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In a small prospective study, implantable cardioverter defibrillator (ICD) lead malfunction was found to occur after left ventricular assist device (LVAD) implantation, but with possible improvement over time.
Researchers sought to determine the mechanism of lead malfunction by monitoring lead parameters during LVAD implantation. The authors noted that several mechanisms could explain the parameter changes after implantation including, “mechanical disruption of the leads themselves from insertion of the LVAD, inflammatory and metabolic changes during cardiopulmonary bypass [CPB], and alteration in ventricular geometry due to left ventricular decompression and septal shift”
A total of 32 patients with ICDs who underwent LVAD implantation between May 2011 and January 2014 were evaluated. Patients were at least 18 years of age (mean age: 55.8 ± 13.9 years) with single chamber, dual chamber, or biventricular ICDs. Nineteen had coronary artery disease, 25 had LVAD implantation as destination therapy, and 22 were male.
A subgroup of 20 patients underwent serial intraoperative testing at 11 additional time points during implantation.
Sensing, impedance, and thresholds were tested for each lead at baseline. Right atrium (RA), right ventricle (RV), and LV lead malfunctions were defined as a >50% decrease from baseline or a >50% increase in threshold from baseline. Sensing was considered improved if after decreasing by >50%, it later increased to ≥50% of the baseline value. Likewise, a pacing threshold that increased by >50% from baseline was considered improved if returned to ≤150% of the baseline value.
Finally, if the RV pacing lead increased or decreased by >100 ohms from baseline to final value, it was considered “significantly changed” as was the high voltage (HV) impedance if it increased or decreased by >10 ohms. The authors noted that the definitions were created to “help determine the mechanism of lead malfunction and are not intended to reflect a change that is necessarily clinically significant.”
Researchers compiled data 50.0 ± 46.8 months after ICD implantation. A total of 69 leads were tested before, during, 1 week, and 3 months after implantation.
Seven patients experienced a decrease in RV sensing by >50% from baseline, immediately post-implantation. In 2 of the patients who had decreased sensing, their RV pacing threshold increased >50% from baseline immediately post-implantation and was still elevated at 1 week.
At baseline, the average RV pacing impedance was 429.3 ± 46.5 ohms and 447.6 ± 94.2 ohms at the end of implantation (P=.59). At 1 week, the RV pacing impedance was 418.0 ± 49.5 ohms and 449.7 ± 85.9 ohms at 3 to 12 months follow-up (P=.63).
The average RV HV impedance was 48.9 ± 13.8 ohms at baseline and 41.1 ± 11.2 ohms at the end of implantation (P<.0001). At 1 week, it was 38.9 ± 9.2 ohms (P<.0001) and 44.4 ± 9.6 ohms (P<.0001) at the 3 to 12 month follow-up mark.
Three patients experienced stroke and 2 patients had pump thrombosis. During the follow-up period, 13 of the 32 patients died and 9 underwent orthotopic heart transplant (1 of whom died 3 days later).
“Although proposed in previous reports, mechanical disruption of the leads during surgery did not explain our findings,” the authors wrote. “We found no radiographic changes in positions of the leads before and after VAD implantation. There was no gross radiographic dislodgement observed in any RA, RV, or LV leads by a blinded radiologist comparing pre- and post-LVAD chest X-rays.”
They added, “We hypothesize that ICD lead parameter changes following LVAD are due to unloading of the LV and concomitant leftward shifting of the septum, altering the ICD lead/myocardium conformation.” However, due to the small size of the study, this cannot be definitively confirmed.
Finally, the authors cautioned that ICD lead revisions should only occur after careful weighing potential risks and benefits to the individual patient, especially since lead parameters appear to improve over time.
Reference
Hu YL, Kasirajan V, Tang DG, et al. Prospective evaluation of implantable cardioverter defibrillator lead function during and after LVAD implantation. JACC Clin Electrophisol. 2016. doi: doi:10.1016/j.jacep.2016.01.008.
