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To the Editor:

We agree with Dr. Hübscher that the distinction between congenital HB (CHB) and acquired isolated HB has been (and still is) somewhat confusing. We have defined isolated HB as the absence of intracardiac anatomic malformations considered to be causally related to HB (1). Cardiac malformations included in our present study were hemodynamically insignificant muscular ventricular septal defect, secundum atrial septal defect, patent ductus arteriosus, mild-degree pulmonary valve stenosis, and mild-to-moderate mitral valve regurgitation. CHB was defined as HB diagnosed during pregnancy or at birth; all children had complete HB.

Isolated CHB using the above definitions is practically always associated with antibodies to SSA/Ro and/or SSB/La (2). Pathologic studies suggest that these antibodies cross the placenta and damage the fetal conduction system by fibro-fatty replacement of the atrial connections to the atrioventricular node. However, there are rare cases of seronegative isolated CHB, which may be caused by mass lesions of the conducting system, e.g., fibroma, rhabdomyoma, or hemangioma of the atrial cavity (3).

What is the etiology and pathogenesis of isolated HB diagnosed after the newborn period but before the age of 16 years? We suspect, as Hübscher et al point out in their study (4), that most of the cases previously diagnosed in early infancy are congenital, and this is explained by failure to make the diagnosis during pregnancy. Nowadays, however, late detection of isolated CHB is rare because of the wide use of fetal ultrasound examinations. Another explanation for late detection of isolated CHB is the possible progression of first- or second-degree HB to third degree after birth (5) (one such case was also noted in our series). In addition, there are reports of dilated cardiomyopathy developing after birth as a manifestation of neonatal lupus (1, 6). The above findings are interesting and suggest an ongoing immunologic injury in selected affected hearts.

Data on the etiopathogenesis of truly acquired isolated HB in children are limited. There are occasional reports of atrioventricular block associated with myocarditis, endocarditis, inherited or acquired collagen diseases, different medications, and rare environmental exposures (7).

In our present study, there were 54 children (and their mothers) with isolated HB diagnosed after the newborn period but before the age of 16 years. Some mothers of these children had clinical features suggesting an underlying autoimmune disease. In the majority of the cases, however, we could not find any overt etiology or explanation for the HB in these children during the clinical followup or by examining the hospital case records. In 16 of the 54 children, the HB was diagnosed between 0 and 1 years of age, in 27 children between 1 and 5 years of age, and in 11 children after the age of 5 but before the age of 16. Forty-eight of the mothers of the 54 children are still alive. We hope that the determination of antibodies to SSA/Ro and SSB/La in these mothers could add to our understanding of the etiopathogenesis of isolated “acquired” HB.

REFERENCES

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  • 1
    Eronen M, Siren MK, Ekblad H, Tikanoja T, Julkunen H, Paavilainen T. Short and long-term outcome of the children with isolated congenital complete heart block diagnosed in utero or as newborn. Pediatrics 2000; 106: 8691.
  • 2
    Julkunen H, Kurki P, Kaaja R, Heikkilä R, Immonen I, Chan EKL, et al. Isolated congenital heart block: longterm outcome of mothers and characterization of the immune response to SS-A/Ro and SS-B/La. Arthritis Rheum 1993; 36: 158898.
  • 3
    Allan L, Hornberger L, Sharland G. Fetal cardiac tumors. In: Textbook of fetal cardiology. London: Greenwich Medical Media Limited; 2000. p. 35865.
  • 4
    Hubscher O, Batista N, Rivero S, Marletta C, Arriagada M, Boire G, et al. Clinical and serological identification of 2 forms of complete heart block in children. J Rheumatol 1995; 22: 13525.
  • 5
    McCarron DP, Hellmann DB, Traill TA, Watson RM. Neonatal lupus erythematosus syndrome: late detection of isolated heart block. J Rheumatol 1993; 20: 12124.
  • 6
    Taylor-Albert E, Reichlin M, Toews WH, Overholt ED, Lee LA. Delayed dilated cardiomyopathy as a manifestation of neonatal lupus: case reports, antibody analysis, and management. Pediatrics 1997; 99: 7335.
  • 7
    Bharati S, Lev M. Pathology of atrioventricular block. Cardiovasc Clin 1984; 2: 74151.

Heikki Julkunen MD*, Marianne Eronen MD†, * Peijas Hospital Helsinki University Hospital Vantaa, Finland, † Hospital for Children and Adolescents Helsinki University Hospital Helsinki, Finland