The Electrophysiological Basis Of Right Ventricular Outflow Tract Arrhythmias

Right ventricular outflow tract (RVOT) has been proved as an important source in the initiation of ventricular arrhythmias. Many evidences have been reported that ventricular arrhythmias originated from RVOT in individuals without any heart diseases. However, the underlying ionic mechanisms of ventricular arrhythmias originated from RVOT remain unclear. The purpose of this study was to disclose the ionic basis of such arrhythmia.Using conventional microelectrode technique, three different AP types in RVOT were recorded: pace-making action potentials; slow response action potentials; and fast response action potentials. Then, significant dispersion in APD occurred in this location of right ventricle of rabbit heart. EAD and DAD can be recorded in right ventricular outflow tract without any inducement.Using the whole-cell patch-clamp technique, clear evidence was provided for the existence of a hitherto unreported, voltage-dependent nonselective cation current (NSCC) in rabbit ventricular myocytes. Na⁺, K⁺, Cs⁺ can permeate through the channel and the nonselective cation current can be blocked by Gd³⁺.They were sensitive to Ca²⁺,Mg²⁺-free and insulin in bathing solution. Depleting of Ca²⁺and Mg²⁺ in the bathing solution can increase the amplitudes of this outward current. Insulin (with normal concentration of Ca²⁺and Mg²⁺ in Tyrode's solution) can also increase the amplitude of NSCC.The amplitude of I_To in different group is markedly different while I_k1 and I_k have not significant difference between the two areas. NSCC distributed in all of the cells in right ventricle. But the amplitude of this current is significantly less in some right ventricular outflow tract myocytes, or even lacking. Corresponding to this the action...