His bundle pacing insights from electroanatomical mapping: Topography and pacing targets.

OBJECTIVES: To characterize 3D electroanatomical mapping (EAM) of the His bundle (HB) region. BACKGROUND: Visualization of selective (S) and nonselective (NS) HB capture areas by EAM has not been described and may help guide HB pacing (HBP). METHODS: EAM was performed via NavX system in 17 patients (pts) undergoing HBP. HB cloud, S-HB, NS-HB, and right bundle (RB) capture areas were mapped. RESULTS: S-HBP areas were identified in 11, NS-HBP in 14, and RB in 11 pts. Two NS-HBP areas (upper and lower) either separated by S-HBP (8 pts) or almost contiguous (5 pts) were observed. S-HBP area measured: 1.1 ± 0.9 cm2 , NS upper: -1.2 ± 0.9 cm2 , NS lower: -1.2 ± 0.9 cm2 , RB: -1.7 ± 1.3 cm2 , total His cloud: -4.1 ± 2.7 cm2 . Electrocardiogram (ECG) pacemaps were different between upper and lower NS-HBP areas in 13/14 pts (p = .006). ECG differences between NS clouds were present in inferior leads in 9 pts (more negative QRS complex from lower NS area) and in precordial leads in 5 pts. There was no correlation between HBP lead location and capture threshold. R-wave amplitude was higher at more distal locations on HB cloud (p = .02). CONCLUSION: (1) Pacemapping identifies distinct regions that may correspond to HB anatomy. (2) A linear S-HBP area is typically surrounded by two separate NS areas. (3) Pace-map ECGs from upper and lower NS-HBP areas have different morphologies. (4) These EAM features and pace-mapping may be helpful to the implanter.

Permanent His-bundle pacing using stylet-directed, active-fixation leads placed via coronary sinus sheaths compared to conventional lumen-less system.

BACKGROUND: The use of coronary sinus (CS) sheaths to deliver stylet-driven leads (SDLs) for His-bundle pacing (HBP) has not been described. Conventionally, HBP is achieved using a stylet-less lead delivered through a customized catheter. OBJECTIVE: The purpose of this study was to characterize the acute and early-term HBP experience with stylet-driven, active-fixation leads delivered through CS sheaths compared to the conventional approach. METHODS: Delivery of Medtronic 4471 and 7742 SDLs was attempted in 27 patients. Delivery was facilitated using CS guide catheters and custom-shaped stylets. Procedural characteristics and lead performance were compared to those of a group of 17 patients in whom delivery of 3830 lumen-less leads (LLLs) was attempted. Patients had heterogeneous pacing indications. RESULTS: HBP with SDL was successful in 24 of 27 patients(89%) compared to 15 of 17 patients (88%) in the LLL group. Mean procedural and fluoroscopy times in the SDL and LLL groups were 129 ± 43 minutes vs 104 ± 43 minutes and 9.6 ± 5.2 minutes vs 8.3 ± 5.0 minutes, respectively (both P = NS). There was a significant difference in procedure and fluoroscopy times within the SDL group between the first and second halves of the series, probably secondary to a learning curve. Acute HBP thresholds were higher with SDL than with LLL (2.6 ± 1.5 V vs 1.5 ± 1.2 V; P = .02) and remained stable at 8.4 ± 5.3 months. Both SDLs exhibited similar pacing thresholds. Two crossovers between groups occurred (1 in each group). Four patients with SDL and 1 patient with LLL exhibited high thresholds during follow-up. CONCLUSION: Permanent HBP using stylet-driven, active-fixation leads delivered through conventional CS sheaths is feasible. Procedural characteristics and lead performance were clinically acceptable.

Direct Visualization of the His Bundle Pacing Lead Placement by 3-Dimensional Electroanatomic Mapping: Technique, Anatomy, and Practical Considerations.

BACKGROUND: His bundle pacing (HBP) remains technically challenging and is currently guided by electrograms and 2-dimensional fluoroscopy. Our objective was to describe a new technique for HBP directly guided by electroanatomic mapping (EAM). METHODS: Twenty-eight patients were included. The atrioventricular septum was mapped via EAM, and His bundle (HB) electrograms, selective, and nonselective HB capture sites were tagged. Pacing leads were connected to EAM, navigated to tagged HB target sites and deployed. Intracardiac electrograms and pacing parameters were recorded. Lead location was tagged on the cloud of HB sites, which was divided into 3 arbitrary segments. In 5 patients, atrioventricular nodal ablation was performed with direct visualization of the HBP lead by EAM. RESULTS: Reproducible navigation of the pacing lead to predetermined HBP locations guided by EAM was achieved in all patients. The lead was successfully deployed in 25 patients. HB cloud area was 360 (212) mm2. There was no correlation between HBP threshold and lead location on the His cloud. The intracardiac electrograms atrial/ventricular ratio at the lead deployment site correlated with its EAM position on the His cloud ( P=0.045). Procedure, fluoroscopy, and mapping times were 116.0 (38.8), 8.6 (6.3), and 9.0 (11.4) minutes, respectively. HBP threshold at implant was 1.5 (2.3) V at 1.5 (1.0) ms. Distance between HB lead and ablation sites was 10.0 (1.3) mm in patients undergoing atrioventricular nodal ablation. CONCLUSIONS: Direct guidance of HBP by EAM allows for direct visualization of the pacing lead on the HB cloud and reproducible navigation to predetermined HB capture sites. Intracardiac electrograms atrial/ventricular ratio at the lead deployment site correlates with His cloud location. EAM can be applied during standard HBP procedures or combined with atrioventricular nodal ablation.

Refractory Hypotension as an Initial Presentation of Bilateral Subclavian Artery Stenosis.

Bilateral subclavian stenosis is a rare clinical condition. An interbrachial pressure difference of 15 mm Hg can raise suspicion for unilateral subclavian artery stenosis, but the diagnosis of bilateral subclavian artery stenosis can be challenging. We present a case of a 75-year-old woman who presented with refractory hypotension after surgery. Initial vitals revealed blood pressure in the 60s/50s mm Hg in both arms. Cardiopulmonary examination was remarkable for diminished pulses in all 4 extremities and audible carotid bruits. She continued to be hypotensive despite aggressive fluid resuscitation. Troponin T peaked at 0.24 ng/mL (reference < 0.04), and an echocardiogram revealed a reduction in ejection fraction (37% from 50%). Left and right heart catheterization demonstrated normal filling pressures and cardiac output. During the procedure, however, it was noted that the patient's central blood pressure was 70-80 mm Hg higher than cuff pressures obtained in either arm. Selective angiography revealed 90% left subclavian ostial stenosis as well as 70% stenosis of the right subclavian artery.

First experience of 3D rotational angiography fusion with NavX electroanatomical mapping to guide catheter ablation of atrial fibrillation.

BACKGROUND: Rotational angiography of the left atrium with 3-dimensional reconstruction (3DATG) is a new imaging tool to guide atrial fibrillation (AF) ablation. Its role as part of a complex imaging strategy with NavX has not yet been evaluated. OBJECTIVE: To determine the feasibility of using 3DATG fusion with NavX in guiding AF ablation. METHODS: 3DATG was performed in 24 consecutive patients undergoing AF ablation by using the Philips Allura Xper FD 10 system. The 3DATG anatomical shell was fused with NavX data (fusion group). Procedural characteristics of the fusion group were compared to 12 patients (control group) who underwent AF ablation guided by NavX only during the preceding 6 months. RESULTS: 3DATG/NavX fusion was successful in all patients and required 12 ± 2 fiducial points. Total radiation dose, fluoroscopy, and procedural times were significantly lower in the fusion group despite additional time and radiation exposure from 3DATG (total radiation dose of 20.4 mSv in the fusion group vs 34.0 mSv in the control group; P = .04; fluoroscopy time 50.5 minutes vs 69.7 minutes; procedural time 4.3 hours vs 5.1 hours). Ablation was successful acutely in 35 of 36 patients. At follow-up, 14 of 24 (58.3%) patients in the fusion group and 6 of 12 (50%) patients in the control group were in sinus rhythm. There was 1 complication in each group. CONCLUSIONS: AF ablation guided by 3DATG/NavX fusion is associated with reduced procedural time and radiation exposure and similar clinical outcomes when compared with NavX mapping only. 3DATG/NavX fusion may provide a lower radiation alternative to NavX only or preprocedural cardiac computed tomography as part of complex imaging strategies.

First experience with rotational angiography of the right ventricle to guide ventricular tachycardia ablation.

BACKGROUND: Rotational angiography with three-dimensional reconstruction (3DRA) is a new imaging tool recently introduced to guide mapping and ablation of the left atrium. OBJECTIVE: The purpose of this study was to determine the utility of 3DRA for imaging the ventricles and guiding ventricular tachycardia (VT) ablation. METHODS: Using the Philips Allura Xper FD10 system, 3DRA was performed in eight patients referred for right ventricular outflow tract (RVOT) VT ablation. The imaging protocol for right ventricular (RV) injection is described. IV contrast was injected at the RA/IVC junction over 4 sec and 3DRA was obtained immediately. Images were segmented manually on the EP Navigator workstation and registered on live fluoroscopy. Intracardiac electrograms were superimposed on 3DRA creating a true electroanatomic map (ElectroNav). CARTO mapping and echocardiograms were performed on all patients, cardiac computed tomography (CT) in 4, and magnetic resonance imaging (MRI) in 1. RESULTS: Three-dimensional rotational angiography was successful in 7 of 8 patients. Image interpretation was unsuccessful in one patient due to poor isocentering. RV imaging was performed with 82 ± 18 mL of contrast. RV image segmentation required 19 ± 5 minutes. CARTO maps of the RVOT required 43 ± 12 minutes and additional fluoroscopy. Three-dimensional rotational angiography was used to guide VT ablation by providing realistic anatomic images of the pulmonary valve plane, endo-views of the ventricle, and ablation point tagging. Anatomic detail provided by 3DRA was qualitatively superior to CARTO. VT ablation was acutely successful in all patients. Close concordance between echocardiographic, CT/MRI, and 3DRA measurements of the RVOT was observed (r = 0.9, P <.01). CONCLUSION: Three-dimensional rotational angiography of the RV and RVOT is a feasible imaging technique that utilizes a protocol of timed angiography, manual segmentation, image registration, and superimposition of intracardiac electrograms to create an angiogram-based electroanatomic model of these structures.

Relationship between intended sites of RF ablation and post-procedural scar in AF patients, using late gadolinium enhancement cardiovascular magnetic resonance.

BACKGROUND: Radiofrequency (RF) ablation of the left atrium (LA) in patients with atrial fibrillation (AF) is guided by electroanatomic mapping systems. The cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) technique can detect scar after ablation. Direct comparisons between the locations of intended RF ablation sites and locations of scar formation in the LA have not been performed. OBJECTIVE: This study sought to develop and use a method for comparing the sites of RF application with the sites of post-procedural scar formation in the LA. METHODS: A method for rigid registration of CMR LGE images with electroanatomic mapping data (Carto data), visualization of the registered data sets, and quantification of the correlations was developed and used in 19 studies of patients with AF. The distance between the Carto points and the CMR LA surface was measured as the mean integration error. The distance between each Carto ablation and the nearest scar was measured. The gaps in sites of LGE and in Carto ablation were also assessed qualitatively, in 6 sectors of each PV. RESULTS: The custom registration method provided a mean integration error between Carto and CMR of 2.7 +/- 0.7 mm. The average distance between Carto and LGE scar was 3.6 +/- 1.3 mm. Qualitatively, 20% of sectors with sites of Carto ablation showed no evidence of LGE. CONCLUSION: There was a visual and quantitative correspondence between Carto ablation sites and LGE scar, but for 20% of Carto ablation sites there was no visible corresponding LGE.

Recurrence of atrial fibrillation correlates with the extent of post-procedural late gadolinium enhancement: a pilot study.

OBJECTIVES: We sought to evaluate radiofrequency (RF) ablation lesions in atrial fibrillation (AF) patients using cardiac magnetic resonance (CMR), and to correlate the ablation patterns with treatment success. BACKGROUND: RF ablation procedures for treatment of AF result in localized scar that is detected by late gadolinium enhancement (LGE) CMR. We hypothesized that the extent of scar in the left atrium and pulmonary veins (PV) would correlate with moderate-term procedural success. METHODS: Thirty-five patients with AF, undergoing their first RF ablation procedure, were studied. The RF ablation procedure was performed to achieve bidirectional conduction block around each PV ostium. AF recurrence was documented using a 7-day event monitor at multiple intervals during the first year. High spatial resolution 3-dimensional LGE CMR was performed 46 +/- 28 days after RF ablation. The extent of scarring around the ostia of each PV was quantitatively (volume of scar) and qualitatively (1: minimal, 3: extensive and circumferential) assessed. RESULTS: Thirteen (37%) patients had recurrent AF during the 6.7 +/- 3.6-month observation period. Paroxysmal AF was a strong predictor of nonrecurrent AF (15% with recurrence vs. 68% without, p = 0.002). Qualitatively, patients without recurrence had more completely circumferentially scarred veins (55% vs. 35% of veins, p = NS). Patients without recurrence more frequently had scar in the inferior portion of the right inferior pulmonary vein (RIPV) (82% vs. 31%, p = 0.025, Bonferroni corrected). The volume of scar in the RIPV was quantitatively greater in patients without AF recurrence (p < or = 0.05) and was a univariate predictor of recurrence using Cox regression (p = 0.049, Bonferroni corrected). CONCLUSIONS: Among patients undergoing PV isolation, AF recurrence during the first year is associated with a lesser degree of PV and left atrial scarring on 3-dimensional LGE CMR. This finding was significant for RIPV scar and may have implications for the procedural technique used in PV isolation.

Inducibility of atrial fibrillation with a synchronized external low energy shock post-pulmonary vein isolation predicts recurrent atrial fibrillation.

BACKGROUND: Inducibility of atrial fibrillation (AF) with burst pacing after pulmonary vein (PV) isolation is associated with recurrent AF. OBJECTIVE: This study evaluated whether an external 30 Joule (J) shock synchronized to the R wave, during the vulnerable period of atrial repolarization, is able to risk-stratify patients further for AF recurrence after PV isolation. METHODS: One hundred and sixteen consecutive patients underwent PV isolation for AF. Atrial burst pacing was performed after PV isolation. In patients without AF induced by burst pacing, a biphasic external 30 J shock synchronized to the R wave was delivered as a further test for inducible AF. Patients were followed for a mean of 16 months, and recurrent AF was defined as more than 10 sec of AF on ambulatory monitoring. RESULTS: AF was induced in 19 (16%) of patients with burst pacing. Eighty-one patients who were noninducible with burst pacing had a 30 J shock administered, which induced AF in 16 (20%). In follow-up, 21% of patients who were noninducible with burst pacing or low-energy shock vs 54% who were inducible with either test developed recurrent AF at one year (HR 3.18, P = 0.0004 on multivariate analysis). Among patients who were noninducible with burst pacing, 18% who were noninducible with a low-energy shock vs 60% who were inducible with shock developed recurrent AF at one year (HR = 4.63, P = 0.0006 on multivariate analysis). CONCLUSION: Inducibility of AF by a 30 J shock delivered during atrial repolarization after PV isolation may predict AF recurrence. Evaluation of inducibility of AF with burst pacing and a biphasic external synchronized shock after PV isolation may help guide postprocedure management.

Evaluating the left atrium by magnetic resonance imaging.

The emergence of catheter based ablation therapy for the prevention of recurrent atrial fibrillation has increased interest in the anatomy of the left atrium and pulmonary veins. In this article, we review the magnetic resonance imaging method of imaging the left atrium and the pulmonary veins, normal and variant anatomy, and the utility of imaging before and after atrial fibrillation ablation.

Left atrial function and scar after catheter ablation of atrial fibrillation.

BACKGROUND: Catheter ablation of atrial fibrillation (AF) involves extensive radiofrequency ablation (RFA) of the left atrium (LA) around the pulmonary veins. The effect of this therapy on LA function is not fully characterized. OBJECTIVE: The purpose of this study was to determine whether catheter ablation of AF is associated with a change in LA function. METHODS: LA and right atrial (RA) systolic function was assessed in 33 consecutive patients with paroxysmal or persistent AF referred for ablation using cardiovascular magnetic resonance (CMR) imaging. Steady-state free precession ECG cine CMR imaging was performed before and after (mean 48 days) AF ablation. All patients underwent circumferential pulmonary vein isolation using an 8-mm tip RFA catheter. High spatial resolution late gadolinium enhancement CMR images of LA scar were obtained in 16 patients. RESULTS: Maximum LA volume decreased by 15% (P <.001), and LA ejection fraction decreased by 14% (P <.001) after AF ablation. Maximum RA volume decreased by 13% (P = .018), but RA ejection fraction increased by 5% (P = .008). Mean LA scar volume was 8.1 +/- 3.7 mL. A linear correlation was observed between change in LA ejection fraction and scar volume (r = -0.75, P <.001). CONCLUSION: Catheter ablation of AF is associated with decreased LA size and reduced atrial systolic function. This change strongly correlates with the volume of LA scar. This finding may have implications for postprocedural thromboembolic risk and for procedures involving more extensive RFA.

Catheter ablation vs antiarrhythmic drug therapy for atrial fibrillation: a systematic review.

BACKGROUND: Circumferential pulmonary vein ablation (CPVA) has become common therapy for atrial fibrillation (AF), but results of large randomized controlled trials comparing this procedure with antiarrhythmic drug therapy (ADT) have not been published to date. We conducted a systematic literature review to assess whether CPVA is superior to ADT for the management of AF. METHODS: We searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials for relevant randomized controlled trials. Data were abstracted to construct a 2 x 2 table for each trial. Recurrence of any atrial tachyarrhythmia (AT) was considered the primary end point of the trials. The estimate and confidence interval for the pooled risk ratio of AT recurrence-free survival in the CPVA group vs the ADT group were obtained using the random-effects model. RESULTS: Four trials qualified for the meta-analysis. In total, 162 of 214 patients (75.7%) in the CPVA group had AT recurrence-free survival vs 41 of 218 patients (18.8%) in the ADT group. The random-effects pooled risk ratio for AT recurrence-free survival was 3.73 (95% confidence interval, 2.47-5.63). In addition, fewer adverse events were reported in the CPVA group compared with that in the ADT group. CONCLUSIONS: We observed statistically significantly better AT recurrence-free survival with CPVA than with ADT. These results highlight the need for larger trials to determine the appropriate role for CPVA in the management of AF. Ongoing clinical trials may provide further guidance on these treatment options for AF.

Coronary magnetic resonance vein imaging: imaging contrast, sequence, and timing.

Recently, there has been increased interest in imaging the coronary vein anatomy to guide interventional cardiovascular procedures such as cardiac resynchronization therapy (CRT), a device therapy for congestive heart failure (CHF). With CRT the lateral wall of the left ventricle is electrically paced using a transvenous coronary sinus lead or surgically placed epicardial lead. Proper transvenous lead placement is facilitated by the knowledge of the coronary vein anatomy. Cardiovascular MR (CMR) has the potential to image the coronary veins. In this study we propose and test CMR techniques and protocols for imaging the coronary venous anatomy. Three aspects of design of imaging sequence were studied: magnetization preparation schemes (T(2) preparation and magnetization transfer), imaging sequences (gradient-echo (GRE) and steady-state free precession (SSFP)), and imaging time during the cardiac cycle. Numerical and in vivo studies both in healthy and CHF subjects were performed to optimize and demonstrate the utility of CMR for coronary vein imaging. Magnetization transfer was superior to T(2) preparation for contrast enhancement. Both GRE and SSFP were viable imaging sequences, although GRE provided more robust results with better contrast. Imaging during the end-systolic quiescent period was preferable as it coincided with the maximum size of the coronary veins.

Cardiac memory induced by QRS widening due to propafenone toxicity.

Propafenone toxicity can cause significant QRS widening and markedly abnormal ventricular activation pattern. Aberrant ventricular activation upon its resolution is known to produce persistent T-wave changes known as "cardiac memory" (CM). A 74-year-old woman presented with a severely abnormal electrocardiogram consistent with propafenone toxicity. As her QRS complex narrowed, T-wave inversions developed with the T-wave axis and resolution kinetics consistent with CM. Abnormal ventricular activation due to propafenone toxicity can result in CM development.

Detection of pulmonary vein and left atrial scar after catheter ablation with three-dimensional navigator-gated delayed enhancement MR imaging: initial experience.

PURPOSE: To prospectively evaluate whether scar caused by radiofrequency (RF) ablation of the left atrium (LA) in patients with atrial fibrillation can be depicted with high-spatial-resolution delayed enhancement magnetic resonance (MR) imaging. MATERIALS AND METHODS: All 23 subjects (16 men, seven women; mean age, 54 years +/- 13 [standard deviation]) provided written informed consent; the study was approved by the local institutional review board and was HIPAA compliant. A high-spatial-resolution free-breathing delayed enhancement MR imaging method was developed to detect scar (ie, ablated tissue) in the LA and pulmonary veins (PVs). The LA in 15 patients before ablation and in 18 patients at least 30 days after ablation was examined. A reader with 4 years of experience assessed presence of delayed enhancement on images and circumferential completeness. Signal-to-noise and contrast-to-noise ratios were measured and compared with an unpaired t test. The relationship between measurements of enhancement thickness at the interatrial septum and the number of days after ablation was investigated. RESULTS: No subject demonstrated preablation delayed enhancement of the atrial or PV wall, whereas postablation delayed enhancement was identified in all (100%). In patients after ablation, a partial to completely circumferential delayed enhancement pattern could be identified for the left inferior PV that encompassed 88% +/- 11 of the circumference, but only 62% of patients demonstrated more than 90% circumferential delayed enhancement. The signal-to-noise ratio of blood was 12, and the signal-to-noise ratios of the pre- and postablation left atrial wall were 15 and 22, respectively (P<.05). A relationship between delayed enhancement wall thickness and the inverse of the time interval from ablation was identified (P<.05). CONCLUSION: High-spatial-resolution delayed enhancement MR imaging allows noninvasive identification of scar induced by RF ablation following isolation therapy of the PV.