The diagnosis of dilated cardiomyopathy is supported by our patient's history of the nearly simultaneous onset of symptoms and signs of biventricular failure. These include both pulmonary and systemic congestion. His history of an enlarged heart on chest X ray also is typical. His physical examination demonstrated findings that reflect low cardiac output, congestive failure and marked cardiomegaly with poor ventricular function.
WHO classification
There have been multiple approaches to the classification of cardiomyopathy. One widely recognized system has been developed by the World Health Organization (WHO). It is base entirely on etiology and divides cardiomyopathies into unknown and known causes. In this classification, the term "cardiomyopathy" is restricted to primary heart muscle disease of unknown cause. The term "specific heart muscle disease" is used when it is due to a secondary or known cause. The latter includes many etiologies, such as infections, toxins and metabolic diseases.
Functional classification
Another approach is the functional classification of cardiomyopathies. It is useful clinically, as nearly all cardiomyopathies can be readily placed in one of the three categories and the therapeutic approaches to each category are distinctly different. The three categories are dilated, hypertrophic and restrictive. The dilated type is most common. It has also been called congestive, because it is often associated with clinical features of congestive heart failure
Cardiomyopathies
These diagrams demonstrate the basic anatomic differences between the three functional categories of cardiomyopathy. The left atrium, left ventricle and aortic valve are labeled.
Dilated cardiomyopathy is characterized by dilatation of both left and right ventricles. Hypertophic cardiomyopathy is characterized by inappropriate left ventricular hypertrophy with reduced chamber size, often with asymmetric septal hypertrophy. Restrictive cardiomyopathy is characterized by near normal cavity size, often with an infiltrative process that affects ventricular function, particularly, diastolic filling.
Dilated
Dilated cardiomyopathy is physiologically characterized by systolic dysfuntion, that is, reduced myocardial contractility of one or both ventricles. It is often idiopathic. A significant proportion of idiopathic cardiomyopathy can be attributed to genetic abnormalities in the protein composing the ventricular contractile apparatus. Interestingly, the same proteins that are abnormal in hypertrophic cardiomyopathy have been associated with dilated cardiomyopathy in some kindred. It can also be due to many identifiable causes including alcohol, viruses, toxic drugs and the peripartum state.
Ischemic
In the category of dilated cardiomyopathy, the term "ischemic cardiomyopathy" has been used to describe patients with underlying coronary artery disease who have myocardial failure due to infarction or severe ischemia. It is very important to rule out significant coronary artery disease in patients suspected of cardiomyopathy, as coronary disease is potentially treatable by reperfusion techniques.
Hypertrophic
Hypertrophic cardiomyopathy is physiologically characterized by diastolic dysfunction, that is, impaired left ventricular filling. In some patients, septal hypertrophy may cause outflow obstruction. The cause is genetic and is frequently familial.
Hypertrophic presentation
Patients with hypertrophic cardiomyopathy may present clinically with symptoms of angina pectoris, syncope or dyspnea. In advanced disease, patients may have a rapid rising carotid arterial pulse and a hyperdynamic impulse at the apex along with a fourth heart sound and systolic murmur.
Restrictive
Restrictive cardiomyopathy is physiologically characterized by diastolic dysfunction. The ventricular walls are excessively rigid and impede ventricular filling. The disease simulates constrictive pericarditis and the differential diagnosis is extremely important, as constrictive pericarditis is frequently operable. Restrictive cardiomyopathy may be idiopathic or due to a number of infiltrative systemic diseases, most commonly, amyloidosis
Restrictive presentation
Patients with a restrictive cardiomyopathy usually present clinically with symptoms of dyspnea and fatigue and signs of systemic venous congestion. On physical examination, an elevated central venous pressure and prominent "x" and "y" descents in the jugular venous wave form are typical.