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Isolated congenitally complete heart block attributable to combined nodoventricular and intraventricular
1Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, Shatin, Hong Kong.
Insights
Intraventricular discontinuity, a rare cause of congenital heart block, often co-exists with nodoventricular discontinuity. This condition can be sporadic, familial, or linked to maternal anti-Ro antibodies.
Area of Science:
- Cardiology
- Pathology
- Pediatrics
Background:
- Congenitally complete heart block (CCHB) is categorized into three main pathological types: atrial-axis, nodoventricular, and intraventricular discontinuity.
- Intraventricular discontinuity is exceptionally rare, with limited prior case reports.
Observation:
- This study histopathologically analyzed the cardiac conduction systems of two CCHB cases: a neonate and an 8-year-old girl.
- Both cases presented a combination of nodoventricular and intraventricular discontinuity, with significant absence of key conduction pathways.
Findings:
- Unlike typical atrial-axis discontinuity, the sinoatrial and atrioventricular nodes were normal in both cases.
- Intraventricular discontinuity co-occurred with nodoventricular discontinuity, differing from previously reported isolated cases.
- Etiologies varied, including sporadic occurrence, familial links, and association with positive maternal serum anti-Ro antibodies.
Implications:
- This research highlights the rarity and specific pathological features of intraventricular discontinuity in CCHB.
- Understanding these distinct patterns is crucial for accurate diagnosis and management of CCHB.
- The findings contribute to the knowledge of CCHB's diverse etiologies, including genetic and autoimmune factors.
Abstract:
Intraventricular together with atrial-axis and nodoventricular discontinuity, in which various parts of the conduction system are replaced by fibrous or fatty tissue, constitute the three major pathological categories of isolated congenitally complete heart block. Intraventricular discontinuity is distinctly rare, with only two previous cases reported in the literature, one of which was associated with a familial history of heart block. The cardiac conduction systems of two cases of isolated congenitally complete heart block were serially sectioned and analyzed histopathologically. The findings were correlated with the clinical features, in particular, the family histories and maternal serum anti-Ro antibodies. Both cases, a 9-day-old neonate and an 8-year-old schoolgirl, showed a combination of nodoventricular and intraventricular discontinuity, with absence of the atrioventricular penetrating bundle, the entire right, and the proximal portion of the left bundle branch. The branching bundle was absent in the first case and replaced by fatty tissue in the second. In contrast to the commoner atrial-axis discontinuity in which the atrioventricular node itself is usually replaced by fibrous or fatty tissue with variable involvement distally, the sinus node, and in particular, the atrioventricular node were normal in both of our cases. There was no family history in either case, whereas tests for the maternal serum anti-Ro antibody were positive in the first but negative in the second case. Intraventricular discontinuity as a cause of isolated congenitally complete heart block is very rare. In our cases, it co-existed with nodoventricular discontinuity. It can be sporadic, familial, or associated with positive maternal serum anti-Ro antibodies.