Key result
Autonomic blockade demonstrated that A-V nodal block is mainly related to intrinsic A-V node disease in patients with organic heart disease, but to autonomic alterations in those without (P<0.001).
Why the study?
Does autonomic blockade alter A-V nodal conduction parameters in patients with first and second degree A-V nodal block?
Does autonomic blockade alter A-V nodal conduction parameters in patients with first and second degree A-V nodal block?
In patients with first and second degree A-V block, conduction disturbances are primarily related to intrinsic A-V node involvement in those with organic heart disease, but to autonomic alterations in those without underlying heart disease.
May guide etiology-specific AV block evaluation; hypothesis-generating before practice change.
Thirty-four patients with a prolonged A-H interval (group I) and 26 with A-V nodal Wenckebach block (group II) were studied in the basal state and after autonomic blockade (propranolol 0.2 mg kg-1 and atropine 0.04 mg kg-1 in order to assess the role of autonomic system in A-V nodal conduction disturbances. In group I, the A-H intervals did not change significantly after autonomic blockade, whereas pacing cycle length for Wenckebach block, effective and functional refractory periods of the A-V node decreased significantly (P less than 0.05). In the 22 patients with organic heart disease these variables did not change significantly after autonomic blockade, whereas in the 12 without underlying heart disease, they decreased in all cases (P less than 0.001). In the former, the variables of intrinsic A-V nodal conduction were normal in only 9% of patients, whereas in the latter they were normal in 66%. Also in group II, the intrinsic A-H intervals were normal in only 6% of patients with cardiac disease but were normal in 63% without underlying heart disease. These data suggest that in the patients with first and second degree A-V nodal block and organic heart disease, the conduction disturbance is predominantly related to intrinsic involvement of A-V node, whereas in the subjects without underlying heart disease the A-V nodal blocks appear mainly related to autonomic alterations.
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Alboni et al. (1986) studied First and second degree atrio-ventricular nodal block (n=60). Autonomic blockade (propranolol and atropine) vs. Basal state was evaluated on Changes in A-V nodal conduction variables (A-H interval, pacing cycle length, refractory periods) (p=<0.05). Autonomic blockade demonstrated that A-V nodal block is mainly related to intrinsic A-V node disease in patients with organic heart disease, but to autonomic alterations in those without (P<0.001).
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