Progressive familial heart block type I (PFHBI, PFHB1) is an autosomal dominant cardiac bundle branch disorder that may progress to complete heart block (Brink and Torrington, 1977; van der Merwe et al., 1986; van der Merwe et al., ... Progressive familial heart block type I (PFHBI, PFHB1) is an autosomal dominant cardiac bundle branch disorder that may progress to complete heart block (Brink and Torrington, 1977; van der Merwe et al., 1986; van der Merwe et al., 1988). It is defined on electrocardiogram by evidence of bundle branch disease, i.e., right bundle branch block, left anterior or posterior hemiblock, or complete heart block, with broad QRS complexes. Progression has been shown from a normal electrocardiogram to right bundle branch block and from the latter to complete heart block. These electrocardiographic features differentiate PFHB type I from progressive familial heart block type II (PFHBII, PFHB2; 140400), in which the onset of complete heart block is associated with narrow complexes. Electrocardiographically the changes represent, respectively, bundle branch disease (PFHB1) and atrioventricular nodal disease with an atrioventricular block and an idionodal escape rhythm (PFHB2). PFHBI is manifested symptomatically when complete heart block supervenes, either with dyspnea, syncopal episodes, or sudden death. Treatment, which is best managed by regular electrocardiographic follow-up, is by the timely implantation of a pacemaker (Brink et al., 1995). - Genetic Heterogeneity of Progressive Familial Heart Block Type I Progressive familial heart block type IB (PFHB1B; 604559) is caused by mutation in the TRPM4 gene (606936) on chromosome 19q13.32.
Progressive cardiac conduction defect (PCCD), also called Lenegre-Lev disease (Lenegre, 1964; Lev et al., 1970), is one of the most common cardiac conduction disturbances. It is characterized by progressive alteration of cardiac conduction through the His-Purkinje system with ... Progressive cardiac conduction defect (PCCD), also called Lenegre-Lev disease (Lenegre, 1964; Lev et al., 1970), is one of the most common cardiac conduction disturbances. It is characterized by progressive alteration of cardiac conduction through the His-Purkinje system with right or left bundle branch block and widening of QRS complexes, leading to complete atrioventricular block and causing syncope and sudden death. It represents the major cause of pacemaker implantation in the world (0.15 implantations per 1,000 inhabitants per year in developed countries). PCCD is considered a primary degenerative disease or an exaggerated aging process with sclerosis affecting only the conduction tissue. DeForest (1956) studied a kindred in which uncomplicated left bundle branch block occurred in 4 persons in 2 generations. Segall (1961) described an instance of father, son, and daughter (of French-Canadian and black intermixture) with right bundle branch block (RBBB) and repeated Stokes-Adams attacks with various atrial arrhythmias and ventricular extrasystoles. The father died at 74 years, 14 years after the first fainting episode. Two asymptomatic brothers showed the electrocardiographic changes of Wolff-Parkinson-White. Combrink et al. (1962) described a South African family in which the mother had RBBB and died at age 35 years in a Stokes-Adams attack. Of 4 children, 3 had RBBB. The mother's parents had both died suddenly in their 30s. One of her brothers was said to have a cardiac conduction disturbance, another had dextrocardia, while 3 other sibs were apparently normal. Follow-up of this kindred revealed RBBB in 1 of 7 grandchildren (Myburgh et al., 1980). Steenkamp (1972) described a South African family in which 6 of 17 members studied showed disturbance of rhythm or conduction. Brink and Torrington (1977) suggested that the disorder they referred to as progressive familial heart block type I is prevalent in South Africa and is the same disorder as that reported by Combrink et al. (1962) and Steenkamp (1972). Type I heart block in their description tends to have the pattern of a right bundle branch block and/or left anterior hemiblock, manifesting clinically when complete heart block supervenes with syncopal episodes, Stokes-Adams seizures, or sudden death. The risk to life appeared to be greatest at or soon after birth, during puberty and the early twenties, and again toward middle age. Greenspahn et al. (1976) presented evidence suggesting that a susceptibility to disorder in conduction that is expressed late in life is inherited. Lorber et al. (1988) observed a father and 2 sons with an electrocardiographic pattern of pseudo left posterior hemiblock and incomplete right bundle branch block that resulted in right axis deviation. Husson et al. (1973) reported a family in which a girl had complete heart block at age 2 years and died at age 10 with ventricular fibrillation. A brother had right bundle branch block at age 15 years and complete heart block at age 17. A sister, aged 17 years, had prolonged intraventricular conduction time with incomplete right bundle branch block. In this family, complete heart block and bundle branch block were expressions of the same genotype.
In a French family with Lenegre-Lev disease, Schott et al. (1999) excluded linkage to the cardiac conduction defect locus on chromosome 19 and to other loci for inherited cardiac diseases associated with conduction defects. Because of the potential ... In a French family with Lenegre-Lev disease, Schott et al. (1999) excluded linkage to the cardiac conduction defect locus on chromosome 19 and to other loci for inherited cardiac diseases associated with conduction defects. Because of the potential role of the sodium current in the infranodal conduction of the cardiac impulse, Schott et al. (1999) analyzed the SCN5A gene and identified a splice site mutation (600163.0009) in affected members of the French family. In a Dutch family with congenital nonprogressive conduction defect, Schott et al. (1999) identified a deletion in the SCN5A gene (600163.0010). The authors suggested that, depending on the consequences of a mutation on the sodium channel characteristics, the resulting phenotype may be progressive or intermediate.