Moderately to markedly dilated human atria exhibited slow response action potentials and longer P wave duration (111 vs 89 msec, P<0.005) compared to normal or slightly dilated atria.
Observational (n=22)
How do the electrophysiologic properties and responses to verapamil and procainamide differ between normal and diseased human atrial fibers?
Diseased human atrial fibers exhibit slow response action potentials and altered responses to antiarrhythmic agents compared to normal fibers, providing mechanistic insights into atrial arrhythmias.
Absolute Event Rate: 111% vs 89%
p-value: p=<0.005
We used standard microelectrode techniques to record action potentials of human right atrial fibers obtained during cardiac surgery, and correlated these potentials with clinical and preoperative ECG data. Human atrial fibers were classified as follows: Group A (ten patients) had a maximum diastolic potential (MDP) of -71.4 +/- 5.1mV (mean +/- SD), and action potentials that were primarily fast responses. These atria were normal or slightly dilated. In group B (12 patients) MDP was 50.3 +/- 5.7 mV; action potentials were slow responses and the atria were moderately to markedly dilated. Atrial arrhythmias occurred in four group B and no group A patients. The ECG revealed a signficant difference (P less than 0.005) in P wave duration: group A, 89 +/- 3.0 msec; group B, 111 +/- 6.0 msec. Verapamil, 0.1 mg/L, markedly depressed only the action potential plateau of group A. Procainamide 1-100 mg/L had equivalent effects on fibers of both groups A and B, effects which were small at dosages of less than 40 mg/L. Procainamide did not depress slow response automaticity, but verapamil (0.1-1 mg/L) did.
Hordof et al. (1976) conducted an observational in Diseased human atria (n=22). Verapamil and Procainamide (in vitro) vs. Normal or slightly dilated atria (Group A) was evaluated on P wave duration (p=<0.005). Moderately to markedly dilated human atria exhibited slow response action potentials and longer P wave duration (111 vs 89 msec, P<0.005) compared to normal or slightly dilated atria.