Chronic total occlusion (CTO) has been identified as an independent predictor of ventricular arrhythmias in the VACTO (Ventricular Arrhythmias and Chronic Total Coronary Occlusion) Primary Study [Nombela-Franco L et al. Ventricular Arrhythmias Among Implantable Cardioverter Defibrillator Recipients for Primary Prevention: Impact of Chronic Total Coronary Occlusion (VACTO Primary Study). Circ Arrhythm Electrophysiol. 2012;5:147-54]. They included all consecutive patients receiving implantable cardioverter defibrillators (ICD) for coronary artery disease and identified seventy one patients out of a total of one hundred and sixty two patients as having at least one chronic total occlusion.
The presence of chronic total occlusion was associated with higher rates of ventricular arrhythmia requiring ICD therapy and higher mortality with a log-rank <0.01. Chronic total occlusion was also independently associated with appropriate ICD intervention on multivariate analysis with a hazard ratio of 3.5 (p=0.003). This was even after accounted for the other usually recognised factors like age, smoking, QRS width, NYHA functional class, renal dysfunction, left ventricular ejection fraction and the use of beta blocker medications. Possible mechanisms of ventricular arrhythmias could be residual ischemic areas and myocardial scars in the area which was supplied by the chronic total occlusion. Ischemia has been documented by other studies even in the presence of collaterals.