Increase in heart rate after radiofrequency catheter ablation is mediated by parasympathetic nervous withdrawal and related to site of ablation

Evaluation of cardiac functions after catheter ablation of atrioventricular nodal reentrant tachycardia

Background/aim

Radiofrequency catheter ablation (RFA) is the most effective method of supraventricular tachycardia therapy. Recurrent supraventricular tachycardia causes systolic dysfunction and dilated cardiomyopathy. The aim of this study was to evaluate the long-term alterations of atrial and ventricular functions after RFAof typical atrioventricular nodal reentrant tachycardia (AVNRT).

Materials and methods

This cross-sectional study included 55 consecutive patients with symptomatic drug-resistant AVNRT who had had an invasive electrophysiology study and RFA. Speckle-tracking–based echocardiographic assessment was performed shortly before and 1 year after the operation. Left ventricle (LV) and right ventricle (RV) peak systolic strain (PSS) and atrial strain measurements were performed.

Results

RFA successfully eliminatedtachyarrhythmia in all patients. LV apical 4-chamber PSS –20.8% (–24.7 to –16.0) vs. –22.8% (–26.6 to –17.0, P < 0.001), LV apical 2-chamber PSS –21.5% (–26.8 to –10.1) vs. –22.0% (–27.8 to –13.7, P < 0.001), LV global PSS –20.4% (–26.4 to –14.4) vs. –23.0% (–27.1 to –2.3, P < 0.001), RV global PSS –26.0% (–30.0 to –18.0) vs. –26.5% (–32.1 to –19.7, P < 0.001), and peak left atrial longitudinal strain 41.0% (19.0–71.8) vs. 54.0% (25.6–82.0, P < 0.001) were significantly improved 1 year after RFA.

Conclusion

RFA of AVNRT not only provides relief of palpitations but also improves cardiac functions.

Potential usage of cardioneuroablation in vagally mediated functional atrioventricular block

An increase in parasympathetic tone may be the main cause of some transient or permanent atrioventricular block cases. Some of these patients, defined as vagally mediated functional atrioventricular block, may be severely symptomatic and refractory to conventional therapies and may necessitate cardiac pacing. Cardioneuroablation is a relatively new strategy for management of patients with excessive vagal activation based on radiofrequency catheter ablation of main ganglionated plexi around the heart. Present review was dedicated to discuss potential usage of cardioneuroablation in patients with vagally mediated functional atrioventricular block.

Stepwise Approach to the Different Parts of Vasovagal Syncope in a Patient Undergoing Cardioneuro Ablation

A 30-year-old man underwent ganglionated plexi ablation due to cardioinhibitory type vasovagal syncope with asystole. After asymptomatic period of 15-month following the procedure, the patient experienced 2 new syncope episodes. Tilt test demonstrated vasodepressor response without significant bradycardia. Following the onset of midodrine therapy, the patient was asymptomatic for 1 year and tilt test demonstrate normal response.

Prognosis of high sinus heart rate after catheter ablation for atrial fibrillation

Aims

Although atrial fibrillation (AF) catheter ablation increases sinus heart rate (HR), its mechanism and prognosis have not yet been clearly elucidated. We hypothesize that post-AF ablation high sinus HR (PA-HSR) is associated with a better clinical outcome of AF ablation without adverse cardiac effects.

Methods and results

We studied 991 AF patients (75% male, 58 ± 11 years old, 70% paroxysmal AF) with HR variability (HRV) at 3 months and 1 year after catheter ablation, and pre- and post-1-year echocardiograms. Post-AF ablation high sinus HR was defined as an average HR greater than 2 SD (≥92 bpm) as measured by 24 h Holter. (1) Average HR increased significantly (P< 0.001), and PA-HSR was observed in 28 patients (2.8%) 3 months after AF ablation. At 1 year after catheter ablation, 21% were taking β-blockers and 36% maintained an average HR of ≥92 bpm. (2) Post-AF ablation high sinus HR was independently associated with pre-procedural high average HR (OR 1.097; 95% CI 1.029-1.169, P= 0.005), high left atrium (LA) electrogram voltage (OR 3.545; 95% CI 1.183-10.618, P= 0.024), and reduced root mean square of differences between successive NN intervals (rMSSD) at 3 months HRV (OR 0.959; 95% CI 0.919-0.999, P= 0.047). (3) At 1 year echocardiography, size reduction of LA (P= 0.055) or LV (P= 0.372) and the improvement in ejection fraction (P= 0.529) were not significantly different between patients with PA-HSR and those without. (4) Throughout 27 ± 17 months of follow-up, patients with PA-HSR showed significantly lower clinical recurrence than those without (log rank, P= 0.020).

Conclusion

Post-AF ablation high sinus HR was observed in patients with smaller LA size and higher LA electrogram voltage and significant vagal modulation without adverse cardiac effects. Post-AF ablation high sinus HR was associated with a significantly lower clinical recurrence of AF after catheter ablation.

Shortening of the atrial-His bundle interval during atrial pacing as a predictor of successful ablation for typical atrioventricular nodal re-entrant tachycardia

Aims

Shortening of the atrial-His bundle (AH) interval during the sinus rhythm is occasionally observed after slow pathway ablation for atrioventricular nodal re-entrant tachycardia (AVNRT). In addition, high-rate atrial pacing is useful for avoiding atrioventricular block. We hypothesized that shortening of the AH interval during slow pathway ablation under high-rate atrial pacing would lead to successful ablation of typical AVNRT.

Methods and results

This retrospective study included 37 patients in whom successful ablation of typical AVNRT was performed under atrial pacing. The AH interval was measured immediately before the first radiofrequency (RF) application and immediately after the last RF application, prior to the first induction. Twenty-five of 37 patients achieved procedural success at the first induction (i.e. successful group). No patients developed a prolonged AH interval or atrioventricular block. The AH interval was shortened by an average of 14.6 ± 7.7 and 1.8 ± 1.2 ms in the successful and other patient groups, respectively (P < 0.01). An AH interval decrease of > 10 ms was observed in 23 of 27 (85%) patients in the successful group, whereas all other patients had an AH interval decrease of < 5 ms.

Conclusion

Shortening of the AH interval during high-rate atrial pacing is a predictor of the successful ablation for typical AVNRT.

Atrioventricular Node Slow-Pathway Ablation Reduces Atrial Fibrillation Inducibility: A Neuronal Mechanism

BACKGROUND

Radiofrequency ablation (RFA) for atrioventricular nodal reentrant tachycardia appears to reduce atrial tachycardia, which might relate to parasympathetic denervation at cardiac ganglionated plexuses.

METHODS AND RESULTS

Compared to 7 control canines without RFA, in 14 canines, RFA at the bottom of Koch's triangle attenuated vagal stimulation-induced effective refractory periods prolongation in atrioventricular nodal and discontinuous atrioventricular conduction curves but had no effect on the sinoatrial node. RFA attenuated vagal stimulation-induced atrial effective refractory periods shortening and vulnerability window of atrial fibrillation widening in the inferior right atrium and proximal coronary sinus but not in the high right atrium and distal coronary sinus. Moreover, RFA anatomically impaired the epicardial ganglionated plexuses at the inferior vena cava‒inferior left atrial junction. This method was also investigated in 42 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia, or 12 with an accessory pathway (AP) at the posterior septum (AP-PS), and 34 patients who had an AP at the free wall as control. In patients with atrioventricular nodal reentrant tachycardia and AP-PS, RFA at the bottom of Koch's triangle prolonged atrial effective refractory periods and reduced vulnerability windows of atrial fibrillation widening at the inferior right atrium, distal coronary sinus and proximal coronary sinus but not the high right atrium. In patients with AP-free wall, RFA had no significant atrial effects.

CONCLUSIONS

RFA at the bottom of Koch's triangle attenuated local autonomic innervation in the atrioventricular node and atria, decreased vagal stimulation-induced discontinuous atrioventricular nodal conduction, and reduced atrial fibrillation inducibility due to impaired ganglionated plexuses. In patients with atrioventricular nodal reentrant tachycardia or AP-PS, RFA prolonged atrial effective refractory periods, and narrowed vulnerability windows of atrial fibrillation.

Evaluation of the effect of radiofrequency catheter ablation on autonomic function in patients with atrioventricular nodal reentrant tachycardia by head-up tilt table test

Background:

One of the recommended treatments for atrioventricular nodal reentrant tachycardia (AVNRT), is radiofrequency catheter ablation (RFCA). However, RFCA may affect the autonomic system. This study aims to evaluate the effect of RFCA on autonomic system in patients with PSVT by head-up tilt table (HUTT) test.

Materials and Methods:

In a before–after study, 22 patients with PSVT were enrolled. Data were collected with a data collection form that included two parts. Electrocardiogram (ECG), echocardiogram, 24-h Holter monitoring, HUTT test, heart rate variability (HRV) indexes, and symptoms of all patients were recorded 24 h before and 1 month after the ablation. Wilcoxon, McNemar, Mann–Whitney U, and Chi-square tests were used to analyze the data.

Results:

Of the total 22 patients, 31.8% were male and 68.2% were female. There were significant differences in heart palpitation (P < 0.0001) and non-specific symptoms (P = 0.031) and no significant difference in head-up tilt test results and HRV indices before and after RFCA. The results showed that there were no significant differences in specific and non-specific symptoms in patients with AVNRT with positive and negative HUTT before and after RFCA.

Conclusions:

The observed difference in heart palpitation and non-specific symptoms emphasized the role of AVNRT in causing these symptoms. Autonomic dysfunction is more probably an accompanying condition of AVNRT than causing symptoms. We could not find any significance in the results of HUTT after RFCA. HUTT cannot determine or predict the symptoms after RFCA.

Improvement of atrioventricular conduction following catheter ablation of atrioventricular nodal reentry tachycardia in a patient with a prolonged PR interval

We herein present the case of a 60-year-old male with narrow QRS tachycardia who had a remarkable PR prolongation during sinus rhythm. The tachycardia was diagnosed as a slow-fast atrioventricular nodal reentry tachycardia. Slow pathway ablation was performed after the confirmation of the presence of an antegrade fast pathway. Following the elimination of the slow pathway, the PR and atrio-His intervals became shortened from 470 and 420 to 170 and 120 ms, respectively. Moreover, the improvement of atrioventricular conduction after the slow pathway ablation lasted for at least 34 months.

Catheter Ablation of Left Atrial Ganglionated Plexi for Atrial Fibrillation

Radiofrequency ablation of pulmonary vein ostia does not provide complete and long-term elimination of atrial fibrillation. Combining this procedure with local radiofrequency application on sites with strong vagal reflexes results in partial parasympathetic denervation and increases the antiarrhythmic effect. A novel catheter-ablation technique to modify ganglionated plexi in the left atrium was assessed in 58 patients (mean age, 52.1 ± 1.9 years, 67% male) with drug-refractory atrial fibrillation, which was chronic in 21 (36%; mean duration, 14.3 ± 2.9 months; range, 5–39 months). The mean left atrial volume was 93.1 ± 6.1 mL. The patients underwent ablation of 4 areas of ganglionated plexi in the left atrium, with no circumferential ablation of the pulmonary veins; atrial fibrillation ceased immediately in 94.1% of them. Transient vagal bradycardia was seen in 93% of patients. For 7.2 ± 0.4 months after the procedure, 86.2% of them were free from arrhythmias, and no antiarrhythmic drugs were administered. Ganglionated plexi ablation is an efficient treatment for atrial fibrillation.

Heart Rate Variability: Does it Change After RF Ablation of Reentrant Supraventricular Tachycardia?

BACKGROUND

Following RF ablation of reentrant supraventricular tachycardia, inappropriate sinus tachycardia may occur. Local parasympathetic denervation is a possible mechanism for these rhythm disturbances. The purpose of this study was to determine the incidence of sinus tachycardia and to determine the relation between endocardial lesions at different ablation sites and alterations in autonomic tone in several different groups of patients with supraventricular tachycardia, using techniques of heart rate variability analysis.

METHODS

The subjects of this study were 75 patients (48 women, 27 men) with a mean age of 39.99 (SD = 13.39). They underwent RF ablation of AV nodal slow pathways (40 cases), posteroseptal APs (23 cases), left lateral and right free wall APs (12 cases) because of symptomatic tachycardias. The mean sinus rate and time domain (standard deviation of RR intervals and root mean square of differences of adjacent RR intervals) and frequency domain (low frequency, high frequency and low frequency/high frequency ratio) analyses of heart rate variability were obtained by use of 24 hour Holter monitoring before and 1 month after ablation compared with pre-ablation values.

RESULTS

Analysis of 24 hour ambulatory Holter-monitors, performed 1 month after RF ablation, showed no significant changes in time and frequency domain parameters of heart rate variability in different groups. A significant increase in mean heart rate was noted after RF ablation at AV nodal slow pathway group and left freewall/right free wall accessory pathways group. Patients undergoing RF ablation of right or left posteroseptal accessory pathways had no significant increase in the mean heart rate.

CONCLUSION

In summary, an increase in sinus tachycardia may be initiated by RF ablation of atrioventricular reentrant tachycardia (AVNRT) and right free wall or left free wall accessory pathways. This finding shows that the modifications of heart rate are not directly related to the posteroseptal region or to the accessory pathways.

Time Course and Predictors of Autonomic Dysfunction After Ablation of the Slow Atrioventricular Nodal Pathway

Withdrawal of parasympathetic tone has been reported after ablation in the posteroseptal right atrium and has been attributed to injury of vagal efferent fibers. The purpose of this study was to assess the time course and predictors of autonomic dysfunction after slow pathway ablation. In 30 patients with AV nodal reentrant tachycardia, time- and frequency-domain measures of heart rate variability (HRV) were measured before, 30 minutes after, and 1 day after slow pathway ablation. There were significant reductions in mean RR interval (724 +/- 163 vs 836 +/- 164 ms, P < 0.05), SD of RR intervals (29 +/- 17 vs 40 +/- 18 ms, P < 0.05), root mean squared difference (15 +/- 8 vs 29 +/- 17 ms, P < 0.05), and high frequency power (4.1 +/- 0.4 vs 4.5 +/- 0.6 log10ms2, P < 0.05) 30 minutes after ablation. However, these parameters returned to baseline 1 day after ablation. Multivariate regression identified isoproterenol dose during the diagnostic study (P = 0.02) and radiofrequency duration (P = 0.02) as statistically significant predictors of heart rate change (R2= 0.45). These findings suggest that changes in autonomic tone after ablation in the posteroseptal right atrium are transitory and resolve within 1 day of the procedure. These short-term changes may be related to procedural variables rather than direct injury to vagal efferent fibers.

Effects of linear ablation at the isthmus between the tricuspid annulus and inferior vena cava for atrial flutter on autonomic nervous activity: analysis of heart rate variability

Heart rate is largely affected by the autonomic nervous system. However, little is known about the anatomic pathway of autonomic nerve fibers innervating the sinus node. The present study: (1) evaluates the effects of cavotricuspid isthmus ablation for common atrial flutter (AFL) on autonomic nervous function by using heart rate variability analysis, and (2) investigates the distribution of autonomic nerve pathways innervating the sinus node. Twelve patients with paroxysmal common atrial flutter who maintained sinus rhythm both before and after radiofrequency ablation were selected for the study. Holter ambulatory recordings were performed before and after (2.3 +/- 1.0 days) radiofrequency ablation of cavotricuspid isthmus. Heart rate and time domain (SDANN, rMSSD, pNN50) and frequency domain (low frequency (LF), high frequency (HF), LF/HF) analysis of heart rate variability were compared before and after ablation. Mean heart rate did not change significantly after ablation (59 +/- 6 vs 61 +/- 9 beats/min); parasympathetic indices of heart rate variability (SDANN, rMSSD, pNN50, HF) did not change significantly (110 +/- 37 vs 117 +/- 20 ms; 32 +/- 21 vs 28 +/- 9 ms; 4.8 +/- 0.9 vs 4.7 +/- 0.71n(ms2)); and sympathetic indices of heart rate variability (LF/HF) did not change significantly (1.1 +/- 0.2 vs 1.2 +/- 0.1). Cavotricuspid isthmus ablation for atrial flutter did not significantly change heart rate and heart rate variability because parasympathetic and sympathetic fibers innervating the sinus node are scarce in this region.

Radiofrequency ablation at the coronary sinus ostium interrupts the vagal efferent input to the atrioventricular node in the canine heart

The fat pad at the junction of the inferior vena cava and inferior left atrium is the area of convergence of vagal projections into the atrioventricular node (AVN) region. The present study investigated whether radiofrequency (RF) ablation applied to the area around the coronary sinus (CS) ostium would impair vagal input to the AVN in the canine heart. Twenty-four dogs were anesthetized by sodium pentobarbital and RF energy was delivered at 20W for 5-10s. In the baseline state without vagal stimulation (10Hz, 2ms), the electrophysiological variables did not change significantly after RF ablation. Vagally induced changes in the sinus cycle length and effective refractory period of the right atrium and left ventricle did not differ after RF ablation. However, the effects of vagal stimulation on the AVN function were impaired after RF ablation to the CS area from the ostium to 10mm within the ostium. After ablation was applied to the fast pathway area, the vagally induced changes in the AVN function decreased, but these changes were not affected after RF ablation in the slow pathway area. RF ablation in the vicinity of the CS would attenuate vagal input to the AVN.

Alterations of heart rate variability after radiofrequency catheter ablation of focal atrial fibrillation originating from pulmonary veins

BACKGROUND

Transient sinus bradycardia and hypotension have been reported as complications during radiofrequency (RF) ablation of focal atrial fibrillation (AF) originating from pulmonary veins (PVs). This study used heart rate variability (HRV) to evaluate the effects of focal PVs ablation on autonomic function.

METHODS AND RESULTS

Thirty-seven patients with paroxysmal AF were referred for ablation. The study group included 30 patients who underwent transseptal ablation of PVs, and the control group included 7 patients who underwent the transseptal procedure without ablation. The mean sinus rate and time-domain (standard deviation of RR intervals and root-mean-square of differences of adjacent RR intervals) and frequency-domain (low frequency, high frequency, and low-frequency/high-frequency ratio) analyses of HRV were obtained by use of 24-hour Holter monitoring before and 1 week, 1 month, and 6 months after ablation. All the triggering points of AF were from PVs, and they were successfully ablated. Severe bradycardia and hypotension were noted during ablation of PVs in 6 patients (group IA); 24 patients without the above complication belonged to group IB. Compared with preablation values, a significant increase in mean sinus rate and low-frequency/high-frequency ratio and a significant decrease in standard deviation of RR intervals, root-mean-square of differences of adjacent RR intervals, low frequency, and high frequency were noted in groups IA and IB patients 1 week after ablation. The changes in HR and HRV recovered spontaneously in the 2 subgroups by 1 month later. These parameters of HRV did not change in the control group after the transseptal procedure.

CONCLUSIONS

Transient autonomic dysfunction with alterations in HR and HRV occurred after ablation of focal AF originating from PVs.

Effect of radiofrequency catheter ablation on parasympathetic denervation: a comparison of three different ablation sites

Radiofrequency (RF) catheter ablation of supraventricular tachycardias (SVT) has been shown to result in local parasympathetic denervation. The purpose of this study was to estimate the correlation between RF cumulative energy and parasympathetic denervation at three different ablation sites.

METHODS

45 patients who underwent RF ablation of 36 AV reentrant tachycardias and 9 AV nodal reentrant tachycardias were studied. Twenty patients had left free-wall accessory pathways (group L), 8 patients right free-wall accessory pathways (group R), and 17 patients septal accessory pathways (n = 8) or slow pathways (n = 9) (group S). Time and frequency domain analysis of heart rate variability on 24-hour ambulatory ECG recordings was performed before and after RF ablation. pNN50 and the high frequency (0.15 to 0.40 Hz, HF) component were measured to examine the effects on parasympathetic nerve activity. The values of delta pNN50 and delta HF were expressed as the percent change of pNN50 and HF that occurred after versus before RF ablation.

RESULTS

Both pNN50 and HF significantly decreased after RF ablation in all three groups. In group S, there was a significant correlation between RF cumulative energy and delta pNN50 (r = 0.66, P < 0.01) or delta HF (r = 0.58, P < 0.05). In contrast, there was no correlation between RF cumulative energy and delta pNN50 or delta HF in either group L or group R.

CONCLUSION

These data suggest that RF ablation produces parasympathetic denervation at all three sites along the mitral or tricuspid annulus and that parasympathetic fibers may be located predominantly in the septal area.