Dilated Cardiomyopathy (DCM) is a disease where the heart muscle is affected, leading to mechanical failure. This condition is characterized by the heart becoming enlarged and weakened, making it difficult to pump blood effectively to the rest of the body. The primary issue is a reduction in the heart’s ability to contract forcefully, which begins with structural changes to the main pumping chamber.
Structural Changes in the Heart Muscle
Dilated cardiomyopathy is defined by ventricular remodeling, the progressive stretching of the heart’s chambers. This structural change typically begins in the left ventricle, the main pumping chamber responsible for sending oxygenated blood to the body. As the chamber stretches, the muscular walls become thinner and the cavity size increases, making the heart appear more rounded than its normal cone shape.
This thinning and stretching compromises the heart’s ability to contract with adequate force. The muscle fibers are overextended, much like a stretched-out rubber band, reducing the efficiency of each heartbeat. This leads to a decline in the percentage of blood ejected from the ventricle with each contraction, known as the ejection fraction (EF). An EF below 40% indicates a significantly weakened heart muscle and functional failure.
The progressive dilation and weakening of the left ventricle can spread to the right ventricle and the upper chambers (atria). This structural compromise is often accompanied by the development of scar tissue, or fibrosis, within the heart muscle. This fibrotic tissue further inhibits the muscle’s ability to contract and conduct electrical signals, contributing to the decline in heart function.
Impact on Blood Circulation
The inability of the weakened, dilated ventricle to pump blood efficiently results in heart failure. When the heart struggles to eject blood, the volume remaining in the chamber after contraction increases, raising the pressure within the heart. This functional failure leads to systemic issues as blood begins to back up in the circulatory system.
A significant consequence is fluid congestion, which occurs because blood cannot move forward quickly enough. The backup of blood into the vessels draining the lungs causes pulmonary congestion, resulting in shortness of breath, especially during activity or when lying flat. Simultaneously, increased pressure in the venous system causes fluid to leak out and accumulate in the body’s tissues.
Fluid retention is commonly observed as swelling (peripheral edema) in the legs, ankles, feet, and sometimes the abdomen. The reduced ejection fraction means less oxygen-rich blood reaches the body, causing fatigue and a reduced ability to exercise. The heart’s attempt to compensate by beating faster can lead to irregular heart rhythms (arrhythmias), a serious complication.
Identifying the Underlying Causes
Determining the specific origin of DCM is important, as the cause often influences the treatment plan. DCM is broadly categorized into familial (genetic) and acquired forms. When the cause remains unknown, it is referred to as idiopathic DCM. Genetic factors play a role in 20% to 40% of cases, showing a familial inheritance pattern.
Mutations in genes that encode structural proteins, such as Titin (TTN) and Lamin A/C, are frequently implicated in inherited DCM. These genetic variants disrupt the muscle’s structure and function within the heart cells, leading to characteristic dilation. Lamin A/C gene mutations are important to identify because they are associated with an increased risk of dangerous heart rhythm disturbances.
Acquired forms of DCM stem from various external or environmental factors that directly injure the heart muscle. Viral infections, such as those causing myocarditis, can lead to inflammation and subsequent damage that progresses to DCM later. Exposure to toxins, including excessive alcohol use, certain chemotherapy agents (like doxorubicin), and illegal drugs (like cocaine), are established causes. Other underlying health conditions, such as uncontrolled high blood pressure, thyroid disease, or excessive iron accumulation (hemochromatosis), can also stress the heart muscle.
Controlling the Condition
Management of DCM focuses on two primary goals: alleviating the symptoms of heart failure and slowing the progressive worsening of the heart muscle’s function. Medical therapy is the foundation of treatment. It aims to reduce the workload on the heart and block the harmful neurohormonal pathways that contribute to remodeling. Medications such as Angiotensin-Converting Enzyme (ACE) inhibitors, Beta-blockers, and mineralocorticoid receptor antagonists are commonly prescribed to improve heart function and extend survival.
Diuretics (water pills) are used to manage fluid buildup associated with heart failure, reducing swelling and easing breathing. If drug therapy is insufficient or if there is a risk of sudden cardiac arrest due to abnormal rhythms, device therapy may be utilized. An Implantable Cardioverter-Defibrillator (ICD) monitors the heart rhythm and delivers a corrective electrical shock if a life-threatening arrhythmia occurs. For patients with severe heart failure refractory to other treatments, options include a Left Ventricular Assist Device (LVAD) or a heart transplant.