Pacing in obstructive hypertrophic cardiomyopathy: a therapeutic option?

Hypertrophic cardiomyopathy (HCM) is a heterogeneous disease of cardiac muscle which can present with myriad functional and clinical manifestations. When symptoms and left ventricular outflow gradients are present, it is primarily treated with pharmacologic agents. For refractory patients, dual chamber pacing has been proposed; by altering timing and site of cardiac electrical activation, the hemodynamic abnormalities in HCM may be modified. Results of non-randomized and randomized trials have shown an average gradient reduction of 50%. However, pressure gradient reduction within the left ventricular outflow tract (LVOT) has not translated into improved objective functional measurements, even though subjective parameters may improve. Dual chamber pacing cannot be recommended as primary treatment for obstruction except in a subset of patients who are elderly or have significant comorbidities that preclude surgery. However, many patients will now receive implantable cardioverter-defibrillators (ICD) which will include both right atrial and right ventricular leads. This will allow DDD pacing which may be utilized for symptom palliation. Future investigations will determine if alternate forms of pacing, including left atrial or left ventricular pacing, may improve objective measures in these patients.