This review explains how the heart responds to physiologic or pathologic conditions.
Exercise, pregnancy, and postnatal growth cause physiologic growth; neurohumoral
activation, hypertension, and myocardial injury cause hypertrophic growth, which increases
the risk of heart failure and malignant arrhythmia. Atrophy of the heart can arise from
protracted bed rest, prolonged weightlessness, or mechanical unloading with a ventricular
assist device.