Definition
Inherited Cardiac Conditions (ICC) refers to a group of conditions caused by monogenetic changes (that is, caused by changes in just 1 or very few genes) that affect the heart, its conducting system and muscle structure.
Prevalence
There is, currently, a lack of epidemiological statistics on ICC but estimates put the prevalence at 500:10,000 (see individual conditions described below.)
Inherited Cardiac Conditions:
- heart muscle conditions which affect the heart muscle and rhythm (cardiomyopathies)
- heart rhythm conditions which cause problems with the heart rate and rhythm (arrhythmias)
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Heart Muscle Conditions
- Hypertrophic cardiomyopathy (HCM): Unexplained ventricular hypertrophy in a non-dilated ventricle. Prevalence c.1:500, making it one of the more common ICCs.
- Familial dilated cardiomyopathy: Characterised by ventricular enlargement and systolic dysfunction. Estimated prevalence is between 1:250-1:500.
- Arrythmogenic right ventricular cardiomyopathy (ARVC): Prevalence 1:1,000-1:1,250. The walls of the right ventricle have dysplasia (thin and stretched). Important cause of Sudden Cardiac Death (SCD).
- Left Ventricular noncompactation cardiomyopathy (LVNC): This is characterised by a “spongy myocardium”, with a thin, compacted epicardial layer and a noncompacted endocardial layer with trabeculations and recesses. The exact prevalence of LVNC is not known but improvements in diagnostic and imaging technology means more cases are being diagnosed.
Heart Rhythm conditions
- Long QT syndrome (LQTS): Disorder of ventricular repolarisation. Characterised by a prolonged QT interval on ECG and a predisposition to cardiac arrhythmia, syncope and sudden death. Estimated prevalence of 1:2,000.
- Brugada syndrome (BrS): Characterised by abnormal ECG, an increased risk of ventricular arrhythmia and sudden death, Prevalence of about 1:2,000.
- Catecholaminergic polymorphic ventricular tachycardia (CPVT): Disorder where there is ventricular tachycardia triggered by the adrenergic nervous system. Estimated prevalence is about 1:10,000.
- Sudden arrhythmic cardiac death syndrome (SADS): Most cases of SADS are the result of inherited cardiac ion channel abnormalities of the heart which predispose individuals to fatal arrhythmias. These include the 3 conditions listed above.
Pulse point
One genetic cardiac condition which does not fall into either of the 2 categories above is Familial Hypercholesterolaemia. This is caused by genetic mutations in one of the 3 genes that control the uptake of cholesterol in the bloodstream, leading to very high blood levels of cholesterol and low density lipoprotein (LDP). This, in turn, leads to a high risk of early onset coronary atherosclerosis and heart disease.
