br Conflict of interest br Introduction
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Discussion Dextrocardia is commonly associated with situs inversus totalis (incidence: 2 in 10,000 individuals) and rarely associated with situs solitus (incidence: 1 in 20,000 individuals). While associated cardiac anomalies are seen in approximately 5% of patients with dextrocardia and situs inversus, the majority (>90%) of patients with dextrocardia and situs solitus have associated anomalies, the most common of which are atrioventricular discordance and transposition complexes . Literature describing transvenous pacemaker implantation techniques in patients with congenital h2 receptor antagonist disease is scarce . There is no description of dual chamber pacemaker implantation techniques in patients with dextrocardia, especially in those with situs solitus and corrected transposition of the great arteries. Since dextrocardia with situs inversus is a mirror image of the normal anatomy, the use of a flipped image and opposite angulated views, that is, RAO in place of LAO and vice versa, has been suggested with no further details on implantation technique . This method, however, cannot be used in dextrocardia with normal situs and other cardiac malpositions in which the heart is not a mirror image of normal. In dextrocardia with normal situs, both atria, with their appendages and connecting veins, retain their normal positions, while the ventricles are rotated to the right (Fig. 4). Since a majority of such malformations have associated cardiac defects in the form of ventricular inversion, fluoroscopic orientation becomes very difficult and lead positioning is extremely challenging. To circumvent this problem and to guide the implantation of the leads, we used venous angiograms that were obtained by inserting a 6F-valved introducer with a side port via the second access. Cine angiograms acquired in the LAO, RAO, and AP views served as roadmaps to facilitate lead positioning in the atria and the ventricle. In addition to serving as roadmaps, the cine films also revealed important anatomical information regarding the orientation of the septum and morphology of the systemic venous chambers. The initial lead position that seemed to be septal in the AP and LAO projections was in fact on the lateral wall, which was evident on the angiogram obtained in the RAO view. The RAO view not only served as a guide to position the ventricular lead, but also provided useful information on the anatomy of the septum and the lack of trabeculation in the venous ventricle. The coexistence of CCTGA has important implications with regard to the mode of lead placement (endocardial vs. epicardial) and the type of lead used for transvenous implantation. In a series of patients with isolated CCTGA requiring pacemaker implantation, endocardial lead placement has been shown to have equally favorable long-term outcomes compared with epicardial lead placement . Active fixation leads are preferred over passive fixation leads for stable transvenous pacing in CCTGA because of the lack of trabeculations in the smooth-walled venous ventricle, which is a morphologically left ventricle. Although septal pacing was attempted with an active fixation lead, the lack of trabeculations and ridges along with the abnormal orientation of the septum made it impossible to obtain a stable position over the septum; therefore, we ultimately fixed the lead to the apex of the ventricle. Angiography was also helpful in identifying the right atrial appendage and assisted in the positioning of the atrial lead.
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