Chronic total occlusion (CTO) an independent predictor of ventricular arrhythmias

Chronic total occlusion (CTO) an independent predictor of ventricular arrhythmias

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 1. 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.

Sixteen percent incidence of ventricular arrhythmias in this cohort was comparable to previous studies. 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 accounting 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.

Forty four percent of these patients had chronic total occlusions, that was rather a high percentage in this cohort. Other studies have reported CTO in the range of 15 – 30%. It is possible that there is a selection bias in that those with more extensive disease will have lower ejection fraction and get an implantable cardioverter defibrillator implanted. Large areas of silent and residual ischemias have been documented in the territory of chronic total occlusion, even in the presence of collaterals [2]. Probably collaterals were not sufficient enough to prevent exercise induced ischemia which could trigger ventricular arrhythmias.

Presence of a chronic total occlusion meant higher ventricular arrhythmias and mortality on long term follow up. Probably another reason for the CTO enthusiasts to intervene with complex CTO opening procedures. But we will need evidence later to show that opening up CTO improves the outcome on long term.

Reference

  1. Nombela-Franco L, Mitroi CD, Fernández-Lozano I, García-Touchard A, Toquero J, Castro-Urda V, Fernández-Diaz JA, Perez-Pereira E, Beltrán-Correas P, Segovia J, Werner GS, Javier G, Luis AP. 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.
  2. Werner GS, Fritzenwanger M, Prochnau D, Schwarz G, Ferrari M, Aarnoudse W, Pijls NH, Figulla HR. Determinants of coronary steal in chronic total coronary occlusions donor artery, collateral, and microvascular resistance. J Am Coll Cardiol. 2006; 48:51–58.