Hypertrophic Cardiomyopathy (MHC) is an asymmetric hypertrophy of the left ventricle with or without obstruction that preferentially affects the interventricular septum that exceeds 15 mm thick.  It is a genetic disease with autosomal dominant inheritance involving several genes. It is called familial hypertrophic cardiomyopathy in case of a family history of MHC.  Its prevalence is 0.2% and affects both men and women with a male predominance. Patients with MHC are mostly asymptomatic but sometimes they may experience symptoms such as exercise dyspnea, palpitations and exertion syncope. The latter is of very bad prognosis.  In more than 50% of cases the Electrocardiogram (ECG) is abnormal and shows hypertrophy of the left ventricle (HVG) or fine and deep q waves of pseudo necrosis.  The holter ECG can record in 25% of cases bursts of unsupported ventricular tachycardia whose presence evokes a risk of sudden death.  Cardiac Doppler ultrasound confirms the diagnosis by showing an HVG of more than 15 mm or 13 mm in case of familial MHC and asymmetrical character.

Unlike ventricular and supraventricular rhythm disorders, the occurrence of a complete atrioventricular block (BAV) requiring a pacemaker is a rare complication.  Our patient benefited from a biological assessment that turned out to be normal which allowed us to eliminate a metabolic or infectious cause of BAV.  On the other hand, certain elements of orientation of this clinical case such as the family history of MHC, the absence of high blood pressure and the age of the patient could suggest a family MHC.  Some authors recommend genetic testing in patients with MHC and their relatives, but their use in the management of this patient has been limited by cost.

Medical treatment for MHC is symptomatic and uses first-line beta-blockers. Studies by Fananapazir L and Jeanrenaud X have shown that implanting a double-chamber pacemaker would reduce the severity of the gradient of the left ventricular flow pathways and relieve symptoms during short- and medium-term follow-up periods [2,3].  Cases of complete BVD requiring permanent pacemaker implantation have been observed following surgery (5%) and after alcoholization (20%) for septal reduction in patients who remain symptomatic despite optimal medical treatment.  The risk of developing a complete BAV is low (less than 5%)) if the surface ECG shows no conductive disorder.  However, it is very high if the patient is already a carrier of a BBG because in 50% of cases septal alcoholization is complicated by a BBD promoting the occurrence of a complete BAV [4].  Thus, this patient benefited from pacemaker implantation and monitoring for MHC in accordance with current recommendations.