Pulse arrival time variation as a non-invasive marker of acute response to cardiac resynchronization therapy.

AIMS: Successful cardiac resynchronization therapy (CRT) shortens the pre-ejection period (PEP) which is prolonged in the left bundle branch block (LBBB). In a combined animal and patient study, we investigated if changes in the pulse arrival time (PAT) could be used to measure acute changes in PEP during CRT implantation and hence be used to evaluate acute CRT response non-invasively and in real time. METHODS AND RESULTS: In six canines, a pulse transducer was attached to a lower limb and PAT was measured together with left ventricular (LV) pressure by micromanometer at baseline, after induction of LBBB and during biventricular pacing. Time-to-peak LV dP/dt (Td) was used as a surrogate for PEP. In twelve LBBB patients during implantation of CRT, LV and femoral pressures were measured at baseline and during five different pacing configurations. PAT increased from baseline (277 ± 9 ms) to LBBB (313 ± 16 ms, P < 0.05) and shortened with biventricular pacing (290 ± 16 ms, P < 0.05) in animals. There was a strong relationship between changes in PAT and Td in patients (r2 = 0.91). Two patients were classified as non-responders at 6 months follow-up. CRT decreased PAT from 320 ± 41 to 298 ± 39 ms (P < 0.05) in the responders, while PAT increased by 5 and 8 ms in the two non-responders. CONCLUSION: This proof-of-concept study indicates that PAT can be used as a simple, non-invasive method to assess the acute effects of CRT in real time with the potential to identify long-term response in patients.

Microsurgical decompression for central lumbar spinal stenosis: a single-center observational study.

OBJECTIVE: To assess outcomes and complications in patients undergoing microsurgical decompression for central lumbar spinal stenosis (LSS) without radiologic instability. METHODS: Prospective data for patients operated at the Department of Neurosurgery, St. Olavs University Hospital, Norway, were obtained from the Norwegian Registry for Spine Surgery (NORspine) from 2007 to 2012. The primary outcome was change in Oswestry disability index (ODI) at 1 year. The secondary endpoint was perioperative complications. Complications were graded according to the Ibanez classification system. RESULTS: For all patients (n = 125), the mean improvement in ODI at 1 year was 16.9 points (95% CI 13.5-20.2, p < 0.001). Seventy-six (71.7%) patients achieved a minimal clinically important difference in ODI (defined as ≥8 points improvement). The total number of complications within 3 months of surgery was 22 (17.6%). There were 14 medical and eight surgical complications, and all were Ibanez grade I or II (mild or moderate) complications. Four (3.2%) complications occurred while being admitted to the hospital and 18 (14.4%) occurred within 3 months following hospital discharge. The most common complication was urinary tract infection (n = 11, 8.8%). CONCLUSIONS: Microsurgical decompression for central LSS in the absence of radiological instability is an effective and safe treatment.