Sleep apnea affects ablation efficacy
BARCELONA, SPAIN. Obstructive sleep apnea (intermittent loss of breathing during sleep) is a common disorder affecting about 4% of middle-aged American men and about 2% of middle-aged American women. It is strongly linked to increasing age and obesity. Obstructive sleep apnea (OSA) is characterized by a collapse of soft muscle tissue in the throat leading to blockage, restricted airflow and ultimately deoxygenation of red blood cells. OSA can be diagnosed during a sleep study (polysomnography) and its severity is described via the apnea-hypopnea index (AHI), which represents the number of obstructive respiratory events per hour of sleep. An AHI of less than 10 is considered normal, an AHI of 10-20 is mild, 20-30 is moderate, and more than 30 events per hour characterizes severe OSA. OSA can usually be successfully treated by the use of a continuous positive airway pressure (CPAP) machine which supplies a constant, uninterrupted flow of air pressurized just enough to keep the airway open.

Cardiac arrhythmias are common in patients with OSA. They occur mainly at night, in contrast with arrhythmias in patients with structural heart disease, which occur mainly during daytime. A nighttime AF episode in an OSA patient starts out with a bradycardia (abnormally low heart rate) due to parasympathetic (vagal) hyperactivity followed by tachycardia (an abnormally high heart rate) as a consequence of awakening from sleep. Nighttime bradycardia and subsequent AF episodes in OSA patients can, in most cases, be avoided by the use of a CPAP machine. A recent study observed OSA in 49% of 151 patients with atrial fibrillation, so it clearly is not an uncommon cause of AF. A Mayo Clinic study concluded that among subjects under the age of 65 years the cumulative probability of developing afib was about twice as high in subjects with OSA as compared to those without OSA. It is also of interest to note that patients with OSA tend to have a greatly increased frequency of premature ventricular beats (PVCs) during sleep as compared to the frequency during wakefulness. They also, in general, tend to have more ventricular ectopy (non-sustained ventricular tachycardia and ventricular bigeminy, trigeminy, and quadrigeminy). Again, treatment with a CPAP machine has been found to reduce ventricular ectopy quite substantially.

Now Spanish researchers report that patients with OSA and AF are substantially less likely to have a successful ablation than are those without OSA. Their study involved 174 consecutive AF patients (56% paroxysmal) who were scheduled to undergo a circumferential pulmonary vein isolation (PVI) procedure. All patients completed the Berlin Questionnaire (BQ) which is designed to discover the possible presence of OSA. Fifty-one of the patients (29.3%) had a high BQ score and underwent a sleep study (polysomnography). Of these patients 14.4% were found to have severe OSA (mean AHI of 54), and 9.8% had mild OSA (mean AHI of 18). Most patients (86%) had no underlying heart disease so were thus lone afibbers. However, structural heart disease was substantially more common among patients with OSA (28%) than among those without (11.3%). Hypertension was also much more prevalent among patients with severe OSA (64%) than among those without (34%) as was the presence of permanent AF (28% vs. 11.4%).

All patients underwent an anatomically-guided PVI procedure (Pappone protocol) with additional left atrium roof and posterior wall lesions as needed. Follow-up consisted of outpatient visits and 24- or 48-hour Holter monitoring at 1, 4, and 7 months following the ablation, and every 6 months thereafter. Patients were also encouraged to report symptomatic episodes if and when they occurred. Mean follow-up was 17 months.

Complete success rates (no AF, no antiarrhythmics) at one year following the initial procedure (Kaplan-Meier estimate) was 48.5% in the non-OSA group, 30.4% in the mild OSA group, and only 14.3% in the severe OSA group. A second PVI was performed in 29.5% of the non-OSA group, 47.1% in the mild OSA group, and in 44% of those in the severe OSA group. Following the second procedure, final complete success rates were 68.8%, 43.8%, and 14.3% respectively.

The Spanish researchers conclude that severe OSA markedly reduces the likelihood of having a successful PVI procedure. They also note, albeit based on a very small sample, that using a CPAP machine prior to their PVI did not affect success rates among patients with severe OSA suggesting that once the damage (electrical and structural remodeling) to the atrium is done, CPAP cannot restore sinus rhythm. In an accompanying editorial, Dr. Christoph Stellbrink of the Bielefeld Medical Center in Germany points out that patients in the severe OSA group were generally older, more likely to be obese, and more likely to have hypertension, structural heart disease and permanent AF. Thus, severe OSA may not have been the only cause for the poor ablation efficacy in this group of patients.

Matiello, M, et al. Low efficacy of atrial fibrillation ablation in severe obstructive sleep apnea patients. Europace, Vol. 12, 2010, pp. 1084-89
Stellbrink, C. Arrhythmia recurrence after ablation of atrial fibrillation: should we be concerned about sleep apnea? Europace, Vol. 12, 2010, pp. 1051-52

Editor's comment: It is clear that severe OSA is not only a risk factor for the development of AF, but may also reduce the chance of a successful PVI procedure. Furthermore, there is evidence as seen from LAF Survey 14 that afibbers with sleep apnea can substantially reduce their afib burden through the use of a properly calibrated CPAP machine. There is also some evidence that weight reduction and cessation of alcohol consumption can reduce the severity of OSA. Thus afibbers who have interrupted sleep, daytime sleepiness, or a greater incidence of PVCs (measured on a Holter monitor) during the night might do well to consider a properly conducted sleep study and the use of a CPAP machine if indicated.