John V. Wylie

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.

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.

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.

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 (T2 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 T2 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. Magn Reson Med, 2007.

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.

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.

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.

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.

Delayed occurrence of unheralded phase IV complete heart block after ethanol septal ablation for symmetric hypertrophic obstructive cardiomyopathy.

Ethanol septal ablation has emerged as a less invasive alternative to surgical myomectomy for treatment of asymmetric hypertrophic obstructive cardiomyopathy (ASH). The procedure has very low mortality, but high‐degree AV conduction block is a frequent complication. Prior studies have documented baseline left bundle branch block and high volume of ethanol injection (greater than 4 mL) as risk factors. Complete heart block is often preceded by postprocedure conduction abnormalities and generally develops within 48 hours after ethanol ablation. We present a unique case of a patient with symmetric hypertensive hypertrophic obstructive cardiomyopathy (SHOCM) who developed phase IV complete heart block >96 hours postprocedure without preceding conduction abnormalities or other classic risk factors. 3

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.