A large inherent delay between the ECG and EGM signals in the pacing system analyzer from Medtronic makes it unsuitable to estimate timing events during CRT implantation.

BACKGROUND: Following an observation of pacing markers being placed after the beginning of the paced QRS complex when using the analyzer module 2290 of the Medtronic 2090 programmer, we decided to determine the delay between the EGM and the ECG channels and comparing it to the St Jude Merlin® programmer. METHODS: We obtained ECG lead I simultaneously from both the ECG cable and by attaching the atrial clamps of the EGM cable on the left and right shoulder. We were then able to directly measure any delay. Then we compared measurements of start QRS to LV sense (qLV) in patients implanted with CRT in the last year where we had data on qLV at implant and at 6-month follow-up. At implant qLV was measured by the analyzer modules and at 6-month follow-up, it was measured in the pacing devices. RESULTS: We found that the delay between the EGM and ECG channels was 59 ±â€¯4 ms in the Medtronic analyzer (ECG first) and 4 ±â€¯3 ms in the St Jude analyzer (EGM first). In 16 CRT patients where the Medtronic analyzer had been used, the difference between qLV at implant and qLV at 6 months was 60 ±â€¯27 ms whereas this difference was 2 ±â€¯28 ms in 34 CRT patients where the St Jude analyzer had been used (p < 10-7). CONCLUSION: There is a delay of about 60 ms between the EGM and ECG channels of 2290 analyzer module of the Medtronic 2090 programmer making it unsuitable for determining timing measurements between QRS and EGM.

Optimal Cardiac Resynchronization Therapy Pacing Rate in Non-Ischemic Heart Failure Patients: A Randomized Crossover Pilot Trial.

BACKGROUND: The optimal pacing rate during cardiac resynchronization therapy (CRT) is unknown. Therefore, we investigated the impact of changing basal pacing frequencies on autonomic nerve function, cardiopulmonary exercise capacity and self-perceived quality of life (QoL). METHODS: Twelve CRT patients with non-ischemic heart failure (NYHA class II-III) were enrolled in a randomized, double-blind, crossover trial, in which the basal pacing rate was set at DDD-60 and DDD-80 for 3 months (DDD-R for 2 patients). At baseline, 3 months and 6 months, we assessed sympathetic nerve activity by microneurography (MSNA), peak oxygen consumption (pVO2), N-terminal pro-brain natriuretic peptide (p-NT-proBNP), echocardiography and QoL. RESULTS: DDD-80 pacing for 3 months increased the mean heart rate from 77.3 to 86.1 (p = 0.001) and reduced sympathetic activity compared to DDD-60 (51±14 bursts/100 cardiac cycles vs. 64±14 bursts/100 cardiac cycles, p<0.05). The mean pVO2 increased non-significantly from 15.6±6 mL/min/kg during DDD-60 to 16.7±6 mL/min/kg during DDD-80, and p-NT-proBNP remained unchanged. The QoL score indicated that DDD-60 was better tolerated. CONCLUSION: In CRT patients with non-ischemic heart failure, 3 months of DDD-80 pacing decreased sympathetic outflow (burst incidence only) compared to DDD-60 pacing. However, Qol scores were better during the lower pacing rate. Further and larger scale investigations are indicated. TRIAL REGISTRATION: ClinicalTrials.gov NCT02258061.