Dr.S.Venkatesan MD

AV nodal tissue is a not compact structure as we would be believe  . But it is a fact ,  AV  node  do attempt  to compact after birth.

It is never complete.

Note the islands of his bundle entrapped .   Image source : M. Paz Sua´rez-Mier J Am Coll Cardiol 1998;32:1885–90 From the Section of Histopathology, Institute of Toxicology and †Department of Pathology, La Paz Hospital, Madrid, Spain.

All specialised cells should coalesce  to form the compact zone .This fails to happen in many . Failure of AV nodal compaction  results  in islands of slow conducting cells in around AV node . Some of them can mutate  , and   acquire fast conducting properties as well . (Accessory pathway )

This failure of AV nodal compaction is termed as  persistent fetal dispersion of AV node .

In the his bundle  same phenomenon is called as his bundle  de-fragmentation .These abnormalities are noted in pathological  specimens  of  Pokkuri sudden death in Asians .

Unexplained sudden deaths and instant bradycardias and complete heart blocks are related to these dispersion of  AV nodal cells downstream . This also explains some of patients with infra hisian escape show junctional characteristics.

Many cardiac pathologists have observed this . Still  there is a  missing  link  .

References

M. Paz Sua´rez-Mier,Carlos Gamallo  J Am Coll Cardiol 1998;32:1885–90) Atrioventricular Node Fetal Dispersion and His Bundle Fragmentation  of the Cardiac Conduction System in Sudden Cardiac Death

Kirschner RH, Eckner FAO, Baron RC. The cardiac pathology of sudden,unexplained nocturnal death in Southeast Asian refugees. JAMA 1986;256:2700–5.

Hudson REB. The conducting system: anatomy, histology and pathology in acquired heart disease. In: Silver MD, editor. Cardiovascular Pathology. New York: Churchill Livingstone, 1991:1367– 427.

James TN. Normal variations and pathologic changes in structure of the cardiac conduction system and their functional significance. J Am Coll Cardiol 1985;5:71B– 8B.

James TN, Marshall TK. De Subitaneis Mortibus XVIII. Persistent fetal dispersion of the atrioventricular node and His bundle within the central  fibrous body. Circulation 1976;53:1026 –34.

Persistent Fetal Dispersion of the Atrioventricular Node  Association With the Wolff-Parkinson-White Syndrome Claude Brechenmacher, MD; Jean-Paul Fauchier, MD; Thomas N. James, MD Arch Intern Med. 1980;140(3):377-382.