In Hyperthyroidism increased cardiac output is due to all the following except::

Ans: A (Increased afterload) Ref: Harrison's Principles of Internal Medicine 18th edition & DeGroot WJ, Leonard JJ. Hyperthyroidism as a high cardiac output state. Am Heart J. 1970 Feb;79(2):265-75.Explanation:Hyperthyroidism is the most common cause of hyperkinetic circulatory disease.Thyroid hormone probably produces this high output state by inducing vasodilatation of the circulatory beds supplying muscle and skin.This hormone induced effect lowers the total peripheral resistance which increases cardiac output.The heart responds to the low peripheral resistance by accelerating the heart rate and augmenting stroke volume.Thyroid hormone enhances ventricular contractility.These cardiac responses are generated by a direct effect of thyroid hormone on the cardiovascular system and are essentially independent of autonomic influence.