Effect of Using Bilateral Internal Mammary Artery on Long-Term Survival

To the Editor:

We read with interest the paper by Itoh et al, who researched the outcomes of bilateral internal mammary artery (BIMA) and single mammary artery (SIMA) grafting in patients over the age of 75 years.¹ We think that we can contribute 2 points based on this extremely well-written article. First, we noticed that the 2 groups were not homogeneous in terms of some preoperative parameters that may affect postoperative outcomes. These parameters are age, female sex, hyperlipidemia, hypertension and incidence of urgent surgery. In many studies it is maintained that these parameters are the predictors of mortality and major cardiac and cerebrovascular events (MACCE) after coronary bypass surgery.^2,3 If there was no difference between the 2 groups, Itoh et al’s postoperative outcomes might have been more valuable. On the other hand it is not clear whether the surgical technique was off-pump or on-pump. If both techniques were used it should be stated if any difference existed between groups in terms of on-pump technique. If only the on-pump technique was used for both groups it should be also stated if there was any difference between the groups in terms of cardiopulmonary bypass (CPB) time because there are many certain effects on CPB such as the parameters mentioned above. In some studies it is noted that off-pump technique is a mortality predictor in long-term follow-up.⁴

Second point that we want to contribute is whether there will be any effect of using BIMA or SIMA on long-term outcomes. Interestingly it is stated that SIMA had better outcomes than BIMA in terms of long-term survival but there was no difference between groups in terms of MACCE, which may be the most important factor for long-term survival. So the question is: which mechanism provides the better long-term survival rates in the BIMA group? If this mechanism is not cardiac event-related with the use of more than 1 arterial graft that provides long-term graft patency, then there is no difference between the 2 groups in that regard. We want to ask authors about this issue.

We would be most grateful and it will be useful for their study if the authors could clarify the issues that we have raised.

• Orhan Gokalp, MD
• Yuksel Besir, MD
• Hasan Iner, MD
• Levent Yilik, MD
• Gamze Gokalp, MD
• Ali Gurbuz, MD
• Department of Cardiovascular Surgery, Faculty of Medicine (O.G., Y.B., L.Y., A.G.),
• Department of Cardiovascular Surgery, Ataturk Education and Research Hospital (H.I.), Izmir Katip Celebi University, Izmir;
• Departmant of Pediatric Emergency, Tepecik Education and Research Hospital, Izmir (G.G.), Turkey

(Released online October 14, 2016)

References

• 1.    Itoh  S,  Kimura  N,  Adachi  H,  Yamaguchi  A. Is bilateral internal mammary arterial grafting beneficial for patients aged 75 years or older? Circ J 2016; 80: 1756–1763.
• 2.    Raja  SG,  Shah  J,  Navaratnarajah  M,  Amin  F,  Amrani  M. Outcomes and predictors of mortality and stroke after on-pump and off-pump coronary artery bypass surgery in octogenarians. Innovations (Phila) 2013; 8: 269–275.
• 3.    Mao  Z,  Zhong  X,  Yin  J,  Zhao  Z,  Hu  X,  Hackett  ML. Predictors associated with stroke after coronary artery bypass grafting: A systematic review. J Neurol Sci 2015; 357: 1–7.
• 4.    Nicolini  F,  Fortuna  D,  Contini  GA,  Pacini  D,  Gabbieri  D,  Zussa  C, et al. Comparison between off- and on-pump coronary artery bypass grafting: Long-term results of a real-world registry. Eur J Cardiothorac Surg 2016; 50: 567–574.