Integration of high-detail-three-dimensional anatomical evaluation of the atrium with functional and metabolic factors to improve safety and effectiveness of catheter ablation of supraventricular arrhythmias

Since the first successful pacemaker implantation in 1958, pacing remains the only reliable treatment for severe bradycardia. So far, pacing technology consists of a hermetically sealed can enclosing a battery and electronic circuits that is connected to the heart by transvenous leads to deliver the pacing therapy. Despite continuous technological improvements, cardiac pacing remains associated with a nontrivial rate of complications related to the pocket containing the can and/or to the transvenous leads. Leadless pacemakers were designed to reduce these complications. The Micra TPS of Medtronic, currently the only available leadless pacing device for human use was introduced in clinical practice in 2015. At that time, little was known about its safety and efficacy beyond/outside investigational settings. In a first part of our PhD work we assessed the efficacy and safety of this leadless pacemaker in the real-world setting. In a single center study, we showed that the Micra can be successfully implanted very safely in a challenging population when a predefined ‘step by step’ implantation protocol is followed. As investigator in the post-market observational registry, we contributed to the confirmation of its safety and efficacy in a large population. In dialysis patients and patients after valvular interventions, known to have higher risk of complications with the use a conventional pacing,  we demonstrated the safety and efficacy of leadless pacing. Our work confirmed the low infectious risk of the leadless pacemaker after bacteremia in an elderly population.

In the second part of this PhD work we wanted to optimize the implantation procedure. We confirmed the feasibility to implant the Micra device in three septal positions including the basis of the RVOT. We demonstrated that poor lower limb vascular access and the presence of a prominent septo-marginal trabeculation in the right ventricle lengthened the implant procedure. However, operator experience remains the most important determinant of the implant duration.

The third part of this PhD work was dedicated to the initial evaluation of dedicated software enabling atrial mechanical sensing by the ventricular leadless pacemaker allowing VDD like physiologic pacing. In the Marvel 1 and 2 prospective multicenter studies the feasibility of AV synchronous pacing was demonstrated leading to, respectively 80% and 89.2% of AV synchrony with the use of MARVEL software. In the MARVEL Evolve study performed only in our center, we showed that the atrial sensing by the Micra device was stable over time and that the software behaved appropriately in the presence of atrial arrhythmia. Finally, we showed that the atrial function evaluated by 2D-echocardiography before the implantation was the main determinant of appropriate atrial sensing by a Micra AV (enabling AV synchrony).

In conclusion, safety and efficacy of the leadless pacing were confirmed in the general population but also in challenging populations for conventional pacing. Our work validated the feasibilty to implant Micra device in different regions of the right ventricle. The current development of the Micra AV, enabling AV synchrony pacing, the ongoing research on an atrial leadless device and devices for left ventricular pacing suggest the expanding use of leadless technology in the future.