Mechanisms of inherited cardiac conduction disease.

Cardiac conduction disease (CCD) is a serious disorder of the heart. The pathophysiological mechanisms underlying CCD are diverse. In the last decade the genes responsible for several inherited cardiac diseases associated with CCD have been identified. If CCD is of an inherited nature (ICCD), its underlying mechanism can be either structural, functional or there can be overlap between these two mechanisms. If ICCD is structural in nature, it is often secondary to anatomical or histological abnormalities of the heart. Functional ICCD is frequently found as a "primary electrical disease" of the heart, i.e. resulting from functionally abnormal, or absent proteins encoded by mutated genes, often cardiac ion channel proteins involved in impulse formation. It can thus be hypothesised that patients with inherited structural or functional ICCD suffer from fundamentally different diseases. It is worthwhile to consider this hypothesis, since it could have implications for diagnosis, treatment, prognosis and, possibly, for the patient's relatives. In this review we aim to find evidence for the idea that functional and structural ICCD are fundamentally different diseases and, if so, whether this has diagnostic and clinical consequences.