[Correction of rate and structure of ventricular rhythm in permanent atrial fibrillation: a novel pathogenetic approach].

Aim: To analyze action of digoxin and some non-digitalis drugs (beta-blockers, verapamil, amiodarone, d,l-sotalol) and their combinations on electrical activity of atria, frequency and structure of ventricular rhythm in patients with permanent atrial fibrillation.

Material And Methods: One hundred patients with permanent atrial fibrillation and heart rate at rest above 80 bpm were divided into 9 treatment groups. High-resolution orthogonal Frank lead ECG was recorded before and after allocated treatment. Analysis included construction of ff-waves periodograms, histograms of RR interval, cardiointervalograms and application of autocorrelation function.

Results: It was demonstrated that frequency and form (structure) of ventricular rhythm was determined not only by the state of AV conduction but also by value of basic period of ff-waves. The mechanisms of ventricular rate deceleration by investigated drugs were not identical. beta-blockers and verapamil directly slowed AV conduction without changing parameters of ff-waves and differed from each other only in action on parameters of concealed conduction in AV node. Action of digoxin in patients with ff-waves period equal to or exceeding 0,15 s was biphasic. During phase I shortening of ff-wave period (by 0.025+/-0.012 s) occurred. This was associated with increase of their concealed conduction through AV node. The latter phenomenon represented independent mechanism of ventricular rhythm deceleration. During phase II of digoxin action direct inhibition of AV conduction took place. Amiodarone and d,l-sotalol increased basic ff-waves period. This facilitated their conduction through AV node. Greater heart rate slowing effect of d,l-sotalol was attributed to its ability to augment concealed conduction. Due to their antiarrhythmic qualities amiodarone and d,l-sotalol slowed heart rate in patients with peak RR duration in the region of 0.28-0.46 s. These patients often had bi- and tri-modal structure of interval RR histogram. Changes of ventricular rhythm structure during use of various drugs were different. Action of digoxin was most whilst that of beta-blockers least favorable.

Conclusion: Choice of a drug for treatment of permanent atrial fibrillation should be conducted with consideration of ff-waves periodicity, parameters of RR interval histogram, and characteristics of ventricular rhythm structure.