Cardiomyopathies and myocarditis

Cardiomyopathies are diseases of the heart muscle that affect the structure and function of the chambers of the heart and ventricles in particular. Diseases of the heart muscle resulting from high blood pressure, myocardial infarction, valvular diseases, or congenital heart diseases are not cardiomyopathies.
Dilated cardiomyopathy is characterised by a decrease in the left ventricle's ability to contract, and enlargement of the ventricle cavity. Typical symptoms include reduced physical performance, shortness of breath during physical activity, arrhythmia, and, eventually, heart failure. At least one in every three cases is congenital, and some cases result from viral myocarditis. Heavy alcohol consumption may contribute to the development of this condition. However, a definite cause cannot always be determined. Diagnosis is by echocardiography and the exclusion of other possible conditions causing myocardial damage. Diagnosis is often confirmed by coronary angiography (to rule out the possibility of stenoses). Sometimes further examinations such as cardiac MRI and endomyocardial biopsy are also required. Other forms of treatment include medications (beta blockers and angiotensin-converting enzyme (ACE) inhibitors), and pacemaker or ICD therapy. Heart transplantation is considered when heart failure is extreme.
Hypertrophic cardiomyopathy is characterised by an abnormal thickening of the left ventricle walls due to a hereditary gene defect. The condition may cause variable symptoms, including shortness of breath, chest pains, and paroxysmal loss of consciousness during physical activity. Arrhythmia may also occur. However, sometimes there are no symptoms, although the condition's existence is indisputable. In one in every three patients, myocardial hypertrophy and thickening of the interventricular septum, in particular, obstruct the outflow of blood from the left ventricle. Diagnosis is confirmed by echocardiography, but the condition can be suspected based on the findings from ECG testing and clinical examinations. Because the condition is hereditary, its familial occurrence should be mapped and the close relatives of diagnosed patients should be screened. Genetic analyses (DNA analysis) can be used as diagnostic tools. Treatment is based on the symptoms and findings. In addition to medical treatment, select patients benefit from surgical or catheter myectomy, which reduces the thickness of the interventricular septum, or placement of an implantable cardioverter defibrillator (ICD) when the risk of severe arrhythmia is considered high.

Restrictive cardiomyopathy is a rare condition. In Finland, it is typically caused by abnormal protein fibres accumulating in the myocardium (cardiac amyloidosis). Sometimes it is related to an increase in connective tissue growth (myocardial fibrosis) of unknown origin or caused by non-infectious myocardial inflammation (sarcoidosis, eosinophilic diseases). Restricted cardiomyopathy causes the myocardium to become stiff, thus reducing the stretching and filling capacity of the ventricles, in particular. In advanced cases, ventricular contracting is reduced. The most common symptoms include heart failure and arrhythmia. Sometimes the underlying storage disease or inflammation can be treated, but often the only option is unspecific treatment of heart failure and its consequences. In select cases, heart transplantation can be considered.
In Finland, myocarditis refers to an acute inflammation or damage of the myocardium caused by a viral (e.g. influenza A) or bacterial (e.g. mycoplasma, streptococcus, borreliosis) infection. Typical symptoms include chest pain and arrhythmia that occur during a febrile infectious disease or shortly afterwards. In most cases, myocardial damage is mild, heals rapidly and completely, and does not affect the pumping function of the heart. However, myocardial inflammation may sometimes cause extensive myocardial damage, leading to myocardial failure. This life-threatening condition requires rapid care at a specialist facility. Fortunately, this condition, which is known as fulminant myocarditis, is very rare. The diagnosis of myocarditis is based on clinical findings, ECG changes, laboratory tests, and echocardiography. Immediate coronary angiography is required in cases where the symptoms and ECG results are suggestive of acute myocardial infarction caused by a coronary artery occlusion.
Endomyocardial biopsy and the related microscopic studies are performed in certain specific situations, and especially when extensive myocardial damage is suspected. In mild cases of myocarditis, sufficient treatment includes rest and limiting physical activity until the symptoms have passed and there are no more abnormal findings. In severe cases, arrhythmias and insufficient cardiac pumping function are managed by applying the usual treatment methods. In these cases, physical activity should be limited for a longer period of time (6 months). If the virus or bacteria causing the condition can be identified, medications targeted against them are prescribed. In the case of severe, life-threatening myocarditis, cardiac function is supported and blood circulation maintained using an external pump, while myocardial function recovers. The patient is transferred to a university hospital without delay. If the myocardium does not recover, a ventricular assist device (VAD) is implanted in the thoracic cavity and heart transplantation is performed eventually. Myocarditis may sometimes cause dilated cardiomyopathy (see above). This development occurs through an immunological mechanism over several months or even years.