Another potentially important contributor to ventricular function that has been studied with regard to genetic polymorphism related variability is the Beta1-adrenergic receptor (Beta1-AR). The Beta1-AR is the primary myocardial receptor for the catecholamines epinephrine and norepinephrine, which increase myocardial contractility and blood pressure. Several polymorphisms in the Beta1-AR gene have been associated with an increased risk for congestive heart failure and with exercise capacity in patients with ischemic or idiopathic cardiomyopathy.