We need more high-volume myectomy centres in Europe

This article refers to ‘Long-term outcomes for different surgical strategies to treat left ventricular outflow tract obstruction in hypertrophic cardiomyopathy’, by R. Collis et al., published in this issue on pages 398–405.

Dynamic left ventricular (LV) outflow obstruction is the most frequent cause of heart failure symptoms in patients with hypertrophic cardiomyopathy (HCM) and is associated with progressive clinical deterioration and reduced survival.1 Outflow obstruction results in reduced LV output, secondary mitral valve regurgitation, diastolic dysfunction and myocardial oxygen supply–demand mismatch,1 and is identified at rest or with physiological exercise in about 60–70% of HCM patients evaluated at tertiary referral centres.2

For almost 50 years, transaortic septal myectomy has been the standard treatment for patients with obstructive HCM and severe symptoms refractory to medical therapy. During the last 15 years, improved surgical techniques have reduced the rate of in-hospital mortality for isolated septal myectomy to <1% at HCM surgical centres of excellence.1 In addition, optimal haemodynamic results and sustained improvement to New York Heart Association (NYHA) class I or II have been documented in >90% of patients over long-term follow-up.3-5 The exceedingly favourable results of septal myectomy, with extended survival equivalent to that of patients with non-obstructive HCM, are now well documented in high-volume centres.1, 3, 4

In this issue of the Journal, Collis et al. report on the results of surgical treatment of obstructive HCM at four main HCM referral institutions in London over a period of almost 30 years, from 1988 to 2015.6 A total of 347 HCM patients underwent surgical treatment for LV outflow obstruction, representing an average of about 13 patients per year. The majority of patients were operated by three surgeons. Of these patients, 272 (78%) underwent isolated septal myectomy, 55 (16%) septal myectomy with mitral valve repair/replacement, and 20 (6%) isolated mitral valve replacement. There were five perioperative deaths and eight perioperative strokes. At 1-year follow-up, about 70% of patients reported symptomatic improvement with a decrease in NYHA functional class and about 90% of patients had no significant postoperative LV outflow gradient (≥30 mmHg) at rest. Over a median follow-up period of 5.2 years, 20 of the patients who survived surgery died, including five of cardiovascular causes, seven of non-cardiac and eight of unknown causes; nine patients were lost to follow-up.6

With regard to perioperative mortality and long-term survival, the results of this study6 would not appear to differ substantially from those reported by high-volume centres for surgical septal myectomy. However, rather than being encouraging, this conclusion raises some important questions. Guidelines for cardiovascular surgery, as well as the general surgical approach to cardiovascular disorders, are similar in North America and Europe. In particular, the North American guidelines for the treatment of HCM recommend surgical septal myectomy, when performed by experienced operators, as the standard treatment for most patients with obstructive HCM and drug-refractory symptoms.1 Why then was septal myectomy performed in fewer than 15 patients per year at four major tertiary HCM referral centres in London over a period of about 30 years? This finding is even more surprising given that these institutions have been major referral centres in Europe for the management of HCM for more than 40 years.

The results of this study6 suggest a possible answer to this question. The authors report that, at 1-year follow-up, about 30% of patients did not improve in NYHA functional class and about 30% described exertional chest pain, pre-syncope, syncope, or palpitations.6 Therefore, in many patients, quality of life did not improve after surgery, as instead occurs in most patients operated at HCM surgical centres that perform high volumes of myectomy operations.1, 3-5 Furthermore, almost 20% of the study patients developed atrial fibrillation and 19 required cardiac resynchronization therapy (CRT) or CRT defibrillator implantation to treat heart failure symptoms unresponsive to medications.6 Indeed, in the first paragraph of their discussion, the authors comment that this high incidence of non-fatal disease-related complications after surgical treatment represents the most important and novel finding in their investigation.6 We may add that these results could, in part, be explained by the low volume of myectomies performed, as this number of septal myectomies is substantially lower than the 10 myectomies per operator/year recommended as reasonable experience by the recent European Society of Cardiology HCM guidelines,7 and is well below the volume of myectomies per operator recommended by the 2011 North American HCM guidelines.1

This small number of HCM patients submitted to surgical septal myectomy in London reflects a similar situation all over Europe. Why are most European HCM patients eligible for myectomy not offered the option of a surgical treatment that, in high-volume myectomy centres, is associated with optimal haemodynamic results, sustained clinical improvement and extended survival? The approach to invasive management of LV outflow obstruction adopted in Europe over the last two decades answers this question. In 1995, percutaneous alcohol septal ablation was introduced in Europe by Dr Sigwart as a possible alternative to septal myectomy to reduce the outflow gradient and heart failure symptoms in patients with obstructive HCM.8 This procedure is based on the injection of ethanol into a proximal septal branch of the left anterior descending coronary artery with the aim of causing a myocardial infarction of the basal septum with a decrease in septal contractility. The septal scarring and thinning widen the LV outflow tract and decrease or abolish the outflow gradient. This procedure, made attractive by its less invasive nature in comparison with surgery, was rapidly adopted in many catheterization laboratories in Europe. As a result, within a few years, most time-honoured European surgical myectomy programmes were replaced by an extensive use of alcohol septal ablation.5 At present, only a few European surgical centres, mainly in Italy and the Netherlands, continue to perform high volumes of myectomy operations and are included amongst the best international referral centres for this highly specialized surgical procedure.9

Unfortunately, alcohol septal ablation has important limitations. Injecting ethanol into a proximal branch of the anterior descending artery does not guarantee that the distribution of alcohol and myocardial infarction will be confined to the basal septum. Therefore, the myocardial scar can be substantially larger than predicted and extend to areas other than the septum.10, 11 In addition, patients with obstructive HCM often have abnormalities of the mitral valve apparatus, including anterior and apical displacement of the papillary muscles in the ventricular cavity, fibrotic and retracted secondary mitral valve chordae, and markedly elongated mitral valve leaflets, that contribute importantly to outflow obstruction.12, 13 In such patients, a septal myocardial infarction caused by alcohol cannot abolish the outflow gradient. Furthermore, HCM is a myocardial disease associated with risk for life-threatening ventricular tachyarrhythmias, and the sizable septal scar resulting from alcohol injection may increase this risk.10, 11 In a recent multicentre European study, appropriate implantable cardioverter-defibrillator shocks for ventricular tachycardia or fibrillation were eight-fold more common after septal ablation than after surgical myectomy.14 Given these limitations, alcohol ablation can be regarded as a possible alternative to surgical septal myectomy only in selected patients with suitable features, including appropriate coronary artery anatomy, septal morphology and obstruction pathophysiology. Indeed, Dr Sigwart, who first conceived alcohol septal ablation, believed that this procedure ‘…was never devised to replace surgery for symptomatic obstructive HCM’.15

What can we do for those many European HCM candidates for invasive treatment of outflow obstruction who do not have access to septal myectomy? The answer can be found in a recent consensus commentary published in the Journal of Thoracic and Cardiovascular Surgery and co-authored by seven surgeons (only one European) with extensive septal myectomy experience: ‘We need more septal myectomy surgeons.’9 This, however, is not an easy objective to achieve. The learning curve for surgical myectomy can be long because the experience required for this operation is increased by the unusual surgical technique, which is based on a septal muscular resection through the limited visual field allowed by an aortotomy, and is often associated with mitral valve repair.5 Previous experience in the treatment of congenital heart diseases associated with LV outflow tract obstruction and in the repair of mitral valve regurgitation may reduce the learning curve for myectomy.5 Furthermore, starting a myectomy programme requires not only surgeons experienced with HCM and septal myectomy, but also a team-based approach that includes cardiologists familiar with HCM and experienced in collaborating with myectomy surgeons. However, recent initiatives have shown that it is possible to develop successful myectomy programmes,5 an effort that finds its justification in the high number of European HCM patients with outflow obstruction and important functional limitation who would benefit from surgical myectomy in terms of both quality and duration of life.

Conflict of interest: none declared.