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OBJECTIVE: Right parasternal mediastinotomy (RPMS) with right atriotomy has been utilized for pacemaker insertion. Although a similar approach might benefit patients with intrapericardial adhesions and technical barriers (8-13% of patients) to left ventricular lead insertion for cardiac resynchronization, appropriate introducers and techniques have not been described.
METHODS: Anesthetized pigs underwent computerized axial thoracic tomography (CAT). Each digitized scan was used to define an introducer shape unique to the parent animal, using thee-dimensional (3-D) modeling software. Each pig finally underwent RPMS demonstrating coronary sinus lead insertion using its custom configured introducer. With Institutional Review Board approval, 65 patients were identified who had undergone conventional endocardial coronary sinus lead insertion followed by CAT scanning. Scans were used to fabricate 3-D molds for introducer configuration via RPMS.
RESULTS: Fifty-two introducer paths were defined following anatomic pathways and avoiding bends inconsistent with materials use for commercial strip away introducers. Each path was defined by a distance, bend, and twist relative to the long axis of the superior vena cava. The commonest dimensions were: distance 28.8 mm, bend angle 89.8 degrees, and twist 80 degrees. A prototype cannula was tested for fit in an appropriate postmortem human specimen, preserved by fresh freezing.
CONCLUSIONS: The RPMS approach to the coronary sinus for cardiac resynchronization is feasible. Human CAT scans can be used to define curvatures and dimensions for commercially produced introducers.