Sustrato electroanatómico de la taquicardia ventricular de probable origen epicárdico en pacientes con miocardiopatía dilatada no isquémica

La incidencia de taquicardia ventricular monomórfica sostenida (TVMS) en pacientes con miocardiopatía dilatada no isquémica (MCDNI) es baja, estimándose que ocurre en menos de un 5% de los pacientes. Sin embargo, sus implicaciones clínicas son muy importantes ya que su aparición conlleva un elevado riesgo de muerte. El tratamiento de las arritmias ventriculares en este contexto se basa fundamentalmente en el implante de un desfibrilador automático implantable (DAI). No obstante, en los últimos años la ablación con catéter ha emergido como una terapia adyuvante de primera línea.En el segundo de los artículos que conforman esta tesis se describe la importancia de delimitar el trayecto del nervio frénico izquierdo durante los procedimientos de ablación epicárdica de TV en pacientes con MCDNI. La mayor parte de los pacientes con MCDNI presentan zonas de cicatriz epicárdica que preferentemente se localizan en la pared lateral del ventrículo izquierdo, que es justamente la zona de transcurso habitual del nervio frénico izquierdo. Mediante la estimulación con el catéter de ablación situado en el epicardio se puede delimitar su curso y de este modo evitar la parálisis frénica durante la aplicación de radiofrecuencia en estas zonas. 1.5mV. Scar is defined by the presence of signals 1.5mV and dense scar is defined when amplitude is below 0.5 mV. However, there is a lack of reference values for the signals obtained during epicardial mapping. Traditionally the same reference values previously described for the endocardium have been applied in the epicardium, but this assumption may be inaccurate. Epicardial fat, which is normally distributed around the coronary vessels and the auriculo-ventricular groove may be responsible for low voltage signals obtained in the epicardium that are not real pathologic scars. For that reason we firstly established normal criteria for the signals obtained in the epicardium of 8 patients without structural heart disease who underwent epicardial electroanatomical mapping during ablation of idiopathic VT. These reference values were then applied to the electroanatomical endo and epicardial mapping of 22 patients with NICM and VT suspected to be of epicardial origin. Detailed mapping showed the presence of substantial epicardial substrate with confluent areas of epicardial scar in 82% of patients compared with only 54% of patients showing confluent areas of scar in the endocardium. Moreover, the epicardial scar area was significantly larger in the epicardium when compared with endocardial scar areas. Epicardial scar areas were characterized not only by the presence of low voltage but also by the presence of wide, split and late potentials. In these patients , the ablation of the epicardial substrate was associated with a high success rate of 71%. The second article configuring this doctoral thesis describes the significance of a proper delimitation of the left phrenic nerve curse during epicardial VT ablation in patients with NICM. Most patients with NICM show confluent epicardial scar areas typically located in the left lateral wall, which is also the typical left phrenic nerve course. High output pacing with the ablation catheter can deliniate the phrenic nerve course in order to avoid the phrenic nerve palsy during radiofrequency application in these areas