Susceptibility of the right and left canine atria to fibrillation in hyperglycemia and hypoglycemia.

The objective of this study was to investigate the changes in the refractory period and in the susceptibility to fibrillation of canine atria associated with different levels of glycemia, and the differences in these parameters between the two atria. In 20 anesthetized, open-chest dogs weighing 24 kg, the effective refractory period was measured by atrial pacing with a run of 8 stimuli (S1-S1 350 ms) followed by a progressively earlier S2 until no stimulation of the atrial tissue occurred. The susceptibility to fibrillation was assessed by applying DC at 2, 3, and 4 V for 3 seconds, 7 times each, on the atrial appendage. If fibrillation occurred and persisted for 3 minutes, a transthoracic synchronized shock was delivered (200 J). The refractory period and the susceptibility to fibrillation were assessed under normoglycemia first, and then under hypo and hyperglycemia, in the right and left atrium successively, in random order. The incidence of induced atrial fibrillation in the right atrium was: hypoglycemia 31.96% (132 of 413 attempts); normoglycemia 24.11% (81 of 336; p < 0.05); and hyperglycemia 20.23% (85 of 420). Results for the left atrium were hypoglycemia 52.06% (215 of 413); normoglycemia 40.18% (135 of 336; p < 0.005); and hyperglycemia 32.86% (138 of 420; p < 0.05). Sustained atrial fibrillation (> 3 minutes) occurred significantly more often under hypo rather than hyperglycemia and stimulated the left rather than the right atrium. The refractory period was shortest under hypoglycemia in the left atrium and longest under normo or hyperglycemia in the right atrium.(ABSTRACT TRUNCATED AT 250 WORDS)