pain score <7. Myocardial ischemia was identified perioperatively using continuous 3-lead Holter monitoring. By measuring creatine kinase (CK) MB levels preoperatively, at entry to the intensive care unit (ICU), and every 12 h for 48 h; and by obtaining serial 12-lead electrocardiograms (ECG) (preoperatively; 2, 4, 12, 24, and 48 h after ICU admission, 8:00 AM the morning after surgery; and 5 min pre- and postextubation), myocardial infarction was identified. Endocrine stress response was assessed by measuring serum cortisol levels preoperatively, on admission to the ICU, and 24 h postoperatively. In a subset of patients (LOW n = 10, HIGH n = 11), plasma and urinary catecholamine levels were also measured. There were no between-group differences in demographics, operative course, hemodynamic variables, or cortisol levels while in the ICU. The VAS pain score and target RSS were achieved and sustained, and they differed between groups. There were three myocardial infarctions in each group by CKMB criteria alone. No ECG-identifiable myocardial infarction occurred. The ST segment versus time curve (LOW 187 +/- 295 versus HIGH 1071 +/- 2137 mm/min) differed between groups. Urinary and plasma catecholamine levels were similar between groups over the observation period. We conclude that the use of a reduced sedation regimen in combination with adequate analgesia did not result in an increased endocrine stress response or risk of myocardial ischemia. Implications: This randomized study of patients after coronary artery bypass surgery examined whether light (versus heavy) sedation with propofol in the intensive care unit was associated with an increased degree of myocardial ischemia. Using techniques to detect myocardial ischemia, including Holter monitoring, electrocardiogram, and myocardial enzyme measurements, no differences were found. We conclude that light sedation does not increase the endocrine stress response or the risk of myocardial infarction. (Anesth Analg 1997;85:971-8)

Medtronic intact porcine bioprosthesis experience to twelve years

BACKGROUND The Medtronic Intact porcine bioprosthesis was further evaluated to determine the influence of zero-pressure glutaraldehyde fixation on structural valve deterioration (SVD). METHODS From 1986 through 1996, at three Canadian centers, 1,272 patients had 1,296 procedures: 836 aortic valve replacement (AVR), 332 mitral valve replacement (MVR), 14 tricuspid valve replacement, 3 pulmonary valve replacement, and 111 multiple valve replacements. The mean age of the patient population was 67 years (range 9 to 91 years). The total follow-up was 8,011 patient-years (mean 6.2 years). RESULTS The late mortality (overall) was 4.8% and 6.7% per patient-year for AVR with or without concomitant procedures, respectively; and 4.7% and 10.4% per patient-year for MVR, respectively. There were 51 cases of SVD (AVR 22 of 836; MVR 23 of 332; pulmonary valve replacement 1 of 3; and multiple valve replacement 5 of 111). The actuarial freedom from SVD at 12 years for AVR was 94.3%+/-3.3% for patients aged 61 to 70 years and 97.7%+/-1.1% for those more than 70 years; for MVR actuarial freedom from SVD at 12 years was 93.7%+/-3.9% for patients more than 70 years. The actual freedom at 12 years from SVD for AVR was 92.4%+/-3.1% for patients aged 51 to 60 years, 96.1%+/-2.1% for those 61 to 70 years, and 98.4%+/-0.7% for those older than 70 years; for MVR actual freedom from SVD at 12 years was 89.6%+/-3.2% for patients 61 to 70 years and 96.6%+/-3.4% for those more than 70 years. CONCLUSIONS The Medtronic Intact porcine bioprosthesis, formulated with tissue preservation at zero-pressure fixation, has encouraging freedom from structural failure.

Medtronic intact porcine bioprosthesis: 10 years’ experience

BACKGROUND The Medtronic Intact porcine bioprosthesis experience was evaluated over a period of 10 years to determine the influence of structural valve deterioration by valve position in various age groupings. METHODS From 1986 to 1996 inclusive, at three centers, 1,272 patients had the prosthesis implanted in 1,296 procedures. The mean age of the population was 67 years (range, 9 to 91 years). There were 836 aortic valve replacements (AVR) (64.5%), 333 mitral valve replacements (MVR) (25.7%), and 110 multiple valve replacements (MR) (8.5%). RESULTS The early mortality was 7.3% (94 of 1,296 procedures). The early mortality with concomitant procedures (primarily coronary artery bypass grafting) was 9.8% (52 of 528) and without, 5.5% (42 of 768). The late mortality was 4.25%/patient-year. The linearized rate of major thromboembolism was 0.86%/patient-year. The rate of reoperation was 1.19%/patient-year and valve-related mortality, 1.06%/patient-year. There were 36 cases of structural valve deterioration for aortic valve replacement (16), mitral valve replacement (15), tricuspid valve replacement (2), and multiple valve replacement (3). The freedom from structural valve deterioration for aortic valve replacement was in patients 21 to 40 years, 62.5%+/-25.8% at 7 years; 41 to 50 years, 75.0%+/-15.3% at 7 years; 51 to 60 years, 91.0%+/-4.5% at 8 years; 61 to 70 years, 98.7%+/-0.7% at 10 years; and older than 70 years, 98.3%+/-1.0% at 10 years (p < 0.05). The freedom from structural valve deterioration for mitral valve replacement was for patients 41 to 50 years, 91.7%+/-8.0% at 7 years; 51 to 60 years, 85.9%+/-9.9% at 8 years; 61 to 70 years, 86.3%+/-6.8% at 8 years; and older than 70 years, 93.9%+/-4.8% at 8 years (not significant). CONCLUSIONS The Medtronic Intact porcine bioprosthesis has acceptable freedom from structural valve deterioration in both the aortic and mitral positions approaching 10 years of evaluation.

Complete revascularization is compromised in off-pump coronary artery bypass grafting

OBJECTIVE Patients who undergo off-pump coronary artery bypass grafting (OPCAB) commonly receive fewer bypass grafts and are more often incompletely revascularized compared with those receiving conventional coronary artery bypass (CCAB) recipients. Because this can compromise survival, we sought to determine whether patients undergoing OPCAB are incompletely revascularized and whether this affects long-term survival and freedom from cardiac events. METHODS OPCAB cases (n = 411) performed from January 1, 1997 to June 30, 2003 were considered for inclusion and matching with 874 randomly selected, contemporary CCAB cases. After propensity matching, 308 OPCAB cases and 308 CCAB cases were included in the final analysis. We compared the number of bypass grafts and the completeness of revascularization by coronary territory. Survival and readmission for cardiac causes were monitored for up to 10 years postoperatively, with a median follow-up period of 5.9 years. RESULTS On average, the patients undergoing OPCAB received significantly fewer distal anastomoses than did those undergoing CCAB (mean ± standard deviation, 2.6 ± 0.9 vs 3.0 ± 1.0, P < .0001). The circumflex territory was the most likely territory to be ungrafted during OPCAB in patients with angiographically significant obstruction (P = .0006). The frequency of complete revascularization was significantly different between the 2 groups (OPCAB, 79.2% vs CCAB, 88.3%; P = .0.002). The OPCAB group had a significantly greater rate of total arterial grafting (OPCAB, 66.6% vs CCAB, 49.7%; P = .0001). No difference was seen in 8-year survival or freedom from cardiac cause hospital readmission between the 2 groups. CONCLUSIONS Despite receiving fewer distal anastomoses and the decreased frequency of complete revascularization, OPCAB and CCAB techniques produced comparable results.

Assessing the risk of waiting for coronary artery bypass graft surgery among patients with stenosis of the left main coronary artery

Background: Significant controversy remains over how urgently coronary artery bypass graft surgery (CABG) should be scheduled, particularly for patients with stenosis of the left main coronary artery. Our main objective was to evaluate the safety of waiting for CABG among patients with left main coronary artery disease using a standardized triage system. Methods: We identified 561 consecutive patients with stenosis of the left main coronary artery who were scheduled to undergo CABG between Apr. 1, 1999, and Mar. 31, 2003. Using standardized triage criteria, patients were assigned to 1 of 4 waiting queues: “emergent,” “in-hospital urgent,” “out-of-hospital semi-urgent A” and “out-of-hospital semi-urgent B.” Postoperative outcome measures were in-hospital death from any cause and a composite outcome measure of in-hospital death from any cause, a prolonged requirement for postoperative mechanical ventilation (> 24 h) and a prolonged postoperative hospital stay (> 9 d). Waiting-time variables included the specific queue, whether patients waited longer than the standard time established for each queue and whether patients were upgraded to a more urgent queue. Logistic regression analysis was used to identify independent predictors of the composite outcome; propensity scores (probability of being assigned to a specific queue) were entered into the model to adjust for patient variability among queues. Results: Of the 561 patients, 65 (11.6%) were assigned to the emergent group, 343 (61.1%) to the in-hospital urgent group, 91 (16.2%) to the semi-urgent A queue and 62 (11.1%) to the semi-urgent B queue. Four patients (0.7%) died while waiting for surgery. The median waiting times were as follows: emergent group, 0 days; in-hospital urgent group, 2 days; 30 days in the semi-urgent A group and 49 days in the semi-urgent B group. A total of 52 patients (9.3%) were upgraded to a more urgent queue, and 147 patients (26.2%) waited longer than the standard times for their respective queue. The overall in-hospital mortality was 5.5% (n = 31), and the composite outcome was 32.6% (n = 183). Independent predictors of the composite outcome were myocardial infarction within 7 days before surgery, preoperative renal failure, ejection fraction of less than 40%, age greater than 70 years and stenosis of left main coronary artery greater than 70%. Waiting-time variables were associated with neither a significantly higher mortality nor morbidity outcome. Interpretation: For selected patients with stenosis of the left main coronary artery, waiting for CABG did not appear to be associated with increased mortality or morbidity.