Diabetes associated with poorer ablation outcome
TAIPEI, TAIWAN. Recent research has shown that type 2 diabetes is a risk factor for the development of atrial fibrillation (AF). However, it is not clear why this is so. A team of electrophysiologists from the Taipei Veterans General Hospital now reports that diabetes and impaired fasting glucose alters the substrate in both the left and right atria so as to encourage the arrhythmia. They also observed that patients with abnormal glucose metabolism (diabetes or impaired fasting glucose) were more likely to experience recurrence after catheter ablation of AF than were patients with normal glucose metabolism. The study included 228 patients with symptomatic paroxysmal AF (average age of 52 years with 73% being male). A total of 65 patients (28.5%) had either diabetes (32 patients with average fasting glucose level of 129 mg/dL) or impaired fasting glucose (33 patients with average fasting glucose level of 109 mg/dL). The only significant differences between the impaired and normal glucose metabolism groups were that the latter group was older (56 vs. 51 years), had a higher average fasting glucose level (average of 119 vs. 87 mg/dL), and glycated hemoglobin (6.2% vs. 5.5%) as well as a larger left atrium (40.1 mm vs. 37.8 mm).

All patients underwent an electrophysiologic study followed by a catheter ablation. The study was carried out in sinus rhythm, while the circumferential pulmonary vein isolation (PVI) procedure was performed after the patients had been provoked into AF. The electrophysiologic study revealed that both right and left atrium total activation times were significantly longer in the abnormal glucose metabolism group and bipolar voltages in both the left and right atria were significantly lower in the abnormal metabolism group. The researchers suggest that the observed intra-atrial conduction delay and the lower atrial voltage may be associated with atrial fibrosis caused by oxidative stress.

All patients were followed up every 1 to 3 months with 24-hour Holter monitoring or 7-day event recording. If AF recurred they were offered a repeat ablation or prescribed previously ineffective antiarrhythmics. After an average follow-up of 18 months, 18.5% of the members of the abnormal glucose metabolism group had experienced AF recurrence (after a 2-month blanking period) as compared to only 8.1% in the normal metabolism group. After adjusting for age, left atrial diameter, left ventricular ejection fraction, and the use of antiarrhythmic medications, the researchers conclude that abnormal glucose metabolism is associated with a 3.2-fold increase in the risk of AF recurrence. They point out that the electrical abnormalities found in the abnormal glucose metabolism group were more pronounced in the "full-blown" diabetes group than in the impaired fasting glucose group indicating that the electrical remodeling observed is a gradual process which may be slowed by lifestyle and diet changes aimed at halting the progression to diabetes.

Chao, TF, et al. Atrial substrate properties and outcome of catheter ablation in patients with paroxysmal atrial fibrillation associated with diabetes mellitus or impaired fasting glucose. American Journal of Cardiology, Vol. 106, 2010, pp. 1615-20

Editor's comment: The "take home" message of this study is that afibbers with abnormal glucose metabolism are more likely to experience AF recurrence after a PVI procedure than are those with normal fasting glucose levels. The risk of recurrence would seem to increase with the degree of glucose metabolism impairment; therefore making efforts as early as possible to prevent progression is imperative for potential ablatees.