New ESC guidelines on hypertrophic cardiomyopathy: new insights in invasive treatment?

Hypertrophic cardiomyopathy (HCM) is a complex, yet relatively common genetic cardiac disease and has been the subject of intensive investigation since its first description in 1958. HCM is defined by the presence of an increased left ventricular wall thickness that is not solely explained by abnormal loading conditions. Histologically, HCM is characterised as left ventricular hypertrophy due to an abnormally hypertrophied muscular structure of predominantly the septum ('myocardial fibre disarray') [1]. Approximately 30 % of patients with HCM develop left ventricular outflow tract (LVOT) obstruction under resting conditions [2–4]. By convention , LVOT obstruction is defined as an instantaneous peak Doppler LVOT gradient of>30 mmHg at rest or during physiological provocation. A gradient of>50 mmHg is usually considered to be the threshold at which LVOT obstruction becomes haemodynamically significant. Pharmacological therapy using negative inotropic agents (non-vasodilating beta-blocking agents, calcium antagonists in particular verapamil, and disopyramide) is effective in the majority of patients. However, 5–10 % of patients experience drug-refractory symptoms most likely due to an increased LVOT gradient. In those patients, surgical septal myectomy (Morrow procedure) has been advocated to reduce outflow obstruction and relieve symptoms. However, over the years there have been many controversies over the efficacy of myectomy as there were, and still are, serious doubts about the haemodynamic impact of the septal obstruction. Is HCM due to an abnormal ejection or due to an abnormal filling of the left ventricle; in other words, is HCM primarily a systolic or a diastolic problem? On one side, it was Maron and Braunwald (Minneapolis, Boston) who emphasised the importance of the obstruction [5], on the other hand, Criley (UCLA, California) and Murgo (San Antonio, Texas) defended the filling theory [6, 7]. Still in the year 2010 Murgo wrote the following words in JACC [6]: there is no evidence that outflow is compromised as a result of an LVOT gradient. Such an understanding does not imply that elimination of LVOT gradients is not potentially beneficial. Rather, one hopes that when one does recommend an intervention to eliminate such gradients, one understands that that intervention is not designed to improve ejection itself. Of course this was contradicted by Maron and Braunwald, who supported the obstruction theory and therefore advocated the surgical approach. It is also of interest to take notice of the paper by Maron et al. [8], published in 2011(!) in the European Heart Journal (EHJ), where they encouraged the European …