It is a disease characterised by a dilation of both ventricles, whose systolic function is decreased (especially the left ventricle).
Ultimately, islands of fibrosis develop in the heart muscle, causing arrhythmias, which can be severe. However, most cases evolve to heart failure, the major cause of mortality in subjects with this disease.
There are primary forms (probably of genetic origin) and secondary forms, caused by the chronic evolution of other conditions (myocardial infarction, myocarditis) or the use of toxic substances.
The term “myocarditis” is used to indicate an inflammation of the heart, usually of infectious or autoimmune origin, which can present either in an acute manner (with fever, tachycardia, dyspnoea, chest pain, ECG abnormalities, pericarditis and pericardial effusion) or in a chronic manner, following acute myocarditis.
Cell necrosis and ventricular wall oedema, which are present in the acute forms, cause arrhythmias, which can be fatal. In the chronic forms, it is the fibrosis, secondary to the inflammatory process, that is highly arrhythmogenic.
Long QT syndrome (LQTS)
This condition is characterised by an abnormal prolongation of the QT interval on the ECG, it has a familial genetic origin and must therefore be distinguished from the forms of long QT interval due to transient causes (electrolyte imbalances, use of certain medicines).
A number of genes have been identified as causing changes in the flow of Potassium (K) and Sodium (Na) inside the cell and form the basis of this syndrome. Diagnosis is formulated on the basis of electrocardiographic and genetic findings.
The elongation of the QT interval causes triggered-activity arrhythmias, which may occur during exertion or when sleeping, depending on the gene responsible for the syndrome. The longer the QT interval, the more severe the syndrome.
This disease is characterised by elevation of the ST segment in the right precordial leads (V1-V3) on the electrocardiogram.
It has a genetic origin and is due to changes in the sodium (Na) channels.
According to the various studies conducted, only a small percentage of cases (approximately 20%) have alterations of the SCN5A gene (the first to be discovered) and other genes have been found to be responsible for the disease, but all of them in very small percentages of patients.
The disease is almost always asymptomatic; however, in particular cases it can cause arrhythmias that can be fatal (ventricular fibrillation).
The reason for such diverse behaviour is not clear, although hypokalaemia and the use of certain medicines undeniably favour arrhythmia.