Lenegre Disease

Lenegre disease, also known as progressive cardiac conduction defect (PCCD), is described as an alteration in the cardiac conduction network [1] [2]. It is believed that this disease is caused by a mutation in the SCN5A gene in combination with age-related degeneration and fibrosis of the His-Purkinje system and its branches [3] [4]. An electrocardiogram (EKG) performed in affected individuals will reveal a conduction delay in the His-Purkinje tissues and varying degrees of arterioventricular (AV) block and differing types of branch block [5] [6]. The cardiac structure and function are typically normal in these patients.

Lenegre disease is considered as one of the most predominant conductive disturbances and is a common cause of pacemaker implantation worldwide. Moreover, it is diagnosed in patients below the age of 50 who have unexplained conduction disease but normal heart structure and likely a family history positive for Lenegre disease [7].

While some patients exhibit no symptoms, others experience dyspnea, lightheadedness, dizziness, abdominal pain, and syncope. As a result of complete AV heart block, complications such as left ventricular dilatation, heart failure, and sudden cardiac death may ensue. The latter commonly occurs in advanced cases of first-degree AV block accompanied by a bi- fascicular block as well as patients with symptomatic AV block. However, pacemaker implantation improves the prognosis significantly.

Patients with the symptoms described above (such as syncope) or incidental EKG findings suggestive of a cardiac conductive defect warrant a thorough evaluation. In addition to ascertaining the personal history, the workup should include a detailed family history of diseases and manifestations such as syncope or sudden death. Patients should also undergo a complete physical exam with a focus on the cardiovascular system. Finally, affected individuals should be assessed with specific studies like electrocardiogram, echocardiogram etc.

Electrocardiogram (EKG)

Findings associated with Lenegre disease include prolonged PR interval, wide QRS complexes, right and/or left bundle branch block, as well as disturbances in other conductive tissues. An exercise stress test in patients with a complete AV block may reveal arrhythmias such as ventricular tachycardia and Torsade de Pointes.

Imaging

An echocardiogram and/or cardiac magnetic resonance imaging (MRI) are performed to assess the contractile function and structure of the heart and to rule out underlying abnormalities such as cardiomyopathy and congenital heart disease [7].

Other

Genetic testing is advised in young individuals with Lenegre disease.

1. Lev M, Kinare SG, Pick A. The pathogenesis of atrioventricular block in coronary disease. Circulation. 1970;42(3):409-25.
2. Lev M, Cuadros H, Milton HP. Interruption of the atrioventricular bundle with congenital atrioventricular block. Circulation. 1971;43(5):703-10.
3. Probst V, Kyndt F, Potet F, Trochu JN, Mialet G, Demolombe S, Schott JJ, Baró I, Escande D, Le Marec H. Haploinsufficiency in combination with aging causes SCN5A-linked hereditary Lenegre disease. J Am Coll Cardiol. 2003; 41(4):643–652.
4. Schott JJ, Alshinawi C, Kyndt F, et al. Cardiac conduction defects associate with mutations in SCN5A. Nat Genet. 1999; 23(1):20–21.
5. Baruteau AE, Probst V, Abriel H. Inherited progressive cardiac conduction disorders. Curr Opin Cardiol. 2015;30(1):33-9.
6. Lev M. The pathology of complete atrioventricular block. Prog Cardiovasc Dis. 1964;6:317-26.
7. Bharati S, Lev M, Dhingra RC, et al. Electrophysiological and pathological correlations in two cases of chronic second degree atrioventricular block with left bundle branch block. Circulation. 1975;52(2):221-9.

• Prevention
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