Tachycardia Induced Electrical Remodeling of the Atria and the Autonomic Nervous System in Goats

Abstract

Atrial fibrillation (AF) shortens the atrial effective refractory period (AERP). To investigate the role of the autonomic nervous system during this so-called electrical remodeling of the atria (ERA) and during recovery from ERA we analyzed heart rate variability (HRV). In 12 goats atrioventricular (300:150 beats/min) pacing was performed for 24 hours, interrupted at 4, 8, 16, and 24 hours for recording of 500 atrial (AA) intervals during sinus rhythm and measurement of the AERP(430ms) at 7.4 +/- 0.6 sites. After 24 hours, pacing was stopped and the electrophysiological study and recording of the AA intervals was repeated at 4, 8, 16, and 24 hours after cessation of pacing. Time- and frequency-domain parameters were computed from each 500 AA interval recording. After 24 hours of rapid pacing the AERP had shortened significantly (147 +/- 5.6 to 102+/- 6.4 ms, P < 0.0001). No significant changes in HRV and dispersion of refractoriness (AAERP) (47 +/- 7.1 to 44 +/- 4.2 ms) were observed. After cessation of pacing, the AERP prolonged again (102 +/-6.4 to 135+/-8.8 ms, P < 0.0001) and was paralleled by a significant increase in AAERP (44 +/- 4.2 to 63+/- 7.1 ms, P = 0.01). Furthermore, HRV increased significantly. At each time point an inverse relation between the logarithmically transformed vagal parameter HF (InHF) and AERP was observed. We calculated the mean InHF for each goat using all time points and used the median value to divide the 12 goats into high and low vagal tone groups. We compared the degree of ERA and recovery from ERA for both groups. The AERP shortened 47.4 +/- 6.5 versus 43.0+/-5.0 ms (NS) for goats with high and low vagal tone, respectively. During recovery from ERA the AERP lengthened 23.6 +/- 4.0 versus 42.5 +/- 1.7 ms (P = 0.001) for goats with high and low vagal tone, respectively. Multivariate regression analysis indicated a short AERP as the single independent determinant of the inducibility of AF during ERA and recovery from ERA (P < 0.0001). During recovery from ERA, the AERP prolonged and vagal tone and AAERP increased. A high vagal tone during recovery from ERA was associated with a short AERP and an attenuated recovery of ERA.

Rapid fluctuations in atrial fibrillatory electrophysiology detected during controlled respiration

“…All patients had long durations of AF; thus, by present understanding, electrical remodeling would be expected to be "complete" (4,13). The degree of spectral power shift to 0.125 Hz with controlled respiration was variable.…”

Morphological Properties of Atrial Fibrillation Waves in Patients with Left Ventricular Dysfunction—Spectral Analysis of Atrial Fibrillation Waves in Dilated Cardiomyopathy—

“…[8][9][10][11] Although electrical remodeling is considered to occur even in clinical cases, little is known about this phenomenon, mainly because of the technical limitation in measuring the atrial effective refractory period (ERP). Measurement of ERP using premature stimulus via a catheter is the standard method, but it is invasive and it is impossible to evaluate the ERP during AF.…”

“…Although several experimental reports documented the shortening of atrial ERP under continuous rapid atrial activation, i.e., AF, [8][9][10][11] other studies reported no change in ERP in heart failure. Li et al studied the effect of rapid atrial pacing on atrial ERP in heart failure, and reported that the atrial ERP and wavelength were not affected by rapid pacing, whereas they were significantly shortened by rapid pacing in patients without heart failure.…”

“…[4][5][6][7] As determinants for the reentry, the myocardial refractory period plays a key role, and electrical remodeling, i.e., the shortening of the atrial refractory period due to AF, is considered to exaggerate the AF itself. [8][9][10][11] In contrast, several investigators have reported a prolongation of, or no change in, the atrial electrophysiological properties (e.g., action potential duration) in heart failure cases, 12,13) probably due to the down-regulation of several potassium channels. 13) Therefore, it is unclear whether the atrial refractoriness would be prolonged or shortened in cases with AF and LV dysfunction because LV dysfunction and AF can exaggerate each other.…”

Monitoring the Progression of the Atrial Electrical Remodeling in Patients With Paroxysmal Atrial Fibrillation. Analysis of the f-f Interval During Ambulatory ECG Monitoring.

“…[2][3][4][5][6][7] This phenomenon leads to the shortening of the wavelength and results in the promotion of both the initiation and maintenance of AF. Electrical remodeling is considered to contribute to the PAF in clinical cases.…”