Quantitative assessment of transient autonomic modulation after single-shot pulmonary vein isolation with pulsed-field ablation

INTRODUCTION

Pulmonary vein isolation (PVI) with thermal energy is characterized by concomitant ablation of the surrounding ganglionated plexi (GP). Pulsed-field ablation (PFA) selectively targets the myocardium and seems associated with only negligible effects on the autonomic nervous system (ANS). However, little is known about the dynamic effects of PFA on the GP immediately after PVI. This study sought to investigate the degree and acute vagal modulation induced by the FarapulseTM PFA system during PVI compared with single-shot thermal ablation.

METHODS

A total of 76 patients underwent first-time PVI with either FarapulseTM PFA (PFA group, n = 40) or cryoballoon ablation (thermal ablation group, n = 36) for paroxysmal atrial fibrillation (AF). The effect on the ANS in the two groups was assessed before and after PVI with extracardiac vagal stimulation (ECVS). To capture any transient effects of PFA on the ANS, in a subgroup of PFA patients ECVS was repeated at three predefined timepoints: (1) before PVI (T0); (2) immediately after PVI (T1); and (3) 10 min after the last energy application (T2).

RESULTS

Despite similar baseline values, the vagal response induced by ECVS after PVI almost disappeared in the thermal ablation group but persisted in the PFA group (thermal group: 840 [706-1090] ms, p < .001 compared to baseline; PFA group: 11 466 [8720-12 293] ms, p = .70 compared to baseline). Intraprocedural vagal reactions (defined as RR increase >50%, transitory asystole, or atrioventricular block) occurred more frequently with PFA than thermal ablation (70% vs. 28%, p = .001). Moreover, heart rate 24 h post-PVI increased more with thermal ablation than with PFA (16.5 ± 9.0 vs. 2.6 ± 6.1 beats/min, p < .001). In the subgroup of PFA patients undergoing repeated ANS modulation assessment (n = 11), ECVS demonstrated that PFA determined a significant acute suppression of the vagal response immediately after PVI (p < .001 compared to baseline), which recovered almost completely within 10 min.

CONCLUSION

PVI with the FarapulseTM PFA system is associated with only transitory and short-lasting vagal effects on the ANS which recover almost completely within a few minutes after ablation. The impact of this phenomenon on AF outcome needs to be further investigated.

Autonomic Responses During Acute Anterior Versus Inferior Myocardial Infarction: A Systematic Review and Meta-Analysis

Autonomic responses elicited by myocardial infarction vary depending on the site of injury, but accurate assessment using heart rate variability during the acute phase is limited. We systematically searched PubMed without language restrictions throughout July 2023. We reviewed studies reporting autonomic indices separately for anterior and inferior infarcts, followed by a meta-analysis of those reporting the standard deviation of the inter-beat interval between normal sinus beats during the initial 24 hours after the onset of symptoms. Six studies were included, comprising 341 patients (165 anterior, 176 inferior infarcts), all with satisfactory scores on the Newcastle-Ottawa quality scale. The estimated average of the standardized mean difference (based on the random-effects model) was -0.722 (95% confidence intervals: -0.943 to -0.501), which differed from zero (z=-6.416, p<0.0001). This finding indicates sympathetic and vagal dominance during acute anterior and inferior infarcts, respectively, with excessive responses likely contributing to early arrhythmogenesis. Despite the amelioration of autonomic dysfunction by revascularization, infarct location should be considered when commencing β-adrenergic receptor blockade, especially after delayed procedures.

Recurrent Episodes of Paroxysmal Supraventricular Tachycardia Triggered by Dyspepsia: A Rare Case of Gastrocardiac Syndrome

Supraventricular tachycardia (SVT) refers to the narrow complex tachycardia originating at or above the bundle of His. Several risk factors are associated with the development and recurrence of SVT, but its association with gastric problems, especially dyspepsia, is relatively rare. We report the case of a 54-year-old female who presented to the emergency room (ER) with palpitations, which were diagnosed as an episode of paroxysmal supraventricular tachycardia (PSVT). She had a history of PSVT in the past, along with hypertension and dyspepsia. After thorough history and examination, dyspepsia was identified as the common trigger of her PSVT episodes, pointing towards the likelihood of gastrocardiac symptoms. Therefore, an appropriate regimen of beta-blockers, proton pump inhibitors (PPIs), and anti-foaming agents (simethicone) was prescribed to manage her symptoms with the plan to perform a catheter ablation later.

Asystole During Nasopharyngeal Swab: Is COVID-19 to Blame?

The use of nasopharyngeal (NP) swab sampling for the detection of various respiratory pathogens has been a standard procedure in medicine for many years. While this is a fairly common procedure, there has been a significant increase in utilization recently due to the SARS-CoV-2 pandemic. We describe a case of a 40-year-old SARS-CoV-2 positive patient with no prior cardiac history who developed asystole while an NP swab was being used to obtain a sample for a SARS-CoV-2 assay. Return of normal sinus rhythm was achieved with chest compressions alone. The incident was deemed to have been an exaggerated vagal response to intranasal stimulation; better known as the trigeminocardiac reflex. This is the first reported case describing asystole during use of an NP swab. This case occurred in a patient with no known cardiac disease and highlights the potential importance of the arrhythmogenic nature of COVID-19 that could potentiate the vagal response in susceptible individuals undergoing NP sampling.

Sympathetic and Vagal Responses Elicited by Acute Stress in Rats

Introduction

Acute emotional stress triggers autonomic responses that affect sympathovagal balance. However, the temporal pattern of changes in each autonomic arm during stress and recovery remains unclear. Therefore, we analyzed separately sympathetic and vagal activity, elicited by acute unpredictable stress in a rat model.

Methods

Continuous electrocardiographic recording was performed during (32 minutes) and after (two hours) successive use of restraint and air-jet stress in 10 rats, whereas five rats served as controls. Sympathetic and vagal indices were calculated non-invasively after heart rate variability analysis. Voluntary motion was quantified during recovery, as an index of continuing anxiety.

Results

The sympathetic nervous system index increased during stress and remained elevated during the initial stage of recovery. The parasympathetic nervous system index decreased immediately after the onset of stress and remained low throughout the observational period. During recovery, voluntary activity was more pronounced in the stress group than in the controls.

Conclusion

Successive restraint and air-jet stress in rats increased sympathetic activity and decreased vagal activity. These changes displayed only partial recovery post-stress and were accompanied by enhanced voluntary motion. Our findings may be important in the evaluation of the cardiac electrophysiologic implications of autonomic changes elicited by acute emotional stress.

A case of prolonged sinus arrest for 5 minutes after Cryo-balloon ablation to the left superior pulmonary vein

A 63-year-old man was referred to our hospital for his palpitation due to atrial fibrillation. He was admitted for catheter ablation. Cryoablation was applied to the left superior pulmonary vein for 180 seconds, and its potential disappeared in 22 seconds. The lowest temperature was -45°C. Suddenly, sinus arrest was observed 1 minute after the completion of freezing. The right ventricle was paced but no atrial potential was observed for 5 minutes until normal sinus rhythm resumed. We report a case of severe sinus arrest after cryoablation to the left pulmonary vein.

Heart Rate Variability Responses of Individuals With and Without Saline-Induced Obstructive Sleep Apnea

STUDY OBJECTIVES

Postoperative development of obstructive sleep apnea (OSA) has been attributed to the fluid overloaded state of patients during the postoperative period. In this context, alterations in cardiac autonomic regulation caused by OSA may explain the increased postoperative risk for adverse cardiovascular events. This study tests the hypothesis that individuals with fluid overload-induced OSA will experience autonomic dysregulation, compared to those without fluid overload-induced OSA.

METHODS

Twenty-one normotensive, nonobese (mean body mass index 24.5 kg/m²) males (mean age 37 years) underwent a sleep study. Participants were randomly assigned to infusion with saline during sleep either at the minimum rate (control) or as a bolus of 22 mL/kg body weight (intervention). Participants were blinded to the intervention and crossed over to the other study arm after 1 week. Measures of heart rate variability were calculated from electrocardiography recordings presaline and postsaline infusion in the intervention arm. Heart rate variability measures computed were: standard deviation of the RR interval; root mean square of successive differences; low-frequency, high-frequency, and total power; and the ratio of low-frequency to high-frequency power.

RESULTS

Although presaline infusion values were similar, postsaline infusion values of the standard deviation of the RR interval and high-frequency power were lower in the group whose apnea-hypopnea index increased in response to saline infusion, compared to the group whose apnea-hypopnea index did not increase in response to saline infusion (P < .05 for both).

CONCLUSIONS

Fluid overload-induced OSA is accompanied by a reduction in heart rate variability, consistent with vagal withdrawal. Future work should explore autonomic dysregulation in the postoperative period and its association with adverse events.