Restrictive cardiomyopathy (RCM) is a rare myocardial disease characterized by impaired ventricular compliance, with pathological stiffness of the cardiac walls that limits diastolic filling. Unlike dilated cardiomyopathy or hypertrophic cardiomyopathy, the ventricles have normal or only mildly increased wall thickness, but show a severe impairment in their ability to stretch, resulting in increased filling pressures and progression towards heart failure.
The main pathophysiological alterations in RCM involve the loss of myocardial elasticity and increased stiffness of the cardiac tissue, often caused by infiltration of pathological substances (such as amyloid or iron) or progressive myocardial fibrosis. These changes lead to a diastolic filling deficit, resulting in increased atrial pressures and symptoms of congestive heart failure, predominantly affecting the right side.
Epidemiology
Restrictive cardiomyopathy is the least common among primary cardiomyopathies, with an estimated prevalence of less than 1 case per 100,000 individuals. However, its true incidence may be underestimated due to diagnostic difficulties and the clinical variability with which it presents.
It mainly affects adults aged 40 to 60 years, but can also be diagnosed in childhood, especially in genetic forms or hereditary amyloidosis.
The causes can be primary (idiopathic or genetic) or secondary, resulting from infiltrative or fibrotic diseases, such as:
Cardiac amyloidosis: the leading cause of RCM in elderly patients, due to the accumulation of amyloid fibrils in the myocardium.
Hemochromatosis: excessive iron deposition in tissues, damaging myocardial structures.
Cardiac sarcoidosis: a systemic granulomatous disease that may involve the heart.
Endomyocardial fibrosis: a rare condition characterized by deposition of fibrous tissue that limits ventricular compliance.
Fabry disease: a lysosomal storage disorder causing accumulation of globotriaosylceramide in myocytes.
Exposure to radiation or chemotherapeutic agents (anthracyclines): toxic factors inducing myocardial fibrosis.
In Western countries, the most frequent cause is cardiac amyloidosis, while in tropical regions, endomyocardial fibrosis is the predominant form of restrictive cardiomyopathy.
Pathophysiology
Restrictive cardiomyopathy is characterized by impaired diastolic function with reduced ventricular filling capacity. Pathophysiologically, the heart becomes progressively stiffer due to infiltrative or fibrotic processes, limiting ventricular chamber expansion during diastole.
The main pathophysiological mechanisms include:
Increased myocardial stiffness: reduction of ventricular compliance due to infiltration of abnormal substances or diffuse interstitial fibrosis.
Elevated filling pressures: impaired ventricular filling leads to increased atrial pressure, resulting in atrial chamber dilation.
Low output heart failure: despite a relatively preserved ejection fraction, the reduction in filling volume leads to decreased cardiac output.
Systemic venous stasis: right ventricular dysfunction leads to hepatic congestion, ascites, and peripheral edema.
Unlike other forms of heart failure, RCM is characterized by a preserved or only mildly reduced ejection fraction, but with marked systemic venous congestion and symptoms of right heart failure.
In patients with advanced amyloidosis, protein infiltration may also involve the conduction system, predisposing to arrhythmias and atrioventricular blocks.
Over time, disease progression leads to reduced cardiac output, which may result in hypotension, syncope, and severe functional impairment. In end-stage cases, RCM may evolve to refractory heart failure requiring advanced support, such as ventricular assist devices or heart transplantation.
Clinical Presentation
The clinical presentation of restrictive cardiomyopathy (RCM) varies according to etiology and disease stage.
In the early stages, symptoms may be mild or absent, while progression of ventricular stiffness leads to signs of right heart failure and low cardiac output.
Main signs and symptoms
Exertional dyspnea: due to increased filling pressures and pulmonary congestion.
Peripheral edema: a sign of right heart failure with fluid retention.
Ascites and hepatomegaly: due to hepatic venous congestion.
Asthenia and hypotension: secondary to reduced cardiac output.
Palpitations: due to atrial fibrillation, common in patients with atrial dilation.
Syncope: in advanced cases, due to cerebral hypoperfusion or arrhythmias.
Unlike dilated cardiomyopathy, where systolic dysfunction predominates, in RCM the heart maintains a relatively preserved ejection fraction, but diastolic impairment results in a reduced filling volume and symptoms of systemic congestion.
Physical examination
On physical examination, the most common signs of RCM include:
Elevated jugular venous pressure: often with prominent "y" descent, indicative of diastolic dysfunction.
Pulsus paradoxus: typical of cases with cardiac tamponade secondary to pericardial effusion.
Mitral or tricuspid regurgitation murmur: due to atrial dilation with secondary valvular dysfunction.
Kussmaul's sign: paradoxical increase in jugular venous pressure during inspiration, characteristic of advanced forms.
Normal or slightly reduced apex beat: unlike dilated cardiomyopathy, the apex is not hyperdynamic.
In many patients, RCM may be confused with constrictive pericarditis, a condition sharing many similar hemodynamic features. For this reason, distinguishing between the two diseases is crucial for proper management.
Diagnosis
The diagnosis of restrictive cardiomyopathy is based on a combination of instrumental investigations aimed at demonstrating diastolic dysfunction, atrial dilation, and identifying any underlying causes such as amyloidosis or hemochromatosis.
Diagnostic tests
Electrocardiogram (ECG): often shows atrial fibrillation, low QRS voltages (especially in amyloidosis), and sometimes atrioventricular blocks.
Transthoracic echocardiography: first-line test, reveals dilated atria, non-dilated ventricles with stiff walls, and diastolic filling abnormalities.
Tissue Doppler and strain imaging: useful for identifying subclinical myocardial dysfunction.
Cardiac magnetic resonance imaging (CMR): essential for diagnosing amyloidosis (with diffuse late enhancement) or hemochromatosis (with iron deposition).
Endomyocardial biopsy: reserved for selected cases, allows definitive diagnosis of amyloidosis, sarcoidosis, or other infiltrative diseases.
Genetic testing: indicated in patients with suspected familial form, such as Fabry disease.
Differential diagnosis
It is essential to distinguish RCM from other conditions with similar symptoms, including:
Constrictive pericarditis: often confused with RCM, distinguished by the presence of pericardial calcifications and response to pericardiectomy.
Hypertrophic cardiomyopathy: characterized by asymmetric hypertrophy and outflow tract gradient.
Dilated cardiomyopathy: features dilated ventricles with reduced ejection fraction.
Treatment
The treatment of restrictive cardiomyopathy aims to control symptoms and manage complications, as in most cases there is no specific curative therapy. The therapeutic approach depends on the underlying cause.
Pharmacological management
Diuretics: used to reduce venous congestion, with attention to the risk of hypotension.
Beta-blockers or calcium channel blockers: may be useful to slow heart rate and improve diastolic filling.
Anticoagulants: indicated in patients with atrial fibrillation to prevent thromboembolic events.
In patients with cardiac amyloidosis, specific treatment involves drugs such as tafamidis, which stabilizes transthyretin and slows disease progression. In hemochromatosis, phlebotomy and iron chelators can improve myocardial function.
Advanced options
Heart transplantation: indicated in patients with refractory heart failure.
Ventricular assist devices: in selected cases, as a bridge to transplantation.
Prognosis
The prognosis of restrictive cardiomyopathy depends on etiology and the rate of disease progression. Patients with infiltrative forms, such as advanced amyloidosis, have an average survival of less than 5 years, while less aggressive forms may allow a good quality of life with adequate therapeutic support.
Main complications
Refractory right heart failure: main cause of hospitalization.
Ventricular arrhythmias and atrial fibrillation: increase the risk of stroke and sudden death.
Pulmonary thromboembolism: due to venous stasis and atrial fibrillation.
Early identification and multidisciplinary management can improve prognosis and quality of life in patients with RCM.
References
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