Pacing for hypertrophic obstructive cardiomyopathy: an update and future directions.

In hypertrophic cardiomyopathy (HCM) patients with symptoms caused by left ventricular outflow tract obstruction (LVOTO), treatment options include negative inotropic drugs, myectomy, septal alcohol ablation and AV sequential pacing with or without an implantable cardioverter defibrillator (ICD). Pacing is rarely used in spite of its relative simplicity and promising results. In this review the current evidence of AV sequential pacing from observational, randomised studies and long and very long-term follow-up studies is given and put in the context of present guidelines recommendations. These studies indicate that AV sequential pacing improves symptoms and quality of life through decreases in LVOTO, systolic anterior movement and mitral regurgitation. Effects on morbidity and mortality are lacking. We describe the mechanisms of action, the prerequisites for successful pacing and provide practical advice on how to optimise therapy. Moreover, the role of the ICD for primary and secondary prevention is discussed with reference to the ESC HCM guidelines. In summary, AV sequential pacing for HOCM is underused in clinical practise despite evidence from two randomised controlled studies. This concept is currently the focus of two randomised studies: a planned randomised controlled study that will compare AV sequential pacing to TASH and an ongoing study that compares CRT to AAI pacing in HOCM patients. In this review we highlight the current evidence and the new interest for this therapy.