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Mitral annular calcification: Bad versus worse

We congratulate Alexis et al. and the structural heart teams from Mount Sinai and Columbia for this series of high‐risk patients with mitral annular calcification (MAC) undergoing mitral intervention and for their novel classification of MAC based on treatment algorithm. Surgically, the presence of MAC is associated with risk of valve replacement over repair and risk of ventricular rupture, myocardial infarction, and atrioventricular dissociation. For transcatheter mitral valve replacement (TMVR), MAC is associated with risk of left ventricular outflow tract obstruction (LVOTO) and mortality. The authors conceptualize MAC as partial or type I and horseshoe or type II, which can be further subdivided into low (A) and high risk (B) of LVOTO. Type I patients underwent surgical and hybrid transatrial TMVR (an open surgical implantation of a TMVR device) as there was insufficient calcium to anchor percutaneous TMVR. Type II patients were poor surgical candidates due to excessive MAC. Type IIA had sufficient MAC to anchor a transcatheter valve and were low risk of LVOTO. Therefore, Type IIA patients underwent primarily percutaneous TMVR, while Type IIB patients underwent hybrid transatrial TMVR due to risk of LVOTO. The majority of the study population was female, which is reflective of the high rates of MAC in female patients. This is a high‐risk patient cohort (mean STS predicted risk of mortality of 9.4%) with 43.9% of patients having prior cardiac surgery. The authors report 46% mortality in the intervention group, and 39% in the medical group. Interestingly, this study reported 100% mortality for all patients undergoing percutaneous TMVR with Type IIA MAC, which is considerably higher than that reported in the MITRAL Trial or TVT Registry. Indeed, MAC is ominous as it portends stroke, cardiovascular disease, congestive heart failure, cardiovascular mortality, as well as all‐cause mortality. This issue of futility in treating such high‐risk patients with available technologies. This is true given that outcomes in the prohibitive risk medical therapy group compared favorably versus those who underwent intervention. What is clear is that LVOTO significantly increases risk of mortality and that patients are hard to rescue once it occurs. Using this classification, the cut‐off for risk of LVOTO is between the more accommodating end‐systolic measure proposed by Meduri et al. and the more restrictive parameter determined by Wang et al. Further optimization of this model may include incorporating a less restrictive cut‐off value for LVOTO, thus allowing for greater use of percutaneous TMVR. An interesting possibility is the adjunctive use of LAMPOON or alcohol septal ablation in reducing the risk of LVOTO preoperatively in appropriate candidates. Another important point is that this patient population primarily had mitral stenosis or mixed stenosis‐regurgitation with only 9.8% of the patients with pure mitral regurgitation. Whether this MAC classification can be applicable to patients with MR remains to be seen. Alexis et al. propose a simple and potentially powerful conceptual model of mitral intervention based on MAC and risk of LVOTO. As the growth of transcatheter mitral interventions continues particularly for elderly patients, we are appreciating the growing importance of MAC both for technical success but also as a harbinger for poor overall prognosis.