NEW YORK (Reuters Health) – Mitral isthmus ablation is a technically challenging procedure and acute subclinical circumflex ‘injury’ following the procedure “is not uncommon,” clinicians from the United Kingdom report the European Heart Journal, available online now.
Among 54 patients who had catheter ablation procedures that included mitral isthmus ablation for treatment of atrial fibrillation, 15 (28%) had angiographic changes following ablation, Dr. Timothy Betts and colleagues from Oxford Heart Centre, John Radcliffe Hospital NHS Trust in Oxford report.
Eight patients had mid-circumflex narrowing only, one had circumflex and obtuse marginal (OM) artery narrowing, one had OM narrowing only, and five had distal circumflex occlusion/narrowing.
Five patients had significant narrowing (50% to 84%), which resolved with intracoronary glycerine trinitrate, which, the researchers say, suggests that the main underlying mechanism may be spasm as described by other clinicians.
Mitral isthmus block was successfully achieved in 89% of patients (60% required CS ablation).
During follow up, no patient experienced angina during follow up and there was never any evidence of electrocardiographic or echocardiographic abnormalities.
Dr. Betts and colleagues identified several risk factors for acute circumflex injury after mitral isthmus ablation, including ablation within the coronary sinus (CS); 14 (93%) of the patients with this injury had CS ablation. A long mean CS ablation time (5.0 vs. 2.6 minutes) also increased the risk of acute circumflex injury.
“Operators should exercise caution during mitral isthmus ablation and consider performing coronary angiography in patients who have had extensive ablation especially in the CS,” they advise.
Close proximity of the circumflex artery to the CS (3.2 vs. 5.6 mm), and a small distal circumflex diameter (1.0 vs. 2.1 mm) also emerged as significant risk factors for this injury.
Dr. Betts and colleagues say additional studies are needed to elucidate the precise mechanism behind acute coronary artery injury after radiofrequency ablation and its longer term sequelae.
Eur Heart J 2011.
