Systolic heart failure affects an estimated 3.5 million people in the U.S. alone. Also known as HFrEF (heart failure with reduced ejection fraction) or dilated cardiomyopathy (DCM), diseases of systolic heart failure are all characterized by a heart that is unable to contract (or pump) with sufficient force to meet the needs of the body for oxygenated blood. In DCM, the loss of contractility leads the walls of the left ventricle to become thin and over-expanded, functioning under increased stress. DCM may have diverse causation factors; some genetic forms occur when mutations disrupt the ability of individual myosin motors to form cross-bridges with actin, decreasing the force of contraction.
DCM is a life-threatening progressive disease. Typical symptoms include shortness of breath, fatigue, swelling in the extremities or an irregular heartbeat. Once symptoms appear, a person’s condition typically declines steadily over the next few years. As the disease progresses, DCM patients may become increasingly debilitated and experience persistent shortness of breath, even at rest.
In addition to the inability to pump effectively, the diastolic function of the DCM heart is also impaired because the heart is expanded, inhibiting the ability for the left ventricle to properly relax and fill with blood. The heart itself may become deprived of an adequate supply of oxygen and contribute to fibrosis and the risk of dangerous heart rhythm disturbances. In addition, whether or not symptoms have appeared, patients with dilated cardiomyopathy are at risk of sudden cardiac death.
DCM patients are typically prescribed one or more drugs indicated for the treatment of systolic heart failure generally, such as diuretics, beta blockers, angiotensin receptor-neprilysin inhibitors, angiotensin converting enzyme inhibitors and aldosterone antagonists. By treating various signs and symptoms of heart disease, these drugs may reduce overall morbidity and mortality; however, none of the treatments address the underlying cause of disease or eliminate disease progression. Surgical or interventional options available to DCM patients include use of an implantable cardioverter-defibrillator, a biventricular pacemaker, and in refractory patients, a left ventricular assist device and cardiac transplant.