Dilated cardiomyopathy and coronary flow reserve.

Dilated cardiomyopathy and coronary flow reserve We read with interest the article by Rigo et al. 1 about the prognostic impact of coronary flow reserve (CFR) by Doppler echocar-diography in dilated cardiomyopathy. The authors conclude that in patients with idiopathic dilated cardiomyopathy, the prognostic role of impaired microvascular CFR has been shown to be unfavourable. In our opinion, some points of this work are not completely clear. First of all, it is not correct to diagnose an idiopathic dilated cardiomyopathy only upon exclusion of ischaemic heart disease after coronary angiography. Authors excluded patients with myocarditis. How can they exclude myocarditis without performing endomyocardial biopsies? Myocarditis is only diagnosed by established histopatholo-gical, histochemical, or molecular criteria on endomyocardial biopsy. 2 Clinical suspicion may be raised by global left ventricular dys-function, acute congestive heart failure, or cardiogenic shock associated with left ven-tricular dilatation and/or segmental wall motion abnormalities. When myocarditis is suspected clinically, an endomyocardial biopsy may resolve an otherwise ambiguous situation by virtue of diagnostic inflamma-tory infiltrate and necrosis (i.e. the Dallas criteria). The diagnostic yield of myocardial biopsies is enhanced substantially by molecular analysis with DNA–RNA extraction and polymerase chain reaction amplification of the viral genome. Moreover, it is recognized that patients with biopsy-proven inflammatory infiltrates have a diminished CFR due to reduced coronary vasodilator capacity. 3 Experimental data also showed that CFR measured by transthoracic Doppler echocardiography is reduced in cox-sackievirus myocarditis in mice. 4 Low CFR is associated with progressive heart failure indicating that dysfunction of coronary circulation is a determinant of poor outcome in viral myocarditis. 3 Therefore, we think that endomyocardial biopsy should be performed in order to exclude myocarditis. The event-free survival in the group of patients with a CFR. 2 is nearly 100% in the first 3 years; this could be due to high incidence of myocarditis in this patients group and higher proportion of subjects with a spontaneous recovery. It would have been very interesting to have a second measurement of CFR in the follow-up period. Did the authors see a CFR improvement in this patients group? Secondarily, the CFR cutpoint of .2 is arbitrary ; in fact, it is took on loan from ischae-mic heart disease, in which it has the best accuracy as a predictor of significant LAD stenosis. 5 To the best of our knowledge, there are no data dealing with the optimal CFR cutoff in identifying worse prognosis in …