Persistence of functional atrioventricular accessory pathways in postseptated embryonic avian hearts : Implications for morphogenesis and functional maturation of the cardiac conduction system

During heart development, the ventricular activation sequence changes from a base-to-apex to an apex-to-base pattern. We investigated the possibility of impulse propagation through remnants of atrioventricular (AV) connections in quail hearts. In 86 hearts (group A, HH30-34, n=15; group B, HH35-44,...

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Published in:Circulation (New York, N.Y.) N.Y.), 2007-01, Vol.115 (1), p.17-26
Main Authors: KOLDITZ, Denise P, WIJFFELS, Maurits C. E. F, BLOM, Nico A, VAN DER LAARSE, Arnoud, MARKWALD, Roger R, SCHALIJ, Martin J, GITTENBERGER-DE GROOT, Adriana C
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Blood and lymphatic vessels
Blood coagulation
Bundle of His - embryology
Bundle of His - physiology
Cardiology. Vascular system
Coturnix
Diseases of the peripheral vessels. Diseases of the vena cava. Miscellaneous
Embryonic Development - physiology
Fundamental and applied biological sciences. Psychology
Heart Conduction System - embryology
Heart Conduction System - physiology
Investigative techniques, diagnostic techniques (general aspects)
Lymphatic system
Medical sciences
Morphogenesis - physiology
Vertebrates: cardiovascular system
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Summary:During heart development, the ventricular activation sequence changes from a base-to-apex to an apex-to-base pattern. We investigated the possibility of impulse propagation through remnants of atrioventricular (AV) connections in quail hearts. In 86 hearts (group A, HH30-34, n=15; group B, HH35-44, n=65; group C, 5 to 6 months, n=6) electrodes were positioned at the left atrium, right ventricular base, left ventricular (LV) base, and LV apex. In group A, LV base activation preceded LV apex activation in the majority of cases (60%; 9 of 15), whereas hearts in group B primarily demonstrated an LV apex-to-base activation pattern (72%; 47 of 65). Interestingly, in group B, the right ventricular base (17%; 11 of 65) or LV base (8%; 5 of 65) exhibited premature activation in 25% (16 of 65) of cases, whereas in 26% (17 of 65), the right ventricular base or LV base was activated simultaneously with the LV apex. Morphological analysis confirmed functional data by showing persistent muscular AV connections in embryonic hearts. Interestingly, all myocardial AV connections stained positive for periostin, a nonmyocardial marker. Longitudinal analysis (HH35-44) demonstrated a decrease in both the number of hearts that exhibited premature base activation (P=0.015) and the number (P=0.004) and width (P=0.179) of accessory AV pathways with developmental stage in a similar time course. In the adult quail hearts, accessory myocardial AV pathways were functionally and morphologically absent. Thus, impulse propagation through persistent accessory AV connections remains possible at near-hatching stages (HH44) of development, which may provide a substrate for AV reentrant arrhythmias in perinatal life. Periostin positivity and absence of AV pathways in the adult heart suggest that these connections eventually lose their myocardial phenotype, which implicates ongoing AV ring isolation perinatally and postnatally.
ISSN:0009-7322
1524-4539
DOI:10.1161/CIRCULATIONAHA.106.658807