sccncmvt.ppt

Most outflow tract tachycardias originate in perivalvular tissue, which may be anatomically predisposed to fiber disruption that enhances arrhythmogenesis. In addition, the proximity of the outflow tract to the epicardial fat pads containing the ganglionated plexuses and the unique response to exercise and hormonal changes suggest that the autonomic nervous system also plays a role in this arrhythmogenesis. Lerman et al have shown that most forms of RVOT VT are sensitive to adenosine and the most likely mechanism is catecholamine mediated delayed afterdepolarizations and triggered activity. Mediated by the activation of cyclic AMP that causes an increase in intracellular calcium and an oscillatory release of calcium from sarcoplasmic reticulum. The right coronary cusp (RCC) of the aortic valve is directly posterior to the thick posterior infundibular portion of the RVOT. The true septum of the RVOT is not leftward but rather posterior and similarly, the septal portion of the LVOT is its anterior portion, just behind the RVOT. catheter placed in the RCC will record a large amplitude ventricular electrogram, the origin of which is mainly the right ventricular myocardium and partly the supravalvar left ventricular myocardium Recordings from the left coronary cusp (LCC) may map a supravalvar left ventricular myocardium, portions of the distal peripulmonary valve, posterior right myocardium, as well as the mitral annular left ventricular myocardium. The noncoronary cusp (NCC) of the aortic valve generally is surrounded only by atrial structures, and thus, mapping in the NCC will identify predominately atrial signals that may arise either from the right atrium, left atrium, or the interatrial septum. Therefore, ablation in the NCC is rarely required for ventricular tachycardia, but more often for atrial tachycardias from these regions. However, supravalvar posterior left ventricular tachycardias can occasionally be ablated with a catheter placed in the depths of the NC