CORRESPONDENCE: LETTER TO THE EDITOR
May Active Myocarditis Mimick Arrhythmogenic Right Ventricular Cardiomyopathy Phenotype by Electroanatomic Mapping?
Gaetano Thiene, MD*,
Cristina Basso, MD, PhD and
Domenico Corrado, MD, PhD
* University of Padua, Pathological Anatomy, Via A. Gabelli, 61, 35121 Padova, Italy (Email: gaetano.thiene{at}unipd.it).
We read with interest the study of Pieroni et al. (1). Although we fully agree on the superiority of endomyocardial biopsy (EMB) for a specific diagnosis of the underlying disease, especially considering that fibro-fatty replacement and low electrical voltage also may occur in the setting of sarcoid cardiomyopathy (2), we have some concerns with regard to their findings.
The authors report that 50% of patients with the clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) had "active myocarditis." This means that an ARVC phenotype (inverted T-wave in right pre-cordial leads, ventricular tachycardia of left bundle branch block morphology, morphological abnormalities of the right ventricle at echocardiography/angiography/magnetic resonance imaging [MRI], late potentials, >2,000 premature ventricular beats at Holter monitoring) frequently corresponds to myocarditis with predominant involvement of the right ventricle. In our longstanding experience with EMB, this is a rare occurrence. Additionally, 30 patients with an ARVC phenotype collected in 1 year seem unrealistic for a single center.
An inflammatory infiltrate of 7 lymphocytes/mm2 is too scanty to be considered diagnostic for active myocarditis. This number is within the normal limits. In all the published literature on voltage mapping, none have previously reported a positive voltage map with "active myocarditis" (3,4). Only a phenomenon of scarring associated with myocarditis may account for such a loss of myocardium to generate low electrical voltage, and this may occur in the setting of chronic (nonacute) myocarditis.
Although it has not been documented, MRI did not show significant differences between patients with "active myocarditis" and ARVC in terms of delayed enhancement, which was high both in the right and in the left ventricular walls, a finding again suggestive of extensive replacement-type fibrosis in both subgroups. Surprisingly, the authors did not find any evidence of fibrosis at EMB in any patient with "active myocarditis," positive electroanatomic mapping, and delayed enhancement at MRI.
It is noteworthy that the patient in Figure 2 of Pieroni et al. (1), with positive electroanatomic mapping and a histological diagnosis of active myocarditis, shows a clear-cut picture at angiography of "pile d'assiettes," which is almost pathognomonic of ARVC (5).
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1. Pieroni M, Dello Russo A, Marzo F, et al. High prevalence of myocarditis mimicking arrhythmogenic right ventricular cardiomyopathy: differential diagnosis by electroanatomic mapping-guided biopsy J Am Coll Cardiol 2009;53:681-689.[Abstract/Free Full Text]2. Santucci PA, Morton JB, Picken MM, Wilber DJ. Electroanatomic mapping of the right ventricle in a patient with a giant epsilon wave, ventricular tachycardia, and cardiac sarcoidosis J Cardiovasc Electrophysiol 2004;15:1091-1094.[CrossRef][Web of Science][Medline] 3. Corrado D, Basso C, Leoni L, et al. Three-dimensional electroanatomic voltage mapping increases accuracy of diagnosing arrhythmogenic right ventricular cardiomyopathy/dysplasia Circulation 2005;111:3042-3050.[Abstract/Free Full Text] 4. Avella A, d'Amati G, Pappalardo A, et al. Diagnostic value of endomyocardial biopsy guided by electroanatomic voltage mapping in arrhythmogenic right ventricular cardiomyopathy/dysplasia J Cardiovasc Electrophysiol 2008;19:1127-1134.[CrossRef][Web of Science][Medline] 5. Daliento L, Rizzoli G, Thiene G, et al. Diagnostic accuracy of right ventriculography in arrhythmogenic right ventricular cardiomyopathy Am J Cardiol 1990;66:741-745.[CrossRef][Web of Science][Medline]
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- Maurizio Pieroni, Francesca Marzo, Fulvio Bellocci, and Filippo Crea
J. Am. Coll. Cardiol. 2009 54: 1190-1191.
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