Dilated cardiomyopathy is a primary myocardial disease characterized by progressive dilation of the left ventricle (or both ventricles) and systolic dysfunction not attributable to pressure or volume overload, as seen in hypertensive or valvular heart disease. The dilated ventricle gradually loses the ability to contract effectively, resulting in a decline in ejection fraction and a reduction in the volume of blood pumped into the circulation.
This condition is distinguished from other cardiomyopathies by the predominance of eccentric ventricular remodeling, with an increase in ventricular chamber diameter not accompanied by adequate compensatory hypertrophy. The end result is a reduction in contractile performance, with impaired cardiac output and progressive activation of neurohormonal compensatory mechanisms, which in the long term worsen myocardial damage.
Dilated cardiomyopathy is the most common form of primary cardiomyopathy and represents one of the main causes of chronic heart failure.
The prevalence in the general population is estimated at 1 case per 250 individuals, with an annual incidence of about 7–10 cases per 100,000 inhabitants.
The disease can affect individuals of any age but occurs most frequently between 20 and 50 years. It is more common in males, with a ratio of approximately 3:1 compared to females. This difference appears to be related to hormonal, genetic, and increased exposure to environmental risk factors.
In industrialized countries, dilated cardiomyopathy accounts for about 40% of cases of non-ischemic heart failure and is the leading cause of cardiac transplantation in adults. Advances in diagnostic techniques, particularly molecular genetics, have led to the recognition of an increasing number of familial forms, making screening of first-degree relatives of affected patients essential.
Dilated cardiomyopathy results from progressive ventricular remodeling that impairs the heart’s pumping function. Under normal conditions, increased ventricular diastolic volume allows maintenance of adequate stroke volume through the Frank-Starling mechanism: the greater the myocardial fiber stretch in diastole, the greater the contractile force. However, in dilated cardiomyopathy, excessive chamber dilation exceeds the physiological limit of this mechanism, leading to a progressive loss of contractility.
The immediate consequence is a reduction in ejection fraction, resulting in reduced peripheral perfusion and a series of compensatory responses. The sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS) are activated in an attempt to increase contractility and fluid retention to maintain blood pressure and perfusion of vital organs. However, when these mechanisms are prolonged, they worsen myocardial damage through chronic overload and interstitial fibrosis.
A key aspect of the pathophysiology of dilated cardiomyopathy is the progressive alteration of ventricular geometry. As the ventricular diameter increases, mitral annular displacement occurs, preventing proper leaflet coaptation and leading to functional mitral regurgitation. This further worsens ventricular dilation and establishes a vicious circle of deterioration in cardiac function.
Moreover, reduced ventricular contractility promotes blood stasis, especially at the apex of the left ventricle, creating an environment conducive to mural thrombus formation. These may fragment and cause systemic thromboembolic events, with severe consequences such as ischemic stroke or peripheral arterial embolism.
As the disease progresses, pressure overload is transmitted to the pulmonary circulation, causing increased atrial filling pressures and, in advanced cases, the development of secondary pulmonary hypertension. This condition gradually leads to right ventricular involvement, worsening biventricular function and further aggravating the clinical picture.
The anamnesis of a patient with dilated cardiomyopathy must be accurate and aimed at identifying both specific symptoms of the disease and any predisposing factors. It is essential to investigate the family history, as about 30–50% of cases have a genetic basis. The presence of relatives with heart failure, arrhythmias, sudden cardiac death, or cardiac transplantation should raise suspicion of a familial form.
It is also necessary to investigate the presence of toxic factors or acquired causes, such as alcohol abuse, use of cardiotoxic substances (anthracyclines, cocaine), previous viral infections suggestive of myocarditis, or systemic diseases that may secondarily involve the myocardium (hemochromatosis, amyloidosis, sarcoidosis, thyroid disorders).
The patient may report a progressive exercise intolerance, often underestimated in the early stages, followed by worsening with the gradual appearance of symptoms related to the degree of systolic dysfunction.
The patient may initially be asymptomatic, but as the disease advances, the following appear:
On physical examination, patients with advanced dilated cardiomyopathy may exhibit signs of cardiomegaly, functional valvular insufficiency, and hemodynamic alterations.
Palpation of the apex beat reveals a lateral and downward displacement of the point of maximal cardiac impulse, indicating increased left ventricular volume. Cardiac auscultation may reveal a third heart sound (S3), indicative of abnormal ventricular filling, and a holosystolic murmur at the apex, a sign of secondary mitral regurgitation. In patients with progression to right ventricular dysfunction, jugular vein distension, congestive hepatomegaly, and peripheral edema may be present.
Diagnosis of dilated cardiomyopathy requires a multimodal approach, based on instrumental tests aimed at confirming ventricular dilation and systolic dysfunction, while excluding other secondary cardiac diseases.
The diagnosis of dilated cardiomyopathy is based on a combination of clinical criteria and instrumental investigations.
Echocardiographic evidence of a dilated left ventricle with reduced ejection fraction (<40%) in the absence of secondary conditions (such as ischemic heart disease, valvular disease, or chronic hypertension) is sufficient to establish the diagnosis of dilated cardiomyopathy.
In patients with a positive family history, genetic testing is recommended to confirm a hereditary form.
Coronary angiography may be indicated in subjects with suspected underlying ischemic heart disease, while cardiac magnetic resonance is useful to rule out infiltrative or fibrotic pathologies.
The treatment of dilated cardiomyopathy is based on strategies aimed at reducing ventricular remodeling, improving systolic function, and preventing complications. Therapy includes pharmacological approaches, implantable devices, and, in more advanced cases, heart transplantation.
The cornerstone of drug therapy consists of agents that modulate the renin-angiotensin-aldosterone system and the sympathetic nervous system, reducing hemodynamic overload and improving myocardial performance.
The most commonly used drugs are:In patients with severely reduced ejection fraction and high risk of sudden death, devices capable of preventing malignant arrhythmias and improving ventricular synchrony are indicated.
In patients with refractory heart failure to drug therapy and progressive deterioration of ventricular function, heart transplantation is the only definitive option. Indication is evaluated on a case-by-case basis, considering strict selection criteria to ensure organ allocation to those in greatest need.
The prognosis of dilated cardiomyopathy is variable and depends on the severity of ventricular dysfunction, response to therapy, and the presence of complications.
With optimal treatment, 5-year survival has improved significantly, reaching 50–70% in patients receiving advanced medical therapy.
In patients with aggressive genetic forms or rapidly progressive disease, outcomes are poorer. Early identification and timely treatment are crucial to improving quality of life and reducing mortality.
The complications of dilated cardiomyopathy arise primarily from progressive ventricular dysfunction and myocardial structural changes. The main ones include:
In patients with severe ventricular dysfunction, the risk of malignant ventricular arrhythmias such as sustained ventricular tachycardia or ventricular fibrillation is high. These arrhythmias may cause sudden cardiac death, especially in patients with EF <35%. For this reason, ICD implantation is recommended in at-risk individuals.
Ventricular dilation and reduced contractility promote blood stasis, predisposing to mural thrombus formation, most frequently at the apex of the left ventricle. These thrombi may embolize, causing ischemic stroke or systemic embolism. In patients with high thrombotic risk, anticoagulant therapy is indicated.
Ventricular dilation alters cardiac geometry, with mitral annular displacement resulting in functional mitral regurgitation. This condition further worsens ventricular dilation and symptoms, contributing to heart failure progression.
Increased left ventricular filling pressures are transmitted to the left atrium and then to the pulmonary circulation, resulting in secondary pulmonary hypertension. In advanced cases, pressure overload extends to the right ventricle, causing progressive dysfunction and symptoms of systemic congestion (peripheral edema, ascites, congestive hepatomegaly).