Heart disease is defined as any functional, structural, or electrical abnormality of the heart. It encompasses a wide range of abnormalities, including congenital abnormalities (see Congenital and Inherited Anomalies of the Cardiovascular System) as well as anatomic and physiologic disorders of varying causes. Heart disease can be classified by various characteristics, including whether the disease was present at birth or not (eg, congenital or acquired), cause (eg, infectious, degenerative, genetic or heritable), duration (eg, chronic or acute), clinical status (eg, left heart failure, right heart failure, or biventricular failure), by anatomic malformation (eg, ventricular septal defect), or by electrical disturbance (eg, atrial fibrillation, ventricular premature complexes).