CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Maurizio Pieroni, MD, PhD*,
Francesca Marzo, MD,
Fulvio Bellocci, MD and
Filippo Crea, MD
* Cardiology Department, Catholic University, Largo A. Gemelli 8, 00168 Rome, Italy (Email: mauriziopieroni{at}yahoo.com).
We appreciate the interest of Dr. Thiene and colleagues in our work (1). However, despite their longstanding experience in this field, some of their comments could cause a misleading interpretation of our findings.
In particular, their concern regarding the prevalence of right ventricular myocarditis among patients with a diagnosis of noninvasive arrhythmogenic right ventricular cardiomyopathy (ARVC) is surprising when considering that in a recent study (2) they diagnosed an active myocarditis in 40% of patients with a clinical diagnosis of ARVC (10 of 25 patients with a definite histological diagnosis). As well as Padua University, our institution is a referral center for arrhythmias and cardiomyopathies, and a significant proportion of the patients enrolled in 1 year were referred for further invasive studies from southern Italian hospitals after noninvasive evaluation suggested a diagnosis of ARVC.
With regard to histological evaluation, we clearly stated that the diagnosis of active myocarditis was based on Dallas criteria but also required the demonstration of a significant number of activated and cytotoxic T lymphocytes. An amount of >7 lymphocytes/mm2, even if identified as activated/cytotoxic, can be still considered arbitrary, as it is the case for other criteria adopted by other groups (3). Moreover, confusion should be avoided between the terms "active" and "acute" representing, respectively, a histological and clinical definition. It is evident from the text and tables that all of our patients were affected by a chronic active myocarditis, a well-established clinico-pathologic entity characterized by ongoing myocardial inflammation and necrosis with different degrees of replacement fibrosis in patients with chronic symptoms (in this case, ventricular arrhythmias). Although not detailed in this study, we previously reported that patients with chronic active myocarditis mimicking ARVC present, at histomorphometric analysis, values of fibrosis comparable to patients with a histological diagnosis of ARVC (4). Accordingly, as clearly documented in Table 2 of the present study (1), we failed to observe any difference in terms of delayed enhancement between the 2 groups. Nevertheless, we think that fibrosis should not be considered the unique histological substrate of low-voltage areas, grossly defined by electrophysiologists as "scar." We learned from cardiac magnetic resonance how delayed enhancement, initially considered synonymous with fibrosis, could indeed result from any cause of interstitial expansion including edema, necrosis, inflammation, or amyloid deposition. Similarly, inflammation might modulate electrical properties of myocardium inducing a low-voltage area before replacement fibrosis occurs. The adoption of the simplistic equation: low-voltage = fibrosis, may retard the comprehension of arrhythmogenesis in myocardial disorders.
Our study demonstrates that current diagnostic criteria should be revisited and suggests that further studies including both electroanatomic mapping-guided endomyocardial biopsy and genetic analysis of patients with familial and sporadic forms of ARVC will allow clarification of the complex link between desmosomal abnormalities, inflammation, and fibrofatty replacement.
It is noteworthy that the angiographic picture of "pile d'assiettes" [pile of dishes] in a patient with myocarditis was chosen to emphasize the possible overlap of angiographic findings between ARVC and myocarditis.
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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. 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] 3. Caforio AL, Calabrese F, Angelini A, et al. A prospective study of biopsy-proven myocarditis: prognostic relevance of clinical and aetiopathogenetic features at diagnosis Eur Heart J 2007;28:1326-1333.[Abstract/Free Full Text] 4. Chimenti C, Pieroni M, Maseri A, Frustaci A. Histologic findings in patients with clinical and instrumental diagnosis of sporadic arrhythmogenic right ventricular dysplasia J Am Coll Cardiol 2004;43:2305-2313.[Abstract/Free Full Text]
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May Active Myocarditis Mimick Arrhythmogenic Right Ventricular Cardiomyopathy Phenotype by Electroanatomic Mapping?
- Gaetano Thiene, Cristina Basso, and Domenico Corrado
J. Am. Coll. Cardiol. 2009 54: 1190.
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