Pathologic reports and animal models of congenital complete AV block(CCAVB) suggest that the sinus node may be affected in this disease. Assessment of chronotropic competence of the sinus node has not been performed in large numbers of patients with CCAVB. Demonstration of chronotropic competence of the sinus node in these patients would influence the choice of pacing device, application and mode (VDD vs DDDR). METHODS: To assess the chronotropic competence of the sinus node, we evaluated the intrinsic atrial rate at peak exercise during Bruce treadmill exercise tests in 27 CCAVB patients (59% female) age 12.2±3.3 years and compared them to published normal data. RESULTS: The data summarised below indicate that normal atrial rate response to exercise testing was present in 24/27 patients (89%), but 3/27 (11%) demonstrated atrial chronotropic incompetence. CONCLUSION: Although the majority of patients with CCAVB show an appropriate atrial rate response to exercise, it remains important to evaluate the chronotropic competence of the sinus node prior to deciding on the specific pacemaker therapy they require. In the majority a VDD system would suffice. Figure

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