Elimination of phrenic nerve stimulation occurring during CRT

Background  

Phrenic nerve stimulation (PNS) occurs at follow-up in approximately 20% of patients with bipolar leads. The quadripolar Quartet model 1458Q (St. Jude Medical, Sylmar, CA, USA) left ventricular lead (LV) has four electrodes (one distal tip and three ring) capable of ten different pacing vectors which may allow reprogramming to eliminate PNS.     

Upgrading to biventricular pacing guided by pressure-volume loop analysis during implantation

Pressure–Volume Loop Analyses during CRT Implants. Introduction: cardiac resynchronization therapy (CRT) may improve prognosis in patients with chronic right ventricular (RV) pacing, and optimal lead position can decrease nonresponders. We evaluated the clinical and echocardiographic response to CRT in patients with previous chronic RV pacing, using pressure–volume loop analyses to determine the optimal left ventricular (LV) lead position during implantation. Methods and Results: In this single‐blinded, randomized, controlled crossover study, 40 patients with chronic RV apical pacing and symptoms of heart failure, decreased LV ejection fraction (LVEF) or dyssynchrony were included. During implantation, stroke work (SW), LVEF, cardiac output, and LV dP/dt_max were assessed by a conductance catheter. Clinical and echocardiographic response was studied during a 3‐month period of RV pacing (RV period, LV lead inactive) and a 3‐month period of biventricular pacing (CRT period). At the optimal LV lead position, SW (37 ± 41%), LVEF (16 ± 13%), cardiac output (29 ± 16%), and LV dP/dt_max increased (11 ± 11%) significantly during biventricular pacing compared to baseline. Additional benefit could be achieved by pressure–volume loop guided selection of the best left‐sided pacing location. RV outflow tract pacing did not improve hemodynamics. During follow‐up, symptoms improved during CRT, VO_2,max increased 10% and significant improvements in LVEF, LV volumes, and mitral regurgitation were observed as compared to the RV period. Conclusions: CRT in patients with chronic RV pacing causes significant improvement of both LV function as measured by pressure–volume loops during implantation and clinical and echocardiographic improvement during follow‐up. Pressure–volume loops during implantation may facilitate selection of the most optimal pacing site . (J Cardiovasc Electrophysiol, Vol. 22, pp. 677‐683, June 2011)     

Effect of Left Ventricular Function on Long-Term Left Ventricular Pacing and Sensing Threshold

Background: The effect of left ventricular (LV) systolic function on the long-term left ventricular pacing and sensing threshold is unclear. Methods and Results: We studied the effect of LV ejection fraction (LVEF) on the LV pacing and sensing threshold in 56 patients (mean age: 70.2 ± 10.5 years) underwent permanent LV pacing using a self-retaining coronary sinus lead (Model 1055 K, St Jude Medical, USA). In 49 patients, the LV lead was implanted for conventional pacemaker indication (sick sinus syndrome = 14, heart block = 26 or slow atrial fibrillation = 9). The remaining 7 patients were implanted for congestive heart failure. The LV pacing and sensing threshold, and lead impedance were compared between patients with LVEF <40% (Group 1, n = 28) and LVEF >40% (Group 2, n = 28) during implant and at 3-month follow up. The LV pacing lead was successfully implanted in all patients without any lead dislodgement on follow-up. At implant, Group 1 patients had a significant lower R wave amplitude, but similar LV pacing threshold and lead impedance as compared to Group 2. However, at 3-month follow-up, Group 1 patients had a significantly higher LV pacing threshold compared to Group 2 patients. There were no significant differences in the sensing threshold and lead impedance between the two groups. Furthermore, there was also a significant interval increase in LV pacing threshold in Group 1 patients (0.94 ± 0.12 V) after 3 months, but not in Group 2 patients (0.16 ± 0.08 V, p < 0.01). Conclusions: The results of this study suggest that the LV systolic function has a significant impact on the long-term LV pacing threshold. The long-term left ventricular pacing threshold in patients with left ventricular systolic dysfunction increased after implant and was higher than patients with normal left ventricular systolic function.     

Acute changes in electromechanical parameters during different pacing configurations using a quadripolar left ventricular lead

Purpose

Quadripolar left ventricular (LV) leads allow for several pacing configurations in candidates for cardiac resynchronization therapy (CRT). Whether different pacing configurations may affect LV dyssynchrony and systolic function is not completely known. We aimed to evaluate the acute effects of different pacing vectors on LV electromechanical parameters in patients implanted with a quadripolar LV lead.

Methods

In this two-centre study, within 1 month of implantation 21 CRT patients (65?±?8 years, 76 % men, 38 % ischemic) receiving a quadripolar LV lead (Quartet 1458Q, St Jude Medical) underwent LV capture threshold assessment, intracardiac electrogram optimization, and two-dimensional echocardiography during four pacing configurations: D1-P4, P4-RV coil, D1-RV coil, and P4-M2. LV dyssynchrony and contractile function were expressed by septal-to-lateral delay and global longitudinal strain (GLS).

Results

LV capture threshold varied between the configurations (P?P?=?0.003 and P?=?0.033 vs. spontaneous rhythm, respectively). GLS improved significantly vs. spontaneous rhythm only in the configuration D1-P4 (from ?8.6?±?3.5 to ?11.0?±?3.2 %, P?=?0.001). Accordingly, an increase in stroke volume and a decrease in mitral regurgitation were observed in the configuration D1-P4 (P?≤?0.001 vs. spontaneous rhythm).

Conclusions

In CRT patients receiving a quadripolar LV lead, significant variations in electromechanical parameters were observed by changing pacing vector. Individually targeting the optimal pacing site may enhance the acute haemodynamic response to CRT.     

Phrenic nerve stimulation in CRT patients and benefits of electronic lead repositioning: the ERACE trial

Purpose

Despite novel left ventricular (LV) lead technologies, phrenic nerve stimulation (PNS) remains an adverse effect observed in many patients with cardiac resynchronization therapy (CRT). Beyond anatomic repositioning, modern CRT devices allow avoidance of PNS also by software-based adaption of the pacing configuration. The Electronic Repositioning With Acuity and Easytrak Leads study evaluated the incidence of PNS in a CRT population and examined how often LV lead relocation can be avoided by “electronic repositioning” (ER).

Methods

Patients who had an indication for implantation of a first CRT defibrillator with the option of ER were enrolled. Primary endpoint was the efficiency of ER determined by the frequency of PNS with the standard pacing configuration (LV tip to RV coil) avoidable by ER. PNS and pacing parameters were evaluated during implant, predischarge, and first routine follow-up (FU) using four different pacing configurations available by ER.

Results

In total, 292 patients were enrolled and provided with a transvenous LV lead (82.2 % male, 65.5?±?9.2 years old). The majority of the population was in NYHA III (84.2 %) with a LV ejection fraction of 25.3?±?6.8 % and mean QRS width of 155?±?27 ms, ischemic cardiomyopathy was present in 43.6 %. Median FU was 116 days. In the standard pacing configuration, PNS was inducible in 19.0/25.6/24.6 % at implant/predischarge/FU, respectively, resulting in 32.2 % of the patients presenting at least once with PNS. The safety margin for the standard pacing configuration between LV and PNS threshold was <1.0 V at 0.5 ms in 5.6/7.0/5.0 % of the patients, corresponding with a total rate of 11.6 % during the FU. In the finally chosen configuration, clinically relevant PNS occurred in 1.0/2.2/1.3 %. The four vector configurations allowed all but 6 of 292 (2 %) patients to be reprogrammed using ER without reoperation.

Conclusions

The incidence of inducible PNS in CRT patients is considerable. In this study, PNS could be avoided in the majority of the patients by means of electronic repositioning. Thus, the use of ER should be considered for CRT patients.     

Safety and Feasibility of Coronary Sinus Left Ventricular Leads Extraction: A Preliminary Report

Background: transvenous positioning of the left ventricular (LV) lead in a branch of the coronary sinus (CS) is generally the preferred implantation technique in biventricular pacing. Very few data are reported about removal of LV pacing leads positioned in a CS branch. Aim of the study was to describe our experience with percutaneous extraction of LV pacing leads in order to evaluate feasibility and safety of this procedure.Methods: we enrolled 392 patients who underwent a biventricular pacing implant. The indication for catheter removal was considered in case of definite diagnosis of infection and in some cases of lead dislodgement or diaphragmatic stimulation. LV lead extraction was first attempted by manual traction; in case of failure a locking stylet or locking stylet plus radiofrequency could be used.Results: twelve of 392 patients implanted needed LV lead removal. The leads had been in place for 13.9 ± 11.7 months. Extraction was indicated in 5 of them for LV lead dislodgement or diaphragmatic stimulation, and in 7 patients for lead infection. In all cases manual traction succeeded to remove the LV lead. In 7 cases of infection, the right atrial and ventricular leads were removed. The mean total procedure time was 69 ± 22 min. No complications were observed.Conclusions: our study suggests that CS leads could be easily and safely removed without any complication, also when placed in a CS branch, at least for relatively young catheters.Dr. Giuseppe De Martino is currently a clinical consultant of St. Jude Europe and Guidant Italia srl.     

Single-center experience of a quadripolar pacing lead for cardiac resynchronization therapy

AIM

Recent studies have shown that a quadripolar left ventricular (LV) lead can result in low rates of dislocation and phrenic nerve stimulation (PNS) acutely and on medium-term follow-up in cardiac resynchronization therapy (CRT). We evaluated the outcomes of CRT patients in whom a quadripolar LV lead was implanted in our institution.

Methods

We studied 45 consecutive heart failure patients (75 % men; age, 70.3?±?9.0 years) following successful implantation of a quadripolar LV lead. Demographic and clinical data were collected preoperatively, and patients were followed up for 18.9 months.

Results

The implantation success rate was 100 %. Mean overall duration was 100.1?±?34.6 min, and X-ray exposure time was 13.20?±?13.5 min. The most distal effective pacing site was used as the final pacing configuration in all patients. Acute dislodgment requiring reoperation occurred before discharge in three cases (6.6 %). Six patients (13 %) suffered PNS during follow-up; we solved this problem by changing the stimulation vector. Three months after implantation, a mean of six out of ten effective sites (threshold <2.5 V at 1.5 ms, no PNS) per patient was recorded.

Conclusions

Over the relatively long term, the quadripolar LV lead was associated with excellent pacing thresholds and low rates of dislocation and PNS.     

Treatment of a degenerative stenosed CoreValve® aortic bioprosthesis by transcatheter valve‐in‐valve insertion

Background : Transcatheter aortic valve insertion (TAVI) is an emerging therapy in patients at high risk for open heart surgery. The long‐term durability of the bioprosthesis is unknown. This is the first report of a severely degeneratively stenosed 2nd generation 26 mm CoreValve^® aortic bioprosthesis which occurred five and a half years after TAVI. Methods and Results : A 92‐year‐old patient presented with decompensated heart failure NYHA class IV, pulmonary edema, and severe pulmonary hypertension. Echocardiography revealed critical AV‐stenosis due to heavily calcified bioprosthetic valve leaflets. Due to high surgical risk with an EuroSCORE of 64.97% and a STS‐mortality score of 27.0%, we decided to attempt a valve‐in‐valve insertion of a 3rd generation CoreValve^® prosthesis of the same size. Following the delicate retrograde passage of the calcified valve with a preformed stiff wire, balloon valvuloplasty of the severely stenosed CoreValve^® prosthesis under rapid right ventricular pacing was complicated by two balloon catheter ruptures. Insertion of the 3rd generation CoreValve^® prosthesis of the same size was quite complex but finally it was successfully completed. There was mild periprosthetic regurgitation and significant decrease in transaortic pressure without residual transvalvular gradient immediately after TAVI. Echocardiography and clinical follow‐up at 72 hr after TAVI confirmed excellent valve function with a decrease in systolic pulmonary artery pressure from 70 mm Hg to 35 mm Hg, increase in LV‐EF from 35% to 45%, and improvement of functional status from NYHA IV to NYHA II. The patient was discharged in good medical conditions at day eight. Conclusion : Degenerative stenosis of a CoreValve^® bioprothesis may be observed during long‐term follow‐up after successful TAVI for the treatment of severe aortic valve stenosis. A second valve‐in‐valve insertion appears feasible but may require particular interventional approaches. © 2011 Wiley Periodicals, Inc.     

Electrical Delay in Apically Positioned Left Ventricular Leads and Clinical Outcome After Cardiac Resynchronization Therapy

Electrical Delay in Apically Positioned LV Leads. Introduction: In recent studies, an anatomical apical left ventricular (LV) lead pacing location has been associated with deleterious outcome after cardiac resynchronization therapy (CRT). The differential impact of the LV lead electrical location in these patients remains unknown. Methods and Results: Thirty‐one consecutive CRT patients (mean age 71.7 ± 12.7 years, 55% left bundle‐branch block [LBBB] morphology) with an apical LV lead and LV lead electrical delay (LVLED) were studied. Anatomical LV lead location was determined via review of coronary venography and chest radiographs. Electrical location was assessed through intraprocedural LVLED measurement. Patients were dichotomized into either “long” LVLED (LVLED ≥ 50% of QRS) or “short” LVLED groups (LVLED < 50%). Patients in the long LVLED group demonstrated significantly greater freedom from a primary composite endpoint of all‐cause death, heart failure hospitalization, and cardiac transplantation at 2 years (81% vs 30%, P = 0.007 vs short LVLED patients). Longer LVLED was also associated with more favorable LV remodeling (LV end‐systolic volume –41.9 ± 10.3 mL vs –4.3 ± 17.2 mL; P = 0.05), and greater improvement in LV ejection fraction (+9.4 ± 2.9% vs +2.3 ± 7.5%; P = 0.04). Even after multivariate adjustment, LVLED remained an independent predictor of the primary composite endpoint (HR 0.47, P = 0.031). Conclusions: Electrical lead localization, as estimated by LVLED ≥ 50%, is associated with improved long‐term clinical outcome and measures of LV remodeling in patients with apical LV leads. Intraprocedural LVLED assessment may provide incremental utility in targeting lead placement even in conventionally unfavorable anatomical segments. (J Cardiovasc Electrophysiol, Vol. 24, pp. 182‐187, February 2013)     

Pulmonary Vein Antral Isolation and Nonpulmonary Vein Trigger Ablation without Additional Substrate Modification for Treating Longstanding Persistent Atrial Fibrillation

PV Ablation for Persistent Atrial Fibrillation. Introduction: Effectiveness of antral pulmonary vein isolation (PVAI) and ablation of non‐PV triggers (non‐PVTA) in controlling longstanding persistent atrial fibrillation (AF) has not been reported. We sought to describe clinical outcomes with this ablation strategy in patients (pts) followed for at least 1 year. Methods: Two hundred pts underwent PVAI for longstanding persistent AF and were followed for recurrence. Thirty‐three pts with <1‐year follow‐up and 37 pts with additional RF atrial ablation were excluded, leaving 130 pts for analysis. Results: All 130 pts (108 men, mean LA 4.7 ± 0.6 cm, mean AF duration of 38 ± 44 months) underwent PVAI with entrance/exit block. In addition, 24 pts (15 pts during the initial procedure and 9 additional pts at repeat ablations) had 40 non‐PVTA, including 3 with AVNRT. During follow‐up, atrial flutter (AFL) was noted in 7 (5%) pts. The AF‐free survival after single procedure without antiarrhythmic drugs (AAD) was 38%. Repeat AF or AFL ablation was performed in 37 pts (28%) with PV reconnection uniformly identified (3.7 ± 0.5 veins/pt). During mean follow‐up of 41.1 ± 23.8 months (range 12–103 months), 85/130 pts (65%) were in sinus rhythm with 65 pts (50%) off AAD, 20 pts (15%) on AAD. Additionally, 9 pts (7%) have had rare episodes of AF such that 72% of pts have had good long‐term clinical outcome. Of the 36 pts with recurrent AF, 20 pts have not had a repeat procedure. Conclusions: PVAI with non‐PVTA for longstanding persistent AF provides good long‐term AF control in over 70% of patients with infrequent (5%) AFL. AAD therapy and repeat PVAI may be required for this optimal outcome. (J Cardiovasc Electrophysiol, Vol. 23, pp. 806‐813, August 2012)     

High‐Rate Pacing Reduces Variability of Repolarization and Prevents Repolarization‐Dependent Arrhythmias in Dogs With Chronic AV Block

High‐Rate Pacing Prevents Drug‐Induced Arrhythmias. Introduction: High‐rate pacing may have an inhibitory effect on the initiation of Torsade de Pointes arrhythmias (TdP). However, permanent pacing is only indicated in high‐risk patients. We performed a proof of concept study into automatic overdrive pacing for prevention of drug‐induced TdP, using short‐term variability of repolarization (STV) as a feedback parameter of arrhythmic risk. Methods and Results: The minimal signal sampling frequency required for measuring STV was determined through computer simulation. Arrhythmogenic response to dofetilide (25 μg/kg/5minutes) was tested at two different paced heart rates (60–65 bpm vs 100–110 bpm) in 7 dogs with chronic atrioventricular block, while recording right and left ventricular (LV) monophasic action potential (MAP) and LV electrogram (EGM). Simulations showed a sampling frequency of 500 Hz is sufficient to capture relevant STV values. High‐rate pacing prevented dofetilide‐induced TdP seen at the low rate (low: 6/7 vs high: 1/7). At the low rate, STV from LV MAP duration increased before occurrence of spontaneous, ectopic activity and TdP (1.7 ± 0.6–3.0 ± 1.8 ms, P < 0.05), but at the high‐rate STV did not change significantly (0.9 ± 0.2–1.5 ± 1.4 ms, NS). Regression analysis showed a close relation between STV calculated from LV MAP and from LV EGM (R²= 0.71). Conclusions: High‐rate pacing increases repolarization reserve in dogs with chronic atrioventricular block, preventing dofetilide‐induced TdP. Changes in repolarization reserve are reflected in values of STV. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1384‐1391, December 2010)     

Phrenic nerve stimulation in cardiac resynchronization therapy

In cardiac resynchronization therapy (CRT), the electrical impulse delivered by the left ventricular (LV) lead may incidentally cause phrenic nerve stimulation (PNS). The purpose of this state-of-the-art review is to describe the frequency, risk factors, and clinical consequences of PNS and to present the most recent options to successfully manage PNS. PNS occurs in 2 to 37 % of implanted patients and is not always detected in the supine position during implantation. Lateral and posterior veins are at higher risk of PNS than anterior veins, and apical positions are at higher risk of PNS than basal positions. The management of PNS discovered during implantation may include mapping the course of the target vein in order to find a PNS-free site, targeting another vein if available, and pacing with alternative configurations before changing the lead location. Non-invasive options for management of post-operative PNS depend on the difference between PNS and LV stimulation thresholds and include reducing the LV pacing output, automatic determination of LV stimulation threshold and minimal output delivery by the device, increasing the pulse duration, and electronic repositioning. New quadripolar leads allow to pace from different cathodes, and the multiple pacing configurations available have proved superior to bipolar leads in mitigating PNS. This electronic repositioning addresses almost all of the clinically relevant PNS and should markedly reduce the need for invasive lead repositioning or CRT abandon, which is actually the last option for 2 % of patients.     

Contractile Reserve Assessed Using Dobutamine Echocardiography Predicts Left Ventricular Reverse Remodeling after Cardiac Resynchronization Therapy: Prospective Validation in Patients with Left Ventricular Dyssynchrony

Background: The presence of viable myocardium may predict response to cardiac resynchronization therapy (CRT). The aim of this study is to evaluate in patients with left ventricular (LV) dyssynchrony whether response to CRT is related to myocardial viability in the region of the pacing lead. Methods: Forty‐nine consecutive patients with advanced heart failure, LV ejection fraction < 35%, QRS duration > 120 ms and intraventricular asynchronism ≥ 50 ms were included. Dobutamine stress echocardiography was performed within the week before CRT implantation. Resting echocardiography was performed 6 months after CRT implantation. Viability in the region of LV pacing lead was defined as the presence of viability in two contiguous segments. Response to CRT was defined by evidence of reverse LV remodeling (≥15% reduction in LV end‐systolic volume). Results: Thirty‐one patients (63%) were identified as responders at follow‐up. The average of viable segments was 5.9 ± 2 in responders and 3.2 ± 3 in nonresponders (P = 0.0003). Viability in the region of the pacing lead had a sensitivity of 94%, a specificity of 67%, a positive predictive value of 83%, and a negative predictive value of 86% for the prediction of response to CRT. Conclusions: In patients with LV dyssynchrony, reverse remodeling after CRT requires viability in the region of the pacing lead. This simple method using echocardiography dobutamine for the evaluation of local viability (i.e., viability in two contiguous segments) may be useful to the clinician in choosing the best LV lead positioning. (Echocardiography 2010;27:668‐676)     

Preferred left ventricular lead position for upgrade from right ventricular pacing to cardiac resynchronization therapy

Introduction

Cardiac resynchronization therapy (CRT) is well-established for treating symptomatic heart failure with electrical dyssynchrony. The left ventricular (LV) lead position is recommended at LV posterolateral to lateral sites in patients with left bundle branch block; however, its preferred region remains unclear in patients being upgraded from right ventricular (RV) apical pacing to CRT. This study aimed to identify the preferred LV lead position for upgrading conventional RV apical pacing to CRT.

Methods

We used electrode catheters positioned at the RV apex and LV anterolateral and posterolateral sites via the coronary sinus (CS) branches to measure the ratio of activation time to QRS duration from the RV apex to the LV anterolateral and posterolateral sites during RV apical pacing. Simultaneous biventricular pacing was performed at the RV apex and each LV site, and the differences in QRS duration and LV dP/dt_max from those of RV apical pacing were measured.

Results

Thirty-seven patients with anterolateral and posterolateral LV CS branches were included. During RV apical pacing, the average ratio of activation time to QRS duration was higher at the LV anterolateral site than at the LV posterolateral site (0.90 ± 0.06 vs. 0.71 ± 0.11, p < .001). The decreasing ratio of QRS duration and the increasing ratio of LV dP/dt_max were higher at the LV anterolateral site than at the posterolateral site (45.7 ± 18.0% vs. 32.0 ± 17.6%, p < .001; 12.7 ± 2.9% vs. 3.7 ± 8.2%, p < .001, respectively) during biventricular pacing compared with RV apical pacing.

Conclusion

The LV anterolateral site is the preferred LV lead position in patients being upgraded from conventional RV apical pacing to CRT.     

Multi-Axes Lead With Tetrahedral Electrode Tip for Cardiac-Implantable Devices: Creative Concept for Pacing and Sensing Technology

BackgroundWe developed a multi-axes lead (Max_Lead) incorporating 4 electrodes arranged at the lead-tip, organized in an equidistant tetrahedron. Here, we studied Max_Lead performance in sensing, pacing, and activation wavefront-direction analysis.MethodsSixteen explanted animal hearts (from 7 pigs, 7 sheep, and 2 rabbits) were used. Pacing threshold was tested from all axes of Max_Lead from right-ventricular (RV) apex before and after simulated dislodgement. In addition, conduction-system pacing was performed in sheep heart preparations from all axes of Max_Lead. Sensing via Max_Lead positioned at RV apex was tested during sinus rhythm (SR), pacing from RV and left-ventricular (LV) free-wall, and ventricular fibrillation (VF). Max_Lead-enabled voltage (Max^V), defined as the largest span of the sensed electric field loop, was compared with traditional lead-tip voltage detection.ResultsPacing: Max_Lead minimized change in pacing threshold owing to lead dislodgement (average voltage change 0.2 mV; 95% confidence interval [CI], –0.5 to 0.9), using multiple bipoles available for pacing. In animals with high conduction system-pacing thresholds (> 2 mV) in 1 or more bipoles (3 of 7), acceptable thresholds (< 1 mV) were demonstrated in an average of 2.5 remaining bipoles. Sensing: Max^V of SR and VF was consistently higher than the highest bipolar voltage (voltage difference averaged –0.18 mV, 95% CI, –0.28 to –0.07), P = 0.001). Electric field-loop geometry consistently differentiated ventricular activation in SR from that during pacing from RV and LV free walls.ConclusionsThe multi-axes Max_Lead electrode showed advantages in pacing, sensing, and mapping and has the potential to allow for improvements in lead-electrode technology for cardiac-implanted electronic devices.     

Long‐Term Mechanical Consequences of Permanent Right Ventricular Pacing: Effect of Pacing Site

Optimal Right Ventricular Pacing Introduction: Long‐term right ventricular apical (RVA) pacing has been associated with adverse effects on left ventricular systolic function; however, the comparative effects of right ventricular outflow tract (RVOT) pacing are unknown. Our aim was therefore to examine the long‐term effects of septal RVOT versus RVA pacing on left ventricular and atrial structure and function. Methods: Fifty‐eight patients who were prospectively randomized to long‐term pacing either from the right ventricular apex or RVOT septum were studied echocardiographically. Left ventricular (LV) and atrial (LA) volumes were measured. LV 2D strain and tissue velocity images were analyzed to measure 18‐segment time‐to‐peak longitudinal systolic strain and 12‐segment time‐to‐peak systolic tissue velocity. Intra‐LV synchrony was assessed by their respective standard deviations. Interventricular mechanical delay was measured as the difference in time‐to‐onset of systolic flow in the RVOT and LV outflow tract. Septal A’ was measured using tissue velocity images. Results: Following 29 ± 10 months pacing, there was a significant difference in LV ejection fraction (P < 0.001), LV end‐systolic volume (P = 0.007), and LA volume (P = 0.02) favoring the RVOT‐paced group over the RVA‐paced patients. RVA‐pacing was associated with greater interventricular mechanical dyssynchrony and intra‐LV dyssynchrony than RVOT‐pacing. Septal A’ was adversely affected by intra‐LV dyssynchrony (P < 0.05). Conclusions: Long‐term RVOT‐pacing was associated with superior indices of LV structure and function compared with RVA‐pacing, and was associated with less adverse LA remodeling. If pacing cannot be avoided, the RVOT septum may be the preferred site for right ventricular pacing. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1120‐1126)     

Heterogeneity of ventricular fibrillation dominant frequency during global ischemia in isolated rabbit hearts

Introduction : Ventricular fibrillation (VF) studies show that ECG‐dominant frequency (DF) decreases as ischemia develops. This study investigates the contribution of the principle ischemic metabolic components to this decline. Methods and Results: Rabbit hearts were Langendorff‐perfused at 40 mL/min with Tyrode's solution and loaded with RH237. Epicardial optical action potentials were recorded with a photodiode array (256 sites, 15 × 15 mm). After 60 seconds of VF (induced by burst pacing), global ischemia was produced by low flow (6 mL/min), or the solution changed to impose hypoxia (95% N₂/5% CO₂), low pH_o (6.7, 80% O₂/20% CO₂), or raised [K⁺]_o (8 mM). DF of the optical signals was determined at each site. Conduction velocity (CV), action potential duration (APD90), effective refractory period (ERP), activation threshold, dV/dt_max, and membrane potential were measured in separate experiments during ventricular pacing. During VF, ischemia decreased DF in the left ventricle (LV) (to [58 ± 6]%, P < 0.001), but not the right (RV) ([93 ± 5]%). Raised [K⁺]_o reproduced this DF pattern (LV: [67 ± 12]%, P < 0.001; RV: [95 ± 9]%). LV DF remained elevated in hypoxia or low pH_o. During ventricular pacing, ischemia decreased CV in LV but not RV. Raised [K⁺]_o did not change CV in either ventricle. Ischemia and raised [K⁺]_o shortened APD90 without altering ERP. LV activation threshold increased in both ischemia and raised [K⁺]_o and was associated with diastolic depolarization and decreased dV/dt_max. Conclusions: These results suggest that during VF, decreased ECG DF in global ischemia is largely due to elevated [K⁺]_o affecting the activation thresholds in the LV rather than RV.     

Clinical Performance of the St. Jude Medical Riata Defibrillation Lead in a Large Patient Population

Clinical Performance of the St. Jude Medical Riata Defibrillation Lead in a Large Patient Population . Objective: The purpose of this large multicenter study was to evaluate the long‐term reliability of an implantable cardioverter defibrillator (ICD) lead to determine the incidence of adverse events (AEs). Background: A recent concern has been the performance of cardiac defibrillator leads. There have been conflicting reports regarding the rate of lead perforation and other AEs. Methods: Medical records from patients implanted from 6‐1‐2001 to 11‐27‐2007 with the St. Jude Medical Riata family of RV leads at 23 US (N = 12,969) and 5 German (N = 2,418) centers were reviewed for chronic lead‐related AEs. These included perforation, dislodgment, conductor fracture and insulation damage. The mean follow‐up period was 18.0 months. AEs were defined as those that required Riata lead revision, extraction, or replacement. Results: The incidence of lead AEs was <1% for each AE type. Perforation occurred in 0.38%, dislodgement in 0.93%, conductor fracture in 0.18%, and insulation damage in 0.21% of patients studied. Conclusions: During the follow‐up of the 15,387 patients with Riata leads, the incidence of AEs which included perforation, dislodgement, conductor fraction and insulation damage was low and within the range of what is considered clinically acceptable. (J Cardiovasc Electrophysiol, Vol. 21, pp. 551‐556, May 2010)     

The right ventricular septum presents the optimum site for maximal electrical separation during left ventricular pacing

Septum Presents the Optimum Site for Maximal Electrical Separation. Cardiac resynchronization therapy (CRT) benefits selected heart failure (HF) patients. The optimal placement of the right ventricle (RV) lead during biventricular pacing has not been assessed. Greater electrical separation (ES) between left ventricle (LV) and RV leads has been associated with better clinical outcomes. The site of maximal electrical separation(MES) in the RV is unknown. Methods: Prospective study of 50 CRT patients. The LV lead was placed in a postero‐lateral branch of the coronary sinus. ES was recorded at 6 sites within the RV during LV pacing at 600 milliseconds cycle length (CL). The median ES was recorded with a roving deflectable catheter at the RV outflow tract (RVOT), high septum, inflow septum, mid‐septum, apical septum and apex. Results: Mean age was 67 ± 7 years, 39 were male (78%). Thirty had ischemic etiology (60%). Mean left ventricular ejection fraction (LVEF) was 25 ± 7%, QRS duration pre and post was 165 ± 26 milliseconds and 138.5 ± 15.6 milliseconds (P < 0.001). Mapping ES showed a difference between 20 and 50 milliseconds distributed across the RV in the majority of patients (40/49). However, 7 subjects demonstrated delay distribution of between 50 and 82 milliseconds. ES was significant greater in the RV mid‐septum (161.2 ± 23.7 milliseconds) compared with RVOT (154.1 ± 20.8 milliseconds) and apex (148.0 ± 25.5 milliseconds; P < 0.001). The site of Maximal ES was most commonly found at the mid‐septum (40 patients, 80%) and only rarely at the RVOT (5, 10%) and apex (5, 10%; P < 0.01). Conclusion: MES was observed most commonly at the RV septum and rarely at the RV apex. Better correction of electrical and mechanical dyssynchrony by CRT may be achieved by placing the RV lead in a site outside of the apex in the majority of patients. Clinical studies exploring RV septal pacing in CRT seem warranted.     

Two Versus One Repeat Freeze-Thaw Cycle(s) After Cryoballoon Pulmonary Vein Isolation: The ALSTER EXTRA Pilot Study

Two versus One Repeat Freeze–Thaw Cycle(s) . Background: Repeated freezing (bonus applications) during cryoballoon pulmonary vein isolation (PVI) has been suggested to improve lesion durability. However, the long‐term clinical effects of repeated freezing have not been investigated. Methods and Results: A total of 51 patients (pts) with paroxysmal atrial fibrillation (AF) underwent PVI using the single big (28 mm) cryoballoon technique. One (27 pts, group I) or 2 bonus applications (24 pts, group II) were performed at all PVs subsequent to PVI. Clinical follow‐up consisted of continuous rhythm monitoring by an implantable cardiac monitor (ICM, 24 pts) and serial 7‐day Holter‐ECG recording (7DH, 27 pts). The primary endpoint was defined as recurrent AF or atrial tachycardia. Acute PVI of all PVs was obtained in 50/51 pts (98%). The median (Q1;Q3) follow‐up duration in this study was 384 (213;638) days. The primary endpoint occurred in 48% (group I, 15 pts ICM, 12 pts 7DH) and 46% (group II, 9 pts ICM, 15 pts 7DH), P = 0.84. Procedure‐ and fluoroscopy‐time for group I versus group II was 193 ± 56 minutes versus 207 ± 27 and 33 ± 13 minutes versus 34 ± 11 minutes, respectively. Right phrenic nerve palsy (PNP) occurred in 3 pts (all group II, time to resolution: 128 ± 112 days). In 2 of these pts, PNP occurred during the second bonus application. Conclusion: Application of 2 when compared to 1 freeze–thaw cycle(s) following cryoballoon PVI did not result in improved clinical success but was associated with a higher complication rate. (J Cardiovasc Electrophysiol, Vol. 23, pp. 814‐819, August 2012)