The role of MDCT in management of arrhythmias in congenital and acquired pediatric heart diseases

Abstract

Due to the rapid evolution of the treatment of arrhythmias by catheter ablation which attacks the anatomical foci of arrhythmias by the radio frequency, cardiologist are in need to a road map for the heart structures before intervention which could be afforded by intra-cardiac Echocardiography, conventional catheterization methods, MDCT or MRI. In comparison to the conventional catheterization method MDCT overcomes the limitations such as the overlap of the adjacent cardiovascular structures, difficulties in simultaneously depicting the systemic and the pulmonary vascular systems, the catheter-related complications, especially the prolonged time of exposure in ablation of the arrhythmogenic foci, also it gives simultaneous evaluation of the cardiovascular structures and the lung parenchyma which is important in patients with congenital heart diseases, obtains functional data about motion of the ventricular wall. MDCT produces the highest spatial resolution; which allows the best postprocessing of anatomic detail for three-dimensional reconstructions, which often is important in patients with complex congenital heart disease, in whom anatomic relationships help in presurgical and precatheter planning. Also it gives the best evaluation of the vascular system of the heart; Coronary arteries anomalies could be the cause of the fatal cases and arrhythmias, such as, malignant course of the coronary arteries, or the anomalous origin of Left main coronary artery from the pulmonary artery ALCAPA which leads to death in the majority of cases within the first 2 years. On the other side cardiologists need to map the arterial system accurately to avoid arterial injury during the Electrophysiological procedures. 137 Coronary venous system also acts as a bridge for the conduction system of the heart, transferring the normal and abnormal signals, e.g. the coronary sinus which can transfer atrial fibrillation waves from the abnormal foci in the atria to the ventricles. This bypasses the natural protective barrier of the heart the AV node. Also the coronary sinus can be the origin of the arrhythmia as in case of persistent vein of Marshall or persistent left SVC. On the other side Cardiologists need to map and measure the dimensions and extensions of the venous system as it is the site of insertion of the CRT leads. MDCT gives sufficient information about the pulmonary venous system in case of AF, the cardiologist needs to know; the normal anatomy, the anatomic variants and number of the pulmonary veins, the ostial diameters of each vein in 2 orthogonal dimensions which can be obtained in a perpendicular plans to the vein e.g. coronal and axial and the distance to the first-order branch (trunk length) as this helps to determine the size of the used catheters, the saddle distance between the 2 adjacent pulmonary veins on one side, Early branching (ostial branch) of the PV (from the first 1 cm of the trunk), Presence of accessory or supernumerary PVs. All these variants can be the foci of the arrhythmia. The variations of middle lobe and lingual PV connections can be traced by using the MDCT, as they may be connected to the inferior PVs or directly to the left atrium, which could be a leading point of arrhythmia. It delineates the anatomic course of the esophagus relative to PVs and the posterior left atrial wall to precise the amount of energy used.