Impact of the left ventricular lead on the efficacy of Cardiac Resynchronization Therapy for heart failure. : Electrophysiologic and clinical trials investigating active fixation left ventricular lead in cardiac resynchronization therapy.
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Background: This thesis examines the performance of different left ventricular (LV) leads and in particular a novel bipolar LV lead with a side helix for active fixation. Cardiac resynchronization therapy (CRT) provides improved cardiac performance and clinical outcome in heart failure patients with wide QRS complex. Placement of the LV lead in a segment remote from the region with latest mechanical activation or in a segment with myocardial scar is associated with high risk for non-response. The ability to reach the desired position, the rate of lead dislodgements, occurrence of phrenic nerve stimulation (PNS) and clinical outcome are affected by properties of the LV leads. Methods and results: In the first paper (Paper I) we presented the results from a prospective non-randomized trial of 106 patient who received a CRT-device with a novel active fixation bipolar LV lead. The primary objectives were to assess the lead implant success, the degree of LV lead concordance to the pre-decided target location, procedure times and perioperative adverse events. The secondary objectives were to evaluate the long-term performance concerning lead stability, long-term pacing capture thresholds (PCT), occurrence of PNS and need for repositioning of the lead. In 103 patients, the active fixation LV lead Attain Stability model 20066/4796, (Medtronic, Minneapolis, MN, USA) was implanted. We showed that this novel lead allowed placement of the lead over a wide range of vein anatomies. The average LV PCT at implant was low (1.04±0.6 V), remained stable at follow-up (0.92±0.5V) and no late dislodgements were observed. Moreover, the lead was placed in an LV segment concordant to the segment with latest mechanical activation in 73 % of the patients and in an adjacent segment in 24 % of the patients. In a subsequent trial that is the basis for Paper II and Paper III, the objective was to compare the active fixation LV lead and a quadripolar passive fixation LV lead. A randomized and blinded trial, that included 63 patients scheduled for CRT device implantation, was performed and the patients were followed up for 12 months. The latest contracting LV segment was identified as target segment by radial strain speckle-tracking echocardiography. In Paper II, we compared the electrical performance and the ability to achieve a stable proximal position in a coronary vein located concordant to the target segment. The success rate in reaching the target location was not significantly different between the two LV leads (p=0.69). Upon implantation, the quadripolar lead demonstrated a lower PCT than the bipolar lead (0.77±0.2V vs 1.09±0.48V, p= 0.02), but at follow-up, there was no difference. There were no differences in the LV lead implant times or radiation doses. The active fixation did not facilitate a higher grade of concordance to the target LV segment nor a more proximal position of the stimulating electrode. In the third article we compared the clinical outcome in terms of improvement of cardiac performance assessed by echocardiography. At follow-up, the reduction of LV end-systolic volume, and LV reverse remodeling responder rate, defined as LV end-systolic volume reduction >15 % was 77 % in the active fixation group and 84 % in the quadripolar group, which was not significantly different. (p=0.51). From baseline to 6 months follows-up the LV ejection fraction (LVEF) improved significantly in both groups, and more in the quadripolar group, but at 12 months follows-up the LVEF did not differ between the two groups. There were no significant differences between the two groups in changes in NYHA functional class or score in Minnesota Living with Heart Failure Questionnaire. The occurrence of PNS was 19 % in the active fixation group versus 10 % in the quadripolar group (p=0.30) and was resolved in all cases by reprogramming the device. All patients were alive at 12 months follow-up. There was no device infection. Conclusion: This thesis demonstrates that a novel active fixation bipolar LV lead may be placed over wide range of vein anatomies. We were not able to prove superiority over quadripolar passive fixation LV leads in terms of electrophysiologic parameters, ability to reach target segment or clinical outcome.
Består avPaper I: Active fixation of a thin transvenous left-ventricular lead by a side helix facilitates targeted and stable placement in cardiac resynchronization therapy. Keilegavlen H, Hovstad T, Faerestrand S. Europace. 2016;18(8):1235-40. Full text not available in BORA due to publisher restrictions. The article is available at: https://doi.org/10.1093/europace/euv272
Paper II: Performance of an active fixation bipolar left ventricular lead vs passive fixation quadripolar leads in cardiac resynchronization therapy, a randomized trial. H. Keilegavlen, P. Schuster, T. Hovstad, S. Faerestrand. Journal of Arrhythmia 2020 Nov 8;37(1):212-218. The article is available in the thesis. The article is also available at: https://doi.org/10.1002/joa3.12450
Paper III: Clinical outcome of cardiac resynchronization therapy in patients randomized to an active fixation bipolar left ventricular lead versus a passive quadripolar lead. H. Keilegavlen, P. Schuster, T. Hovstad, S. Faerestrand Scandinavian Cardiovascular Journal 2021;Jan 10;1-7. Full text not available in BORA due to publisher restrictions. The article is available at: https://doi.org/10.1080/14017431.2020.1869299