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Does coronary artery bypass surgery improve survival?
Helena Rexius1, Gunnar Brandrup-Wognsen, Rolf Ekroth
1Department of Molecular and Clinical Medicine/Cardiothoracic Surgery, Sahlgrenska University Hospital Göteborg, Sweden.
Insights
Coronary bypass surgery significantly lowers the risk of death in high-risk patients compared to pre-surgery. This survival benefit is most pronounced in those with the highest preoperative risk, suggesting a prognostic gain from the procedure.
Area of Science:
- Cardiovascular Surgery
- Medical Outcomes Research
- Public Health
Background:
- Current guidelines recommend coronary bypass surgery for high-risk patients, but supporting evidence is over 20 years old.
- Long waiting lists for coronary bypass surgery present a unique opportunity to assess pre- and post-operative mortality risks.
- A recent cohort is needed to re-evaluate the efficacy of coronary bypass surgery in contemporary high-risk populations.
Purpose of the Study:
- To test the hypothesis that the risk of death is lower after coronary bypass surgery than before the operation in high-risk patients.
- To compare mortality risk in high-risk patients during the waiting period for surgery versus the post-operative period.
- To determine if the prognostic gain from coronary bypass surgery varies based on preoperative risk levels.
Main Methods:
- Utilized Poisson regression to calculate death hazard functions for patients scheduled for bypass surgery between January 1995 and July 2005.
- Analyzed mortality risk in two distinct periods: pre-admission (optimal medication) and post-surgery (up to 11 years).
- Employed multivariable functions incorporating individual risk profiles to calculate the probability of death.
Main Results:
- Significant differences in hazard functions were observed between pre- and post-surgery periods.
- Angiographic severity of coronary lesions was associated with a lower risk of death post-surgery.
- Left ventricular impairment risk decreased post-surgery (beta coefficients -0.0546 vs. -0.0234, p <0.001), while age remained a risk factor.
- Risk reduction was dependent on preoperative risk, with greater gains in high-risk patients; however, low-risk patients experienced increased risk due to surgical mortality.
Conclusions:
- Coronary bypass surgery is associated with a lower risk of death compared to the pre-operative state in high-risk patients.
- The observed benefit is likely due to a prognostic gain achieved through bypass surgery.
- The magnitude of this gain is greatest in high-risk individuals and minimal or non-existent in low-risk patients.
Objectives:
According to guide-lines, coronary bypass surgery improves survival in high risk patients. The evidence for this is more than 20 years old and may be questioned. Long waiting lists for coronary bypass surgery are detrimental but offer the possibility to compare the risk of death before and after surgery. We hypothesized that the risk of death is lower after bypass surgery than before the operation in high risk patients in a more recent cohort.
Design And Results:
Death hazard functions were calculated by the use of Poisson regression scheduled for bypass surgery between 1 Jan 1995 and 31 July 2005. The analyses were performed in two states: 1) in the period after triage until admission for surgery during which optimal medication was intended and 2) after surgery and up to 11 years (corresponding to 57,548 patient years). The probability of death was calculated by entering individual risk profile data into the two multivariable functions. There were several significant differences between the hazard functions in the two states. All variables reflecting angiographic severity of coronary lesions indicated lower risk of death after bypass surgery. The risk associated with left ventricular impairment was lower after surgery (beta coefficients - 0.0546 vs. - 0.0234, p <0.001). Only one variable, age, indicated higher risk after surgery (which is also seen in a general population over time). The reduction of risk was dependent on preoperative risk with a large reduction when preoperative risk was high and vice versa. When preoperative risk was low, however, the risk increased due to surgical mortality.
Conclusions:
The risk of death is lower after bypass surgery than before the operation in high risk patients. This is most likely explained by a prognostic gain from bypass surgery. The gain is largest in high-risk patients but small or absent in low risk patients.
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