Treatment of postoperative atrial fibrillation.

Postoperative atrial fibrillation can occur in approximately 30% of patients. Although often a benign complication, it can result in significant morbidity and prolong hospitalization with attendant increased expenditure of health care resources. A rigid approach for prophylaxis and treatment is illogical, but with separate focus on rate control and cardioversion, a sinus mechanism can be safely and reliably achieved with minimal patient discomfort.

Does age limit the effectiveness of clinical pathways after coronary artery bypass graft surgery?

BACKGROUND: Clinical pathways have been shown to be effective in reducing the length of hospital stay after isolated CABG. Few studies, however, have focused specifically on the outcomes of the pathways in regard to the elderly population. METHODS AND RESULTS: We reviewed our experience with 445 consecutive patients (299 < 70 years old [mean age, 58.2 +/- 0.5 years] and 146 > or = 70 years old [mean age, 75.6 +/- 0.3 years]) who underwent isolated CABG with the expectation of progressing through the same 5-day postoperative pathway. Preoperatively, the elderly had a smaller body surface area (1.87 +/- 0.02 versus 2.00 +/- 0.01; P < 0.001) and a higher incidence of female gender (45.9% versus 26.8%; P = 0.001), cerebrovascular disease (13.7% versus 7.0%; P = 0.022), congestive heart failure (22.6% versus 13.4%; P = 0.013), and 3-vessel coronary artery disease (76.7% versus 65.9%; P = 0.024). Postoperatively, the elderly had a higher incidence of red blood cell transfusion (28.8% versus 9.0%; P = 0.001), atrial fibrillation (37.6% versus 11.7%; P = 0.001), and overall rate of complications (46.6% versus 23.4%; P = 0.001). Mortality rate and length of stay were 5.5% and 7.9 +/- 0.4 days for the elderly versus 1.0% and 6.4 +/- 0.4 days for those < 70 years old (P = 0.004 and P = 0.008), respectively. Of those > or = 70 years old, 34% were discharged in < or = 5 days, 64% in < or = 7 days, and 82% in < or = 10 days versus 64%, 85%, and 93%, respectively, for younger patients (P = 0.001 for all). Multivariate analysis of preoperative variables identified age (P < 0.001), female gender (P < 0.001), hypertension (P = 0.017), chronic obstructive pulmonary disease (P = 0.002), preoperative intra-aortic balloon pumping (P = 0.002), and body surface area (P = 0.003) as significantly related to length of stay. However, when the postoperative variables found to be different by univariate analysis are added to the model, age is only marginally significant (P = 0.079), and red blood cell transfusion and atrial fibrillation are the strongest predictors of increased length of stay, along with intra-aortic balloon pumping and pneumonia (P < 0.001 for all). CONCLUSIONS: These data suggest that extraordinary modifications of clinical pathways are not needed for success with elderly patients. The increased length of stay is largely attributable to the increased incidence of atrial fibrillation.

Effect of payer status on outcomes of coronary artery bypass surgery in blacks.

BACKGROUND: Black patients with coronary artery disease have a higher mortality rate than white Americans. They also have a higher prevalence of hypertension, diabetes mellitus, and renal disease, which may have an effect on mortality rates. The deleterious effect of these comorbidities may be exacerbated by impaired access to secondary prevention strategies and longitudinal care. Therefore, the presence or absence of comprehensive care as indicated by payer status may then affect survival on surgically treated patients. In this study we examined the role of cardiovascular risk factors and insurance carrier status on early outcomes of coronary artery bypass grafting (CABG) surgery in blacks versus white Americans. METHODS AND RESULTS: From January 1990 to December 1996, 2776 patients (2003 men, 773 women; mean age 63 +/- 10 years), underwent isolated CABG in a multispecialty practice serving a major metropolitan population. There were 494 (17.8%) black patients and 2282 (82.2%) white patients. The proportion of black patients in each payer category was 17.8% commercial, 14.1% managed care, 52.9% Medicaid, and 19.5% Medicare. The effect of preoperative risk factors, including status of operation (elective, urgent, or emergent), sex, race, redo CABG, presence of renal disease, diabetes mellitus, congestive heart failure, myocardial infarction, the completeness of revascularization, age, and left ventricular ejection fraction were analyzed with the chi 2 test for categorical variables and the Student t test for age and ejection fraction. A multiple logistic regression analysis was performed to assess the effect of all variables on mortality rates simultaneously. Black patients had a higher incidence of diabetes mellitus, hypertension, and renal disease than white patients (P < 0.001). Overall, 30-day mortality rate was 2.5% (58 of 2282) in white patients versus 5.5% (25 of 494) for black patients (P < 0.003). Multivariate analysis showed that only emergency surgery status (OR 3.59, P < 0.01), redo CABG (OR 3.78, P < 0.001), hypertension (OR 2.32, P < 0.03), history of congestive heart failure (OR 2.1, P < 0.004), older age (OR 1.07, P < 0.001), and low ejection fraction (OR 0.98, P < 0.003) correlated with mortality rates. Race and payer status were not significant predictors of death. CONCLUSIONS: These data on CABG surgery in black patients suggest that early death is due to associated risk factors and not due to race or insurance payer status.

A randomized, double-blind comparison of intravenous diltiazem and digoxin for atrial fibrillation after coronary artery bypass surgery.

BACKGROUND: Atrial fibrillation (AF) after coronary bypass graft surgery may result in hypotension, heart failure symptoms, embolic complications, and prolongation in length of hospital stay (LOHS). The purpose of this study was to determine whether intravenous diltiazem is more effective than digoxin for ventricular rate control in AF after coronary artery bypass graft surgery. A secondary end point was to determine whether ventricular rate control with diltiazem reduces postoperative LOHS compared with digoxin. METHODS AND RESULTS: Patients with AF and ventricular rate > 100 beats/min within 7 days after coronary artery bypass graft surgery were randomly assigned to receive intravenous therapy with diltiazem (n = 20) or digoxin (n = 20). Efficacy was measured with ambulatory electrocardiography (Holter monitoring). Safety was assessed by clinical monitoring and electrocardiographic recording. LOHS was measured from the day of surgery. Data were analyzed with the intention-to-treat principle in all randomly assigned patients. In addition, a separate intention-to-treat analysis was performed excluding patients who spontaneously converted to sinus rhythm. In the analysis of all randomly assigned patients, those who received diltiazem achieved ventricular rate control (> or = 20% decrease in pretreatment ventricular rate) in a mean of 10 +/- 20 (median 2) minutes compared with 352 +/- 312 (median 228) minutes for patients who received digoxin (p < 0.0001). At 2 hours, the proportion of patients who achieved rate control was significantly higher in patients treated with diltiazem (75% vs 35%, p = 0.03). Similarly, at 6 hours, the response rate associated with diltiazem was higher than that in the digoxin group (85% vs 45%, p = 0.02). However, response rates associated with diltiazem and digoxin at 12 and 24 hours were not significantly different. At 24 hours, conversion to sinus rhythm had occurred in 11 of 20 (55%) patients receiving diltiazem and 13 of 20 (65%) patients receiving digoxin (p = 0.75). Results of the analysis of only those patients who remained in AF were similar to those presented above. There was no difference between the diltiazem-treated and digoxin-treated groups in postoperative LOHS (8.6 +/- 2.2 vs 7.7 +/- 2.0 days, respectively, p = 0.43). CONCLUSIONS: Ventricular rate control occurs more rapidly with intravenous diltiazem than digoxin in AF after coronary artery bypass graft surgery. However, 12- and 24-hour response rates and duration of postoperative hospital stay associated with the two drugs are similar.

The paradox of on-bypass transfusion thresholds in blood conservation.

BACKGROUND: While most reports on blood conservation define a specific transfusion trigger, few have primarily focused on the role of the predefined transfusion threshold in initiating blood utilization. This study was undertaken to test the hypothesis that rigid adherence to an arbitrarily defined protocol paradoxically increases homologous blood usage during isolated primary coronary artery bypass graft. METHODS AND RESULTS: Prospectively, 100 consecutive patients were transfused on bypass solely for low venous oxygen saturation (SvO2), ie, <55%, without regard to hematocrit (Hct), postoperative for Hct <20, or if clinically warranted. During bypass the lowest Hct value was <25% in 72 patients, <22% in 52 patients, <20% in 39 patients, <18% in 23 patients, and <15% in 2 patients. These data, then, represent the percentage of patients who would have received blood on bypass had each respective level been used as a trigger, and hence the minimum number of patients who would have been transfused overall. In this study only 13 patients received 2.2+/-0.3 U of red blood cells; 4 on bypass, 5 in the intensive care unit within 24 hours, and 4 on postoperative days 2 or 3. Of the 87 patients not transfused, 15 arrived in the intensive care unit with Hct <25%, 4 with Hct <22%. By postoperative day 1, there were 7 patients with Hct <25% and only 1 <22%, confirming that many of these patients would have been unnecessarily transfused had we adhered to any of the noted on-bypass transfusion triggers. There were no deaths, no strokes, one Q wave myocardial infarction, and one sternal infection. Postoperative blood loss and discharge Hct were 741+/-131 mL and 29.3+/-0.5 versus 573+/-27 mL and 29.1+/-1.0 in transfused and nontransfused patients (P=.24 and P=.88, respectively). CONCLUSION: These data suggest that avoiding use of a numerical on-bypass hematocrit trigger is safe and extremely effective in minimizing the use of homologous blood during isolated primary coronary artery bypass graft. Conversely, unless the chosen level is sufficiently low, ie, <15, setting arbitrary thresholds will paradoxically increase homologous blood utilization; data are mean+/-SEM.

Enrollment in the Health Alliance Plan HMO is not an independent risk factor for coronary artery bypass graft surgery.

BACKGROUND: Henry Ford Hospital is the sole provider of cardiac surgical services for the Health Alliance Plan, a health maintenance organization (HMO) that presently serves 450,000 enrollees. METHODS AND RESULTS: To determine the effect of managed care referral patterns on the outcome of coronary artery bypass graft (CABG) surgery, we retrospectively reviewed two concurrent groups of patients, 569 HMO patients and 225 patients with free-for-service (FFS) insurance, who had undergone isolated primary CABG surgery between January 1, 1990 and January 31, 1994. The 605 patients with Medicare operated on during the same time frame were excluded to obviate age bias. Age, sex, use of cardiac medications, history of prior percutaneous transluminal coronary angioplasty or thrombolytic therapy, history of recent and remote myocardial infarction, extent of coronary disease, presence of preexisting comorbid conditions, and incidence of unstable clinical syndromes and left ventricular dysfunction (ejection fraction < 40%) were comparable for both groups. In hospital mortality (HMO group, 1.9%; FFS group, 2.2%), mean ICU stay (HMO, 2.6 +/- 0.3 days; FFS, 2.3 +/- 0.3 days), and total hospital length of stay (HMO, 9.8 +/- 0.8 days; FFS, 8.6 +/- 0.6 days) were likewise similar. CONCLUSIONS: These data refute the notion that the gate-keeper mentality often associated with managed-care health insurance vehicles results in delayed referral of patients with coronary artery disease and results in suboptimal outcome.

Endothelial function following ischemia.

The consequences of ischemia and reperfusion on endothelial dependent and independent coronary flow patterns following a variety of ischemic insults in isolated perfused rabbit hearts were studied. A blood perfused ex vivo model was developed that provided reliable and stable systolic performance comparable to crystalloid perfused hearts, but with a four to sevenfold decrease in resting coronary flow and a three to six fold increase in coronary flow reserve compared to Krebs' perfusion. Following incremental graded 37 degrees C ischemia of 10 to 45 minutes, blood perfused hearts had compromised systolic performance, but unaffected response to exogenous endothelial dependent and independent agonists whereas in crystalloid perfused hearts, the response to these same agonists was blunted prior to noting a decrement in systolic function. Further studies assessed the consequences of 30 and 45 minutes of ischemia on the regulatory role of basal nitric oxide released by the coronary endothelium. In both blood and crystalloid perfused hearts, basal nitric oxide secretion had a significant and persistent regulatory role on coronary vascular tonus over a tenfold range of coronary flow despite ischemic injury that severely depressed systolic performance. Finally, hearts were preserved in University of Wisconsin (UW) or St. Thomas' (ST) solutions for 4 hours at 4 degrees C. With crystalloid perfusion, ST results in impaired postischemic response to both endothelial dependent and independent agonists. After UW preservation and with all blood perfused hearts, postischemic flow patterns were unchanged. Using physiological blood perfusion protocols, the endothelium and arterial smooth muscle were found more resistant to ischemia-reperfusion injury than the myocyte.

Coronary flow reserve after ischemia and reperfusion of the isolated heart. Divergent results with crystalloid versus blood perfusion.

Mechanical function and coronary hemodynamics were assessed in 73 isolated rabbit hearts randomly subjected to 0, 10, 20, 30, or 45 minutes of 37 degrees C global ischemia and 45 minutes of reperfusion in either a modified Krebs buffer or homologous blood-perfused Langendorff mode (n = 7 to 9 hearts per group). Isovolumic developed pressure, resting coronary flow, and response to endothelium-dependent (bradykinin) and -independent (nitroglycerin) agonists were quantitated at defined preload and heart rate. Perfusate did not influence systolic performance, which was impaired after 30 minutes of ischemia and fell to 64% to 72% of preischemic values after 45 minutes of ischemia (p < 0.05). However, basal coronary flow was at least sixfold greater in crystalloid-perfused hearts. Moreover, coronary hyperemia (p < 0.05) persisted for Krebs-perfused hearts subjected to all but the longest ischemic interval. After equilibration, all postischemic blood-perfused hearts had basal flow unchanged from before ischemia. Bradykinin and nitroglycerin induced similar increases in coronary flow for each group before and after each ischemia interval. However, the magnitude of this increase was greater in blood-perfused hearts (p < 0.01) and was not attenuated by the ischemic times encompassed in this protocol. In contrast, endothelium-dependent and -independent coronary flow reserve was abolished after 20 minutes of ischemia or longer in Krebs-perfused hearts. These data suggest that the unphysiologic resting flow patterns of crystalloid-perfused isolated hearts obfuscate interpretation of the interaction between coronary flow reserve and ischemic injury.

Blood conservation in coronary artery surgery.

BACKGROUND: Most patients undergoing coronary artery bypass surgery receive homologous blood transfusions despite the availability of multiple pharmacologic and blood salvage conservation strategies. METHODS: The efficacy of defining strict transfusion criteria as the sole blood conservation strategy was adjudicated prospectively by comparing homologous blood product usage in 314 consecutive patients undergoing isolated primary coronary artery bypass surgery (group 2) with a retrospective group of 947 consecutive patients undergoing the same procedure but transfused without protocol (group 1). RESULTS: The incidence of red cell transfusion and plasma transfusion decreased from 40.5% to 25.8% and 23.8% to 13.4% in groups 1 and 2, respectively (p < 0.001). The percentage of patients receiving no homologous blood products increased from 47.6% in group 1 to 68.5% in group 2 (p < 0.001). Decreasing body weight and preoperative hematocrit were found to be highly significant predictors of the need for red blood cell transfusion (p < 0.001). Significant postoperative determinants included intensive care unit and hospital length of stay and reoperation for bleeding (p < 0.001 each). CONCLUSIONS: Because major determinant of homologous blood transfusion during coronary bypass surgery is the predictable and unavoidable dilution of a small red cell mass that occurs when instituting cardiopulmonary bypass, adherence to defined transfusion criteria alone is a simple, safe, and effective strategy for decreasing blood product utilization.

Myocardial oxygen consumption after reversible ischemia.

There is a marked dissociation between return of contractile function and oxidative metabolism in stunned myocardium. Initial observations in isovolumically contracting hearts demonstrated that postischemically, the MVO2 to generate a given peak-developed pressure was augmented compared to preischemia. This metabolic inefficiency was independent of coronary hyperemia and myocellular oxygen extraction and not evident in the vented, empty beating state. In an ejecting heart model, the highly linear relationship between external mechanical work (integrated area of dynamic pressure-volume loops) increased non-working oxygen needs not to the efficiency of ejecting a given stroke volume. More sophisticated mathematical modeling to further compartmentalize chemomechanical transduction in the globally stunned heart has confirmed deranged energetics, but ascribing specific work components to inefficient oxygen need is predicated on the biological validity of each model. The findings in regionally stunned myocardium are more uniform, demonstrating paradoxically normal oxygen consumption despite persistent systolic bulging or markedly decreased systolic shortening. The relatively increased MVO2 in stunned hearts is not due to uncoupling of oxidative phosphorylation, but inefficient cellular ATP utilization.

Prospective evaluation of malignant neoplasms in cardiac transplant recipients uniformly treated with prophylactic antilymphocyte globulin.

Although there is convincing evidence that prophylactic administration of high doses of the monoclonal antibody OKT3 predisposes patients to an increased prevalence of early posttransplantation malignancy, particularly posttransplantation lymphoproliferative disease, it is indeterminate whether polyclonal antilymphocyte globulin poses a similar hazard. We reviewed the outcome of 112 consecutive cardiac transplant recipients who received uniform immunosuppression, including induction therapy with antilymphocyte globulin, and were prospectively followed-up for a median duration of 41.5 months (range 1 to 81 months). No patients had posttransplantation lymphoproliferative disease. Nine malignant neoplasms (8%) were detected from 6 to 70 months after transplantation. Four patients with cutaneous neoplasms were alive and well at the time this article was written. Three patients died of disseminated adenocarcinoma 6 months, 17 months, and 60 months after transplantation. One patient was undergoing treatment of Kaposi's sarcoma at the time this article was written, and another was undergoing treatment of transitional bladder cell carcinoma. Actuarial survival for all patients was 88% at 1 year and 79% at 5 years. Moderate doses of induction antilymphocyte globulin may facilitate rapid reduction of maintenance cyclosporine and steroid doses, thereby decreasing the duration of intense immunosuppression and lowering the risk of posttransplantation lymphoproliferative disease. Testing this hypothesis would require the development of reliable and reproducible in vivo assays to prospectively assess immune status.

Reduced incidence and severity of accelerated graft atherosclerosis in cardiac transplant recipients treated with prophylactic antilymphocyte globulin.

Allograft coronary artery disease (ACAD) is the major factor limiting long-term survival of cardiac transplant recipients (CTRs). Although cyclosporine based triple drug immunosuppression has not decreased the occurrence of ACAD, some preliminary data suggests that prophylactic antilymphocyte preparations may reduce the incidence of this problem. All CTRs at Henry Ford Hospital have uniformly received prophylactic Minnesota Antilymphocyte Globulin (ALG), thereby providing a unique opportunity to investigate this hypothesis. One hundred three CTRs were followed for a median duration of 34 months with annual angiograms begun one year after transplant. Patients who died without an angiogram were considered to have ACAD based on autopsy results or if their death was clinically suspicious. Ninety-two patients underwent at least one angiogram. Fourteen patients had abnormal angiograms. Nine patients were identified as having ACAD by non-angiographic criteria. Five had autopsy proven disease, 3 died suspiciously, and 1 underwent successful re-transplantation for ACAD. By Kaplan-Meier analysis, the risk of developing ACAD was 12% in 1 year, 16% in 2 years, 22% in 3 years, 26% in 4 years, and 29% in 5 years. Risk of ACAD increased with older recipient's age, higher triglyceride levels, and diabetes, but was not affected by active CMV infection, number of acute rejection episodes, and HLA mismatching. These results suggest that prophylactic ALG reduces the occurrence of ACAD.