Effect of Bilateral Internal Mammary Artery on Long-Term Survival: A Meta-Analysis Approach
Background—Although the potential survival benefit of bilateral internal mammary artery (BIMA) grafting compared to single internal mammary artery (SIMA) has been emphasized by many investigators, use of BIMA is still low in clinical practice in the absence of randomized trials and long-term results. In the current study, we aimed to assess if there is a long-term survival benefit of BIMA up to ten years after coronary bypass surgery.
Methods and Results—We selected published articles comparing survival between SIMA and BIMA patients with follow-up duration of more than a mean of nine years. We evaluated the log hazard ratio with 95% CI for included studies using a random-effects meta-analysis. Nine eligible observational studies provided 15,583 patients (8,270 SIMA and 7,313 BIMA) for meta-analysis. Five studies used propensity score methods for statistical adjustment, two with propensity score-based patient matching method and three with quintile based stratification. A significant reduction in mortality by using BIMA was observed (hazard ratio 0•79, 95% CI 0•75-0•84) with no study showing any significantly harmful effect of BIMA on survival. Subgroups of studies using different statistical approaches - 'unmatched', 'quintile' based propensity score analysis, and propensity score based 'exact' patient matching - all showed survival benefit of BIMA grafting.
Conclusions—BIMA grafting appears to have better survival with up to ten years follow-up compared to SIMA grafting. Long-term survival benefit of BIMA seems to continue in the second decade after surgery. An ongoing randomised trial comparing SIMA and BIMA group will add evidence on this issue.
- Received June 4, 2013.
- Revision received May 23, 2014.
- Accepted May 28, 2014.