ABC | Volume 112, Nº1, January 2019

Elias Nero et al ARVC/D - Diagnosis and treatment Arq Bras Cardiol. 2019; 112(1):91-103 Review Article Table 2 – Cardiac magnetic resonance imaging findings in cardiomyopathy / arrhythmogenic right ventricular dysplasia Functional abnormalities Regional abnormalities of RV wall movement Focal aneurysms RV Dilation Diastolic/systolic dysfunction of the RV Morphological abnormalities Intramyocardial fat infiltration Focal fibrosis Focal decrease of RV wall thickness Wall hypertrophy Trabecular disarrangement Hypertrophy of the moderating band RVOT diameter change RV: right ventricle; RVOT: right ventricular outflow tract. Frequent ventricular ectopy recording in the 24-hour Holter (> 500 VEx/24h) is considered a minor criterion. 7 Few studies have evaluated the frequency of supraventricular arrhythmia in ARVC/D. Although not related to mortality, the presence of atrial arrhythmia is associated with an increase in disease morbidity, and to the increase of inappropriate therapies by ICD. The incidence of atrial arrhythmia in ARVC/D varies between 14% and 24%, and atrial fibrillation is the most prevalent supraventricular arrhythmia (Figure 1B). 24,25 The occurrence of atrial arrhythmia is particularly associated with the presence of tricuspid insufficiency, atrial involvement and significant RV dilation. 9 Complementary examinations Echocardiogram A structural and functional evaluation is fundamental for the diagnosis of ARVC/D. Echocardiography, as a result of its accessibility, has been the image exam of choice for the beginning of the investigation of ARVC/D. However, the unique geometry and complex pattern of RV contraction, together with the increased recognition that structural abnormalities may not be apparent in the earlier stages of the disease, limit its diagnostic utility. 7 Echocardiographic findings suggestive of ARVC/D include: (1) global or segmental abnormality of the ventricular wall in association with dilatation of the cavity (mainly right); (2) RV hypertrophy and systolic dysfunction; (3) dilatation of the RV outflow tract (diameter > 30mm). 6 Cardiac magnetic resonance In the last decade, CMR has emerged as the image modality of choice in the ARVC/D investigation, because it allows for a non-invasive morphological and functional evaluation, as well as for analysis of the tissue changes (fibro-fatty transformation) that characterize this pathology. 6,7 However, misinterpretation of CMR findings is the most common reason for misdiagnosis of ARVC/D. The most common errors include inadequate diagnosis of physiological or artefactual fat infiltration, misinterpretation of normal variants of RV wall movement, and inappropriate diagnosis in cases of sarcoidosis and myocarditis. This “pathological” connotation given to the existence of fat in the RV led to a high incidence of false positivity, especially when using the TFC criteria of 1994. 2010 TFC brought a better definition of the criteria to be sought in the CMR, leaving the use of specific protocols for fat screening in the right chamber aside. Abnormalities of CMR in ARVC/D can be grouped into morphological and functional abnormalities (Table 2). These abnormalities were initially observed in the classically described “triangle of dysplasia” 3 which refers to the RV entry tract, the outflow tract and the apex. However, a recent study suggests that these changes preferentially involve the subtricuspid epicardial region, the RV free basal wall and the LV lateral wall, with the RV apex and the endocardium generally spared. 6,9 In addition to the parameters included in the TFC 2010, there are other characteristic abnormalities of the ARVC/D that can also be visualized by the CMR. These parameters include the RV microaneurysms and the presence of an “accordion signal”, which is the focal wrinkling of the RVOT or RV free subtricuspid wall, which is more prominent during the systole. In addition, the presence of intramyocardial fat in the RV suggests ARVC/D; however, its presence is not specific and has been observed in the elderly, in chronic users of steroids, and in other cardiomyopathies. 4,5 Although the increase in late enhancement by gadolinium (LE) has been frequently detected in patients with ARVC/D, this criterion was not incorporated in 2010 TFC due to several limitations (RV thin walls, difficulty in differentiating fat from fibrosis, and irregular impairment of the RV). Despite this, we believe that it is of diagnostic value, especially those with biventricular or left dominant forms. 4 The increasing use of CMR is leading to the recognition that LV is more frequently changed than previously thought, leading to the expression arrhythmogenic cardiomyopathy. LV involvement is mainly located in the inferior and basal inferolateral walls, typically in the form of fat infiltration extending from the epicardium to the myocardium. These sites may also present LE, often without an association of ventricular wall motility abnormality. Electrophysiological study The electrophysiological study (EFS) with programmed ventricular pacing is nowadays less used in the diagnostic and therapeutic evaluation of ARVC/D. 7 The largest multicenter study on patients withARVC/Dwho received ICD implantation showed that the EFS has limited value in predicting the risk of a severe arrhythmia. In this study, the incidence of effective therapies for fatal events (VF/VFL) did not differ significantly among patients with inducible arrhythmia or not, during baseline EFS. 26 In spite of these recent results, 2010 TFC considers that the EFS should be taken into account for the diagnosis and 6