Delayed Enhancement Cardiac MRI Research Articles

MRI in Cardiac Electrophysiology: The Emerging Role of Delayed-Enhancement Mri in Atrial Fibrillation Ablation

Catheter ablation of atrial fibrillation has emerged as a viable therapeutic option for those patients who have failed conventional medical therapy. This treatment strategy has been introduced in the past decade following the discovery of ectopic foci in the pulmonary veins capable of initiating this arrhythmia. The basis of current ablation techniques relies on inducing myocardial necrosis at distinct anatomical landmarks in order to electrically isolate these ectopic foci and to disrupt pulmonary vein and left atrial conduction pathways. The recent introduction of a delayed-enhancement cardiac MRI sequence now allows for the noninvasive assessment of the location and extent of left atrial scarring following the ablation procedure. In this review, we describe this novel scan sequence and its current and potential role in catheter ablation of atrial fibrillation.

Abstract 4192: Unrecognized Myocardial Infarctions are Common in Cardiac Asymptomatic Subjects at High Vascular Risk

Unrecognized myocardial infarction (UMI), generally assessed by the presence of a Q-wave on the electrocardiogram, is commonly found. Furthermore, mortality associated with UMI appears to be similar as for recognized myocardial infarction. With delayed enhancement cardiac MRI (DE-CMR) both Q-wave and non-Q wave infarctions can be identified. The aim of this study was to investigate the prevalence and determinants of UMI in high risk subjects without symptomatic coronary artery disease using DE-CMR. A DE-CMR was performed in 502 subjects with clinically manifest non-coronary atherosclerotic disease or marked risk factors for atherosclerosis. As all subjects had no known history of coronary artery disease, subendocardial and transmural scar tissue on DE-CMR was considered an UMI. In all subjects information on atherosclerotic risk factors was collected. Multivariable logistic regression was used to study the relation of risk factors with UMI. DE-CMR was of sufficient image quality in 480 (95.6%) subjects. Interobserver agreement was excellent (weighted kappa = 95%). An UMI was present in 45 (9.4%) of all subjects, and in 38 (13.1%) of 291 men and in 7 (3.7%) of 189 women. The risk of UMI increased from 6.0% (95%CI 2.2 – 9.8%) in those with two risk factors up to 26.2% (95%CI 15.2 – 37.3%) in those with 4 or 5 risk factors (male gender, age above mean of 53 years, ever smoking, history of stroke, and history of aneurysm of the abdominal aorta (AAA)). In multivariable analysis the risk of UMI was related to male gender (OR 2.6 (95%CI 1.1– 6.3)), age (OR 1.0 (95%CI 1.0 –1.1) per year), ever smoking (OR 3.1 (95%CI 1.0 –9.0), history of stroke (OR 2.1 (95%CI 1.0 – 4.4)) and history of AAA (OR 2.3 (95%CI 0.9 –5.9)). In high risk cardiac asymptomatic subjects UMI is common. The risk of UMI increases with increasing presence of risk factors.

Abstract 4117: A Comparison of Cardiac MRI Peri-Infarct Border Zone Quantification Strategies for the Prediction of Ventricular Tachycardia Inducibility

Peri-infarct border zone (BZ) as quantified by delayed-enhancement cardiac MRI (CMR) has been proposed as a risk stratification tool, and is associated with increased mortality, but has been measured by various methods in the literature. We assessed which BZ analysis best predicts inducible arrhythmia during electrophysiological study (EPS). Methods: CMR was performed in 47 patients with CAD referred for EPS to assess for ventricular tachyarrhythmias (VT). CMR data was analyzed for BZ quantification by three methods. Method I used pixels 2–3 standard deviations over the mean of normal tissue, expressed as % of LV mass. Method II (Yan) used the same pixels but is expressed as % of infarct size. Method III (Schmidt) used a full-width, half-max method. EPS results were classified as negative (non-inducible) or positive (monomorphic VT). Patients with indeterminate EPS outcomes (VF or polymorphic VT, n=9) were not included in this analysis. Results: There were 38 subjects-age 60.2 ± 10.8 yrs, 68% male. During EPS, 20 patients were non-inducible and 18 had induced monomorphic VT (MVT). EF was not significantly different between non-inducible patients and those with MVT (33.4 ± 11.9% vs. 28.1 ± 9.3, p=0.13). Infarct size was significantly different (15.0 ± 11.6% vs. 26.4 ± 12.0%, p = 0.005). BZ by method I was significantly different (1.4 ± 1.3% vs. 3.1 ± 1.5%, p = 0.001), but not by method II (15.2 ± 21.3% vs. 8.0 ± 4.8%, p = 0.17) or method III (4.1 ± 4.5g vs. 3.7 ± 3.7g, p = 0.756). Multivariate analysis demonstrated that BZ by method I was an independent predictor of EPS outcome after controlling for infarct size (OR 1.97 per % change, 95% CI 1.04 to 3.73, p = 0.04). Method I BZ remained an independent predictor when controlling for both infarct size and EF, (OR 2.12 per % change, 95% CI 1.06 to 34.22, p = 0.03). Correlation between techniques was variable (Method I vs. Method II R=0.77, p=0.001; Method I vs. Method III R=0.03, p=0.86; Method II vs. Method III R=0.15, p<0.32). Conclusion: This study demonstrates significant variability between the published methods for measuring BZ. We also show that large BZ by Method I is a stronger predictor of inducible MVT during EPS than EF and infarct size. BZ may be yet another CMR marker of elevated risk of arrhythmia, but requires more rigorous definition.

Quantification of peri-operative myocardial infarction after coronary artery bypass surgery

Dear Editor, In a recent study in the Journal , Steuer and colleagues1 report that elevated biochemical markers after on-pump CABG correspond to the amount of peri-operatively infarcted myocardium as measured by delayed-enhancement cardiac MRI (DE-MRI). They found that 18 out of 23 (78%) patients studied demonstrated delayed hyper-enhancement (HE) on MRI, with a median mass of 4.4 g. While we applaud the use of state of the art imaging techniques to address fundamental questions regarding the pathophysiology of peri-operative myocardial injury, this study suffers from a number of …