Risk of ventricular fibrillation by HFS in the coronary sinus
In Case 7, HFS within the CS inadvertently captured ventricular myocardium leading to ventricular fibrillation (Figure 4A, B). Po et al. advised against HFS delivered within 2 cm of the ventricle to avoid inducing ventricular fibrillation.6 The CS runs along the mitral annulus so that the catheter within the CS would be located close to the ventricular myocardium. We carefully performed trial pacing at 20 V before HFS to confirm the stimulus would not capture the ventricle. However, the respiratory motion of the heart or ventricular refractoriness due to rapid ventricular responses under ISP infusion might result in either transient capture or loss of capture. Hence, the ablation of AF-Nests might be an alternative to HFS within the CS.