Dofetilide is a well-tolerated antiarrhythmic drug with a high conversion rate of AF to sinus rhythm. One third of patients maintained sinus rhythm at 1 year. Proarrhythmia can occur and initiation of therapy must be performed in-hospital.

Although morphologic findings in many of the cardiac arrhythmias of acute and chronic disease have been elusive, the correlates of heart block (particularly atrioventricular block) are abundant. Pathologic features of sinoatrial, atrioventricular, and bundle-branch block are reviewed. Lev and Lenegre diseases (idiopathic bilateral bundle-branch fibrosis) are also reviewed.

Normal anatomic and histologic features of the atrioventricular junction (transitional cell zone, atrioventricular node, penetrating portion of bundle) and the bifurcation of the penetrating portion into bundle branches are reviewed. Terminal ventricular Purkinje fibers are also discussed.

Summary: Metastatic tumor involvement of the heart as a basis for the genesis of various cardiac arrhythrmas is reviewed. The morphologic basis of pre-excitation syndromes and right ventricular dysplasia are also reviewed.

Normal anatomic and histologic features of the sinus node, atrial myocardium, and interatrial conduction of the cardiac impulse are reviewed. The controversy surrounding atrial conduction via specialized atrial cells versus specific internodal tracts (between sinus and atrioventricular nodes) is discussed.