Effect of coronary artery bypass grafting on subsequent hospitalization

Predictors of hospital readmission two years after coronary artery bypass grafting

OBJECTIVE

To determine the clinical factors before, and in association with, coronary artery bypass grafting (CABG) that increase the risk of readmission to hospital in the first two years after surgery.

PATIENTS

All patients in western Sweden who had CABG without simultaneous valve surgery between 1 June 1988 and 1 June 1991.

METHODS

All patients who were readmitted to hospital were evaluated by postal inquiry and hospital records.

RESULTS

A total of 2121 patients were operated on, of whom 2037 were discharged from hospital. Information regarding readmission was missing in four patients, leaving 2033 patients; 44% were readmitted to hospital. The most common reasons for readmission were angina pectoris and congestive heart failure. There were 12 independent significant predictors for readmission: clinical history (a previous history of either congestive heart failure or myocardial infarction, or CABG); acute operation; postoperative complications (time in intensive care unit greater than two days, neurological complications); clinical findings four to seven days after the operation (arrhythmia, systolic murmur equivalent to mitral regurgitation); medication four to seven days after the operation (antidiabetics, diuretics for heart failure, other antiarrhythmics (other than beta blockers, calcium antagonists, and digitalis), and lack of treatment with aspirin).

CONCLUSION

44% of patients were readmitted to hospital two years after CABG. The most common reasons for readmission were angina pectoris and congestive heart failure. Four clinical markers predicted readmission: clinical history; acute operation status; postoperative complications; and clinical findings and medication four to seven days after operation.

Rehospitalizations after coronary revascularization among Medicare beneficiaries

The rehospitalization experience of Medicare beneficiaries undergoing coronary artery bypass surgery or percutaneous transluminal coronary angioplasty in 1986 and 1987 was studied by following 53,715 patients who underwent coronary artery bypass and 28,817 patients who underwent angioplasty for 1 year using Medicare hospital claims data. The 1-year rehospitalization rate after bypass and angioplasty was 629 and 863 per 1,000, respectively, compared to a rate of 607 for the Medicare patient population in general. About 45% of rehospitalizations after bypass and two thirds after angioplasty were in categories determined by an expert panel to be possibly related to the original procedure. After angioplasty, there were 61 discharges per 1,000 for bypass surgery and 140 per 1,000 for a repeat angioplasty. Rehospitalization rates for coronary artery bypass surgery after angioplasty were significantly lower for female and black patients who underwent angioplasty. The volume of rehospitalization after revascularizations makes it an important outcome measure. Medicare administrative records provide a unique source of information on rehospitalizations and make possible the monitoring of broad trends in the frequency and outcomes of coronary revascularization. The lower rates of bypass surgery after angioplasty for black and female patients are in line with other studies and bear further investigation.

Ten-year follow-up of quality of life in patients randomized to receive medical therapy or coronary artery bypass graft surgery. The Coronary Artery Surgery Study (CASS)

Quality of life indexes were assessed in 780 patients 10 years after randomization to medical therapy (n = 390) or coronary artery bypass graft surgery (n = 390) in the Coronary Artery Surgery Study. At 10 years, mortality was 21.8% in the medical group and 19.2% in the surgical group (p = NS), and 144 (37%) of the medical group had undergone surgery because of increasing chest pain. At study entry, 22% of medical and surgical patients were angina free; at 1 and 5 years after entry, the frequency of asymptomatic patients was 66% and 63% in the surgical group and 30% and 38% in the medical group. However, by 10 years after entry, the proportion of patients free of angina had fallen to 47% in the surgical group and to 42% in the medical group. Activity limitation and use of beta-blockers and long-acting nitrates were less in the surgical than the medical group at 1 and 5 years after entry but little different from the medical group at 10 years after entry. Throughout follow-up, recreational status, employment status, frequency of heart failure, use of other medications, and hospitalization frequency were similar between the two groups. Thus, indexes of quality of life such as angina relief, increased activity, and reduction in use of antianginal medications initially appear superior in patients with stable manifestations of ischemic heart disease assigned to surgery, but by 10 years after entry, these advantages are much less apparent. Although the observed similarities of the medically and surgically assigned groups at 10 years reflect return of symptoms in the surgical group to some extent, a more important explanation is the performance of late surgery in a large proportion of the medically assigned patients, rendering them asymptomatic.

Time to first new myocardial infarction in patients with mild angina and three-vessel disease comparing medicine and early surgery: a CASS registry study of survival. Coronary Artery Surgery Study

Two categories--patients alive and free from new myocardial infarction (MI) and time to first new MI (nonfatal and fatal)--were compared in medical and early surgical groups in the Coronary Artery Surgery Study (CASS) registry with Class I or II angina and three-vessel disease in a six-year follow-up. There were 413 in the medical group and 443 in the early surgical group. A broad definition of MI using ECG and clinical criteria on hospital discharge and follow-up was used to include as many new MIs as possible, including perioperative MIs. Stratification was by left ventricular wall motion score and number of proximal segment stenoses and by quintile of propensity score to reduce selection bias in therapy groups. Adjusted by propensity analysis, 79% of medical and 88% of surgical patients (p = .005) were free from new MI; death without diagnosis of new MI was censored. Similarly adjusted, 57% of medical and 76% of surgical patients (p less than .0001) were alive and free from new MI at six years. For patients with previous MI, surgery offered the probability of protection from new MI: with multiple prior MIs, 66% of medical and 88% of surgical patients were free from new MI at six years (p = .0019). This is a nonrandomized, observational study with the limitations of such studies: the need to adjust for differences in baseline traits in medical and surgical groups and the unknown effects of unobserved variables. Fifty-one variables, including therapy, were tested by Cox model with time to new MI as the end point. Early surgery was the strongest independent predictor of freedom from new MI (p = .002) with a relative risk of 51% compared with medical therapy (95% confidence limits of 33 to 78%). In patients with multiple prior MIs, the new MI risk with early surgery was 24% of that for medicine, with an upper 95% confidence point of 64%.

Myocardial infarction and mortality in the coronary artery surgery study (CASS) randomized trial

The long-term benefit of coronary bypass surgery in terms of longevity and prevention of major ischemic events in patients who have mild angina is not well defined. The randomized Coronary Artery Surgery Study (CASS) was designed to evaluate this issue; it consists of 780 patients who were considered operable and who had mild stable angina pectoris or who were free of angina after infarction. As a result of the randomization process there were no significant differences in base-line variables between patients randomly assigned to medical and to surgical therapy. The likelihood of death in the five-year period after randomization was only 8 per cent in the medical cohort, as compared with 5 per cent in the surgical cohort (not significant). The likelihood of nonfatal Q-wave myocardial infarction was 11 and 14 per cent, respectively (not significant). The five-year probability of remaining alive and free of infarction was 82 per cent in the patients assigned to medical therapy and 83 per cent in the patients assigned to surgery (not significant). There were no statistically significant differences in the survival rate or in the myocardial-infarction rate between subgroups of patients randomly assigned to medical and to surgical therapy when they were analyzed according to initial group assignment, number of diseased vessels, or ejection fraction. Therefore, as compared with medical therapy, coronary bypass surgery appears neither to prolong life nor to prevent myocardial infarction in patients who have mild angina or who are asymptomatic after infarction in the five-year period after coronary angiography.