Reply by the Authors of the Original Article: SYNTAX Score and Left Ventricular Reverse Remodeling after Bypass

The Prognostic Role of SYNTAX Score in Moderate Ischemic Mitral Regurgitation Puzzle

We thank the authors for their interest in our article on surgical repair of moderate ischemic mitral regurgitation (MR).[1] We demonstrated that the addition of mitral valve repair/replacement (MVR/Re) to coronary artery bypass grafting (CABG) did not afford any clinically meaningful benefit, while at the same time increasing the risk of adverse events. Thus, we concluded that based on the currently available evidence, a strategy of MVR/Re for all patients undergoing CABG with coexistent moderate ischemic MR cannot be recommended. However, as we state in the article, there may be subgroups of patients who are at high risk for worsening MR or having persistent MR after CABG only. For instance, patients with large inferior wall aneurysms or thinned akinetic myocardium are unlikely to recover inferolateral myocardial function following revascularization with CABG.[2] [3] This predisposes them to tethering of the posterior mitral leaflet which leads to worsening of MR. Also, the progressive left ventricular dilatation altering left ventricular geometry causes annular dilatation, making the MR even worse. Thus, these patients with inferior scar without viability may represent a subgroup that may benefit from MVR for moderate MR at the time of bypass and merits future investigation.[4]

The authors of the letter suggested that the SYNTAX score[5] may be another predictor of remodeling and may help guide decisions regarding MVR/Re for moderate ischemic MR during CABG. Although the SYNTAX score has demonstrated great prognostic value in terms of recurrent ischemic events, myocardial infarction, and cardiovascular death,[6] this is primarily driven by its ability to evaluate the complexity and extent of coronary anatomic lesions, and thereby provide an estimate of risk of subsequent plaque rupture risk throughout the coronary tree. That is why in patients with high SYNTAX score, CABG is superior to percutaneous coronary intervention (PCI), as the entire vessel at high risk of plaque rupture is bypassed by CABG unlike PCI that treats only one segment of coronary plaque at a time. That said, the standard SYNTAX score does not use any information about myocardial health or viability, and therefore is less likely to provide useful information about potential reversibility of ischemic MR with CABG alone. Although newer predictive scores such as the SYNTAX II[6] or Global Risk Classification[7] incorporate clinical characteristics such as ejection fraction, age, and gender into decision making, these scores also do not include information on left ventricular geometry or inferior wall viability, and are therefore unlikely to be predictive of remodeling and reduction in MR after isolated CABG. Thus, we do not believe that the SYNTAX score by itself will be helpful in this population for predicting MR progression at the time of CABG, although it will continue to be useful in guiding the initial decision between CABG and PCI.

• References

• 1 Anantha Narayanan M, Aggarwal S, Reddy YN. , et al. Surgical repair of moderate ischemic mitral regurgitation—a systematic review and meta-analysis. Thorac Cardiovasc Surg 2017
• 2 Michler RE, Smith PK, Parides MK. , et al; CTSN. Two-year outcomes of surgical treatment of moderate ischemic mitral regurgitation. N Engl J Med 2016; 374 (20) 1932-1941
• 3 Capoulade R, Zeng X, Overbey JR. , et al; Cardiothoracic Surgical Trials Network (CTSN) Investigators. Impact of left ventricular to mitral valve ring mismatch on recurrent ischemic mitral regurgitation after ring annuloplasty. Circulation 2016; 134 (17) 1247-1256
• 4 Penicka M, Linkova H, Lang O. , et al. Predictors of improvement of unrepaired moderate ischemic mitral regurgitation in patients undergoing elective isolated coronary artery bypass graft surgery. Circulation 2009; 120 (15) 1474-1481
• 5 Farooq V, Head SJ, Kappetein AP, Serruys PW. Widening clinical applications of the SYNTAX Score. Heart 2014; 100 (04) 276-287
• 6 Farooq V, van Klaveren D, Steyerberg EW. , et al. Anatomical and clinical characteristics to guide decision making between coronary artery bypass surgery and percutaneous coronary intervention for individual patients: development and validation of SYNTAX score II. Lancet 2013; 381 (9867): 639-650
• 7 Serruys PW, Farooq V, Vranckx P. , et al. A global risk approach to identify patients with left main or 3-vessel disease who could safely and efficaciously be treated with percutaneous coronary intervention: the SYNTAX Trial at 3 years. JACC Cardiovasc Interv 2012; 5 (06) 606-617