Intraoperative characterization of interventricular mechanical dyssynchrony using electroanatomic mapping system--a feasibility study.

BACKGROUND: Interventricular mechanical dyssynchrony (VVMD) is a strong predictor of cardiac resynchronization therapy (CRT) response. However, no simple and reliable clinical method of measuring VVMD during CRT implant is currently available. We tested the hypothesis that the EnSite™ NavX™ system (St. Jude Medical, St. Paul, MN, USA) can be used intraoperatively to determine VVMD, thereby facilitating CRT optimization. METHODS: During CRT implant, the leads in the right atrium (RA), right ventricle (RV), and left ventricle (LV) were connected to the EnSite™ NavX™ system to record the real-time 3D motion of the lead electrodes. The distances from RA to RV lead electrodes (RA-RV) and RA to LV lead electrodes (RA-LV) were computed over ten cardiac cycles during each of RV pacing and biventricular (BiV) pacing, respectively. The degree of synchrony was computed from the distance waveforms between RA-RV and RA-LV by a cross-covariance method to characterize VVMD. Septal-to-posterior wall motion delay (SPWMD) from M-mode echocardiography (echo) was measured for reference at each pacing intervention. VVMD was present in all five patients undergoing CRT implant. RESULTS: Four of the five patients demonstrated clear improvement in EnSite™ NavX™-derived VVMD during BiV versus RV pacing, which corresponded to the SPWMD results by echo. CONCLUSIONS: It is feasible to characterize VVMD and resynchronization in CRT patients with the EnSite™ NavX™ system during implant, demonstrating its potential as a tool for intraoperative CRT optimization.

The use of telescoping guide catheters for coronary sinus cannulation and sub-selecting tributaries in left ventricular lead placement.

INTRODUCTION: Failure to enter the coronary sinus (CS) with a guiding catheter and entering its tributaries remains challenging in left ventricle (LV) pacing lead implants for cardiac resynchronization therapy (CRT). A dual telescoping catheter system (8F outer/6F inner) is designed to provide the ability to adjust the catheter curve size, shape and/or reach to the patients' anatomy avoiding the need for catheter change. METHODS: Five different designs for CS cannulation were randomly tested in 64 patients scheduled for CRT device implant. RESULTS: In 33 consecutive patients three adaptable telescoping guiding catheter systems were tested per patient, the adaptable catheters had higher overall cannulation success rates (68, 63 and 62%) compared to the fixed shape catheter (46%) and an greater cannulation success rate when the CS location was not known (70, 53 and 72% vs 33% for the fixed shape). In a second group of 31 CRT patients the two telescoping catheters had similar high levels of success (71-80%), with or without using the inner catheter. CONCLUSIONS: The telescopic system is adaptable to a wide range of anatomical variations in patients and can result in a higher CS cannulation success rate due to its adjustability in the RA in search for the CS ostium. On top of this the inner catheter allows for sub-selecting the CS tributaries.

Clinical evaluation of two different evoked response sensing methods for automatic capture detection in the left ventricle.

BACKGROUND: This acute feasibility study compared two different automatic capture detection methodologies, the reduced coupling capacitor (RCC) and the independent pace/sense (IPS) methods, for the left ventricle (LV). METHODS: LV threshold tests were performed in DDD mode, with LV-only and bi-ventricular (BiV) pacing using an external cardiac resynchronization therapy (CRT) defibrillator. Evoked response (ER) signals from LV leads were recorded using the LV(Tip) (LV(Tip)-->Can) and LV(Ring) (LV(Ring)-->Can) to empty pulse generator (Can) housing sensing vectors to evaluate the two methodologies. Pacing vector, pulse duration, atrioventricular delay, and interventricular delay were varied to assess their effects on ER. The minimum ER amplitude (ER(min)), signal-to-artifact ratio (SAR), and ER amplitude voltage dependence were evaluated. ER(min)>2 mV and SAR(min)>2 define potential automatic LV capture detection for the two methodologies. RESULTS: Data collected from 43 patients (63.7 +/- 11.0 years) were analyzed, including unipolar and bipolar (14/29) LV leads. Neither ER sensing method was affected by changing the pacing vector. The LV(Tip)-->Can ER(min) was significantly decreased at the 1.0-ms pulse duration when compared to 0.4-ms (p < 0.05). During BiV pacing, LV(Tip)-->Can ER(min) increased at negative interventricular delays and decreased at positive interventricular delays relative to simultaneous pacing. LV(Tip)-->Can resulted in fewer patients with sufficient ER characteristics for capture detection, albeit only significantly at the extended pulse duration (79% vs 97%, p < 0.05) and at simultaneous and positive interventricular delays (81% vs 97%, p < 0.05). CONCLUSIONS: Though LV capture detection was feasible using both investigated methods, the RCC method (LV(Tip)-->Can) sensitivity to the evaluated pacing parameters suggests the IPS method (LV(Ring)-->Can) provides a more robust performance.