Catheter ablation of atrial fibrillation (AF) has favourable effects on cerebral blood flow, particularly in non-paroxysmal AF, research published in JACC: Clinical Electrophysiology.
The results may partially explain the association between cognitive decline and AF, Yoshihide Takahashi (Tokyo Medical and Dental University, Tokyo, Japan) and colleagues have suggested, with non-paroxysmal AF at baseline having been identified as an independent predictor of increases in cerebral blood flow, suggesting an impact of tachyarrhythmia burden on this outcome.
Recent studies have revealed that AF is a risk factor for cognitive impairment, the study team writes in their JACC: Clinical Electrophysiology paper, adding that findings from recent studies suggest that anticoagulation therapy does not sufficiently address the problem of dementia associated with AF.
The researchers hypothesised that the beneficial effects of catheter ablation of AF on cognitive impairment could be attributable to improved brain perfusion. Additionally, they wrote, hippocampal atrophy—which is a risk factor for dementia—has been observed in AF patients, though changes in post-ablation hippocampal volume have not been studied. In light of this, Takahashi and colleagues aimed to assess whether catheter ablation of AF led to increases in cerebral blood flow and hippocampal volume.
To test their hypothesis, the study team assessed patients undergoing catheter ablation, with AF patients treated by medical therapy forming the control group. Patients with contraindications for magnetic resonance imaging (MRI), including those with implantable electronic devices, and those with a history of carotid artery disease, were excluded from the study.
Patients underwent brain MRI one day before their catheter ablation procedure, and then again after six months, with the researchers assessing cerebral blood flow, brain perfusion, total brain volume and hippocampal volume.
A total of 59 patients were included in the study, two of whom were lost to follow-up and did not undergo a second MRI scan. Patients in the study arm had a mean age of 64 years (compared to 67 in the control group) and the majority were male (78.9%).
All patients were followed up for at least six months, and 48 of the 57 study patients (84.2%; paroxysmal AF: 21 of 22; non-paroxysmal AF: 27 of 35) were free from any atrial tachyarrhythmias after the three-month blanking period, Takahashi and colleagues report.
Of the eight non-paroxysmal AF patients who had recurrence of atrial tachyarrhythmia, atrial tachyarrhythmia burden decreased from persistent to paroxysmal form in four patients. During both the periprocedural and six-month follow-up periods, no adverse events, including stroke or transient ischaemic attack, occurred in either the study or control patients, the study team notes.
Of the 57 study patients, heart rhythm during the MRI scanning before ablation was AF and sinus in 35 and 22 patients, respectively, Takahashi et al note, adding that on baseline MRI, “patchy” T1 hypointensity areas consistent with old cerebrovascular lesions were found in 11 patients (19.3%). No other abnormalities were found in any patient, they add.
MRI scanning at the six-month follow-up was performed during AF and sinus rhythm in five and 52 patients, respectively. A small T1 hypointensity lesion newly appeared in two patients (3.5%), both of whom had a lacunar lesion. Of the 11 control patients, heart rhythm during MRI scanning at baseline and six months later was AF and sinus in seven and four, respectively. On baseline MRI, four patients (36.4%) showed small patchy T1 hypointensity lesions. On the 6-month MRI, the study team found no new lesions in any control patients.
Cerebral blood flow and brain perfusion increased significantly from baseline to six months in the study patient group compared to the control group, the authors of the study write, noting that the difference in the adjusted mean change from baseline between patient groups was 74.12 (95% confidence interval [CI]: 18.56‒129.68, p=0.01), and in brain perfusion from baseline was 6.81 (95% CI: 1.74‒11.87, p=0.009).
Total brain volume increased from baseline to six months in the study patient group, the researchers add, but there was no statistically significant difference in the adjusted mean of change from baseline compared to the control patient group (4.71, 95% CI: -4.77 to 14.20, p=0.32). There was no statistically significant difference of the adjusted mean change from baseline to six months for bilateral hippocampal volume between the two groups (-0.01, 95% CI: -0.10 to 0.08, p=0.80).
Detailing what they saw as the major findings from the study, Takahashi et al write that the study showed an increase in cerebral blood flow over six months after catheter ablation, an increase that was significantly greater than that seen in the control patients who underwent medical therapy. Non-paroxysmal AF at baseline was a predictor of increase in cerebral blood flow, the study team adds. No changes in total brain volume or hippocampal volume were documented.
“In our study, patients who had arrhythmia recurrence had less change in cerebral blood flow than those freed from arrhythmia,” the study’s authors write. “Therefore, it appears that maintenance of sinus rhythm rather than denervation by ablation plays an important role in the increase in cerebral blood flow. Catheter ablation of AF improves renal function also. Taken together with the results of this study, it seems that haemodynamic improvement occurs not only in the brain but also systemically after successful catheter ablation.”
The authors note several limitations in their research, namely the observational nature of the study, and that cognitive function was not assessed. Despite this, the researchers note that their study “revealed favourable effects of maintenance of sinus rhythm on brain perfusion,” adding that the results “may partially explain the underlying mechanism of cognitive function decline in AF patients”.
Speaking to Cardiac Rhythm News Takahashi noted that the long-term effects of reduced or increased cerebral blood flow on cognitive function or brain volume are unknown, and added that the long-term effects may stretch beyond the six-month results seen in the study.