AIM:To identify predictors of need for repeat procedures after initial atrial fibrillation (AF) ablation.METHODS:We identified a cohort undergoing first time AF ablation at our institution from January 2004 to February 2014 who had cardiac magnetic resonance (CMR) imaging performed prior to ablation. Clinical variables and anatomic characteristics (determined from CMR) were assessed as predictors of need for repeat ablation. The decision regarding need for and timing of repeat ablation was at the discretion of the treating physician.RESULTS:From a cohort of 331 patients, 142 patients (43%) underwent repeat ablation at a mean of 13.6 ± 18.4 mo after the index procedure. Both male gender (81% vs 71%, P = 0.05) and lower ejection fraction (57.4% ± 10.3% vs 59.8% ± 9.4%, P = 0.04) were associated with need for repeat ablation. On pre-ablation CMR, mean pulmonary vein (PV) diameters were significantly larger in all four PVs among patients requiring repeat procedures. In multivariate analysis, increased right superior PV diameter significantly predicted need for repeat ablation (odds ratio 1.08 per millimeter increase in diameter, 95%CI: 1.00-1.16, P = 0.05). There were also trends toward significance for increased left and right inferior PV sizes among those requiring repeat procedures.CONCLUSION:Increased PV size predicts the need for repeat AF ablation, with each millimeter increase in PV diameter associated with an approximately 5%-10% increased risk of requiring repeat procedures.

BACKGROUND:Novel atrial fibrillation (AF) ablation tools have been designed to facilitate "single-shot" pulmonary vein (PV) isolation using multi-electrode or balloon-based catheters. However, in contrast to point-by-point radiofrequency ablation, these tools may be more dependent on suitable PV anatomy to achieve circumferential PV isolation. METHODS:Three hundred and twenty-two patients underwent gadolinium-enhanced cardiac magnetic resonance angiography to delineate PV anatomy prior to initial AF ablation. Long (a) and short (b) axis measurements of the PV orifice were used to calculate the eccentricity index of the PV ostium. RESULTS:Long axis dimensions of the left superior PV were 18.2 ± 3.3 mm, left inferior PV 17.7 ± 3.9 mm, right superior PV (RSPV) 20.4 ± 4.3, and right inferior PV 18.7 ± 4.7 mm. The long axis dimension of the RSPV was significantly larger than other PVs (p < 0.001). Forty-two patients (13 %) had at least one PV with a long axis dimension >25 mm and 16 patients (5 %) had at least one PV with a long axis dimension >28 mm. Left-sided PV ostia were significantly more ellipse-shaped than the right-sided PVs, which tended to be more spherical. A significant positive correlation was noted between increasing PV size and increased orifice eccentricity. CONCLUSIONS:In this large cohort undergoing initial AF ablation, over 10 % of patients had at least one standard PV with a dimension >25 mm. Additionally, significant differences were noted between left- and right-sided veins with regard to orifice eccentricity. These findings have implications for the design of AF ablation tools and may account for differential isolation rates between PVs noted in some recent studies of novel ablation technologies.

Background: Pulmonary vein (PV) reverse remodeling has been recognized following atrial fibrillation (AF) ablation. However, the extent of physiologic reverse remodeling after AF ablation and the potential impact of reverse remodeling on the radiographic diagnosis of PV stenosis have not been well characterized. Methods: From January 2004 to February 2014, 186 patients underwent paired cardiac magnetic resonance imaging (MRI) to delineate PV orifice dimensions before and after (mean 109 ± 61 days) an initial AF ablation. Results: Negative remodeling of the PV orifice cross sectional area occurred in 67.8% of veins with a mean reduction in area of 21.0 ± 14.1%, and positive remodeling was seen in the remaining PVs with an increase in area of 22.1 ± 23.4% compared to baseline. No PVs demonstrated a reduction in cross-sectional area of > 75% (maximum reduction observed was 58%). Negative remodeling of the PV long axis dimension was observed in 55.2% of veins with a mean reduction of 14.6 ± 9.2% compared to pre-ablation and positive remodeling was observed in 25.3% of PVs with a mean increase in diameter of 14.7 ± 12.6%. Only 1 PV demonstrated a reduction in orifice diameter of > 50%. There were no clinically evident or suspected cases of PV stenosis in this cohort. Conclusions: Negative remodeling of the PV orifice area was noted in the majority of PVs following AF ablation. However, in almost all cases, the extent of negative remodeling was well below commonly used thresholds for the radiographic diagnosis of PV stenosis.

Introduction: Although clinical predictors of the need for repeat procedures after catheter ablation of atrial fibrillation (AF) have been evaluated, anatomic predictors have not been well defined. Hypothesis: Anatomic features on cardiac magnetic resonance (CMR) imaging can identify patients most likely to require repeat ablation. Methods: From Jan. 2004 to Feb. 2014, 307 patients underwent CMR prior to initial AF ablation at our institution. Ablation strategies along with the need for and timing of repeat ablation were determined at the discretion of the treating physician. Results: Out of 307 patients, 119 (38.8%) underwent repeat ablation at a mean of 15.0 ± 19.2 months after the initial procedure. Among repeat procedures, 62% were performed primarily for recurrent AF and the remaining for left atrial tachycardias. Across the entire cohort at the initial procedure, mean age was 62.0 ± 10.8 yrs, 75% were male, 23% had persistent AF, 90% had radiofrequency ablation and the remaining had Cryoballoon ablation, without significant differences between those undergoing a single vs. repeat procedures. Other baseline clinical parameters including EF and presence of hypertension, diabetes and sleep apnea were also similar between groups. However, on CMR performed prior to the first ablation, pulmonary vein (PV) ostial diameters were significantly larger in all PVs among those requiring repeat procedures: right superior PV 19.4 ± 4.0 vs. 21.4 ± 4.5 mm (p 2 ) and left (28.0 ± 5.3 vs. 29.2 ± 6.5 cm 2 ) atrial areas were larger among those requiring repeat procedures, the differences were not significant. Conclusions: Among patients undergoing AF ablation, clinical variables were not significantly different between those requiring a single vs. repeat procedures. However, PV dimensions assessed by CMR were significantly larger among those likely to require repeat procedures. Further study is required to determine whether strategies at the initial ablation can be used to mitigate the increased risk of need for repeat procedures among those with larger PVs.

PurposeTo characterize the postsurgical hemodynamics in aortic valve bypass (AVB) patients, and to determine the relationship between presurgical native aortic valve pressure gradient and postsurgical hemodynamics.Materials and MethodsTwenty patients scheduled for AVB surgery underwent presurgical transthoracic Doppler echocardiography to assess the degree of aortic stenosis and postsurgical cardiac magnetic resonance imaging (MRI) to acquire phase contrast magnetic resonance (PCMR) flow values along the ascending and descending aorta, and in the conduit. Net flow values were calculated from the PCMR images and compared to presurgical aortic valve pressure gradient measurements.ResultsPCMR showed that: 1) The blood flow split between the aorta and the conduit was 35%:65% of cardiac output and 2) 60% of patients had net retrograde blood flow in the superior thoracic aorta over the cardiac cycle. Patients with presurgical pressure gradient (ΔP) > 45 mmHg had significantly less blood flow out of the native aorta than patients with ΔP < 45 mmHg, and had significantly more retrograde flow in the superior thoracic aorta postsurgery.ConclusionIn patients undergoing AVB, presurgical aortic valve pressure gradient is associated with the volume of blood flow out the aorta and the direction of blood flow in the superior thoracic aorta after conduit addition as measured by PCMR. J. Magn. Reson. Imaging 2014;40:899–905. © 2013 Wiley Periodicals, Inc.

Chadid, Tatiana MD; Kalra, Kanika MD; Eisner, Robert MD; Sarin, Eric L. MD; Guyton, Robert A. MD; Thourani, Vinod H. MD, FACS; Padala, Muralidhar PhD Author Information

To quantify periods of low motion of the coronary veins in patients with low and moderate EF in order to optimize acquisition of whole-heart coronary magnetic resonance venograms (cMRV).

Objective: In a recent multi-center trial of gadolinium contrast-enhanced magnetic resonance angiography (Gd-MRA) for diagnosis of acute pulmonary embolism (PE), two centers utilized a common MRI platform though at different field strengths (1.5T and 3T) and realized a signal-to-noise gain with the 3T platform. This retrospective analysis investigates this gain in signal-to-noise of pulmonary vascular targets. Methods: Thirty consecutive pulmonary MRA examinations acquired on a 1.5T system at one institution were compared to 30 consecutive pulmonary MRA examinations acquired on a 3T system at a different institution. Both systems were from the same MRI manufacturer and both used the same Gd-MRA pulse sequence, although there were some protocol adjustments made due to field strength differences. Region-of-interests were manually defined on the main pulmonary artery, 4 pulmonary veins, thoracic aorta, and background lung for objective measurement of signal-to-noise, contrast-to-noise, and bolus timing bias between centers. Results: The 3T pulmonary MRA protocol achieved higher spatial resolution yet maintained significantly higher signal-to-noise ratio (≥13%, p = 0.03) in the main pulmonary vessels relative to 1.5T. There was no evidence of operator bias in bolus timing or patient hemodynamic differences between groups. Conclusion: Relative to 1.5T, higher spatial resolution Gd-MRA can be achieved at 3T with a sustained or greater signal-to-noise ratio of enhanced vasculature.

Purpose: To quantify periods of low motion and cross-sectional area changes of the coronary veins during the cardiac cycle for planning magnetic resonance coronary venograms (MRCV).Materials and Methods: Images were acquired from 19 patients with coronary artery disease (CAD) and 13 patients scheduled for cardiac resynchronization therapy (CRT). The displacement and cross-sectional area of the coronary sinus was tracked, and periods of low motion were defined as consecutive time points during which the position of the coronary sinus remained within a 0.67-mm diameter region. Patients were classified as systolic dominant or diastolic dominant based on the relative duration of their low motion periods.Results: All CRT patients were classified as systolic dominant, and 32% of these had no separate diastolic rest period. All CAD patients with ejection fraction < 35% were classified as systolic dominant, while all CAD patients with ejection fraction > 35%were diastolic dominant. In 77% of all subjects, the cross-sectional area of the coronary sinus was larger in systole than in diastole.Conclusion: The movement of the coronary sinus can be used to classify patients as either having a longer systolic or diastolic rest period. The classification of the CRT patients as systolic dominant suggests that MRCVs be acquired in systole for CRT planning; however, each patient's low motion periods should be categorized to ensure the correct period is being used to minimize motion artifacts.

152 Objectives Normal pharmacologic responses to dipyridamole infusion include increased heart rate, decreased systemic blood pressure and decreased LVESV with resultant increased left ventricular ejection fraction. Our hypothesis was that the LVESV ratio (LVESV measured during dipyridamole effect vs. prior to infusion at rest), was a more accurate method to identify patients with obstructive multivessel CAD vs. TID, decrease in left ventricular ejection fraction (LVEF), or increase in left ventricular end diastolic volume (LVEDV) ratio during dipyridamole infusion. Methods Patients who had undergone both PET/CT Rb-82 myocardial imaging and x-ray coronary arteriography were included. Exclusion criteria included prior revascularization. Patients were divided, based on the absence (Group I, n= 45) or presence of multivessel CAD (Group II, n= 56). One blinded observer [RLE] processed all images using 4DM PET software. Data were analyzed by the area under the curve receiver-operator characteristic curve [AUC-ROC]. Evaluation of perfusion images were excluded from this study. Conclusions The LVESV ratio(AUC 0.86 +/- 0.04) is an accurate method to identify obstructive multivessel CAD, independent of perfusion imaging and superior to measurement of TID, decrease in ejection fraction and increase in LVEDV ratio

1486 Objectives Misalignment of images in cardiac PET-CT imaging may lead to erroneous attenuation correction (AC) and misdiagnosis. Such misalignment is usually corrected by hand prior to clinical assessment. The aim of the study is to assess whether a single automatically aligned rest CT can be used for stress PET AC. Methods 26 patients underwent PET-CT, consisting of 82Rb PET at stress, and 3 free breathing CTs at each of rest and stress. The best aligned stress CT is selected for clinical use.An automatic mutual information registration was used to align each rest CT to the stress PET, first using translation, and then deformable. Registrations were assessed visually, and translations compared to manual alignments. We performed 17-segment polar plot analysis using 4DM-SPECT on each registered image: for each patient, consistency of scores across plots was measured by counting segments with different scores. Results The automatic methods aligning rest CTs to stress PET gave visually acceptable results for 98% of cases. Comparison of the automatic and manual translations showed a mean difference of 8mm +/- 4mm. Consistency across the 3 AC images for each patient showed that there were differences in 13% of segments with manual registration, 8% with automatic translation and 7% with automatic deformable.Comparing to the clinical stress CT chosen for AC, 9% of segments differed with manual, 5% with automatic translation and 5% with deformable. Conclusions Our analysis has shown that automatic registration is a viable option for aligning rest CT to stress PET for AC, with results comparable to that of a manual alignment in comparison to the clinical chosen CT.

Introduction: Prophylactic implantation of a cardioverter/ defibrillator (ICD) has been shown to reduce mortality in patients with chronic myocardial infarction (CMI) and an increased risk for life threatening ventricular arrhythmia (VA).The use of ICDs in this large patient population is still limited by high costs and possible adverse events including inappropriate discharges and progression of heart failure.VA is related to infarct size and seems to be related to infarct morphology.Contrast enhanced cardiovascular magnetic resonance imaging (ceCMR) can detect and quantify myocardial fibrosis in the setting of CMI and might therefore be a valuable tool for a more accurate risk stratification in this setting.Hypothesis: ceCMR can identify the subgroup developing VA in patients with prophylactic ICD implantation following MADIT criteria.Methods: We prospectively enrolled 52 patients (49 males, age 69 ± 10 years) with CMI and clinical indication for ICD therapy following MADIT criteria.Prior to implantation (36 ± 78 days) patients were investigated on a 1.5 T clinical scanner (Siemens Avanto © , Germany) to assess left ventricular function (LVEF), LV end-diastolic volume (LVEDV) and LV mass (sequence parameters: GRE SSFP, matrix 256 × 192, short axis stack; full LV coverage, no gap; slice thickness 6 mm).For quantitative assessment of infarct morphology late gadolinium enhancement (LGE) was performed including measurement of total and relative infarct mass (related to LV mass) and the degree of transmurality (DT) as defined by the percentage of transmurality in each scar.(sequence parameters: inversion recovery gradient echo; matrix 256 × 148, imaging 10 min after 0.2 μg/kg gadolinium DTPA; slice orientation equal to SSFP).MRI images were analysed using dedicated software (MASS © , Medis, Netherlands).LGE was defined as myocardial areas with signal intensity above the average plus 5 SD of the remote myocardium.After implantation, patients were followed up including ICD readout after 3 and than every 6 months for a mean of 945 ± 344 days.ICD data were evaluated by an experienced electrophysiologist.Primary endpoint was the occurrence of an appropriate discharge (DC), antitachycard pacing (ATP) or death from cardiac cause.Results: The endpoint occurred in 10 patients (3 DC, 6 ATP, 1 death).These patients had a higher relative infarct mass (28 ± 7% vs. 22 ± 11%, p = 0.03) as well as high degree of transmurality (64 ± 22% vs. 44 ± 25%, p = 0.05).Their LVEF (29 ± 8% vs. 30 ± 4%, p = 0.75), LV mass (148 ± 29 g vs. 154 ± 42 g, p = 0.60), LVEDV (270 ± 133 ml vs. 275 ± 83 ml, p = 0.90) or total infarct mass (43 ± 19 g vs. 37 ± 21 g, p = 0.43) were however not significant from the group with no events.In a cox proportional hazards regression model including LVEF, LVEDV, LV mass, DT and age, only degree of transmurality and relative infarct mass emerged as independent predictors of the primary end point (p = 0.009). Conclusion:In CMI-patients fulfilling MADIT criteria ceCMR could show that the extent and transmurality of myocardial scarring are independent predictors for life threatening ventricular arrhythmia or death.This additional information could lead to more precise risk stratification and might reduce adverse events and cost of ICD therapy in this patient population.Larger trials are needed to confirm this finding.

Purpose: To develop a method for quantifying left ventricular (LV) internal flow as a measure of dyssynchrony using standard clue cardiac magnetic resonance (CMR) images.Materials and Methods: CMR images were obtained from 10 healthy controls and 10 patients with dyssynchronous heart failure (class III/IV, LV ejection fraction <35%, pattern seen in an electrocardiogram gRS duration > 150 msec). The LV volume was reconstructed and divided into 16 regions. Internal flow was defined as the sum of the regional volume changes minus the global volume change during each time step in the cardiac cycle. Internal flow fraction (IFF) was defined as the total internal flow as a percentage of stroke volume during systole (IFFsystote), diastole (IFFdi-WO, or the whole cycle fFFw,,otJ.Results: IFFwhote was significantly increased in the patients (9.9 5.0% vs. 1.5 -!- 0.5% in the controls, P < 0.001). An IFF,,hote threshold of 4% discriminated between patients and controls with 90% sensitivity and 100% specificity. IFFdiastote (2.3 0.8%) was greater than IFFsysto,e (0.8 -!- 0.5%) in the normal controls (P < 0.001) while the patients had similar IFFdiastoie (7.8 + 4.2%) and IFFsystote (12.0 7.8%).Conclusion: Left ventricular internal flow fraction can be quantified from standard CMR images. In this preliminary study, Left ventricular internal flow fraction discriminated patients with dyssynchronous heart failure from normal controls with 95% accuracy.

Purpose: To evaluate the reproducibility of a new multisite axial pulse wave velocity (PWV) measurement technique that makes use of 2D PCMR data and cross-correlation analysis.Materials and Methods: PWV was estimated with MRI in 13 healthy volunteers by a transit-time technique (TT), a multisite technique utilizing 1D PCMR data in the descending aorta (FOOT), and a new multisite axial technique that uses 2D PCMR data over the ascending, transverse, and descending sections of the aorta (2D-XC).Results: No significant difference was observed between PWV measurements values measured by the three techniques. However, 2D-XC displayed significantly better intertest reproducibility than either the TT or FOOT methodologies. Average percent difference between scans: TT: 15.8% +/- 13.4%, FOOT: 21.3% +/- 16.9%, 2D-XC: 7.72% +/- 4.73%. P = 0.02 for both 2D-XC/TT comparison and 2D-XC/FOOT comparison.Conclusion: 2D-XC is a more reproducible method than either the established TT or FOOT methods to estimate the aortic PWV.