Impact of the sinus node recovery time after termination of atrial fibrillation during catheter ablation on clinical outcomes in patients with persistent atrial fibrillation

Long-term outcome after ablation of persistent atrial fibrillation in patients with postprocedurally unmasked sinus node disease

BACKGROUND

About three percent of patients with persistent atrial fibrillation (AF) additionally suffer from a concealed sinus node disease (SND). We sought to determine the success of ablation one year after ablation of persistent AF in patients with postprocedurally unmasked SND.

METHODS AND RESULTS

In total, 2539 patients with an ablation of persistent AF at our centre were screened for a postprocedurally unmasked SND, which made acute cardiac pacing necessary within one week after ablation. In a propensity score-matched case-control study (1:2 matching), the long-term ablation success of 51 patients (mean age 73 ± 8 years, 59% male) with unmasked SND after ablation of persistent AF was compared to that of 102 patients without SND after ablation of persistent AF. Controls were matched to cases based on the propensity score considering age, body mass index, left ventricular ejection fraction, gender, blood pressure, diabetes mellitus, atrial low voltage, previous number of ablations, and method of ablation. One year after ablation of persistent AF, 20 (39%) patients with postprocedurally unmasked SND and 61 (60%) patients without postprocedurally unmasked SND were in sinus rhythm (OR 0.43, 95% CI 0.22 to 0.90, p = 0.017). The number of repeat ablation procedures within the follow-up year did not differ significantly between cases and controls (mean 0.60 ± 0.68 vs 0.53 ± 0.80, rate ratio 1.14, 95% CI 0.72 to 1.78, p = 0.566).

CONCLUSION

In patients with a postprocedurally unmasked SND after ablation of persistent AF, long-term ablation success seems to be worse compared to patients without postprocedurally unmasked SND.

Sinus node dysfunction and atrial fibrillation-Relationships, clinical phenotypes, new mechanisms, and treatment approaches

Although the anatomical basis of the pathogenesis of sinus node dysfunction (SND) and atrial fibrillation (AF) is located primarily in the left and right atria, increasing evidence suggests a strong correlation between SND and AF, in terms of both clinical presentation and formation mechanisms. However, the exact mechanisms underlying this association are unclear. The relationship between SND and AF may not be causal, but is likely to involve common factors and mechanisms, including ion channel remodeling, gap junction abnormalities, structural remodeling, genetic mutations, neuromodulation abnormalities, the effects of adenosine on cardiomyocytes, oxidative stress, and viral infections. Ion channel remodeling manifests primarily as alterations in the "funny" current (I_f) and Ca²⁺ clock associated with cardiomyocyte autoregulation, and gap junction abnormalities are manifested primarily as decreased expression of connexins (Cxs) mediating electrical impulse propagation in cardiomyocytes. Structural remodeling refers primarily to fibrosis and cardiac amyloidosis (CA). Some genetic mutations can also cause arrhythmias, such as SCN5A, HCN4, EMD, and PITX2. The intrinsic cardiac autonomic nervous system (ICANS), a regulator of the heart's physiological functions, triggers arrhythmias.In addition, we discuss arrhythmias caused by viral infections, notably Coronavirus Disease 2019 (COVID-19). Similarly to upstream treatments for atrial cardiomyopathy such as alleviating CA, ganglionated plexus (GP) ablation acts on the common mechanisms between SND and AF, thus achieving a dual therapeutic effect.

Neonatal Scn1b-null mice have sinoatrial node dysfunction, altered atrial structure, and atrial fibrillation

Loss-of-function (LOF) variants in SCN1B, encoding the voltage-gated sodium channel β1/β1B subunits, are linked to neurological and cardiovascular diseases. Scn1b-null mice have spontaneous seizures and ventricular arrhythmias and die by approximately 21 days after birth. β1/β1B Subunits play critical roles in regulating the excitability of ventricular cardiomyocytes and maintaining ventricular rhythmicity. However, whether they also regulate atrial excitability is unknown. We used neonatal Scn1b-null mice to model the effects of SCN1B LOF on atrial physiology in pediatric patients. Scn1b deletion resulted in altered expression of genes associated with atrial dysfunction. Scn1b-null hearts had a significant accumulation of atrial collagen, increased susceptibility to pacing induced atrial fibrillation (AF), sinoatrial node (SAN) dysfunction, and increased numbers of cholinergic neurons in ganglia that innervate the SAN. Atropine reduced the incidence of AF in null animals. Action potential duration was prolonged in null atrial myocytes, with increased late sodium current density and reduced L-type calcium current density. Scn1b LOF results in altered atrial structure and AF, demonstrating the critical role played by Scn1b in atrial physiology during early postnatal mouse development. Our results suggest that SCN1B LOF variants may significantly impact the developing pediatric heart.