Echocardiographic view of the normal and a dilated heart. Left panel, Parasternal long-axis view of a normal heart in end-diastole, illustrating normal left-ventricular (LV) wall thickness (1.2 cm; curved lines) and cavity dimensions. A normal-sized left atrium (LA) and aortic root (Ao) are shown on this view. Right panel, Dilated cardiomyopathy causing marked increases in the LV diastolic diameter (7.7 cm, arrowed line) and LA enlargement.

Diversity of phenotypes accompanying heritable dilated cardiomyopathy. A, Electrocardiographic tracings, revealing conduction-system abnormalities in patients with dilated cardiomyopathy. Top, First-degree atrioventricular (AV) block with prolonged interval (horizonal bar = .4 s) between atrial P wave (↓) and subsequent ventricular QRS wave. Middle, Second-degree AV block; note that a QRS complex does not follow the third or sixth P wave. Bottom, Presence of atrial fibrillation, with absence of P waves and irregular rhythm of ventricular QRS complexes. B, Plantar (and palmar) keratosis, which accompanies dilated cardiomyopathy in Naxos syndrome. C, Audiogram showing normal hearing (triangles) in comparison to sensorineural hearing loss in patients with dilated cardiomyopathy due to a mutation at chromosome 6q23-24. White circles (○) and crosses (×) denote sound transmitted through air into the right and left ear, respectively. Note that hearing loss is symmetric and affects air and bony (black circles [●]) transmission of sound.

Schematic of the multiple mechanisms leading to dilated cardiomyopathy. Insufficiencies of force production and force transmission, deficits of myocyte energy, and apoptosis or necrosis can each result in ventricular dilation and deficits in myocardial contraction. Note that single gene mutations (inside circle) and some acquired causes (outside circle) of dilated cardiomyopathy perturb the same pathways. The functional consequences of some mutations remain unknown.