Alternate site right ventricular pacing: defining template scoring

Background: Prolonged right ventricular (RV) apical pacing produces dysynchronous ventricular contraction, which may result in left ventricular (LV) dysfunction, whereas septal pacing sites might reflect a more synchronous LV activation. This study examined a method of evaluating alternate RV pacing sites using a template scoring system based on measuring the angle of lead attachment in the 40^o left anterior oblique (LAO) fluoroscopic view and its effect on altering the loop of lead in the RV. Methods: Twenty‐three consecutive patients for RV pacing were enrolled. Conventional active fixation leads were positioned in either the RV outflow tract (RVOT) or mid RV using a stylet designed for septal placement (Model 4140, St. Jude Medical, St. Paul, MN, USA). Using LAO cine fluoroscopy, a generous loop of lead was inserted into the RV chamber and the change in angle of attachment determined. Results: Successful positioning of pacing leads at the RVOT septum (18 patients) and mid‐RV septum (five patients) was achieved. With introduction of more lead into the RV chamber, the angle of attachment in the LAO projection altered over a range of 6^o–32^o for all patients with a mean of 14.6 ± 6.6^o. In 87% of patients, the range was predominantly within the same template score with only minor overlap into another zone. Conclusions: This study shows that the angle of lead attachment in the RV is altered by introducing more lead, but in most cases, the template score remains the same. Further studies are required to determine the accuracy and efficacy of the templates. (PACE 2011; 34:1080–1086)     

Right Ventricular Septal Pacing: The Success of Stylet-Driven Active-Fixation Leads

Background: The detrimental effects of right ventricular (RV) apical pacing on left ventricular function has driven interest in alternative pacing sites and in particular the mid RV septum and RV outflow tract (RVOT). RV septal lead positioning can be successfully achieved with a specifically shaped stylet and confirmed by the left anterior oblique (LAO) fluoroscopic projection. Such a projection is neither always used nor available during pacemaker implantation. The aim of this study was to evaluate how effective is the stylet-driven technique in septal lead placement guided only by posterior-anterior (PA) fluoroscopic view.
Methods: One hundred consecutive patients with an indication for single- or dual-chamber pacing were enrolled. RV septal lead positioning was attempted in the PA projection only and confirmed by the LAO projection at the end of the procedure.
Results: The RV lead position was septal in 90% of the patients. This included mid RV in 56 and RVOT in 34 patients. There were no significant differences in the mean stimulation threshold, R-wave sensing, and lead impedance between the two sites . In the RVOT, 97% (34/35) of leads were placed on the septum, whereas in the mid RV the value was 89% (56/63).
Conclusions: The study confirms that conventional active-fixation pacing leads can be successfully and safely deployed onto the RV septum using a purposely-shaped stylet guided only by the PA fluoroscopic projection. (PACE 2010; 49–53)     

The Road to Right Ventricular Septal Pacing: Techniques and Tools

Prolonged right ventricular (RV) apical pacing is associated with progressive left ventricular dysfunction due to dysynchronous ventricular activation and contraction. RV septal pacing allows a narrower QRS compared to RV apical pacing, which might reflect a more physiological and synchronous ventricular activation. Previous clinical studies, which did not consistently achieve RV septal pacing, were not confirmatory and need to be repeated. This review summarizes the anatomy of the RV septum, the radiographic appearances of pacing leads in the RV, the electrocardiograph correlates of RV septal lead positioning, and the techniques and tools required for implantation of an active‐fixation lead onto the RV septum. Using the described techniques and tools, conventional active‐fixation leads can now be reliably secured to either the RV outflow tract septum or mid‐RV septum with very low complication rates and good long‐term performance. Even though physiologic and hemodynamic studies on true RV septal pacing have not been completed, the detrimental effects of long‐term RV apical pacing are significant enough to suggest that it is now time to leave the RV apex and secure all RV leads onto the septum. (PACE 2010; 888–898)     

The right ventricular outflow tract: a comparative study of septal, anterior wall, and free wall pacing

BACKGROUND: There is marked heterogeneity in right ventricular outflow tract (RVOT) pacemaker lead placement using conventional leads. As a result, we have sought to identify a reproducible way of placing a ventricular lead onto the RVOT septum. METHODS AND RESULTS: A major determinant is the shape of the stylet used to deliver the active-fixation lead. We compared stylet shapes and configurations in patients who initially had a ventricular lead placed onto the anterior or free wall of the RVOT and then had the lead repositioned onto the septum. All leads were loaded with a stylet fashioned with a distal primary curve to facilitate delivery of the lead to the pulmonary artery, then using a pullback technique the lead was retracted to the RVOT. All lead placements were confirmed by fluoroscopy and electrocardiography. Anterior or free wall placement was achieved by the stylet having either the standard curve or an added distal anterior angulation. In contrast, septal lead positioning was uniformly achieved by a distal posterior angulation of the curved stylet. This difference in tip shape was highly predictive for septal placement (P < 0.001). With septal pacing, a narrower QRS duration was noted, compared to anterior or free wall pacing (136 vs 155 ms, P < 0.001). All pacing parameters were within acceptable limits. CONCLUSION: Using appropriately shaped stylets, pacing leads can now be placed into specific positions within the RVOT and in particular septal pacing can be reliably and reproducibly achieved. This is an important step in the standardization of lead placement in the RVOT.     

Long‐Term Nonoutflow Septal Versus Apical Right Ventricular Pacing: Relation to Left Ventricular Dyssynchrony

Background: Right ventricular (RV) apical pacing deteriorates left ventricular (LV) function. RV nonoutflow (low) septal pacing may better preserve ventricular performance, but this has not been systematically tested. Our aim was to assess (1) whether long‐term RV lower septal pacing is superior to RV apical pacing regarding LV volumes and ejection fraction (EF), and (2) if the changes in LV dyssynchrony imposed by pacing are related to the long‐term changes in LV volumes and EF. Methods: In thirty‐six patients with atrioventricular (AV) block, a dual‐chamber pacemaker was implanted. The ventricular electrode was placed either at the apex or at the lower septum, in a randomized sequence. Twenty‐four to 48 hours following implantation, we measured LV volumes, EF, and LV dyssynchrony (by tissue Doppler imaging), both with and without pacing. Patients were reassessed echocardiographically after 12 months. Results: Lower septal pacing induced a more synchronized pattern of LV contraction changes (P < 0.05). Following 12 months, differences were observed between groups regarding LV volumes and EF. EF increased within the septal group (from 52 ± 3.3% to 59 ± 3.0%, P < 0.05). A significant inverse relation was documented between changes in LV dyssynchrony and changes in EF (r =?0.64, P < 0.05). Conclusions: In patients with AV block, RV nonoutflow septal pacing represents an attractive alternative, since it preserves better and may even improve LV volumes and EF. Late changes in EF are associated with the changes in LV dyssynchrony imposed by pacing.     

The ECG Lead I Paradox in Cardiac Resynchronization Therapy

Background: In cardiac resynchronization therapy (CRT), the morphology of the QRS complex plays an important role in the determination of the pacing site and effectiveness of stimulation. Patients and Methods: Review of the electrocardiograms (ECGs) of 737 patients with a CRT device showed a negative QRS complex in lead I during right ventricular (RV) pacing and a positive QRS complex during left ventricular (LV) pacing in four patients. The RV lead was positioned in the high RV septum and the coronary sinus leads in a posterior or postero‐lateral basal level. Reversed ECG lead or pacemaker lead connection, anodal RV stimulation, and scar tissue‐related depolarization abnormalities were excluded as possible causes. Conclusion: Pacing from the high RV septum may rarely lead to a negative QRS complex and basal positions of the LV lead to a positive QRS complex in lead I during LV pacing. The lead I paradox becomes obvious when both phenomena, that are not interrelated, are present in the same patient.     

Electrocardiographic Patterns during Left Ventricular Epicardial Pacing

Background: There is a paucity of data concerning the use of QRS morphology patterns for identifying pacing sites during left ventricle (LV)‐only epicardial pacing in patients with a biventricular device. The objective of this study was to identify QRS patterns during LV‐only pacing, and to establish their relationship with LV lead position. In addition, to validate the diagnostic performance of such electrocardiogram (ECG) patterns for predicting posterolateral versus anterior and apical versus nonapical LV pacing site. Methods: The study retrospectively analyzed data from 376 cardiac resynchronization therapy device patients. Data analyzed included ECGs registered during LV‐only VVI pacing, fluoroscopic projections, and lateral chest roentgenograms that documented postimplantation LV lead position. Phase one of the study involved categorization of the ECG patterns of the first 66 study cases. Phase two of the study examined the association between ECG pattern and different LV lead positions. Results: As the LV epicardial pacing site became more anteroapical, the LV‐only paced QRS complexes in the precordial leads became more negative. Three ECG patterns were identified (posterolateral, intermediate, and anteroapical), and their distribution was found to be associated with LV lead position (P < 0.001). The posterolateral ECG pattern was mostly observed in cases where the LV lead was in the posterolateral area (diagnostic accuracy of 89.1% for predicting a nonapical LV lead position). The anteroapical ECG pattern was associated with LV leads in anteroapical segments (specificity of 98.5%, accuracy of 89.1% for predicting an anteroapical pacing site). Conclusions: Posterolateral and anteroapical ECG patterns are highly predictive of LV lead position. (PACE 2012; 35:1361–1368)     

Right Ventricular Outflow Tract Septal Pacing: Long-Term Follow-Up of Ventricular Lead Performance

Background: The detrimental effects of right ventricular apical pacing on left ventricular function has driven interest in selective site pacing, predominantly on the right ventricular outflow tract (RVOT) septum. There is currently no information on long-term ventricular lead electrical performance from this site.
Methods: A total of 100 patients with ventricular lead placement on the RVOT septum undergoing pacemaker implantation for bradycardia indications were analyzed retrospectively. Lead positioning was confirmed with the use of fluoroscopy. Long-term (1 year) follow-up was obtained in 92 patients. Information on stimulation threshold, R-wave sensing, lead impedance, and lead complications were collected.
Results: Lead performance at the RVOT septal position was stable in the long term. Ventricular electrical parameters were acceptable with stable long-term stimulation thresholds, sensing, and impedance for all lead types. One-year results demonstrated mean stimulation threshold of 0.71 ± 0.25 V, mean R wave of 12.4 ± 6.05 mV, and mean impedance values of 520 ± 127 Ω. There were no cases of high pacing thresholds or inadequate sensing.
Conclusions: This study confirms satisfactory long-term performance with leads placed on the RVOT septum, comparable to traditional pacing sites. It is now time to undertake studies to examine the long-term hemodynamic effects of RVOT septal pacing.     

Optimization of Ventricular Function by Improving the Activation Sequence During Ventricular Pacing

Abnormal electrical activation occurring during ventricular pacing reduces left ventricular (LV) pump function. Two strategies were compared to optimize LV function using ventricular pacing, minimal asynchrony and optimal sequence of electrical activation. ECG and hemodynamics aortic flowpmbe, thermodilution cardiac output, LV pressure and its maximal rates of rise (LVdP/dtpos) and fall (LVdP/dtneg) were measured in anesthetized open-chest dogs (n = 7) with healthy hearts. The QRS duration (a measure of asynchrony of activation) was 47 ± 5 ms during sinus rhythm and increased to 110 ± 12 ms during DDD pacing at the right ventricular (RV) apex with a short AV interval. During pacing at the LV apex and LV base, the QRS duration was 8%± 7% and 15%± 7% (P < 0.05) longer than during RV apex pacing, respectively. Stroke volumes, LVdP/dtpos and LVdP/dtneg, however, were higher during LV apex(15%± 16%, 10%± 12% [P<0.05], and 15%± 10%, respectively) and LV base pacing (11%± 12% [P<0.05], 3%± 12%, and 3%± 11%, respectively) than during RV apex pacing. Systolic LV pressure was not influenced significantly by the site of pacing. Biventricular pacing (RV apex together with one or two LV sites) decreased the QRS duration by approximately 20% as compared with RV apex pacing, however, it did not improve stroke volumes, LVdP/dtpos and LVdP/dtneg beyond those during pacing at the LV apex alone. In conclusion, the sequence of electrical activation is a stronger determinant of ventricular function than the synchrony of activation. For optimal LV function the selection of an optimal single pacing site, like the LV apex, is more important than pacing from multiple sites.     

The right ventricular outflow tract: the road to septal pacing

BACKGROUND: Pacing from the right ventricular apex is associated with long-term adverse effects on left ventricular function. This has fuelled interest in alternative pacing sites, especially the septal aspect of the right ventricular outflow tract (RVOT). However, it is a common perception that septal RVOT pacing is difficult to achieve. METHODS AND RESULTS: In this article, we will review the anatomy of the RVOT and discuss the importance of standard radiographic views and the 12-lead electrocardiogram in aiding lead placement. We will also describe a method utilizing a novel stylet shape, whereby a conventional active-fixation, stylet-driven lead can be easily and reliably deployed onto the RVOT septum.     

Electrocardiographic Diagnosis of Biventricular Pacing in Patients with Nonapical Right Ventricular Leads

Background: Assessment of left ventricular (LV) capture is of paramount importance in patients with biventricular (BiV) pacing. Our goal was to identify electrocardiographic features that differentiate between BiV and right ventricular (RV)‐only pacing in patients with nonapical RV leads. Methods: The study enrolled 300 consecutive patients with BiV devices and nonapical RV leads, and obtained from them 558 electrocardiograms with either BiV pacing (n = 300) or RV‐only pacing (n = 258). RV pacing served as a surrogate for loss of LV capture. Electrocardiograms from the first 150 patients were used to identify BiV‐specific features, and to construct an algorithm to differentiate between BiV and RV‐only pacing. Electrocardiograms from the second 150 patients were used to validate the algorithm. Results: The following electrocardiographic features typical of BiV pacing were identified: QS in lead V6 (specificity = 98.7%, sensitivity = 54.7%), dominant R in lead V1 (specificity = 100%, sensitivity = 23.3%), q in lead V6 (specificity = 96%, sensitivity = 22.7%), and a QRS < 160 ms (specificity = 100%, sensitivity = 66.0%). The algorithm based on those features was found to have an overall diagnostic accuracy of 95.0%, a specificity of 96.0%, and a sensitivity of 93.5%. Conclusions: The study identified QRS features that were very specific for BiV pacing in patients with nonapical RV leads. Sequential arrangement of those features resulted in an algorithm that was very accurate for differentiating between BiV pacing and loss of LV capture. (PACE 2012; 35:1199–1208)     

Search for the Optimal Right Ventricular Pacing Site: Design and Implementation of Three Randomized Multicenter Clinical Trials

Background: The optimal site to permanently pace the right ventricle (RV) has yet to be determined. To address this issue, three randomized prospective multicenter clinical trials are in progress comparing the long-term effects of RV apical versus septal pacing on left ventricular (LV) function. The three trials are Optimize RV Selective Site Pacing Clinical Trial (Optimize RV), Right Ventricular Apical and High Septal Pacing to Preserve Left Ventricular Function (Protect Pace), and Right Ventricular Apical versus Septal Pacing (RASP).
Methods: Patients that require frequent or continuous ventricular pacing are randomized to RV apical or septal pacing. Optimize RV excludes patients with LV ejection fraction <40% prior to implantation, whereas the other trials include patients regardless of baseline LV systolic function. The RV septal lead is positioned in the mid-septum in Optimize RV, the high septum in Protect Pace, and the mid-septal inflow tract in RASP. Lead position is confirmed by fluoroscopy in two planes and adjudicated by a blinded panel. The combined trials will follow approximately 800 patients for up to 3 years.
Results: The primary outcome in each trial is LV ejection fraction evaluated by radionuclide ventriculography or echocardiography. Secondary outcomes include echo-based measurements of ventricular/atrial remodeling, 6-minute hall walk distance, brain natriuretic peptide levels, and clinical events (atrial tachyarrhythmias, heart failure, stroke, or death).
Conclusion: These selective site ventricular pacing trials should provide evidence of the importance of RV pacing site in the long-term preservation of LV function in patients that require ventricular pacing and help to clarify the optimal RV pacing site.     

Right ventricular outflow tract pacing: radiographic and electrocardiographic correlates of lead position

OBJECTIVE: To characterize the pacing site in an unselected series of patients undergoing right ventricular outflow tract (RVOT) lead placement and investigate the role of the electrocardiogram (ECG) in predicting implantation. BACKGROUND: Right ventricular apical pacing is associated with long-term adverse effects on left ventricular function, fuelling interest in alternative pacing sites, especially the RVOT. Previous studies have been conflicting, possibly due to poor definition of pacing site within the RVOT. METHODS: In 150 patients undergoing pacemaker implantation, implanters were asked to place the lead in the RVOT. Radiographs were performed in the antero-posterior (AP) and 40 degrees right and left anterior-oblique projections post procedure. Fifty-six had left lateral radiographs. Lead position was categorized using AP/RAO (right anterior oblique) to confirm RVOT placement and left anterior oblique to distinguish free wall from septum. A 12-lead ECG was performed during ventricular pacing. RESULTS: Leads were below the RVOT in 18. Of the remaining 132, the majority (94%) were in the inferior/low RVOT. Eighty-one out of 132 were septal and 51 free wall. Septal sites were associated with shorter QRS duration (134 ms vs 143 ms, P < 0.02). Free wall sites displayed more frequent notching of the inferior leads (P < 0.01). A negative deflection in lead I provided a positive predictive value of 90% for septal sites. In those with lateral radiographs, a posteriorly projected lead was 100% specific for septal placement. CONCLUSIONS: This study demonstrates the heterogeneity of lead placement within the RVOT. Septal and free wall sites display characteristic ECG patterns which may be used to aid placement. The left lateral radiograph is useful in confirming a true septal location.     

Using the Surface ECG to Identify Right Ventricular Pacing Lead Position: A Cautionary Tale

Chronic right ventricular (RV) apical pacing may lead to the development of heart failure in some patients. Although pacing of the RV septum has been proposed as an alternative, positioning a lead in the true septum has proven challenging. In addition to fluoroscopy at implant, it has been suggested that 12‐lead surface electrocardiogram (ECG) can be used to determine septal lead position; however, studies show this may be inaccurate. We present a case where a change in the ECG QRS axis late after pacemaker insertion with an active fixation lead highlights the difficulties of ECG localization of pacing leads.     

A Comparison of Ventricular Function During High Right Ventricular Septal and Apical Pacing after His-Bundle Ablation for Refractory Atrial Fibrillation

This study compares LV performance during high right ventricular septal (RVS) and apical (RVA) pacing in patients with LV dysfunction who underwent His-bundle ablation for chronic AF. We inserted a passive fixation pacing electrode into the RVA and an active fixation electrode in the RVS. A dual chamber, rate responsive pulse generator stimulated the RVA through the ventricular port and the RVS via the atrial port. Patients were randomized to initial RVA (VVIR) or RVS (AAIR) pacing for 2 months. The pacing site was reversed during the next 2 months. At the 2 and 4 month follow-up visit, each patient underwent a transthoracic echocardiographical study and a rest/exercise first pass radionuclide ventriculogram. We studied nine men and three women (mean age of 68 +/- 7 years) with congestive heart failure functional Class (NYHA Classification): I (3 patients), II (7 patients), and III (2 patients). The QRS duration was shorter during RVS stimulation (158 +/- 10 vs 170 +/- 11 ms, P < 0.001). Chronic capture threshold and lead impedance did not significantly differ. LV fractional shortening improved during RVS pacing (0.31 +/- 0.05 vs 0.26 +/- 0.07, P < 0.01). RVS activation increased the resting first pass LV ejection fraction (0.51 +/- 0.14 vs 0.43 +/- 0.10, P < 0.01). No significant difference was observed during RVS and RVA pacing in the exercise time (5.6 +/- 3.2 vs 5.4 +/- 3.1, P = 0.6) or the exercise first pass LV ejection fraction (0.58 +/- 0.15 vs 0.55 +/- 0.16, P = 0.2). The relative changes in QRS duration and LV ejection fraction at both pacing sites showed a significant correlation (P < 0.01). We conclude that RVS pacing produces shorter QRS duration and better chronic LV function than RVA pacing in patients with mild to moderate LV dysfunction and chronic AF after His-bundle ablation.     

Ventricular activation sequence during left ventricular pacing promotes QRS complex oversensing in the atrial channel

Background: Left ventricular (LV)‐only pacing has a significant effect on delay in depolarization of parts of the ventricles that are likely oversensed in the right atrial channel. The study aimed to assess the impact of ventricular activation sequence on QRS oversensing and far‐field endless‐loop pacemaker tachycardia (ELT) in patients who received cardiac resynchronization therapy (CRT) devices. Methods: The study examined 102 patients with CRT devices. Oversensing artifacts in the atrial channel were inspected on intracardiac electrograms, and their timing with respect to the beginning of QRS was determined during DDD‐right ventricular (RV), DDD‐LV, DDD‐biventricular (BiV), and AAI pacing modes. The occurrence of ELT during DDD‐LV pacing with a postventricular atrial refractory period (PVARP) of 250 ms was also assessed. Results: The timing of oversensing artifacts (in relation to the beginning of surface QRS) was dependent on ventricular activation sequence, occurring promptly following intrinsic activation via the right bundle branch (47.1 ± 26.4 ms), later during RV pacing (108.7 ± 22.5 ms) or BiV pacing (109.4 ± 23.1 ms), and significantly later, corresponding to the final part of the QRS, during LV pacing (209.6 ± 40.0 ms, range: 140–340 ms, P < 0.001). Oversensing was significantly more frequent during LV than during RV pacing (35.3% vs 22.5%, P < 0.001). Far‐field ELT was observed in six patients. Conclusions: Oversensing artifacts in the atrial channel are likely caused by depolarization of the basal part of the right ventricle. The novel mechanism of QRS oversensing outside PVARP, caused by a reversed ventricular activation sequence during LV‐only pacing, may be important in some CRT patients. (PACE 2011; 34:1682–1686)     

Variability of Left Ventricular Electromechanical Activation during Right Ventricular Pacing: Implications for the Selection of the Optimal Pacing Site

Background: The right ventricular septum (RVS) and Hisian area (HA) are considered more “physiological” pacing sites than right ventricular apex (RVA). Studies comparing RVS to RVA sites have produced controversial results. There are no data about variability of electromechanical activation obtained by an approach using fluoroscopy and electrophysiological markers. This study compared the variability of left ventricular (LV) electromechanical activation in patients undergoing short‐term RVA and RVS with that measured during HA pacing based on fluoroscopy and electrophysiological markers. Methods: Tissue Doppler echocardiography was performed in 142 patients before and after RVA (54), RVS (44), and HA (44) pacing. Electromechanical activation was assessed by: (1) electromechanical latency (EML)‐interval between QRS onset and mechanical activation of basal LV; (2) intra‐LV dyssynchrony (intra‐LV)‐interval between earliest to the latest LV basal motion. The intra‐ and interpatients variability among pacing groups were assessed. Results: Pacing from RVA showed longer EML and higher degree of intra‐LV than RVS and HA pacing. RVA and RVS showed a higher variability than HA pacing with regard to intrapatient changes of EML (RVA vs RVS, P = 0.4; RVS vs HA, P = 0.01, RVA vs HA, P = 0.0002) and intra‐LV (RVA vs RVS, P = 0.2; RVS vs HA, P = 0.04; RVA vs HA, P = 0.005). Similar results were found in interpatients variability from paced‐values. Conclusions: RVA and RVS pacing produce a variable effect on LV electromechanical activation that is significantly more pronounced than HA pacing. A pacing site such as HA selected by fluoroscopic and electrophysiological markers maintains baseline and homogeneous LV activation pattern. (PACE 2010; 566–574)     

Septal lead implantation for the reduction of paced QRS duration using passive-fixation leads

In 120 consecutive patients with standard pacing indications, we tested the feasibility of RV septal lead implantation technique guided by surface ECG and the degree to which this technique reduces paced QRS duration compared to RV apical stimulation when passive-fixation leads are used. During implantation, an ECG was recorded with a paper speed of 100 mm/s using the orthogonal Frank leads, and QRS was measured from the earliest to the latest deflection in any of the Frank leads. Pace-mapping of the septum was performed until QRS was minimal. The lead was attached, where QRS, pacing threshold, lead impedance, and EGM amplitude provided the best compromise. An average of 3.7 +/- 2.5 attempts (range 1-18, median 7) was needed until a final implantation site was found. There were no technical problems during implantation. QRS could be reduced by 5-55 ms (mean delta QRS 19 +/- 11 ms) in 83 (69%) of 120 patients. In 22 (18%) patients, QRS was identical with apical and septal pacing, and in 15 (13%) patients, QRS was 5-20 ms (10 +/- 4) longer despite septal stimulation. Average QRS was significantly shorter during septal pacing compared with apical pacing (151 +/- 20 vs 162 +/- 23 ms, P < 0.001). There was a tendency towards greatest QRS reduction when the high septum was stimulated (22 +/- 11 ms reduction) as compared with mid- (18 +/- 11 ms) or apical parts of the RV septum (16 +/- 10 ms). QRS reduction was most likely if apical QRS width was > 170 ms (P = 0.0002), and there was an inverse correlation between apical QRS and delta QRS (r = 0.53, P < 10(-7)). During a mean follow-up of 14 months, there was no pacing or sensing problem and no lead dislodgment occurred.     

Greater three-dimensional ventricular lead tip separation is associated with improved outcome after cardiac resynchronization therapy

Background: Effective cardiac resynchronization therapy (CRT) is more likely with widely separated left ventricular (LV) and right ventricular (RV) pacing leads tips. We hypothesized that lead separation is an important factor in determining the clinical response to CRT. Methods: A retrospective study of 86 consecutive patients age 71 ± 10 years, male (74%), coronary disease (71%), atrial fibrillation (23%), LV ejection fraction (22 ± 9%), QRS duration (160 ± 27 ms), New York Heart Association (NYHA) class III (81%), NYHA class IV (19%) undergoing CRT from January 2006 to September 2008. The median follow‐up was 12 months and clinical response to CRT was defined as reduction of NYHA class by one or more. The three‐dimensional separation between RV and LV pacing lead tips was calculated using measurements obtained from orthogonal posteroanterior and lateral chest radiographs performed the day after implantation. Results: Fifty‐nine patients (69%) responded to CRT. There was a statistically significant association between increased three‐dimensional lead separation and clinical response to CRT (P= 0.005). Stronger association was obtained when lead separation was corrected for cardiac size (P= 0.001). A significantly higher response rate of 88% was achieved in patients with QRS duration of 160 ms or more, and lead separation of 100 mm or more compared with 60% when lead separation was less than 100 mm and QRS duration remained the same (P = 0.027). Conclusions: Greater three‐dimensional separation of LV‐to‐RV leads is associated with improved response to CRT. A prospective multicenter trial is needed to assess lead separation as a predictor for response. (PACE 2010; 33:1490–1496)     

Analysis during Sinus Rhythm and Ventricular Pacing of Reentry Circuit Isthmus Sites in Right Ventricular Cardiomyopathy

Background: The entrainment mapping algorithm is used for ablation of ventricular tachycardia (VT) in right ventricular (RV) cardiomyopathy, but ablation at endocardial isthmus sites has only a moderate success rate. This study was performed to identify additional local electrogram characteristics associated with successful ablation. Patients and Methods: Using entrainment mapping, 45 reentry circuit isthmus sites were detected in 11 patients with RV cardiomyopathy presenting with 13 monomorphic VTs. Local bipolar electrograms were retrospectively analyzed at reentry circuit isthmus sites during VT, sinus rhythm, and programmed stimulation from the right ventricular apex (RVA), and compared between successful and unsuccessful ablation sites. Results: Ablation was successful at 10 reentry circuit isthmus sites and unsuccessful at 35 isthmus sites. During VT, a longer endocardial activation time relative to QRS onset, an increased electrogram‐QRS interval as a percentage of VT cycle length, and a longer electrogram duration were found at successful in comparison to unsuccessful ablation sites. The presence of isolated diastolic potentials during sinus rhythm at reentry circuit isthmus sites, consistent with slow conduction or unidirectional conduction block, was associated with successful catheter ablation. Prolongation of the duration of the local multipotential electrogram by >100 ms during programmed RVA pacing at reentry circuit exit sites, indicating functional conduction disorder was also a marker of successful ablation. Conclusions: The demonstration of multipotential electrogram characteristics indicating fixed or functional conduction block may increase the likelihood of successful VT ablation at exit and central isthmus sites of reentry circuits in RV cardiomyopathy.