Restrictive Cardiomyopathy
Restrictive cardiomyopathy (RCM) is a rare form of myocardial disease that is characterized by restrictive filling of the ventricles. In this disease the contractile function of the heart and wall thicknesses are usually normal, but the filling phase of the heart is abnormal. This occurs because the cardiac muscle is stiff and poorly compliant and does not allow ventricular filling. This inability to relax and fill with blood results in a back-up of blood into the atria. RCM is the least common in children, accounting for 2.5-5% of the diagnosed cardiomyopathies. The average age at diagnosis is 5 to 6 years and it appears to affect girls somewhat more often than boys. There is a family history of cardiomyopathy in approximately 30% of cases. In most cases the cause of the disease is unknown (idiopathic), although a genetic cause is suspected in most cases of pediatric RCM.
Clinical presentation:
Children with RCM frequently have a history of repeated lung infections. Referral to a cardiologist occurs when symptoms of heart failure are reported or cardiomegaly is seen on a chest x-ray. In approximately 10% of cases, syncope may be the first symptom. Sudden death may also be the initial presentation in some patients.
Making the diagnosis:
- The diagnosis of RCM is difficult to establish early in the clinical course due to the lack of symptoms.
- Therefore, in many cases, the diagnosis is made only after presentation with symptoms such as decreased exercise tolerance, new heart sound (gallop), syncope or chest pain with exercise.
- EKG may demonstrate abnormally large electrical forces from enlargement of the atria.
- An echocardiogram may show marked enlargement of the atria, normal sized ventricles and normal heart function. In more advanced disease states, pulmonary artery pressures may be increased.
- Cardiac catheterization is rarely needed to confirm the diagnosis. The pressure measurements often show significantly elevated pressures during diastole and varying degrees of increased pulmonary artery pressures in the absence of any other structural heart disease.
- Myocardial biopsy is rarely needed to confirm the diagnosis.
- Since childhood RCM is often genetic, once this diagnosis is established, it is important to screen other family members.
Management:
- Diuretics, beta-blockers and occasionally afterload reducing agents.
- In children with RCM, there is a risk of clots forming inside the heart possibly leading to a stroke. Anticoagulation medications, are often used in these situations. These include aspirin, dipyridamole, warfarin, heparin, and enoxaparin.
|
Table showing the common differences between constrictive pericarditis and restrictive cardiomyopathy |
||
|
|
Constrictive pericarditis |
Restrictive cardiomyopathy |
|---|---|---|
|
History |
Previous pericarditis, cardiac surgery, trauma, radiotherapy and connective tissue disease |
May have a positive family history |
|
Extra heart sounds |
Early S3, high pitched pericardial knock. No S4 |
Later S3, low pitched triple rhythm. S4 in some cases |
|
Mitral or tricuspid regurgitation |
Absent |
Present |
|
EKG |
Normal P waves
|
Bi-atrial dilation
|
|
CXR |
Pericardial calcification in 20-30% of the cases. Normal atria |
Pericardial calcification rare. Severe atrial dilation |
|
Atrial enlargement
|
Usually mild |
Severe in most cases |
|
Equilibration of end- diastolic pressures in all cardiac chambers |
Within 5 mm Hg in nearly all cases |
Rarely occurs
|
|
MR/CT imaging |
Shows thick pericardium in most cases |
Rarely shows thick pericardium
|
|
Endomyocardial biopsy |
Normal, or non-specific abnormalities |
Shows amyloid in some cases, rarely other specific infiltrative disease |
Myocarditis
Myocarditis is an inflammation of cardiac myocytes associated with necrosis and degeneration.
Infection with Coxsackie B virus or adenovirus is the most common cause of myocarditis. Many other viruses, as well as bacterial infections, mycoplasma, fungi, protozoa, spirochetes and rickettsia have also been reported to cause myocarditis.
Clinical presentation
The common presentation is a history of a recent viral infection followed by the development of signs and symptoms of CHF.
Making the diagnosis
- The patient may have tachycardia and other signs of overt CHF.
- Chest radiography demonstrates cardiomegaly and pulmonary venous congestion. Evidence of pneumonitis may be present.
- The EKG may show sinus tachycardia; premature ventricular contractions or supraventricular tachycardia. Low voltage QRS and inverted T waves are common.
- Echocardiography and cardiac catheterization with biopsy may be necessary to differentiate myocarditis from dilated cardiomyopathy. Viral culture and viral titers may be helpful in making the diagnosis.
Management
Acutely sick patients require intravenous inotropic agents and diuretics until they can be transitioned to oral digoxin, afterload reducing agents and diuretics. The use of anti-inflammatory and immunosuppressive therapy is still controversial.
Hypertrophic Obstructive Cardiomyopathy
Hypertrophic obstructive cardiomyopathy (HOCM) is the most common cause of sudden death in the young. The most important predictors of sudden death are a family history of sudden death and recurrent syncope. Mortality in children with HOCM is twice as high as adults. The condition is usually progressive and the symptoms depend on the age and mode of presentation.
HOCM is an inherited disorder of the cardiac muscle characterized by a hypertrophied, non-dilated left ventricle. The condition is associated with abnormal relaxation of the LV and sometimes with outflow tract obstruction. The mode of inheritance is most often autosomal dominant with variable penetrance and several genetic defects have been described.
Pathology
The hallmark of HOCM is left ventricular hypertrophy (LVH) which is characteristically asymmetric with more involvement of the ventricular septum. This asymmetric septal hypertrophy often produces sub-aortic obstruction that is exaggerated by systolic anterior movement (SAM) of the anterior mitral valve leaflet and its apposition to the bulging septum. Histologically, there is extensive myocardial fiber disarray. The myocardial cells are disorganized and are separated by loose connective tissue. The coronary arteries sometimes run within the myocardium (intramural) and show increased intimal and medial thickening causing luminal narrowing.
Clinical Presentation
Affected individuals may be asymptomatic, may have recurrent exertional dyspnea, chest pain or syncope. The condition may be recognized only after sudden death has occurred. Infants may present with CHF and the diagnosis is often missed.
Making the diagnosis
- Beyond infancy, a heart murmur may be the mode of presentation.
- A prominent "a" wave in the jugular venous pulse may be present because of diastolic dysfunction.
- A systolic ejection murmur may be present due to LV outflow obstruction; the murmur is intensified by maneuvers that decrease the LV volume and increase the systolic anterior movement of the mitral valve leaflet such as standing or performing the Valsalva maneuver. Its intensity decreases by squatting or assuming a supine position. These maneuvers have the opposite effect of an aortic stenosis murmur.
- EKG changes are variable and may show LVH with a strain pattern (inverted T waves in the left precordial leads). Chest radiography may be normal or have evidence of cardiomegaly. MRI and radionuclide studies are helpful in making the diagnosis and assessing systolic and diastolic functions.
- Echocardiography is the most important imaging study for the diagnosis of HOCM and allows an assessment of the pattern and degree of hypertrophy, the extent of LV obstruction as well as the systolic anterior movement (SAM) of the anterior mitral leaflet.
Management
Beta-blockers are helpful in the medical management by reducing the contractility and the heart rate; thereby prolonging the diastolic time. However, these agents have no effect on the degree of LV outflow obstruction or sudden death. Digoxin, other inotropic agents, and ACE inhibitors are contraindicated in HOCM as they worsen the obstruction, though they may have a role in the end-stage dilated thin-walled HOCM hearts with impaired LV systolic function. Diuretics are also usually contraindicated as they reduce the preload and enhance the LV obstruction
Surgical myomectomy may be needed to relieve the LV obstruction. Alcohol ablation of the septal perforating coronary arteries can produce a controlled infarction and relieves the sub-aortic obstruction. There is also a role for a pacemaker or implantable defibrillator (ICD).
Patients with HOCM should avoid strenuous exercise and their families should undergo genetic counseling.
