What medical condition can result in weakened heart muscle?

The condition that results in a weakened heart muscle is cardiomyopathy. This is a disease of the heart muscle that affects its size, shape, and ability to pump blood effectively. In cardiomyopathy, the heart muscle may become enlarged, thickened, or stiff, and this impairment can lead to heart failure and other serious complications. There are different types of cardiomyopathy, including dilated, hypertrophic, and restrictive, each with distinct characteristics but all sharing the common feature of muscle weakening.

Hypertension, while it can contribute to cardiomyopathy and strain the heart, primarily affects the heart's workload rather than being classified as a direct cause of weakened muscle. Similarly, coronary artery disease involves blockages in the heart's arteries, which can lead to ischemia and damage but does not specifically denote weakening of the heart muscle itself. Atrial fibrillation is an irregular heartbeat that can have various underlying causes and complications but does not directly result in a weakening of the heart muscle. Thus, cardiomyopathy is the most accurate answer when specifically discussing the condition that leads to weakened heart muscle.