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Development of Atrioventricular Delay and Insulation in the Murine Heart
Author(s) -
Tallini Yvonne N,
Doran Robert,
Choi BumRak,
Salama Guy,
Kotlikoff Michael
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a313-a
Subject(s) - ventricle , cardiology , medicine , atrium (architecture) , atrioventricular node , electrical conduction system of the heart , atrioventricular canal , sinoatrial node , heart rate , cardiac ventricle , anatomy , electrocardiography , heart disease , tachycardia , atrial fibrillation , blood pressure
The atrioventricular (AV) node delays and insulates conduction of the action potential between the atria and the ventricles, allowing time for filling of the ventricles in the adult heart. In the embryonic tubular two chamber heart, an effective AV delay is observed before a morphologically identifiable AV node. We used conditional cardiac GCaMP2 (ccGC2) Ca 2+ sensor mice to examine the functional maturation of AV delay. At 13.5 dpc the AV delay is shortened from 158 ± 34 ms at 10.5 dpc (n = 6) to 64 ± 7 ms (n = 13) (P<0.001). The differences observed in AV delay between 10.5 dpc and 13.5 dpc are not due to rate changes as there is no statistical difference in heart rates (83 ± 17 beats/min; 76 ± 9 beats/min n=13). In 10.5 dpc mice, atrial excitation wave was conducted directly from the atrium through the AV canal 4–fold slower than atrial wave conduction. After passage through the AV canal (AVC), apical ventricular breakthrough occurred, indicating a connection to the ventricular conduction system occurs at the distal AVC. Spontaneous escape activations initiated in the common ventricle resulted in retrograde transmission of the calcium transient through the AVC and activation of the atria, demonstrating direct atrial and ventricular conduction. From 11.5–13.5 dpc spontaneous retrograde signaling originating in the ventricles was never observed, in several instances electrical pacing of the ventricles induced retrograde signaling in embryonic hearts less than 13.5 dpc. Thus the elimination of myocardial wave transmission through the AVC during septation enables more efficient coordination between atrial and ventricular contractions. Values ± SE. NIH grants HL45239 and DK58795.