Delay Worsens Ablation Outcomes in Atrial Fibrillation Patients

A new retrospective analysis indicates that the interval between the diagnosis of persistent atrial fibrillation (AF) and the use of catheter ablation is inversely related to the procedure’s chance of long-term success.

Investigators gathered medical records for 1,241 consecutive patients who underwent ablation for persistent AF at the Cleveland Clinic between 2005 and 2012. The median diagnosis-to-ablation time was 3 years, but the variance was substantial. The 25^th-percentile delay was 1 year, while the 75^th-percentile delay was 6.5 years.

These differences were associated with significant differences in 2-year outcomes. The recurrence rates for patients in the first, second, third and fourth delay quartiles were 33.6%, 52.6%, 57.1%, and 54.6%, respectively (P_categorical<0.0001).

The significance of the relationship persisted through multivariable Cox analyses. The hazard ratio (HR) for recurrence per +1 Log diagnosis-to-ablation time was 1.27 (95% confidence interval [CI], 1.14—1.43; P<0.0001). The HR for recurrence among patients in the second quartile (compared to patients in the first quartile) was 2.12 (95% CI, 1.43-3.20). It was 2.32 (95% CI, 1.59-3.47) for patients in the third quartile and 2.44 (95% CI, 1.68–3.65; P_categorical<0.0001) for patients in the fourth quartile.

The investigators also found that longer diagnosis-to-ablation times were associated, at the 2-year mark, with significant increases in B-type natriuretic peptide levels (P=0.01), C-reactive protein levels (P<0.0001), and left atrial size (P=0.03).

Despite some limitations to the study, including its retrospective nature and its reliance on data from a single facility, the strength of the findings led the investigators to suggest that physicians who cannot get persistent AF quickly under control with standard drug regimens should refer patients to specialized centers without delay.

“In patients with persistent AF undergoing ablation, the time interval between the first diagnosis of persistent AF and the catheter ablation procedure had a strong association with the ablation outcomes,” they wrote in Circulation: Arrhythmia and Electrophysiology. “Shorter diagnosis-to-ablation times were associated with better outcomes and in direct association with markers of atrial remodeling.”

The study authors hypothesized that delay reduced the effectiveness of ablations by giving the heart more time to remodel itself and to accumulate both scar tissue and fibrosis in the atrium — a theory that’s supported by a study published last year in Europace.

The authors of that paper enrolled 95 patients who were about to undergo a second ablation procedure and compared the recorded size of each patient’s left atrium before the first ablation with its size before the second procedure. They found significant enlargements in 35 patients and no significant change in the other 60 patients.

After an average follow-up of 29.6 months, paroxysmal AF recurred a second time in 33 of the patients, but it was dramatically more common among those whose left atria had expanded between their first and second ablations. The condition recurred a second time in 54.1% of those patients but in just 25.0% of the patients with no left atrium growth (P = 0.017).

Other research has found a number of different factors that may influence ablation success rates.

Researchers from Intermountain Medical Center Heart Institute in Salt Lake City, for example, presented data last year that linked obesity and recurrence. The investigators in that study first pulled records from 1,558 patients who had undergone catheter ablations and remained in the system long enough to provide at least 3 years of follow-up data. They then used body mass index (BMI) information to separate those patients into 4 groups: BMI <20 kg/m², BMI 21-25 kg/m², BMI 26-30 kg/m² and BMI > 30 kg/m².

AF recurrence rates showed a significant positive correlation with BMI. AF recurrence rates rose steadily from 1 group to the next, starting with the BMI <20 kg/m² group and peaking (at nearly 75%) with the BMI >30 kg/m² group (p=0.02). Incidence of heart failure, stroke and death, however, did not follow the same pattern. Stroke rates were statistically similar among all patient groups and death rates, while rising slightly from the BMI <20 kg/m² to the BMI 21-25 kg/m² group, only to decline somewhat thereafter as patients got heavier.