Choose the TRUE/FALSE statements regarding cardicac conduction functions: a) The SA node is composed of a cluster of small fusiform cells in the sulcus terminalis at the right atrial-superior vena caval junction b) The SA nodal aery arises from the right coronary aery in 20 % and the left circumflex aery in 80 % of persons c) SA node dysfunction may be completely asymptomatic d) Almost all patients with SA node dysfunction develop supraventricular tachycardia, usually atrial fibrillation or atrial flutter e) Failure to increase the hea rate with exercise is referred to as chronotropic incompetence
High-Yield Explanation
The SA nodal aery arises from the right coronary aery in 55-60% and the left circumflex aery in 40-45% of persons. One-third to one-half of patients with SA node dysfunction develop supraventricular tachycardia, usually atrial fibrillation or atrial flutter. Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 1869