Advances in Electrocardiographic Features in Arrhythmogenic Right Ventricular Cardiomyopathy

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Publication Date	2015-01-25
Journal	Padua Research Archive (University of Padua)
Authors	Mohamed ElMaghawry

Abstract

Introduction Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic heart muscle disease characterized by electrical instability leading to ventricular arrhythmias and sudden cardiac death. The hallmark pathological lesion of ARVC is the transmural loss of the myocardium of the right ventricular (RV) free wall with replacement by fibro-fatty tissue. Three-dimensional electroanatomic voltage mapping (EVM) by CARTO system (Biosense-Webster, Diamond Bar, California) allows identification and characterization of low-voltage regions, i.e. “electroanatomical scars” (EAS), which in patients with ARVC correspond to areas of fibro-fatty replacement. Although the technique has been demonstrated to enhance the accuracy for diagnosing ARVC, its value for arrhythmic risk stratification remains to be established. Furthermore, the clinical utility of EVM for scar quantification and risk assessment is limited by its invasive nature, low availability and high costs. Thus, in daily clinical practice there is the need of a non-invasive test such as 12-lead electrocardiogram (ECG) for prediction of the amount of RV myocardial scar lesion and assessment of arrhythmic risk. Previous studies demonstrated an association between ECG repolarization/depolarization abnormalities and RV mechanical dilation/dysfunction. In fact, T wave inversion in right pericardial leads is the most common ECG abnormality of ARVC. However, the presence of T wave inversion in leads V1-V3, known as persistence of the juvenile pattern of repolarization, may also be observed in about 3% of healthy adults. The current perspective is that, at variance with healthy subjects, right precordial NTWs persist with exercise in ARVC patients. However, this view is not supported by systematic scientific data. Objective In this work, we aimed to further study some of the electrocardiographic features of ARVC. First, we assessed the prognostic value of EAS detected by EVM and its correlation with various non-invasive characteristics of ARVC, including abnormalities detected by surface ECG. Second, we studied the exercise-induced changes in right precordial negative T waves in patients with ARVC and in a group of healthy young individuals with persistence of the juvenile repolarization pattern Methods and results We first studied 69 consecutive ARVC patients (47 males; median age 35 years [28-45]) who underwent electrophysiological study and both bipolar and unipolar EVM. The extent of confluent bipolar (<1.5 mV) and unipolar (<6.0 mV) low-voltage electrograms was estimated using the CARTO-incorporated area calculation software. Fifty-three patients (77%) showed ≥1 RV electroanatomic scars with an estimated burden of bipolar versus unipolar low voltage areas of 24.8% (7.2-31.5) and 64.8% (39.8-95.3), respectively (P=0.009). In the remaining patients with normal bipolar EVM (n=16; 23%), the use of unipolar EVM unmasked ≥1 region of low-voltage electrogram affecting 26.2% (11.6-38.2) of RV wall. During a median follow-up of 41 (28-56) months, 19 (27.5%) patients experienced arrhythmic events. At multivariate analysis, the only independent predictor was the bipolar low-voltage electrogram burden (hazard ratio=1.6 per 5%; 95% confidence interval, 1.2-1.9; P<0.001). Patients with normal bipolar EVM had an uneventful clinical course. Then we further analyzed a subgroup including 49 patients [38 males, median age 35 years] with ARVC and an abnormal EVM by CARTO system. At univariate analysis, the presence of epsilon waves, the degree of RV dilation, the severity of RV dysfunction and the extent of negative T-waves correlated with RV-EAS% area. At multivariate analysis, the extent of negative T-waves remained the only independent predictor of RV-EAS% area (B=4.4, 95%CI 1.3-7.4, p=0.006) and correlated with the arrhythmic event-rate during follow-up (p=0.03). In a different cohort, we assessed the prevalence and relation to the clinical phenotype of exercise-induced right precordial negative T wave changes in 35 ARVC patients (19 males, mean age 22.2Â±6.2 years). Forty-one healthy individuals with right-precordial negative T waves served as controls. At peak of exercise, negative T waves persisted in 3 ARVC (9%) patients, completely normalized in 12 (34%) and partially reverted in 20 (57%). ARVC patients with or without negative T waves normalization showed a similar clinical phenotype. The overall prevalence of right precordial T-waves changes during exercise (normalization plus partial reversal) did not differ between ARVC patients and controls (92% versus 88%, p=1.0), while there was a statistically non significant trend towards a higher prevalence of complete normalization in controls (59% versus 34%, p=0.06). Conclusion In conclusion, our results showed that the extent of bipolar RV endocardial low-voltage area was a powerful predictor of arrhythmic outcome in ARVC independently of arrhythmic history and RV dilatation/dysfunction. A normal bipolar EVM characterized a low-risk subgroup of ARVC patients. Patients with abnormal ECG have a more severe RV EAS involvement, which is proportional to the extent of T wave inversion across ECG 12-leads and a higher arrhythmic risk. The absence of negative T waves characterizes a low-risk subgroup of ARVC patients with a more favorable clinical course because of a low rate of arrhythmic events. The results also showed that exercise-induced changes of negative T waves were unrelated to ARVC phenotypic manifestations and were of limited value for the differential diagnosis between ARVC and benign persistence of the juvenile repolarization pattern

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