Left Ventricle Lead Research Articles

Early experience with attain stability, an activefixation LV lead: virtues and pitfalls.

Appropriate left ventricle (LV) lead placement is integral to successful cardiac resynchronization therapy (CRT). Lead dislodgement and phrenic nerve stimulation (PNS) are major obstacles. A recent trial of an active fixation LV lead (Attain Stability 20066, Medtronic Inc., Tilburg, the Netherlands) has shown promising results. We share our initial experience with this novel active fixation LV lead. A Medtronic active fixation lead 20066 was used in eight consecutive patients for CRT. An optimal site was chosen and recommended maneuvers were applied for lead fixation. Push and pull maneuvers were used to test stability. There were two initial dislodgements after which we used a transvalvular insertion (TVI) tool that was used in the hemostatic valve during rotation of the lead so that the torque was easily transmitted to the tip. It also allowed better tactile feedback during push-pull tests. There were no further dislodgements in the subsequent six patients. However, in one patient the lead could not be unscrewed due to the tip getting wedged at a distal smaller vein. Repositioning of the LV lead was done in three patients due to PNS or pacing issues. The median time for LV lead placement was 16.5 minutes (interquartile range 9-25 minutes). The Medtronic Attain Stability 20066 active fixation LV lead can potentially be implanted at any pacing site avoiding PNS and providing better stability. The learning curve is short and additional tricks can be learnt to improve success. Use of TVI while the lead is rotated is beneficial.

Usefulness of a novel active fixation left ventricle lead in cardiac resynchronization therapy

Cardiac resynchronization therapy has demonstrated important benefits for selected patients suffering from heart failure. Those benefits include clinical and/or echocardiography assessed improvement, as well as hospitalizations and all-cause mortality reduction. However, about 30% of patients do not benefit from the therapy. Suboptimal left ventricle lead position, post-implant lead dislodgements and undesired phrenic nerve stimulation are potential causes for not responding and it is not always possible to avoid them during the implant procedure. We report a case in which we used a novel left ventricle lead which is actively fixated to the cardiac vein or to the coronary sinus, by means of a helix, in a patient with very limited options to implant the lead. In this patient, a traditional, passively fixated lead would fail to get implanted. This design can help the implanting physician to implant the lead in the desired position, minimizing the possibility of dislodgement, even in very basal positions where traditional leads are more likely to dislodge.

Preventing phrenic nerve stimulation by a patch insulation in an intact swine heart model.

IntroductionPhrenic nerve stimulation (PNS) could be prevented by a silastic patch over the epicardial lead. We studied the effects in preventing PNS by placing a silastic patch directly over an epicardial lead or placing a graft around the phrenic nerve (PN).Methods and ResultsFourteen Lanyu swine were enrolled. A bipolar lead was placed epicardially on the left ventricle (LV) inferior to the PN. An implantable cardioverter-defibrillator (ICD) lead was placed into the right ventricle (RV). The maximal influential distance (MID) was measured under 3 pacing configurations to express the influential electrical field on the PN. The threshold of the LV and PN were evaluated epicardially. Then, PTFE patches of different sizes (10×10 mm, 20×20 mm and 30×30 mm) were placed between the LV lead and PN to study the rise in PN threshold in 7 swine. On the other hand, the PN were surrounded by a PTFE graft of different lengths (10 mm, 20 mm, and 30 mm) in the remaining 7 swine. LV-bipolar pacing showed the shortest MID when compared to the other 2 unipolar pacing configurations at pacing voltage of 10 V. The patch was most effective in preventing PNS during LV-bipolar pacing. PNS was prevented under all circumstances with a larger PTFE patch (30×30 mm) or long graft (30 mm).ConclusionsPNS was avoided by placing a PTFE patch over the LV lead or a graft around the PN despite pacing configurations. Hence if PNS persisted during CRT implantation, a PTFE patch on the LV lead or a graft around the PN could be considered.

Utility of Speckle Tracking Echocardiography to Characterize Dysfunctional Myocardium in Patients with Ischemic Cardiomyopathy Referred for Cardiac Resynchronization Therapy

Assessment of transmural scar at the site of latest mechanical activation is relevant to maximize outcomes in cardiac resynchronization therapy (CRT). Few studies have assessed the ability of speckle tracking echocardiography (STE)-derived short-axis strain to identify segmental myocardial scar, defined by contrast-enhanced cardiac magnetic resonance imaging (CMR), in patients referred for CRT. A total of 26 patients with ischemic cardiomyopathy who underwent preprocedure echocardiography and CMR were studied. Extent of transmural scar was assessed using contrast-enhanced CMR and corresponding peak segmental radial and circumferential strains were derived using two-dimensional (2D) STE. Total left ventricle (LV) scar volume was compared with parameters of global strain. CRT response was defined as >15% reduction in LV end systolic volume (LVESV) at 6months. Speckle tracking short-axis strain analysis was technically possible in over 90% of LV segments. Applying a segmental radial strain cutoff value of 10% distinguished segments with >50% scar area with a high negative predictive value (98%). Global longitudinal strain <-5% predicted CRT response. Two-dimensional STE offers potential to characterize dysfunctional myocardium and define segmental scar offering an integrated imaging approach to guide LV lead placement for CRT.

Anatomical Reconstructions of the Human Cardiac Venous System using Contrast-computed Tomography of Perfusion-fixed Specimens

A detailed understanding of the complexity and relative variability within the human cardiac venous system is crucial for the development of cardiac devices that require access to these vessels. For example, cardiac venous anatomy is known to be one of the key limitations for the proper delivery of cardiac resynchronization therapy (CRT)(1) Therefore, the development of a database of anatomical parameters for human cardiac venous systems can aid in the design of CRT delivery devices to overcome such a limitation. In this research project, the anatomical parameters were obtained from 3D reconstructions of the venous system using contrast-computed tomography (CT) imaging and modeling software (Materialise, Leuven, Belgium). The following parameters were assessed for each vein: arc length, tortuousity, branching angle, distance to the coronary sinus ostium, and vessel diameter. CRT is a potential treatment for patients with electromechanical dyssynchrony. Approximately 10-20% of heart failure patients may benefit from CRT(2). Electromechanical dyssynchrony implies that parts of the myocardium activate and contract earlier or later than the normal conduction pathway of the heart. In CRT, dyssynchronous areas of the myocardium are treated with electrical stimulation. CRT pacing typically involves pacing leads that stimulate the right atrium (RA), right ventricle (RV), and left ventricle (LV) to produce more resynchronized rhythms. The LV lead is typically implanted within a cardiac vein, with the aim to overlay it within the site of latest myocardial activation. We believe that the models obtained and the analyses thereof will promote the anatomical education for patients, students, clinicians, and medical device designers. The methodologies employed here can also be utilized to study other anatomical features of our human heart specimens, such as the coronary arteries. To further encourage the educational value of this research, we have shared the venous models on our free access website: www.vhlab.umn.edu/atlas.

Acute haemodynamic comparison of multisite and biventricular pacing with a quadripolar left ventricular lead

Pacing from multiple sites in the left ventricle (LV) may bring about further resynchronization of the diseased heart compared with biventricular (BiV) pacing. We compared acute haemodynamic response (LV dP/dtmax) of multisite and BiV pacing using a quadripolar LV lead. In 21 patients receiving cardiac resynchronization therapy, a quadripolar LV lead and conventional right atrial and ventricular leads were connected to an external pacing system. A guidewire pressure sensor was placed in the LV for continuous dP/dt measurement. Four multisite pacing configurations were tested three times each and compared with BiV pacing using the distal LV electrode. Nineteen patients had useable haemodynamic data. Median increase in LV dP/dtmax with BiV vs. atrial-only pacing was 8.2% (interquartile range 2.3%, 15.7%). With multisite pacing using distal and proximal LV electrodes, median increase in LV dP/dtmax was 10.2% compared with atrial-only pacing (interquartile range 6.1%, 25.6%). In 16 of 19 patients (84%), two or more of the four multisite pacing configurations increased LV dP/dtmax compared with BiV pacing. Overall, 72% of all tested configurations of multisite pacing produced greater LV dP/dtmax than obtained with BiV pacing. Pacing from most distal and proximal electrodes was the most common optimal configuration, superior to BiV pacing in 74% of patients. In the majority of patients, multisite pacing improved acute systolic function further compared with BiV pacing. Pacing with the most distal and proximal electrodes of the quadripolar LV lead most commonly yielded greatest LV dP/dtmax.

Snare coupling of the pre-pectoral pacing lead delivery catheter to the femoral transseptal apparatus for endocardial cardiac resynchronization therapy

Limitations imposed by the coronary sinus venous anatomy triggered the transseptal approach for endocardial LV lead placement. The alignment of the interatrial septum (IAS) and its neighborhood anatomy does not favor transseptal puncture from the pre-pectoral area. Locating and advancing a pre-pectoral LV lead delivery catheter (PDC) through an opening created in the IAS via femoral transseptal puncture (FTP) is time consuming and technically difficult. We describe a method where the PDC is snare coupled to the femoral transseptal apparatus (FTA). When the FTA is advanced into the left atrium (LA) the coupled PDC follows. The catheter of a 25-mm loop snare kit is replaced with the PDC (SelectSite®). The snare loop is positioned in the right common iliac vein from the pre-pectoral access. The PDC is coupled to the FTA by advancing the transseptal apparatus through the open snare loop. After conventional FTP, the FTA is withdrawn back into the right atrium (RA) over an extra support wire positioned in the LA. The PDC with open snare loop is pulled over the FTA up to the RA. The PDC is advanced to close the snare loop on the extra support wire immediately distal to the tip of the dilator close to the puncture site. The PDC is deflected to align with the FTA. The snare coupled catheters are gently advanced across the IAS into the LA. The PDC is released from the FTA by advancing the snare and opening the loop; the snare is then removed from the PDC. The PDC is deflected and advanced into the left ventricle (LV). After positioning the 4.1 Fr lumen less LV lead, the PDC is sliced and removed. The PDC snare coupled to the FTA was advanced into the LA in all five patients, however, access was lost during catheter manipulation in the one right-sided case. Endocardial LV lead was successfully positioned in all five patients. Snare coupling the pre-pectoral SelectSite® catheter to the FTA is technically simple, reliable and a safe method for transseptal endocardial LV lead placement for left pre-pectoral implantation.

Electrocardiographic Patterns during Left Ventricular Epicardial Pacing

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. 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. 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). Posterolateral and anteroapical ECG patterns are highly predictive of LV lead position.

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

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. 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. 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. 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.

Quad-Site Pacing Using a Quadripolar Left Ventricular Pacing Lead

Pacing the left ventricle (LV) from multiple sites simultaneously may result in a better response to cardiac resynchronization therapy (CRT). We sought to assess whether multisite pacing using a quadripolar LV lead improves acute hemodynamic response (AHR) to CRT. We paced four ventricular sites simultaneously using two vectors of a Quartet lead, a right ventricular apical lead, and an additional LV lead temporarily placed in an anterior branch of the coronary sinus. Multisite pacing using the Quartet lead alone did not improve the AHR but "quad-site" pacing using an additional temporary LV lead did increase dP/dt(max).

The Acute Hemodynamic Response to LV Pacing within Individual Branches of the Coronary Sinus using a Quadripolar Lead

It is not clear whether there is a large difference in acute hemodynamic response (AHR) to left ventricle (LV) pacing in different regions of the same coronary sinus (CS) vein. Using the four electrodes available on a Quartet LV lead, we evaluated the AHR to pacing within individual branches of the CS. An acute hemodynamic study was attempted in 20 patients. In each patient, we assessed AHR in a number of CS veins and along a significant proportion of each CS branch using three different bipolar configurations. We compared the AHR achieved when pacing using each different vector and also the highest AHR achieved in any position within the same patient with the lowest achieved in that patient. Sixty-four different CS positions in 19 patients were successfully assessed. No significant difference in AHR was found overall between the three vectors tested. The mean percentage difference in AHR between the CS branch vectors with the lowest and highest dP/dt(max) was +6.5 ± 5.4% (P < 0.001). A much larger difference of +16.9 ± 6.1% (P < 0.001) was seen when comparing the highest and lowest AHR achieved using any vector in any position within the same patient. A small difference in AHR is seen when pacing within the same branch of the CS compared to pacing in different branches in the same patient. This suggests that although the site of LV lead placement is important, the position within a CS branch is less important than choosing the right vein.

The Right Ventricular Septum Presents the Optimum Site for Maximal Electrical Separation During Left Ventricular Pacing

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. 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. 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). 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.

ORAL PRESENTATION

ORAL PRESENTATION

Left ventricular pacing with long pulse duration can avoid phrenic nerve stimulation

One of the major limitations of left ventricular pacing is phrenic nerve stimulation. We evaluated the characteristics of the strength-duration curves of the left phrenic nerve (PN) and epicardium of the left ventricle (LV). A total of 12 mongrel dogs were studied. Capture threshold was assessed during pacing with 180 beats/min and various pulse durations (0.25 to 2.0 ms) in an open chest model. A commercially available LV lead was inserted through a small hole created in the pericardium. The tip electrode position was maintained at the course of the left PN with gentle manual pressure under visual inspection. The LV threshold was evaluated at the epicardium just below the PN. The LV threshold was defined as the highest amplitude that showed loss of 1:1 capture. The PN threshold was defined as the highest amplitude that could not induce any diaphragmatic contraction. The strength-duration curve of the PN had a higher rheobase and shorter chronaxie than that of the LV. The LV threshold was higher than that of the PN at pulse duration <1.0 ms in bipolar pacing, but significantly lower than that of the PN at a pulse duration of 2.0 ms, especially during unipolar pacing (1.3 ± 0.21 V vs. 2.0 ± 0.56 V, LV vs. PN, P =.012). LV pacing without PN stimulation could be achieved in pacing with long pulse duration. The longer pulse duration option can be considered in the development of devices for LV pacing such as cardiac resynchronization therapy.

Left Ventricular Pacing with Long Pulse Duration Can Avoid Phrenic Nerve Stimulation

Background: One of the major limitations of left ventricular pacing is phrenic nerve stimulation. We evaluated the characteristics of the strength-duration curves of the left phrenic nerve (PN) and epicardium of the left ventricle (LV). Methods: A total of 12 mongrel dogs were studied. Capture threshold was assessed during pacing with 180 bpm and various pulse durations (0.25–2.0 ms) in an open chest model. A commercially available LV lead was inserted through a small hole created in the pericardium. The tip electrode position was maintained at the course of the left PN with gentle manual pressure under visual inspection. The LV threshold was evaluated at the epicardium just below the PN. Results: The strength-duration curve of the PN had a higher rheobase and shorter chronaxie than that of the LV. The LV threshold was higher than that of the PN at pulse duration <1.0 ms in bipolar pacing, but significantly lower than that of the PN at a pulse duration of 2.0 ms, especially during unipolar pacing (1.3±0.21 vs. 2.0±0.56 V, LV vs. PN, p=0.012). Conclusion: LV pacing without PN stimulation could be achieved in pacing with long pulse duration. The longer pulse duration option can be considered in the development of devices for LV pacing such as cardiac resynchronization therapy.

Is cardiac venous anatomy a crucial factor in maximizing the response to cardiac resynchronisation therapy?

Cardiac resynchronization therapy (CRT) restores the synchrony of the heart?s contractions. The most critical issue in CRT implantation is the positioning of the coronary sinus (CS) lead because not every region can be accessed due to variations in coronary venous anatomy. The aim was to determine the correlation between different CS lead positions and hemodynamic changes and clinical outcome over time. Our study prospectively enrolled 51 patients with conventional indications for CRT which was divided into three groups according to the vein in which the left ventricle lead was placed during the procedure (posterior, lateral, and anterior). The groups were compared by baseline demographic characteristics, comorbidity, complications, new hospitalizations as well as by hemodynamic parameters before and six months after the procedure. After six months, all patients responded to CRT in the lateral group, 66.7% patients in the posterior group and 50% in the anterior group (p&lt;0.01). Patients in the anterior group had a smaller decrease in NYHA functional class compared to the posterior and the lateral groups (p&lt;0.01). The largest increase of preoperative ejection fraction value was in the posterior group (68.7%) compared to the lateral (42.2%) and anterior groups (19.8%) (p&lt;0.01, A vs. P&amp;L; P vs. A&amp;L). In the anterior group there was a smaller decrease of QRS complex compared to the posterior and lateral groups (p&lt; 0.05, A vs. P&amp;L). Also there was a smaller decrease in the degree of mitral regurgitation in the anterior group compared to the lateral and posterior groups (p&lt;0.05, A vs. P&amp;L). One of the main determinants of CRT response is the anatomy of CS tributaries, and therefore the position of the LV lead is crucial in maximizing the effect of CRT.

Beating-heart ascending aortic graft replacement in dilated cardiomyopathy

It is still a highly difficult choice with no definitive answer whether to perform cardiac surgery on cardioplegically arrested heart or to operate on a beating heart, especially for patients with dilated cardiomyopathy (DCM). A 73-year-old man, who had ascending aortic aneurysm and DCM with ejection fraction (EF) of 16.5% and the left ventricle (LV) dyssynchrony, underwent graft replacement of the ascending aorta and implantation of the LV lead for cardiac resynchronization. The operation was carried out on a beating heart using tepid hypothermic cardiopulmonary bypass under antegrade/retrograde coronary blood perfusion during graft-aorta proximal anastomosis. Postoperative course was uneventful, though brain natriuretic peptide (BNP) showed transient elevation.

Cardiac Resynchronization Therapy With and Without Implantable Cardioverter-Defibrillator

Cardiac resynchronization therapy (CRT) is recommended to reduce morbidity and mortality in patients with New York Heart Association class III/IV, who are symptomatic despite optimal medical therapy, and who had a reduced left ventricle (LV) ejection fraction and electrical dyssynchrony. The effects of CRT are reflected mainly by the degree and location of dyssynchrony and by working in insertion of optimal LV lead site. Echocardiography and Doppler echocardiography are considered to be good tools to measure LV dyssynchrony directly. However, the large randomized trials have shown that no single echocardiographic measure of dyssynchrony is recommended to improve patient selection for CRT beyond current guidelines. There were several unsolved issues on CRT, such as patient selection, electrical or electromechanical dyssynchrony criteria to patients for CRT, indication of patients with a narrow or slightly prolonged QRS width, indication of patients with atrial fibrillation, and indication of patients with mild heart failure or asymptomatic LV dysfunction, and device selection; CRT alone (CRT-P) or CRT in combination with implantable cardioverter therapy (CRT-D). This review paper summarized the concept of therapy, the current evidence regarding the indications, effectiveness and safety of CRT-P and CRT-D in patients with LV dysfunction, and unsolved issues.

Coronary Sinus Diverticulum Complicating CRT Device Implantation

Coronary sinus diverticula are rare findings usually associated with the presence of accessory pathways. We report the case of a 74-year-old man, who underwent cardiac resynchronization therapy (CRT) device implant. Coronary sinus diverticulum was an incidental finding while attempting to subselectively cannulate the coronary sinus for left ventricle lead implant. The case was able to be completed without complications.

Baseline Scintigraphic Abnormalities by Myocardial Perfusion Imaging Predict Echocardiographic Response to Cardiac Resynchronization Therapy in Nonischemic Cardiomyopathy

Significant myocardial scar in the posterolateral left ventricle (LV) has been associated with a diminished response to cardiac resynchronization therapy (CRT) in patients with coronary artery disease, but the effects of resting perfusion abnormalities in nonischemic cardiomyopathy (NICM) are yet to be described. We sought to characterize the effect of myocardial perfusion abnormalities upon echocardiographic outcomes of CRT in patients with NICM. Twenty-one patients (mean age 64.4 +/- 13.3; 71.4% male; mean left ventricular ejection fraction [LVEF] 20.2 +/- 6.9%) with NICM who underwent CRT implantation and Thallium-201 single positron emission computed tomography (SPECT) myocardial perfusion imaging (MPI) were included. MPI studies were read quantitatively, assigning each of 17 myocardial segments a perfusion score (0-4) and cumulatively generating a summed perfusion score (SPS). The LV lead position was determined by chest radiography. Echocardiograms were performed both before and after (median 12 mo) CRT in 15 patients. Echocardiographic response, defined as > or = 15% relative increase in LVEF, was documented in 8 (53.3%) of 15 patients. All patients (5/5) with an SP < or =6 responded to CRT, whereas only 30.0% (3/10) with an SPS > or = 6 responded (odds ratio 3.33 [95% confidence interval {CI} 1.29-8.59]; p = 0.01). All nonresponders had inferior perfusion defects. Defect density adjacent to the LV lead tip had little demonstrable effect upon CRT efficacy. The presence of significant myocardial perfusion defects negatively influences echocardiographic response to CRT in NICM. These findings warrant prospective confirmation and histopathological correlation with explanted hearts.