A 64-year-old man dies suddenly while playing tennis. In the preceding months, the patient experienced fatigue and some exertional dyspnea. Autopsy reveals rupture of an unsuspected ascending aortic aneurysm. Heart examination shows a septal thickness of 1.1 cm (normal: ≤1.1), a posterior wall thickness of 1.1 cm (normal: ≤1.1), and an internal left ventricular diameter of 6.8 cm (normal: 3.5-5.9). No focal myocardial scarring is seen. Which of the following is the most likely cause of the cardiac findings seen in this individual?
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This individual's autopsy reveals a dilated left ventricular (LV) cavity with relatively thin ventricular walls, a finding consistent with eccentric hypertrophy. Eccentric hypertrophy results from the addition of myocardial contractile fibers in series in response to chronic volume overload. The adaptation allows the left ventricle to increase stroke volume and maintain cardiac output; however, LV wall stress increases, resulting in eventual decompensation and the development of heart failure. Common causes of eccentric hypertrophy include cardiomyopathy, ischemic heart disease, and chronic aortic or mitral valve regurgitation.
In developed countries, aortic root dilation is one of the most common causes of chronic aortic regurgitation. This individual with an ascending aortic aneurysm likely had aortic root dilation with consequent chronic aortic regurgitation, leading to LV volume overload and eccentric hypertrophy.
(Choice B) Aortic stenosis leads to pressure overload of the left ventricle and the development of concentric hypertrophy (thickening of the LV walls via the addition of myocardial contractile fibers in parallel). However, the ventricular cavity size is typically normal or reduced (not increased).
(Choice C) Hypertrophic cardiomyopathy is an inherited cardiomyopathy that involves localized thickening of the LV septal wall and resulting LV outflow tract obstruction. Although sudden cardiac death can occur (mostly in young athletes), the uniform thickness of this patient's ventricular walls and enlarged chamber size is more consistent with eccentric hypertrophy due to aortic regurgitation.
(Choice D) Obstructive coronary artery disease can lead to eccentric hypertrophy via myocardial contractile dysfunction and consequent LV volume overload (ie, ischemic heart disease). However, chronic aortic regurgitation is more likely in this individual with ascending aortic aneurysm and no evidence of myocardial scarring (scarring would suggest previous myocardial infarction).
(Choice E) Restrictive cardiomyopathy involves no change or a slight decrease, rather than an increase, in the LV cavity size.
Educational objective:
Eccentric ventricular hypertrophy results in a dilated cavity with relatively thin ventricular walls due to the addition of myocardial contractile fibers in series in response to chronic volume overload. Chronic aortic regurgitation can result from aortic root dilation and is a common cause of eccentric hypertrophy.