Proposed mechanism of a presystolic murmur during 2:1 atrioventricular block with hyperthyroidism.
A patient who developed 2:1 AV block ten weeks after the initiation of therapy for Graves' disease demonstrated a presystolic murmur related to atrial systole of the conducted beat. The murmur mimicked a pericardial friction rub. With the return of normal conduction as the thyrotoxicosis was finally controlled, the murmur disappeared. We postulate that the murmur resulted frm atrial contraction with rapid late-diastolic inflow into an increased right ventricular volume, causing premature opening of the pulmonic valve. This phenomenon was attainable only during 2:1 AV block with long diastolic filling periods and a hyperkinetic circulatory system. The murmur may be indicative of severe hyperthyroidism. Murmurs found in other disease entities may share similar physiologic principles.
D002302:Cardiac Output; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006326:Heart Auscultation; D006327:Heart Block / Q000209:etiology / Q000503:physiopathology*; D006337:Heart Murmurs; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications*; D008875:Middle Aged; D009200:Myocardial Contraction; D010701:Phonocardiography; D013599:Systole