Introduction
Congestive cardiomyopathy is a broad term characterized by an impaired function of the heart muscle leading to enlargement of the heart chamber size as well as heart failure. Cardiomyopathies can be divided into two broad categories: 1) primary and 2) secondary. In the case of primary cardiomyopathy (also known as idiopathic and is currently known as dilated cardiomyopathy), no specific cause can be identified. Many of the dilated cardiomyopathies have a genetic or inherent background. About 40% of patients with dilated cardiomyopathy have a familial background, and multiple genes have been identified. In this form of cardiomyopathy, no other causes are generally found. Infection, especially viral infection, to the heart muscle can lead to dilated cardiomyopathy. The most common cause is viral myocarditis (inflammation of the heart muscle).
Secondary congestive cardiomyopathies has several diverse causes, the most important being ischemic heart disease (also known as ischemic cardiomyopathy). Other causes include hypertension (high blood pressure), diabetes (known as diabetic cardiomyopathy), valvular heart disease, obesity, and many others. Dilated cardiomyopathy is the most common form of heart muscle dysfunction worldwide. Dilated cardiomyopathy is an important cause of sudden cardiac death and heart failure and is among the leading indication for heat transplant, both in children and adults.
Symptoms
Many patients remain asymptomatic (have no symptoms) or sometimes their symptoms come and go. Symptomatic patients, however, may present with symptoms of heart failure that include shortness of breath, palpitations (irregular heartbeat), pounding in the chest, dizziness, and chest pain.
Diagnosis
Work-up should include history and physical examination (usually done at doctors offices or clinics), family history and genetic testing if familial type is suspected. If the presenting symptoms include palpitations or syncope (loss of consciousness), electrocardiogram (ECG), 24 hour Holter monitoring, X-Ray, echocardiogram, treadmill or exercise testing, cardiac catheterization and coronary angiography, cardiac magnetic resonance imaging, and cardiac computed tomography may be preformed:
1. Electrocardiogram (ECG): A registration of heart electrical activity. The ECG shows heart rate and rhythm and can provide important information regarding the heart chamber size.
2. 24 Hour Holter Monitor: A device worn by the patient for 24 hours that continually monitors and records the heart rate and rhythm.
3. X-Ray: A window to the heart, respiratory system, and the rest of the body that provides important information regarding cardiac function and size. It is an important test, especially in those with resting or external shortness of breath, if the diagnosis of congestive cardiomyopathy is suspected, or in individuals with past cardiac history.
4. Echocardiogram: This test uses ultrasound and examines all four heart chamber sizes and function.
5. Treadmill or Exercise Testing: A very useful test that provides information including heart rate, blood pressure response to exercise, as well as ECG changes during or at recovery from exercising. Treadmill testing provides prognostic information, especially on exercise-induced rhythm disorders.
6. Coronary angiography and cardiac catheterization: These tests provide information on some of the causes of dilated cardiomyopathy, and more importantly measures pressures inside the heart. This technique also provides information on the coronary arteries.
In selected cases, cardiac magnetic resonance imaging and cardiac computed tomography may provide useful information.
Treatment
Depending on the symptoms and etiology of the patient, treatment should include lifestyle modification (such as weight loss and salt restriction), heart failure and arrhythmia management as well as optimal medical therapy including beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, and diuretics.
In patients at risk for sudden cardiac death, implantable cardioverter defibrillator placement or cardiac resynchronization therapy (i.e., left bundle branch block), or catheter ablation of arrhythmias may be considered. Heart transplant is rarely needed; however, it remains the leading indication for dilated cardiomyopathy in children and adults.
Prognosis: 50-60% of patients with dilated cardiomyopathy experience sudden cardiac death. This depends on the severity of the reduced pump function (Left ventricular ejection fraction < 35%). Left ventricular ejection fraction is a prognostic marker for sudden cardiac death and risk marker for implantable cardioverter defibrillator implantation. Annual mortality is about 10-30%, due to sudden cardiac death being high and, as mentioned above, implantable cardiac defibrillator implantation prevents episodes of sudden cardiac death.
Prevention: One should recognize the cause(s) of dilated cardiomyopathy and adhere to the management and therefore avoid triggers that worsen the progression of the disease (such as alcohol, salt intake) and lower the risk of sudden cardiac death, hospitalization, worsening of heart failure, etc.
Mohammad Shenasa MD, San Jose, US
References[1-3]
1. Lakdawala NK, Winterfield JR, Funke BH. Dilated cardiomyopathy. Circ Arrhythm Electrophysiol 2013;6(1):228-37.
2. Jefferies JL, Towbin JA. Dilated Cardiomyopathy. Lancet 2010.
3. Gulati A, Jabbour A, Ismail TF, et al. Association of Fibrosis With Mortality and Sudden Cardiac Death in Patients With Nonischemic Dilated Cardiomyopathy. JAMA 2013;309(9):896-908.