Septal myectomy in patients with hypertrophic cardiomyopathy with lesser septal thickness—mitral valve repair is not necessary

In this article, Lapenna et al. [1] describe their experience of septal myectomy with or without concomitant mitral valve operation in patients with hypertrophic cardiomyopathy (HCM) with lesser septal thickness (18 mm or less). They investigated 76 consecutive patients with basal septal thickness ≤18 mm who underwent septal myectomy; approximately half of their study population required additional mitral valve operation, and these patients were more likely to have lesser basal septal thickness and higher grade of mitral valve regurgitation at preoperative assessment. As expected, patients who underwent additional mitral valve operation experienced longer cardiopulmonary bypass and cross-clamp times and were more likely to display low cardiac output syndrome in the immediate postoperative period. On predischarge echocardiography, patients who underwent concomitant mitral valve surgery had lower rates of mitral valve regurgitation quantified as moderate or greater. However, long-term survival appeared to be better in patients who underwent septal myectomy alone. The data collated by Lapenna et al. confirm results from previous studies, which have shown that septal myectomy alone is sufficient to relieve the mitral valve regurgitation associated with systolic anterior motion seen in patients with HCM. For this reason, many tertiary centres perform septal myectomy without concomitant procedures on the mitral valve in patients with obstructive HCM. Surgery on the mitral valve is reserved for those with intrinsic valve disease. In a review of >2000 septal myectomies performed at our institution between 1993 and 2014, there was a significant decrease in the percentage of patients with mitral valve regurgitation (MR) grade ≥3 following isolated septal myectomy (54.3% vs 1.7%) [2].

In their multivariable analysis, Lapenna et al. demonstrate that older age and history of prior septal ablation increased the risk of death. Interestingly, concomitant mitral valve surgery was not associated with a higher risk of death in patients with obstructive HCM in both univariate and multivariable analyses. Their results are similar to data from our institution, which have shown that prior alcohol septal ablation leads to higher recurrence and subsequent need for reintervention, although survival was similar in propensity score-matched cohorts of patients undergoing either alcohol septal ablation or septal myectomy for obstructive HCM [3].

Overall, the outcomes described by Lapenna et al. are similar to those of larger HCM centres; in the USA, utilization of additional mitral valve procedures appears to be lower in larger centres where higher numbers of myectomy are performed annually, with lower in-hospital mortality and shorter length of stay in patients undergoing isolated septal myectomy [4]. If mitral valve intervention is required, repair of the mitral valve is the preferred choice as mitral valve replacement has worse long-term survival [2, 5].

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