cardiac conduction defect, any impairment of the electrical pathways and specialized muscular fibers that conduct impulses through the heart and result in atrial and ventricular contraction. Conduction defects may develop between the sinus and atrioventricular (AV) nodes, between the sinus node and the AV bundle, or within the AV bundle or the left or right bundle branches. Defective transmission of cardiac impulses may be caused by ischemia, necrosis, drugs, electrolyte disturbances, or trauma. See also heart block.
