CORRESPONDENCE: LETTER TO THE EDITOR
Left Dominant Arrhythmogenic CardiomyopathyA New Clinical Entity Without a Typical Substrate of Myocardial Damage
Gianluca Di Bella, MD*,
Scipione Carerj, MD and
Sebastiano Coglitore, MD
* Clinical and Experimental Department of Medicine and Pharmacology, University of Messina, Via Consolare Valeria N°1, 98100 Messina, Italy (Email: gianluca.dibella{at}tiscali.it).
We read with interest the paper by Sen-Chowdhry et al. (1) about left dominant arrhythmogenic cardiomyopathy (LDAC). The investigators "highlight the interrelation of LDAC and arrhythmogenic right ventricular cardiomyopathy (ARVC) within the same disease spectrum and provide a composite profile of this entity" (1). The investigators identify the salient clinical features of LDAC: unexplained ventricular arrhythmia of left ventricular origin, isolated (infero)lateral T-wave inversion, mild left ventricular dilation and/or systolic impairment, and myocyte loss with fibrofatty or fibrotic replacement. Additionally, the involvement (segmental dilatation and/or wall motion abnormalities) of the right ventricle (RV) showed an important role in the diagnosis of LDAC.
On the basis of myocardial damage, the investigators illustrated 2 phenotypes of LDAC: a fibrofatty and a pure fibrotic form. Therefore, the identification of myocardial damage by histology and/or cardiac magnetic resonance with late gadolinium enhancement added with clinical manifestation of this disease plays a main role in the diagnosis of LDAC.
However, LDAC shows controversial points, particularly in its morphological features. We believe that LDAC is an under-recognized entity because it has many morphological features overlapping with those of other cardiomyopathies, particularly with dilated cardiomyopathy (DCM), biventricular form ARVC, and inflammatory cardiomyopathy (myocarditis).
The investigators suggest differentiating the LDAC phenotype from DCM on the basis of prominent RV abnormalities; however, recognizing "prominent RV abnormalities added with left ventricular involvement" as a diagnostic method for LDAC with respect to the biventricular form of ARVC can be very difficult.
Furthermore, the investigators suggest the localization of myocardial damage (fibrofatty or fibrotic tissue) as an aid to diagnosis. To distinguish these 2 entities (LDAC and DCM), they recommend the epicardial pattern of damage (late gadolinium enhancement) as indicating a suspicion of LDAC, whereas midventricular damage can be observed in both. Nevertheless, the epicardial damage is an unspecific pattern observed in many cardiomyopathies, such as myocarditis, sarcoidosis, Anderson-Fabry disease, and Chagas disease.
According to the investigators, fibrofatty replacement likely represents a nonspecific reparative process. This theory is confirmed by lipomatous metaplasia observed in the context of a myocardial infarction; the lipomatous metaplasia is caused by substitution of muscle fibers with fibrofatty tissue (2).
Recent studies suggest that the LDAC phenotype is the result of chronic myocarditis (3). However, the investigators attribute the myocardial inflammation in the setting of LDAC to a reactive unspecific consequence of loss of myocyte caused by compromised intercellular adhesion and intermediate filament function attributable to mutation in desmosomal genes. On the contrary, Bowles et al. (4) have identified the viral genome in the myocardium of ARVC; therefore, it is also possible that a genetic profile of diseased myocardium has increased the susceptibility to a viral infection that can eventually play a role in the clinical manifestations of the disease (5). Therefore, the role of inflammation in LDAC pathogenesis remains unknown.
Finally, we concur with the view of Sen-Chowdhry et al. (1) that the results described in their article add important clinical features to facilitate the diagnosis of LDAC.
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1. Sen-Chowdhry S, Syrris P, Prasad SK, et al. Left-dominant arrhythmogenic cardiomyopathy: an under-recognized clinical entity J Am Coll Cardiol 2008;52:2175-2187.[Abstract/Free Full Text]2. Schmitt M, Samani N, McCann G. Lipomatous metaplasia in ischemic cardiomyopathy: a common but unappreciated entity Circulation 2007;116:e5-e6.[Free Full Text] 3. Fontaine GH, Fornes P. Letter regarding article by Norman et al, "novel mutation in desmoplakin causes arrhythmogenic left ventricular cardiomyopathy." Circulation 2006;113:e68-e69.[CrossRef][Web of Science][Medline] 4. Bowles NE, Ni J, Marcus F, Towbin JA. The detection of cardiotropic viruses in the myocardium of patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy J Am Coll Cardiol 2002;39:892-895.[Abstract/Free Full Text] 5. 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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