Treating a Structural Heart Disease Using a Non-structural Approach: Role of Cardiac Pacing in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease characterized by a thickened non-dilated ventricle in the absence of another cardiac or systemic condition. Its most important hemodynamic consequence is left ventricular outflow tract (LVOT) obstruction. The primary management strategy of this condition is surgical septal myectomy, but an acceptable alternative treatment in patients who are not suitable for (or who refuse) surgery is alcohol septal ablation (ASA). However, in patients with unfavorable coronary anatomy which precludes ASA (i.e. absence of major septal perforator branch of the left anterior descending (LAD) artery), another reasonable option is dual chamber pacemaker implantation to decrease LVOT outflow gradient. A 77-year-old female, known hypertensive, diabetic with a history of coronary artery disease, presented with 1-week history of worsening chest pain and shortness of breath. She was admitted as a case of acute coronary syndrome and pneumonia. On workup, 2DED revealed hypertrophic obstructive cardiomyopathy (HOCM) with a demonstrated systolic anterior motion (SAM) of the mitral valve with a peak instantaneous gradient of 194 mm Hg across the basal LV cavity. The patient refused surgical myectomy, and ASA was the preferred treatment option. On coronary angiography, there was an incidental finding of absent major septal perforator branch of the LAD coronary artery, rendering her unsuitable for septal ablation. She was referred to electrophysiology for evaluation. She underwent dual chamber pacemaker implantation and documented significant decrease in the peak instantaneous gradient from 194 to 37 mm Hg, with complete obliteration of SAM and improvement in overall wall motion. She remained stable and asymptomatic after pacemaker insertion until her recent outpatient follow-up (1 year after implantation). We present a case of HCM with congenitally absent major septal perforator branch coronary artery treated with dual chamber pacemaker implantation. To our knowledge, this is the first reported angiographically absent first (major) septal perforator coronary anatomy in the setting of HCM, and also the first description of dual chamber pacemaker implantation to relieve the LVOT obstruction. Although the role of dual chamber pacing has become limited in HCM because surgical myectomy and septal ablation have resulted in better decrease in LV outflow gradient and symptom improvement, this modality remains essential and may still be considered as the treatment strategy-of-choice in patients who are unsuitable for surgical myectomy and ASA.