New results support the feasibility of an entirely extracardiac pacing method in a heterogeneous patient population, using a minimally invasive, parasternal delivery approach, with adequate sensing and thresholds suited for temporary pacing. The study, authored by Anne-Floor BE Quast, Niek EG Beurskens (University of Amsterdam, The Netherlands) and colleagues, was recently published in Circulation: Arrythmia and Electrophysiology.
One of the major findings of the study was that a total of 166 out of 174 patients, representing 95% of the cohort, had a viable lead access path through the fourth, fifth, or sixth intercostal space. In addition, accessing the targeted implant location using a custom delivery tool was successful in all five cadavers and three humans without the use of fluoroscopy, with an average lead delivery time of 121±52 seconds. No damage to the lung, pericardium, heart, or internal thoracic vessels occurred. Another important finding was that pacing performance was tested in six human subjects showing a threshold voltage of 4.7 volts, threshold pulse width of 1.8 ms, and an impedance of 1,205 Ohms. R-wave amplitudes measured 9.6 mV.
In order to test the feasibility of the pacing system, the investigators carried out a number of evaluations, including a retrospective computed tomography analysis to characterise anatomic variations related to lead access, accessing the anterior mediastinum in cadavers and human subjects using a custom delivery tool and acute clinical pacing performance.