Author + information
- Received September 26, 2016
- Revision received January 23, 2017
- Accepted January 27, 2017
- Published online August 21, 2017.
- Jonathan M. Behar, MBBS, BSca,∗ (, )
- Peter Mountney, PhDb,
- Daniel Toth, MSca,c,
- Sabrina Reiml, BScd,
- Maria Panayiotou, PhDa,
- Alexander Brost, PhDd,
- Bernhard Fahn, MSc, PhDd,
- Rashed Karim, PhDa,
- Simon Claridge, LLB, MBBSa,
- Tom Jackson, MBBSa,
- Ben Sieniewicz, MBBSa,
- Nik Patel, MBBSa,
- Mark O’Neill, MD, DPhila,
- Reza Razavi, MDa,
- Kawal Rhode, PhDa and
- Christopher Aldo Rinaldi, MDa
- aDepartment of Imaging Sciences and Biomedical Engineering, King’s College London, & Guy’s and St Thomas’ Hospital, London, United Kingdom
- bMedical Imaging Technologies, Siemens Healthineers, Princeton, New Jersey
- cSiemens Healthineers, Frimley, Camberley, United Kingdom
- dSiemens Healthcare GmbH, Erlangen, Germany
- ↵∗Address for correspondence:
Dr. Jonathan M. Behar, c/o Imaging Sciences & Biomedical Engineering, 4th Floor Lambeth Wing, St Thomas’ Hospital, Westminster Bridge Road, London SE1 7EH, United Kingdom.
Objectives This study sought to test the feasibility of a purpose-built, integrated software platform to process, analyze, and overlay cardiac magnetic resonance (CMR) data in real time within a combined cardiac catheter laboratory and magnetic resonance imaging scanner suite (X-MRI) to guide left ventricular (LV) lead implantation.
Background Suboptimal LV lead position is a major determinant of poor cardiac resynchronization therapy (CRT) response, and the optimal site is highly patient specific. Pacing myocardial scar is associated with poorer outcomes; conversely, targeting latest mechanical activation (LMA) may improve them.
Methods Fourteen patients (age 74 ± 5.1 years; New York Heart Association functional class: 2.7 ± 0.4; 86% ischemic with ejection fraction 27 ± 7.6%; QRSd: 157 ± 19 ms) underwent CMR followed by immediate CRT implantation using derived scar and dyssynchrony data, overlaid onto fluoroscopy in an X-MRI suite. Rapid LV segmentation enabled detailed scar quantification, identification of LMA segments, and selection of myocardial targets. At coronary venography, the CMR-derived 3-dimensional shell was fused, enabling identification of viable venous targets subtended by target segments for LV lead placement.
Results The platform was successful in all 14 patients, of whom 10 (71%) were paced in pre-procedurally defined target segments. Pacing in CMR-defined target segments (out of scar) showed a significant decrease in the LV capture threshold (mean difference: 2.4 [1.5 to 3.2]; p < 0.001) and shorter paced QRS duration (mean difference: 25 [15 to 34]; p < 0.001) compared with pacing in areas of CMR determined scar. In 5 (36%) patients with extensive scar in the posterolateral wall, CMR guidance enabled successful lead delivery in an alternative anatomically favorable site. Radiation dose and implant times were similar to historical controls (p = NS).
Conclusions Real-time CMR-guided LV lead placement is feasible and achievable in a single clinical setting and may prove helpful to preferentially select sites for LV lead placement.
- cardiac magnetic resonance (CMR)
- cardiac resynchronization therapy (CRT) image guidance
- image overlay
- targeted LV lead placement
Cardiac resynchronization therapy (CRT) is a highly efficacious treatment for symptomatic patients with heart failure, severe left ventricular (LV) dysfunction, and broad QRS duration (1,2). Despite 2 decades of delivering biventricular pacing for selected patients with heart failure, 30% to 50% fail to undergo LV remodeling (3), with most implanters using empirical placement of the LV lead on the posterolateral wall. However, the optimal site for LV stimulation is highly patient specific (4) and suboptimal lead position is a major determinant of poor response (5). LV lead positioning in or near areas of myocardial fibrosis is associated with poorer outcomes (6–8). Furthermore, targeting LV myocardial segments with latest mechanical activation using speckle tracking echocardiography has demonstrated utility in improving CRT outcomes in single-center randomized studies (9,10). Echocardiography, however, is a highly user-dependent imaging modality and the reproducibility of dyssynchrony metrics is limited (11,12). Cardiac magnetic resonance (CMR) imaging has recently emerged as a highly valuable modality providing unparalleled image quality and information on etiology for patients with heart failure (6); furthermore, it can delineate the location and burden of myocardial scar through late gadolinium enhancement sequences (13) and provide valuable data on mechanical dyssynchrony (14) and LV contraction patterns (15), both of which can inform appropriate placement of the LV lead. We have previously demonstrated the ability to overlay CMR-derived anatomy, scar, and dyssynchrony data onto fluoroscopy for guiding the placement of the LV lead (16,17). This resulted in improved acute response and chronic echocardiographic response above the rates in a standard nonguided approach. However, the large quantity of data, associated lengthy computational processing time, and highly manual process, as well as software limitations at that time meant CMR scans were performed at least 2 weeks before the implant.
The ability to process and display such information in real time would represent a significant advance in the ability to use CMR guidance. In this paper, we report the first demonstration of a real-time, purpose-built user interface in a hybrid cardiac catheter laboratory and magnetic resonance imaging scanner in the same facility with the ability to transfer patients from one to the other (X-MRI) facility to enable the processing, analysis and fusion of CMR-derived data to guide the implanting physician in optimizing the deployment of an LV lead for CRT delivery. Using this technique, the implanting physician can use contemporaneous gold standard myocardial imaging to avoid regions of scar while targeting late activating segments, thereby permitting imaging-guided LV lead implantation in a single procedure.
This study complied with the Declaration of Helsinki and the protocol was approved by the local ethics committee. Informed written consent was obtained from each patient. A comprehensive CRT pre-assessment included New York Heart Association functional class, Minnesota Living with Heart Failure Questionnaire score, 6-min walk distance, peak oxygen uptake on cardiopulmonary exercise testing, and echocardiographic assessment of LV systolic function with 2-dimensional and 3-dimensional (3D) datasets. Patients with a contraindication to CMR or significant renal impairment (estimated glomerular filtration rate: <30 ml/min/1.73 m2) were excluded. Patients fulfilling standard CRT criteria (New York Heart Association functional class II-IV drug refractory heart failure, LV ejection fraction <35%, and QRS >120 ms) were included in the study.
Integrated software module
A custom-made software platform developed by the Department of Imaging Sciences & Biomedical Engineering and Siemens Healthineers was integrated in the X-MRI facility incorporating a Magnetom Aera 1.5T MRI scanner and adjacent Artis Q biplane Angiography system (Siemens Magnetom Artis Combi Suite, Siemens Healthcare GmbH, Erlangen, Germany).
The platform was installed on a dedicated prototype workstation connected to the biplane x-ray system. It was designed for fast, automated data processing to enable information to be extracted from MRI and visualized in the time it takes to transfer the patient from the MRI to angiography suite to minimize any disruption. The platform includes automatic intra- and inter-MRI protocol slice registration, automatic LV segmentation, semiautomatic scar segmentation and metrics for mechanical dyssynchrony, scar distribution, burden, and transmurality. After each automated task, the clinician is given the opportunity to verify and manually adjust the results.
Patient flow and CRT implant
Respiratory and cardiac-gated CMR images were acquired. Two-, 3-, and 4-chamber and multiple slice short-axis balanced steady-state free-precession images were acquired during breath hold (repetition time [TR]: 2.4 ms; echo time [TE]: 1.2 ms; flip angle [FA]: 52°; acquired spatial resolution: 1.3 to 1.8 × 1.9 to 2.8 mm; bandwidth: 930 Hz/pixel; 6-mm slice thickness [long], 8-mm slice thickness [short]) using an 18-channel body coil and a 24-channel spine coil. Late gadolinium enhancement (LGE) sequences in the same views (TR: 2.4 ms; TE: 1.2 ms; FA: 45°; acquired spatial resolution: 1.10 × 2.5 mm; bandwidth: 780 Hz/pixel; 8-mm slice thickness with 2-mm gaps) was performed 10 to 15 min following administration of 0.2 mmol/kg Gadovist (Bayer Healthcare, Berlin, Germany) using conventional inversion recovery techniques to identify areas of myocardial fibrosis (13). Following completion of the scan, the patient was transferred directly to the catheter laboratory (Combi Dockable Table, Siemens Healthcare GmbH) and prepared for CRT implantation, which began immediately after the scan. Simultaneously, the CMR data were uploaded, processed, and analyzed on the prototype platform using the following steps (Figure 1):
1. LV epicardial and endocardial automated segmentation with manual adjustment where necessary.
2. Registration of cine and LGE sequences.
3. Delineation of myocardial fibrosis.
4. Review of location, burden, and transmurality of myocardial fibrosis on a 16-segment American Heart Association (AHA) bull's-eye plot and the associated regional dyssynchrony curves to select optimal target myocardial segments for LV delivery.
LV segmentation and mechanical dyssynchrony computation
The automated segmentation algorithm uses a combination of landmark detection and discrimination between the myocardium and blood pool in each short- and long-axis slice to create a 3D mesh model. The algorithms on which this is based have been previously described (18). Epicardial and endocardial segmented contours are divided into basal, mid, and apical segments. Identification of the right ventricular insertion points further divides segments in line with AHA-recommended nomenclature. Segmental endocardial volumes are computed by multiplication of segmental area by slice thickness. Each AHA regional volume is calculated throughout the cardiac cycle (25 to 30 phases) to produce volume vs. time curves. Time to minimum endocardial volume is assumed to be the time to peak strain and expressed as a fraction of the cardiac cycle length, denoted by a colored dot on each segmental curve (lower left panel, Figure 2). The mechanical activation curves are generated automatically after the user confirms the segmentation of epicardial and endocardial shells from the short-axis cine sequences and has reviewed these segmentations tracking over the cardiac cycle length.
Myocardial fibrosis identification
The cine short-axis sequences are first registered to the LGE sequences to translate myocardial fibrosis to the LV mesh. Subsequently, an automated algorithm computes and highlights regions of scar (LGE) after the user identifies a region of healthy tissue; LGE was defined as 2 standard deviations from the mean gray level. Users can adjust and manually add or remove areas of fibrosis while reviewing each slice.
Data review and target selection
Following the steps described previously, a guidance display is shown from which physicians select target segments according to the principle of avoiding myocardial scar and targeting areas of mechanical dyssynchrony (latest time to peak contraction) in line with our previously published work (15) (Figure 2). Where there was extensive myocardial fibrosis, segments with the smallest scar burden and transmurality were selected. Septal segments were excluded because epicardial LV stimulation in this region does not achieve effective resynchronization. Where scar was absent, target segments with the most delayed time to minimum volume were chosen. Segments with a minimal change in volume and therefore reduced endocardial strain were excluded for selection on the basis of likely nonviability and previously published work linking LV placement in such regions with poor CRT outcomes (19).
A 3D model derived from CMR was coregistered with x-ray images using multimodality imaging markers placed on the left side of the chest overlying the heart (Beekley Medical, Bristol, Connecticut) and visible on both CMR and x-ray images. A 3D spoiled gradient echo, time-resolved angiography with interleaved stochastic trajectories sequence was used to identify the adhesive markers (TR: 2.56; TE: 0.9; FA: 30°; slice thickness: 1.3 mm; acquired spatial resolution: 1.3 × 1.9 mm) on CMR and these were registered to biplane fluoroscopic images using the platform. Six degrees of freedom, translation, and rotation ensured the accuracy of the registration in orthogonal planes. Following this process, the CMR-derived 3D model is registered to the x-ray coordinate system; subsequent x-ray acquisitions during the case are displayed with instantaneous overlay of the correctly oriented 3D model (Figure 3).
Steps 1 through 4 were completed while the patient was being prepared for the implantation. Following coronary sinus (CS) cannulation, occlusive venography in right anterior oblique, anteroposterior, and left anterior oblique projections were obtained and instantaneously fused with the CMR-derived 3D model of the patient’s left ventricle (both epicardium and endocardium), as shown in Figure 4. The number and anatomical location of viable epicardial coronary venous targets was immediately visualized on the AHA 16-segment plot. Scar location and target selection meshes could be selectively highlighted to guide LV lead positioning (Figure 4). LV lead deployment was performed in the standard fashion aiming to place the lead in the targeted segment when CS anatomy was favorable and the target threshold was <2.5 V at 0.5 ms with no phrenic nerve stimulation at 10 V. A quadripolar LV lead was used in all cases.
Before finalizing the LV lead position, to further validate the guidance system in relation to scar and local electrical activation (QLV), all epicardial veins (able to receive an LV lead) were tested. Multiple vector configurations were attempted along each vein where possible and the QLV (ms), capture thresholds (V), and paced QRS (ms) were measured.
A test for normality (Shapiro-Wilk) was performed for each variable. Continuous variables with a Gaussian distribution were described using mean ± standard deviation; those with non-normal distribution were described with median, interquartile range. Categorical data were described by an absolute number of occurrences and associated frequency (%). Because of different numbers of multiple measurements per patient, an ordinary Student t test would not be appropriate and a mixed-effect model was performed. Results were considered statistically significant at p < 0.05. Analysis was performed on PASW Statistics 22 (SPSS Inc., Chicago, Illinois) and Stata (StataCorp, 2014, Statistical Software, College Station, Texas) for the mixed linear model. In the text, capture thresholds are described to 1 decimal place and QLV/biventricular-paced QRS described to no decimal places, for clinical relevance.
Fourteen patients underwent real-time X-MRI-guided lead implantation. Patients were age 74 ± 5.1 years and all were successfully implanted with a new CRT device (CRTD) (13 [93%]). Twelve (86%) patients had subendocardial myocardial fibrosis; 2 patients had nonischemic cardiomyopathy (Table 1). Total procedural time including CMR (45 ± 6 min), data processing and patient transfer/preparation (25 ± 8 min), and CRT implant (115 ± 33 min) was 185 ± 35 min. Radiation dose area product was similar to recent historical controls (conventional CRT implants): 1,893 ± 1,965 cGycm2vs. 1,582 ± 2,122 cGycm2, p = 0.72. There were no post-operative complications and no adverse effect on renal function despite use of intravenous gadolinium and iodinated contrast within a short space of time. Of note, patients in this study had all accessible coronary veins tested for LV lead implantation compared with the historical controls, in which this is not routine practice.
A mean of 3.6 ± 1 epicardial coronary veins were visible at venography (total: 51), of which 2.4 ± 0.8 (total: 33) were judged to be viable targets for LV lead deployment on the basis of anatomical location and vessel caliber. Biventricular stimulation was performed from these sites. A total of 56 data points were acquired across 14 patients (range: 1 to 10) (Online Table 1) in all possible epicardial veins. In some cases, multiple data points were collected along veins using different vectors from the multipolar LV lead. In 10 of 14 (71%) patients, LV lead implantation was achieved in the CMR-defined target segments based upon avoiding scar and targeting mechanical dyssynchrony (e.g., Figure 5). The 4 remaining patients were paced in/adjacent to scar because of a lack of coronary venous anatomy to the target segment. Pacing in CMR-defined target segments (out of scar) showed a statistically decreased mean in the LV lead capture threshold (mean difference: 2.4 [1.5 to 3.2]; p < 0.001) and shorter biventricular paced QRS duration (mean difference: 25 [15 to 34]; p < 0.001) compared with areas in areas of scar as defined by the CMR overlay. There was no significant difference for QLV (mean difference: 8 [-9 to 24]; p = 0.35) (Table 2). Six patients had anterior/anteroseptal scar, 5 patients had posterolateral scar, 1 patient had anterolateral scar, and 2 patients had no scar. In cases where the only viable veins were in or adjacent to scar (particularly those with posterolateral scar), image overlay facilitated positioning of the poles on the multipolar LV lead away from scar as depicted in Figure 5.
This study demonstrates for the first time the safety and feasibility of real-time CMR-defined scar and dyssynchrony to successfully guide LV lead implantation for CRT delivery in a single procedure. Furthermore, pacing within CMR-defined segments (out of scar) showed more favorable electrical properties (lower LV capture thresholds and shorter BV-paced QRS duration) as compared with regions of scar, confirming validity to this approach.
Image-guided CRT: Comparison with previous studies
Two randomized studies have previously shown the benefit of targeted LV lead placement over an empirical approach. The TARGET (Targeted Left Ventricular Lead Placement to Guide Cardiac Resynchronization Therapy) (8) and STARTER (Speckle Tracking Assisted Resynchronization Therapy for Electrode Region) (9) studies showed significant improvements in LV remodeling by using 2-dimensional speckle tracking echocardiography to define and target late activating segments. Cardiac imaging was however, performed at a separate sitting prior to implantation and the images were not fused with fluoroscopy. In 11% of the patients recruited to TARGET, guidance could not be performed due to suboptimal imaging. The authors point out that one of the main limitations of echocardiography is the inability to image scar, which is of key importance given the association between posterolateral wall scar and poor outcomes (7). CMR in comparison has the ability to identify and quantify both scar and dyssynchrony and may represent the optimal imaging modality for CRT guidance (6). A meta-analysis of 511 patients using STARTER, TARGET, and another prospective cohort study (20), confirmed the efficacy of an image-guided approach compared with conventional implants with a higher odds ratio of response to CRT (odds ratio: 2.1; 95% confidence interval: 1.43 to 3.07; p < 0.0001) (21).
We have previously used CMR imaging to delineate scar and dyssynchrony fused with fluoroscopy at the time of implantation (16,17). Using this technique, guided placement of the LV to CMR target segments was associated with a significantly superior hemodynamic response compared with an empirical nontargeted approach. Furthermore, 92% of the echocardiographic responders (>15% reduction in end-systolic volume) were paced in a targeted CMR target segment, compared with 50% of those who were echo nonresponders. Because of the significant time previously required for the software processing of CMR images, the scan was performed on average 2 weeks before the implant. Our current technique represents a paradigm shift, with rapid data processing, analysis, and visualization of the CMR data in the same X-MRI laboratory in a single sitting. This process occurs in parallel with the patient being draped and central venous access being gained. Rapid image coregistration enables immediate image fusion upon CS venography allowing the implanter to perform real-time CMR-guided CRT.
Importantly, our implant times compare very favorably with previous guided CRT studies. In TARGET, implant time was 139 ± 36 min in the guidance group compared with 138 ± 42 min in the standard group (p = NS), although screening time and dose were higher in the guidance group (24 ± 14 min vs. 19 ± 13 min, p = 0.033) (9). The implant time for our patients excluding the CMR was 115 ± 33 min, despite pacing in all accessible venous sites (target and nontarget) as part of validating the system. In the future, we envisage this system being used to directly implant the target vein, likely being associated with significantly shorter implant and fluoroscopy times.
CRT outcomes and myocardial fibrosis
Reported nonresponse rates to CRT are variable depending on which outcome measure is assessed but is at least 30% (3). Myocardial fibrosis, particularly in the posterolateral region where the LV lead is empirically placed, is associated with a poor response to CRT (7). Studies have described using CMR to avoid LV lead placement within scar to improve CRT response (8,22) and using multisite LV stimulation to improve hemodynamic response in this group (23). In the current study, 36% of patients had myocardial scar in the posterolateral region. Given that the majority of patients undergoing CRT have the LV lead implanted in either the lateral or posterior walls (24), it is inevitable that the lead will be in or adjacent to myocardial scar in a sizeable proportion of cases. Prior studies have highlighted the importance of both global scar burden (25) and regional scar occupying the region of the LV lead (26) on CRT outcomes. Our custom-made platform produces information regarding percentage scar burden and transmurality for each myocardial segment; this knowledge may be a useful adjunct in difficult cases with a high global scar burden by guiding the implanting physician to select those sites with the lowest segmental scar burden and transmurality. Furthermore, in cases in which LV lead placement in or adjacent to scar was inevitable because of the distribution of coronary venous anatomy, the CMR scar mask was able to guide the positioning the poles (from the multipolar LV lead) away from islands of scar to achieve more favorable testing parameters.
Study limitations and challenges
This is a small proof of principle study; however, a larger, randomized controlled study would be necessary to demonstrate whether an image-guided approach is superior to the standard of care, which we plan to perform. Given that 2 previous studies using echocardiogram-derived markers (9,10) and 2 recent studies using multimodality imaging (27,28) have all demonstrated improved clinical outcomes, this would infer that a strategy of image guidance may be of clinical benefit.
The use of CMR may not be feasible in all patients because of renal impairment and claustrophobia. Furthermore, heart failure patients especially may struggle with being supine for extended periods; therefore, this technique may not be suitable for all. Scar derivation was from routine LGE sequences in a short-axis slice format (8-mm slice, 2-mm gap), which inevitably leads to an irregularly edged mesh with gapping. Dyssynchrony was derived through endocardial wall motion tracking on routine cine imaging and volume vs. time curves used to identify segments with latest mechanical activation rather than a pure strain calculation. It could be argued that one cannot exclude passive wall motion when tracking the endocardial surface only; however, similar tracking algorithms (using cine CMR) have shown good agreement with strain derived from myocardial tagging (the gold standard for measuring strain) (29).
We anticipate future iterations of the platform to include scar analysis from LGE sequences with higher spatial resolution (higher number of slices or 3D scar) and calculation of dyssynchrony through a range of different metrics including cine sequence–derived strain, as described previously (27). In this study, of importance was that the spatial and temporal resolution were the same as for routine scanning; however, more elaborate and refined sequences may be able to be incorporated in the near future. Finally, we intentionally studied a predominantly ischemic population, given that they have the most to gain from a technique that may be able to improve CRT response. Response rates in nonischemic patients are indeed significantly higher; we would therefore advocate studying a larger number of these patients to evaluate the platform from the perspective of image guidance using dyssynchrony parameters alone.
Coronary venous anatomy has been described using 3D whole heart sequences (electrocardiogram-triggered, respiratory-navigated, steady-state free-precession inversion recovery) applied to the whole heart over a short period (e.g., 60 to 80 ms), obtaining spatial resolution of 1.5 × 1.5 × 2 mm (30). However, this process adds at least 30 min of scanning time and, furthermore, the coronary veins require segmentation to extract onto the 3D mesh model, which can be time consuming and limit the applicability of data utilization in real time. Furthermore, heart failure patients may have worsened breathing when lying supine; therefore, we wanted to keep scanning time to a minimum, before the implant, which also requires them to lie flat.
An increasing proportion of patients undergoing CRT are upgrades from existing devices and, despite the increasing availability of magnetic resonance conditional pacing systems (31), significant artifact image degradation would limit the use of a CMR-based guidance platform. We have previously shown computed tomography (CT) imaging merged with fluoroscopy can facilitate LV lead implantation in previously failed LV lead implants with visualization of CS anatomy (32). Furthermore, cardiac CT may provide a feasible alternative to CMR; measures of strain have shown to correlate between the 2 imaging modalities in an animal model (33) and scar can be demonstrated (34). We envisage using a similar guidance platform with CT data in a similar way in the future.
Given the expense of CMR in some centers, this technique may not be cost-effective; however, the data could be processed offsite and fed back to the core site. The current technique of single-sitting CMR and implant requires an X-MRI laboratory, which is not available in all centers. It is envisaged, however, that in the future, with improved image registration techniques not requiring fiducial markers, the CMR platform could be used in an offline manner with scanning and implantation in separate locations and times.
Finally, it is notable that only 71% of patients were able to have the LV lead delivered to the target segment; this is similar to our previous study of CMR guidance (15). This usually occurs from the lack of a coronary vein subtending the target segments. This may be viewed not as a limitation but as an advantage of the system. One may argue that in those cases in which the target segments are not subtended by viable epicardial veins, the conventional epicardial approach may be switched to an endocardial LV approach at the outset. Endocardial pacing has been shown to be of use in nonresponders to conventional CRT (35); however, the optimal site of stimulation varies greatly between patients (4,36,37). The value of such a system may be to both identify patients in whom such an approach is required and to then use the system to perform targeted endocardial LV lead implantation. Recently, we have shown that such a targeted approach for endocardial LV stimulation using CMR guidance to avoid scar results in improved hemodynamic response (38).
Clinical relevance and future directions
Image guidance is likely to lead to improved response rates in patients undergoing CRT implantation. The ability of CMR to image scar as well as dyssynchrony would appear to make it the ideal clinical tool for such guidance and may result in improved responder rates. The ability to perform imaging and guidance in 1 sitting may be attractive for both the patient and clinician and may result in a more cost-effective approach to CRT. The development of LV endocardial pacing and the use of leadless pacemaker systems that can be deployed into the LV endocardium (39) are likely to be used increasingly in the future, especially in patients who are likely to respond poorly to standard CRT. Endocardial LV pacing is highly site specific, and the use of such an imaging platform to guide endocardial LV stimulation sites may be extremely important in the future.
Real-time CMR guidance for optimal LV lead placement in delivering CRT is safe and feasible and can be performed in a single procedure. Larger scale studies are needed to ascertain whether this process will lead to improved clinical outcome.
COMPETENCY IN MEDICAL KNOWLEDGE: Implantation of CRT using a CMR-derived image guidance platform is feasible and, furthermore, targeted LV lead delivery in myocardial regions that are out of scar and dyssynchronous may improve CRT outcomes.
TRANSLATIONAL OUTLOOK: Given the recent interest and enthusiasm for LV endocardial stimulation and wireless pacing to deliver CRT, this technology and technique may be a highly valuable adjunct for implanting physicians.
The authors acknowledge Drs. Manav Sohal and Shaumik Adhya, who implanted patients using the software platform. The authors also acknowledge Professor Janet Peacock, head of Medical Statistics, King’s College London, for statistics support. The methods presented in this paper are based on research and are not commercially available.
This research was supported from Innovate UK (32684-234174), National Institute for Health Research Biomedical Research Centre based at Guy’s and St Thomas NHS Foundation Trust and Kings College London. Dr. Behar acknowledges support from the Rosetrees Trust. Dr. Claridge has received research fellowship funding from St Jude Medical Ltd. Dr. Jackson has received research fellowship funding from Medtronic Inc. Dr. Rinaldi is consultant to St Jude Medical Ltd., Medtronic, and Spectranetics; and receives research funding from St. Jude Medical and Medtronic, Boston Scientific, and Livanova. Drs. Mountney and Toth are employees of Siemens Healthcare Ltd., Frimley, United Kingdom. Ms. Reiml, Mr. Fahn, and Dr. Brost are employees of Siemens Healthcare GmbH, Erlangen, Germany.
Drs Rhode and Rinaldi contributed equally to this work and are joint senior authors on this paper.
All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- Abbreviations and Acronyms
- cardiac magnetic resonance
- cardiac resynchronization therapy
- coronary sinus
- computed tomography
- flip angle
- late gadolinium enhancement
- left ventricular
- first ventricular depolarization (earliest onset QRS duration on surface 12-lead electrocardiogram) to the nadir signal on the LV lead electrogram
- echo time
- repetition time
- cardiac catheter laboratory and MRI scanner in the same facility with the ability to transfer patients from one to the other
- Received September 26, 2016.
- Revision received January 23, 2017.
- Accepted January 27, 2017.
- 2017 The Authors
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