Imaging Features of Arrhythmogenic Cardiomyopathies.

Arrhythmogenic cardiomyopathy (ACM) is a genetic disease characterized by replacement of ventricular myocardium with fibrofatty tissue, predisposing the patient to ventricular arrhythmias and/or sudden cardiac death. Most cases of ACM are associated with pathogenic variants in genes that encode desmosomal proteins, an important cell-to-cell adhesion complex present in both the heart and skin tissue. Although ACM was first described as a disease predominantly of the right ventricle, it is now acknowledged that it can also primarily involve the left ventricle or both ventricles. The original right-dominant phenotype is traditionally diagnosed using the 2010 task force criteria, a multifactorial algorithm divided into major and minor criteria consisting of structural criteria based on two-dimensional echocardiographic, cardiac MRI, or right ventricular angiographic findings; tissue characterization based on endomyocardial biopsy results; repolarization and depolarization abnormalities based on electrocardiographic findings; arrhythmic features; and family history. Shortfalls in the task force criteria due to the modern understanding of the disease have led to development of the Padua criteria, which include updated criteria for diagnosis of the right-dominant phenotype and new criteria for diagnosis of the left-predominant and biventricular phenotypes. In addition to incorporating cardiac MRI findings of ventricular dilatation, systolic dysfunction, and regional wall motion abnormalities, the new Padua criteria emphasize late gadolinium enhancement at cardiac MRI as a key feature in diagnosis and imaging-based tissue characterization. Conditions to consider in the differential diagnosis of the right-dominant phenotype include various other causes of right ventricular dilatation such as left-to-right shunts and variants of normal right ventricular anatomy that can be misinterpreted as abnormalities. The left-dominant phenotype can mimic myocarditis at imaging and clinical examination. Additional considerations for the differential diagnosis of ACM, particularly for the left-dominant phenotype, include sarcoidosis and dilated cardiomyopathy. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Ventricular arrhythmias in patients with bicuspid aortic valves.

INTRODUCTION: Bicuspid aortic valves (BAV) are the most common congenital heart defects and the extent of ventricular arrhythmias (VA) in patients with BAV is unclear. The objective of this study is to describe VAs and late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR) in patients with BAV. METHODS: A total of 19 patients with BAV (18 males, age: 58 ± 13 years) were referred for VA ablation procedures. Ten patients had BAVs at the time of ablation, nine patients had prior aortic valve replacement for a BAV. All but one patient had LGE-CMR and all patients underwent programmed ventricular stimulation at the time of the ablation. RESULTS: Frequent PVCs were the targeted VAs in 17/19 patients and VT in 2/19 patients. Monomorphic ventricular tachycardia (VT) was inducible in 6 patients. A total of 15 VTs were inducible (2.5 ± 1.0 VTs per patient with a mean cycle length of 322 ± 83 msec). LGE was present in 13 patients. Patients with inducible VT had larger borderzone and core scar compared to non-inducible patients (7.8 ± 2.1 cm3 vs. 2.5 ± 3.1 cm3 and 5.1 ± 2.6 cm3 vs. 1.9 ± 3.0 cm3, p-value < .05 for both). PVCs and VTs were mapped to the periaortic valve area in 12 patients and 4 patients, respectively. The PVC burden was reduced from 27 ± 13 to 3 ± 6 (p < .001) and the ejection fraction improved from 49 ± 13% to 55 ± 9% (p = .005). CONCLUSIONS: VAs in patients with BAV often originate from the perivalvular area and patients often have LGE and inducible VT. LGE may be due to ventricular remodeling secondary to the presence of BAV and harbors the arrhythmogenic substrate for VT.

Value of genotyping and scar-phenotyping for VT ablation procedures in patients with nonischemic left ventricular cardiomyopathies.

INTRODUCTION: Variants of cardiomyopathy genes in patients with nonischemic cardiomyopathy (NICM) generate various phenotypes of cardiac scar and delayed enhancement cardiac magnetic resonance (DE-CMR) imaging which may impact ventricular tachycardia (VT) management. METHODS: The objective was to compare the findings of cardiomyopathy genetic testing on DE-CMR imaging and long-term outcomes among patients with NICM undergoing VT ablation procedures. Image phenotyping and genotyping were performed in a consecutive series of patients referred for VT ablation and correlated to survival free of VT. Scar depth index (SDI) (% of scar at 0-3 mm, 3-5 mm and >5 mm projected on the closest endocardial surface) was determined. RESULTS: Forty-three patients were included (11 women, 55 ± 14 years, ejection fraction (EF) 45 ± 16%) and were followed for 3.4 ± 2.9 years. Pathogenic variants (PV) were identified in 16 patients (37%) in the following genes: LMNA (n = 5), TTN (n = 5), DSP (n = 2), AMLS1 (n = 1), MYBPC3 (n = 1), PLN (n = 1), and SCN5A (n = 1). A ring-like septal scar (RLSS) pattern was more often seen in patients with pathogenic variants (66% vs 15%, p = .001). RLSS was associated with deeper seated scars (SDI >5 mm 30.6 ± 22.6% vs 12.4 ± 16.2%, p = .005), and increased VT recurrence (HR 5.7 95% CI[1.8-18.4], p = .003). After adjustment for age, sex, EF, and total scar burden, the presence of a PV remained independently associated with worse outcomes (HR 4.7 95% CI[1.22-18.0], p = .02). CONCLUSIONS: Preprocedural genotyping and scar phenotyping is beneficial to identify patients with a favorable procedural outcome. Some PVs are associated with an intramural, deeper seated scar phenotype and have an increase of VT recurrence after ablation.

Left and Right PVC-Induced Ventricular Dysfunction.

BACKGROUND: Frequent premature ventricular complexes (PVCs) can result in a reversible form of cardiomyopathy that usually affects the left ventricle (LV). OBJECTIVES: The objective of this study was to assess whether frequent PVCs have an impact on right ventricular (RV) function. METHODS: Serial cardiac magnetic resonance (CMR) studies were performed in a series of 47 patients before and after ablation of frequent PVCs. RESULTS: Patients with RV cardiomyopathy (ejection fraction [EF] <0.45) had more frequent PVCs than did patients without decreased RV function (23% ± 11% vs 15% ± 11%, P = 0.03). Likewise, patients with LV cardiomyopathy (EF <0.50) had more frequent PVCs than did patients without decreased LV function (23% ± 10% vs 14% ± 12%, P = 0.003). LV dysfunction was present in 21 patients (45%). In patients with LV dysfunction, 15 patients (32%) had biventricular dysfunction, and 6 patients (13%) had isolated LV dysfunction. A total of 19 patients (40%) had RV dysfunction, and 4 of the patients with RV dysfunction (9%) had isolated RV dysfunction. Cardiac magnetic resonance was repeated 1.9 ± 1.3 years after ablation. In patients with successful ablation, RV function improved, and in patients without successful ablation, RV function did not significantly change (before and after ablation RVEF 0.45 ± 0.09 and 0.52 ± 0.09; P < 0.001 vs. 0.46 ± 0.07 and 0.48 ± 0.04; P = 0.14, respectively). CONCLUSIONS: Frequent PVCs can cause RV cardiomyopathy that parallels LV cardiomyopathy and is reversible with successful ablation.

Magnetic resonance imaging and histopathology of catheter ablation lesions after ventricular tachycardia ablation in patients with nonischemic cardiomyopathy.

BACKGROUND: Late gadolinium enhanced cardiac magnetic resonance (LGE-CMR) imaging may help identify radiofrequency ablation lesions, which have been poorly described in patients with nonischemic cardiomyopathy (NICM). OBJECTIVES: The purpose of this study was to describe LGE-CMR characteristics of ablation lesions in patients with NICM and correlate them with histopathology. METHODS: Twenty-six patients (24 men; ejection fraction 38% ± 14%; age 61 ± 9 years) who had undergone CMR imaging after ventricular tachycardia (VT) ablation were included. Areas of both dark and bright core lesions correlating with previous radiofrequency ablation lesions were identified. Histology was performed on an explanted heart. RESULTS: Mean time between the ablation procedure and the LGE-CMR study was 8 [2-20] months. Twenty-three of 26 patients demonstrated dark core lesions (volume 2.16 ± 1.8 cm3; thickness 3.6 ± 1.3 mm) with transmurality of 42% ± 16% overlaying areas of intramural or transmural LGE. Fourteen of 26 patients demonstrated bright core lesions (volume 0.8 ± 0.6 cm3; depth 4.15 ± 1.76 mm) with transmurality of 34% ± 14%, which was located in areas without underlying LGE in 11 of 13 patients. Both dark and bright core lesions were visualized on standard clinical LGE-CMR imaging obtained in the acute setting and chronic settings (within 3 days and up to 2090 days postablation). Histopathologic analysis demonstrated coagulation necrosis in the area that corresponded to dark core lesions in the postablation CMR. CONCLUSION: Ablation lesions can be detected by LGE-CMR after VT ablation in NICM patients and have a different appearance than scar tissue. These lesions can be observed in the acute and chronic settings after ablations.

Intramural mapping of intramural septal ventricular arrhythmias.

BACKGROUND: Intramural ventricular arrhythmias (VAs) can originate in patients with or without structural heart disease. Electrogram (EGM) recordings from intramural sources of VA have not been described thoroughly. OBJECTIVE: We hypothesized that the presence of scar may be linked to the site of origin (SOO) of focal, intramural VAs. METHODS: In a series of 21 patients (age: 55 ± 11 years, 12 women, mean ejection fraction 43 ± 14%) in whom the SOO of intramural VAs was identified, we analyzed bipolar EGM characteristics at the SOO and compared the findings with the endocardial breakout site. The patients were from a pool of 86 patients with intramural VAs referred for ablation. RESULTS: In 16/21 patients intramural scarring was detected by cardiac magnetic resonance (CMR) imaging In patients in whom the intramural SOO was reached, intramural bipolar EGMs showed a lower voltage and had broader EGMs compared to the endocardial breakout sites (0.97 ± 0.56 vs. 2.28 ± 0.15 mV, p = .001; and 122.3 ± 31.6 vs. 96.5 ± 26.3 ms, p < .01). All intramural sampled sites at the SOO had either low voltage or broad abnormal EGMs. The activation time was significantly earlier at the intramural SOO than at breakout sites (-36.2 ± 11.8 vs. -23.2 ± 9.1 ms, p < .0001). CONCLUSIONS: Sites of origin of intramural VAs with scar by CMR display EGM characteristics of scarring, supporting that scar tissue localizes to the SOO of intramural outflow tract arrhythmias in some patients. Scarring identified by CMR may be helpful in planning ablation procedures in patients with suspected intramural VAs.

Late gadolinium enhancement cardiac magnetic resonance imaging of ablation lesions after postinfarction ventricular tachycardia ablation: Implications for ventricular tachycardia recurrence.

BACKGROUND: Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) imaging distinguishes between intrinsic postinfarction scar and radiofrequency ablation lesion related scar (dark core lesions [DCLs]) in patients with prior ventricular tachycardia (VT) ablation procedures. OBJECTIVE: To combine LGE-CMR and electroanatomic mapping data to describe the relationship between DCLs and recurrent VT among patients undergoing repeat ablations for postinfarction VT. METHODS: Consecutive patients with repeat ablation for postinfarct VT with LGE-CMR before the repeat procedures were studied. Prior ablation procedures and implantable cardiac defibrillator electrograms were analyzed to determine new versus previously documented VT. DCLs were identified on preprocedure LGE-CMR and registered to electroanatomic maps. A control group of patients undergoing repeat ablation procedures without imaging was included. RESULTS: Nineteen study patients and 14 control patients were followed for 2.6 (1.6-5.6) years (31 [94%] men, age 65.8 ± 8.4 years, ejection fraction 24.7 ± 10.3, p > 0.10 for all). DCLs corresponded to unexcitable tissue during repeat procedures (area 22.4 ± 15.1 vs. 22.9 ± 16.8 cm3 , correlation coefficient = .93). Most VT target sites (39/50 [78%]) were in close proximity (<1 cm) to DCLs. Most DCL related VTs 32/39 (82%) were new VTs. Patients with LGE-CMR imaging incorporated into their ablation procedures had improved 24-month survival from VT (64% vs. 38%, log rank p < 0.02). CONCLUSION: LGE-MRI can identify prior ablation lesions corresponding to nonexcitable tissue during repeat ablation procedures for postinfarction VT. VT target sites are often located in close proximity to the DCL area that may function as a fixed border for reentry circuits. Registration of DCL from prior ablation may facilitate repeat ablation procedures.

A 30-Year-Old Immune Deficient Woman With Persistent Cough and Shortness of Breath.

CASE PRESENTATION: A 30-year-old woman was referred with increasing shortness of breath and cough in the setting of GATA2 deficiency. She initially presented 9 years previously with recurrent episodes of pneumonia and sinusitis. Genetic testing revealed a heterozygous GATA2 mutation (c.988C>T). She has since had multiple infections that have included necrotizing fasciitis of the right thumb, recurrent pilonidal infections (which required 23 procedures), esophageal candidiasis, and human papillomavirus-positive high-grade squamous intraepithelial lesion of the cervix. Serial bone marrow biopsy specimens showed persistent hypocellularity (20% to 60%) with intermittent erythroid atypia and variable detection of trisomy 8, which were concerning for evolving myelodysplastic syndrome. One year before the current admission, she was diagnosed with disseminated Mycobacterium avium complex and was treated with rifabutin, ethambutol, and azithromycin. She was taking voriconazole, acyclovir, and trimethoprim-sulfamethoxazole prophylaxis.

Diagnosis, significance, and management of ventricular thrombi in patients referred for VT ablation.

INTRODUCTION: In patients with structural heart disease presenting with ventricular tachycardia (VT), detection of ventricular thrombi and subsequent management can be challenging. This study aimed to assess the value of multimodality imaging with cardiac magnetic resonance imaging (CMR), contrast-enhanced transthoracic echocardiography (TTE), and computed tomography (CT) for thrombus detection as well as a management algorithm geared towards anticoagulation and deferred ablation for patients referred for VT ablation. METHODS AND RESULTS: A total of 154 consecutive patients referred for VT ablation underwent preprocedural multimodality imaging with CMR, CT, and TTE. In 9 patients (6%) a new ventricular thrombus was detected and anticoagulation was initiated. Thrombi were detected by CMR in nine patients, by CT in seven patients, and by TTE in two patients. Five patients eventually underwent endocardial VT ablation procedures 6.0 ± 2.0 months after initiation of anticoagulation with one patient also requiring an epicardial approach. Two patients died while on anticoagulation, unrelated to ventricular arrhythmia. Four of five patients were rendered non-inducible and no testing was performed in 1/5 patients. Areas containing left ventricular thrombi were non-excitable with pacing. Six of thirty-two inducible VTs were mapped in close vicinity of ventricular thrombi. No clinical embolic events occurred during the ablation procedures. CONCLUSIONS: Ventricular thrombus was detected in 6% of consecutive patients with structural heart disease undergoing VT ablation. CMR was the most sensitive modality, while contrast-enhanced TTE failed to detect the majority of thrombi. Anticoagulation followed by ablation can be safely and successfully performed in patients with ventricular thrombi.

Cardiac Magnetic Resonance Imaging and Ventricular Tachycardias Involving the Sinuses of Valsalva in Patients With Nonischemic Cardiomyopathy.

OBJECTIVES: The goal of this study was to investigate the relationship between cardiac scar on late gadolinium enhancement cardiac resonance imaging (LGE-CMR) and the presence of ventricular tachycardia (VT) ablation target sites within the sinuses of Valsalva (SV). BACKGROUND: Patients with idiopathic dilated cardiomyopathy (IDCM) often have scarring involving the basal myocardium, including the SV, allowing targeting of VTs from within the SV. METHODS: Forty-three consecutive patients with IDCM underwent a VT ablation procedure with pre-procedure LGE-CMR. Retrospectively, scar characteristics were compared between patients with and without VT target sites in the SV. The ratio between SV-related scarring and the total cardiac scarring was defined as the SV scar index: SV-related scarring/total cardiac scarring. RESULTS: VT target sites were identified in the SV in 22 (51%) of 43 patients. LGE-CMR identified peri-aortic scarring involving the SV in 34 patients (79%). Scarring extended to the septum in 26 patients, involved the lateral basal wall in 4, and both areas in 13 patients. Scar volume within the SV was larger in patients with SV-VT targets (1.7 ± 0.9 cm3 vs. 0.7 ± 0.6 cm3; p < 0.0001) compared with other patients. A cutoff scar volume identifying SV-VT targets was 1.23 cm3 in the short-axis view (area under the curve 0.82; sensitivity 0.64; specificity 0.91). The SV scar index was significantly greater in patients who had SV-VT target sites (0.33 ± 0.2 vs. 0.09 ± 0.09; p < 0.0001). CONCLUSIONS: Patients with IDCM undergoing ablation of VT often have peri-aortic scarring visualized on LGE-CMR. Both the presence and the extent of scarring adjacent to the aortic annulus are associated with the presence of VT target sites within the SV.

Factors predictive for delayed enhancement in cardiac resonance imaging in patients undergoing catheter ablation of premature ventricular complexes.

BACKGROUND: Patients undergoing ablation of premature ventricular complexes (PVCs) can have cardiac scar. Risk factors for the presence of scar are not well defined. OBJECTIVES: To determine the prevalence of scarring detected by delayed enhancement cardiac magnetic resonance imaging (DE-CMR) in patients undergoing ablation of PVCs, to create a risk score predictive of scar, and to explore correlations between the scoring system and long-term outcomes. METHODS: DE-CMR imaging was performed in consecutive patients with frequent PVCs referred for ablation. The full sample was used to develop a prediction model for cardiac scar based on demographic and clinical characteristics, and internal validation of the prediction model was done using bootstrap samples. RESULTS: The study consisted of 333 patients (52% male, aged 53.2 ± 14.5 years, preablation ejection fraction 50.9% ± 12.2%, PVC burden 20.7 ± 13.14), of whom 112 (34%) had DE-CMR scarring. Multiple logistic regression analysis showed age (odds ratio [OR] 1.02 [1.01-1.04]/year, P = .019) and preablation ejection fraction (OR 0.92 [0.89-0.94]/%, P < .001) to be predictive of scar. A weighted risk score incorporating age and ejection fraction was used to stratify patients into low-, medium-, and high-risk groups. Scar prevalence was around 86% in the high-risk group and 12% in the low-risk group; high-risk patients had worse survival free of arrhythmia. CONCLUSIONS: Cardiac scar was present in one-third of patients referred for PVC ablation. A weighted risk score based simply on patient age and preprocedural ejection fraction can help discriminate between patients at high and low risk for the presence of cardiac scar and worse arrhythmia outcomes.

The value of cardiac magnetic resonance imaging and programmed ventricular stimulation in patients with ventricular noncompaction and ventricular arrhythmias.

INTRODUCTION: Left ventricular noncompaction (LVNC) is associated with ventricular arrhythmias (VA) including premature ventricular complexes, and ventricular tachycardia (VT). The value of imaging with delayed enhancement cardiac magnetic resonance (DE-CMR) and programmed ventricular stimulation (PVS) for risk stratification in patients with VA and LVNC is unknown. The purpose of this study was to determine whether DE-CMR and PVS are beneficial for risk stratification and whether CMR helps to identify VA target sites. METHODS AND RESULTS: Consecutive patients with LVNC undergoing ablation for VAs were included, all patients had preprocedure DE-CMR. A total of 23 patients (7 women, 46 ± 14 years, ejection fraction 35 ± 14) were included and followed for 2.9 ± 2.2 years. DE-CMR scar was present in 12/23 patients (52%). PVS was performed in 20/23 patients, 8/10 patients (80%) with scar were inducible for VT compared to 0/10 (0%) patients without scar (p < .001). VA target sites in patients with scarring were located adjacent to areas of scarring in all but 1 patient and ablation was successful in 15/23 patients (65%). Patients with scar had worse survival free of VT than those without scar (log rank p = .01) and patients with inducible VT had worse survival free of VT than those who were noninducible (log rank p < .001). CONCLUSIONS: The presence of CMR defined scar in patients with LVNC was associated with inducible VT and worse outcomes. Inducibility for VT was associated with VT recurrence. Furthermore, CMR is beneficial in localizing the arrhythmogenic substrate in LVNC and therefore can aid in procedural planning.

Impact of Intramural Scar on Mapping and Ablation of Premature Ventricular Complexes.

OBJECTIVES: This study sought to determine intramural scar characteristics associated with successful premature ventricular complex (PVC) ablations. BACKGROUND: Ablating ventricular arrhythmias (VAs) originating from intramural scarring can be challenging. Imaging of intramural scar location may help to determine whether the scar is within reach of the ablation catheter. METHODS: Mapping and ablation of premature ventricular complexes (PVCs) was performed in a consecutive series of patients with intramural scarring and frequent PVCs. Data from delayed enhanced cardiac magnetic resonance were assessed and the proximity of the endocardium containing the breakout site to the intramural scar was correlated with outcomes. RESULTS: Fifty-six patients were included, and intramural VAs were successfully targeted in 42 patients (75%) and ablation failed in 14 patients (25%). Scarring was more superficial to the endocardium in patients with successful ablations compared with patients with failed procedures (0.35 mm [interquartile range (IQR): 0.22 to 1.20 mm] vs. 2.45 mm [IQR: 1.60 to 3.13 mm]; p < 0.001). In 18 (32%) patients, ablation at the breakout site resulted in a significant change of the PVC-QRS morphology that could successfully be ablated in 9 of 12 patients from another anatomical aspect of the wall harboring the intramural scar. The scar was larger in size (1.79 cm3 [IQR: 1.25 to 2.85 cm3] vs. 1.00 cm3 [IQR: 0.59 to 1.68 cm3]; p < 0.005) compared with patients who did not have a change in the PVC-QRS morphology with ablation. CONCLUSIONS: VAs in patients with intramural scaring can be successfully ablated especially if the intramural scar is within close proximity to the anatomic area containing the breakout site. Changes in the QRS-PVC morphology often precede successful ablation at another breakout site and indicate larger intramural scars.

Magnetic Resonance Mapping of Catheter Ablation Lesions After Post-Infarction Ventricular Tachycardia Ablation.

OBJECTIVES: This study sought to describe cardiac magnetic resonance (CMR) characteristics of ablation lesions within post-infarction scar. BACKGROUND: Chronic ablation lesions created during radiofrequency ablation of ventricular tachycardia (VT) in the setting of prior myocardial infarction have not been described in humans. METHODS: Seventeen patients (15 men, ejection fraction 25 ± 8%, 66 ± 6 years of age) with CMR imaging prior to repeat ablation procedures for VT were studied. Electroanatomic maps from first-time procedures and subsequent CMR images were merged and retrospectively compared with electroanatomic maps from repeat procedures. RESULTS: The delay between the index ablation procedure and the CMR study was 30 ± 29 months. Late gadolinium-enhanced CMR revealed a confluent nonenhancing subendocardial dark core within the infarct-related scar tissue in all patients. Intracardiac thrombi were ruled out by transthoracic and intracardiac echocardiography. These core lesions matched the distribution of prior ablation lesions, and corresponded to unexcitable areas at repeat procedures. CONCLUSIONS: Ablation lesions can be detected by CMR after VT ablation in post-infarction patients and have a different appearance than scar tissue. These lesions can be observed many months after an initial ablation.

Risk stratification in patients with nonischemic cardiomyopathy and ventricular arrhythmias based on quantification of intramural delayed enhancement on cardiac magnetic resonance imaging.

INTRODUCTION: Intramural scarring is a risk factor for sudden cardiac death. The objective of this study was to determine the value of scar quantification for risk stratification in patients with nonischemic cardiomyopathy (NICM) undergoing ablation procedures for ventricular arrhythmias (VA). METHODS AND RESULTS: Cardiac late gadolinium-enhanced magnetic resonance imaging was performed in patients with NICM referred for ablation of premature ventricular complexes or ventricular tachycardia (VT). Only patients with intramural delayed enhancement were included. Scar volume was measured and correlated with immediate and long-term outcomes. Receiver operator curves, Wilcoxon signed-rank testing, and logistic regression were used to compare patient characteristics. The study consisted of 99 patients (74 males, mean age: 59.6 [54.0-68.1] years, ejection fraction [EF]: 46.0 [35.0-60.0]%). Patients without clinical VT or inducible VT had smaller total and core scar size compared to patients with a history of VT or inducible VT (total scar 1.12 [0.74-1.79] cm3 vs 7.45 [4.16-12.21] cm3 , P < .001). A total scar volume of greater than or equal to 2.78 cm3 was associated with inducibility of VT (AUC 0.94, 95% CI [0.89-0.98], sensitivity 85%, specificity 90%). Scar volume was associated with VT inducibility independent of a prior history of VT or the preprocedure EF (adjusted OR 1.67 [1.24-2.24]/cm3 , P < .01). CONCLUSION: Quantification of scar size in patients with intramural scarring is useful for risk stratification in patients with NICM and VA independent of the EF or a prior history of VT. Scar characteristics of patients without a history of VT who have inducible VT are similar to patients with a history of VT.

Stepwise Approach for Ventricular Tachycardia Ablation in Patients With Predominantly Intramural Scar.

OBJECTIVES: The goal of this study was to assess the value of a stepwise, image-guided ablation approach in patients with cardiomyopathy and predominantly intramural scar. BACKGROUND: Few reports have focused on catheter-based ventricular tachycardia (VT) ablation strategies in patients with predominantly intramural scar. METHODS: The study included patients with predominantly intramural scar undergoing VT ablation. A stepwise strategy was performed consisting of a localized ablation guided by conventional mapping criteria followed by a more extensive ablation if VT remained inducible. The extensive ablation was guided by the location and extent of intramural scarring on delayed enhanced-cardiac magnetic resonance imaging. A historical cohort who did not undergo additional extensive ablation was identified for comparison. A novel measurement, the scar depth index (SDI), indicating the percent area of the scar at a given depth, was correlated with outcomes. RESULTS: Forty-two patients who underwent stepwise ablation (median age 61 years [interquartile range: 55 to 69 years], 35 male patients, median left ventricular ejection fraction 36.0% [25.0% to 55.0%], ischemic [n = 4] or nonischemic cardiomyopathy [n = 38]) were followed up for a median of 17 months (8 to 36 months). A stepwise approach resulted in a 1-year freedom from VT, death, or cardiac transplantation of 76% (32 of 42). Patients who underwent additional extensive ablation had a lower risk of events than a clinically similar historical cohort (N = 19) (hazard ratio: 0.30; 95% CI: 0.13 to 0.68; p < 0.004). SDI>5mm was associated with worse long-term outcomes (hazard ratio: 1.03; 95% CI: 1.01 to 1.06%; p = 0.03), SDI>5mm >16.5% was associated with failed ablation (area under the curve: 0.84; 95% CI: 0.71 to 0.97). CONCLUSIONS: Stepwise ablation using delayed enhanced-cardiac magnetic resonance guidance is a novel approach to VT ablation in patients with predominantly intramural scarring. The SDI correlates with immediate procedural and long-term outcomes.

Risk stratification in patients with frequent premature ventricular complexes in the absence of known heart disease.

BACKGROUND: Frequent premature ventricular complexes (PVCs) can be an indicator of structural heart disease. OBJECTIVE: The purpose of this study was to determine the prevalence of scarring detected by delayed enhancement cardiac magnetic resonance (DE-CMR) imaging in patients with frequent PVCs without apparent structural heart disease and to determine the value of programmed ventricular stimulation (PVS) for risk stratification in patients with frequent PVCs and myocardial scarring. METHODS: DE-CMR imaging was performed in patients without apparent heart disease who had frequent PVCs and were referred for ablation. In the presence of scarring, scar volume was measured and correlated with outcome variables. All patients underwent PVS and were monitored for the occurrence of ventricular arrhythmias. Logistic regression was used to compare imaging and procedural findings with long-term outcomes, with adjustment for postablation ejection fraction (EF). RESULTS: The study consisted of 272 patients (135 men; mean age 52 ± 15 years; EF 52% ± 12%). DE-CMR scar was found in 67 patients (25%), and 7 (3%) were found to have inducible ventricular tachycardia (VT). The presence and amount of DE-CMR were related to the risk of long-term VT independent of EF (hazard ratio 18.8 [95% confidence interval] [2.0-176.6], P = .01; and hazard ratio 1.4 [1.1-1.7] per cm3 scar, P <.001, respectively). The positive predictive value and negative predictive value of PVS for VT during long-term follow-up were 71% and 100%, respectively. CONCLUSION: Preprocedural cardiac DE-CMR and PVS can be used to identify patients with frequent PVCs without apparent heart disease who are at risk for VT.

Left Ventricular Hypertrophy: Evaluation With Cardiac MRI.

OBJECTIVE: Left ventricular hypertrophy (LVH) is a frequent problem in clinical practice and can be caused by diverse conditions including hypertension, aortic stenosis, hypertrophic cardiomyopathy, athletic training, infiltrative heart muscle disease, storage and metabolic disorders. Identification of the precise etiology can be challenging and is a common cause of referral for cardiac MRI (CMR). In this article, CMR findings in various causes of LVH will be reviewed with an emphasis on determination of etiology and emerging role of CMR in risk stratification. CONCLUSIONS: In patients with LVH, CMR allows precise determination of the severity and distribution of hypertrophy, evaluation of ventricular function, and tissue characterization. The information obtained from CMR enables identification of the etiology of LVH and may aid in determining prognosis and therapy.

Metal Artifact Reduction in Cardiovascular MRI for Accurate Myocardial Scar Assessment in Patients With Cardiac Implantable Electronic Devices.

OBJECTIVE. An important application of late gadolinium enhancement (LGE) cardiac MRI is accurate assessment of myocardial scar before ablation. However, this is often limited in patients with cardiac implantable electronic devices (CIEDs) because of metal device-induced artifacts. The purpose of this study was to determine whether a modified wideband inversion recovery (IR) LGE MRI technique decreases artifact volume to allow the assessment of myocardial scar. SUBJECTS AND METHODS. Fifty patients (17 women and 33 men; mean age ± SD, 61 ± 12 years; mean ejection fraction ± SD, 35.9% ± 13.3%) with CIEDs underwent cardiac MRI using conventional and modified wideband IR LGE techniques before ablation. The volume of device-induced artifact was quantified and stratified by tertiles on mild, moderate, and severe. Ordinal logistic regression analysis assessed the association between artifact volume on conventional and wideband images adjusted for patients' demographics. RESULTS. Conventional LGE MRI resulted in device-induced hyperintense artifacts that obscured ventricular segments in 32 of 50 (64%) cases. Wideband LGE MRI significantly reduced severe artifact volume (p < 0.0001) and completely resolved all mild and most moderate artifacts. Overall, wideband techniques resulted in a 56% reduction in total artifact volume for the cohort (p < 0.0001). The wideband LGE MRI sequence minimized artifacts in the most commonly obscured segments on the conventional LGE MRI sequence, with persistent artifacts in seven, eight, and four of 32 cases at the basal anterior, midventricular anterior, and midventricular anteroseptal segments, respectively. CONCLUSION. The modified wideband IR technique completely resolves mild and moderate device-induced hyperintense artifacts and significantly reduces the volume of severe artifact to allow accurate identification of myocardial scar in patients with CIEDs before ablation.