Dilated Cardiomyopathy - causes, symptoms, pathophysiology and treatment

Summary

Cardiomyopathies are a group of heart muscle diseases that often lead to heart failure. Dilated cardiomyopathy, the most common type, involves the dilation and impaired contraction of the ventricles, resulting in reduced ejection fraction and symptoms such as shortness of breath and orthopnea. The condition can be caused by genetic factors, infections, or lifestyle choices like alcohol abuse. Treatment includes heart failure medications, such as diuretics and ACE inhibitors, and may require an implantable defibrillator or heart transplant in severe cases. Understanding the determinants of myocardial performance—preload, afterload, and contractility—is key to managing the disease.

Takeaways

• 😀 Cardiomyopathies are diseases of the heart muscle that can lead to progressive heart failure, with high morbidity and mortality.
• 😀 The heart is a muscular pump, and the focus of cardiomyopathies is on the ventricular heart muscles, the bottom two chambers.
• 😀 Cardiac muscle cells are multinucleated and connected by intercalated discs, which form a synchronized network to coordinate heart contractions.
• 😀 The contractile units of the cardiac muscle are sarcomeres, which shorten to cause contraction (systole) and lengthen during relaxation (diastole).
• 😀 Three major determinants of myocardial performance are preload (blood entering ventricles), afterload (resistance to pumping), and contractility (heart muscle’s strength).
• 😀 The Frank-Starling relationship explains how increased preload (blood filling ventricles) enhances heart contraction and stroke volume.
• 😀 Dilated cardiomyopathy (DCM) is the most common form of cardiomyopathy, characterized by ventricular dilation and impaired contraction, leading to reduced ejection fraction.
• 😀 Symptoms of dilated cardiomyopathy include heart failure signs like shortness of breath, orthopnea, and paroxysmal nocturnal dyspnea, and an S3 gallop on auscultation.
• 😀 Dilated cardiomyopathy can be caused by genetic factors, viral infections (e.g., Coxsackie B), substance abuse, coronary artery disease, and valvular disease.
• 😀 Echocardiograms of patients with DCM show dilated ventricles, reduced ejection fraction, and possible mitral valve insufficiency.
• 😀 Treatment for dilated cardiomyopathy includes fluid restriction, diuretics, ACE inhibitors, beta-blockers, spironolactone, and potentially implantable cardioverter defibrillators (ICDs) for arrhythmia risk, with heart transplantation as a last resort.

Q & A

What are cardiomyopathies and how do they affect the heart?

Cardiomyopathies are diseases of the heart muscle, often leading to progressive heart failure. These conditions affect the heart's ventricular muscles, impairing their ability to pump blood effectively, which can result in significant morbidity and mortality.

What are the main components of cardiac muscle cells?

Cardiac muscle cells, or cardiomyocytes, have a single nucleus, are branched, and are connected by intercalated discs that contain gap junctions. These gap junctions allow the heart to contract in a coordinated manner. The sarcomeres, composed of myosin and actin filaments, are the contractile units of the cardiac muscle.

What happens during systole and diastole in the heart?

During systole, the ventricles contract and pump blood out of the heart. In diastole, the ventricles relax and fill with blood, preparing for the next contraction.

What is the Frank-Starling relationship?

The Frank-Starling relationship describes how an increase in preload (the amount of blood entering the ventricles during diastole) leads to a stronger contraction. This happens because the stretching of the sarcomere builds tension, resulting in increased contractile force during systole.

What are the three main determinants of myocardial performance?

The three main determinants of myocardial performance are preload (the volume of blood entering the ventricles), afterload (the force the heart must overcome to pump blood), and contractility (the heart's inherent ability to contract).

What is dilated cardiomyopathy, and how does it affect the heart?

Dilated cardiomyopathy is the most common type of cardiomyopathy, characterized by dilation and impaired contraction of one or both ventricles. This results in reduced ejection fraction, where the heart cannot pump blood effectively.

What are some clinical features of dilated cardiomyopathy?

Clinical features include symptoms of heart failure, such as dyspnea (shortness of breath), orthopnea, and paroxysmal nocturnal dyspnea. A key clinical sign is the S3 gallop, an additional heart sound occurring after S2 due to rapid filling of a compliant left ventricle.

What causes dilated cardiomyopathy?

Dilated cardiomyopathy can be caused by primary factors like genetic inheritance, or secondary factors such as viral infections (e.g., Coxsackie B virus), substance abuse (alcohol, cocaine), coronary artery disease (ischemic cardiomyopathy), and valvular diseases.

What is the significance of the S3 gallop in diagnosing heart failure?

The S3 gallop, an additional heart sound occurring just after S2, is a specific indicator of heart failure. It results from blood striking a dilated, compliant left ventricle during passive filling.

How is dilated cardiomyopathy diagnosed using echocardiography?

Echocardiography can show a dilated ventricle with reduced ejection fraction, thinning of the ventricular walls, and possible mitral insufficiency, all of which are indicative of dilated cardiomyopathy.

What treatments are available for dilated cardiomyopathy?

Treatment includes fluid restriction, diuretics, ACE inhibitors, beta-blockers, and spironolactone. For patients at risk of arrhythmias, implantable cardioverter-defibrillators (ICD) may be used. In severe cases, a heart transplant may be necessary.