Hyperthyroidism elevates cardiac output, induces tachycardia, can progress from left ventricular hypertrophy to biventricular dilatation and heart failure. Atrial fibrillation and pulmonary hypertension are common complications. Timely treatment is critical to prevent thyrotoxic cardiomyopathy and preserve myocardial function. Early treatment protects your heart and boosts your quality of life.