Therapy with beta-adrenergic blocking agents has been advocated as a p
otential useful approach in heart failure. Recent studies suggest that
histologic parameters may be helpful in assessing the effectiveness o
f beta-blocker treatment in dilated cardiomyopathy (DCM). In order to
predict the response to beta-blockers in DCM, fibrous tissue was evalu
ated at endomyocardial biopsy (EMB) in 45 patients (pts) with a mean l
eft ventricular ejection fraction of 0.28 +/- 0.07, who were successiv
ely long-term treated with metoprolol (M) (mean dosage 138 +/- 26 mg/d
ie). EMB was performed from left (n = 32) or right (n = 13) ventricle
by means of a King's bioptome or the Cordis adaptation of this instrum
ent. Quantification of fibrous tissue was performed at 9 x magnificati
on and with a computerized morphometric system. Qualitative evaluation
at light microscopy distinguished four types of fibrosis: pericellula
r, perivascular, focal, and endocardial. Volume fraction of fibrous ti
ssue ranged from 1.3 to 35.5% (mean 12.1 +/- 9.3%) and was not signifi
cantly correlated with any clinical variable considered. After 24 +/-
12 months of treatment, 25 pts were considered improved (group A), whe
reas the remaining 20 pts were considered not improved (group B), acco
rding to criteria based on ejection fraction, left ventricular end-dia
stolic diameter, filling pattern at Doppler-Echocardiography, cardioth
oracic ratio, NYHA functional class, and exercise duration at ergometr
ic test. Volume fraction of fibrous tissue did not differ significantl
y between the two groups (group A = 12.1 +/- 9.1%; group B = 11.3 +/-
9.6%; p = NS). Dominant pericellular type of fibrosis was equally dist
ributed between the two groups (group A = 9/25 pts, 36%; group B = 10/
20 pts, 50%), whereas a perivascular and/or focal replacement fibrosis
was more frequent in group A (group A = 10/20 pts, 50%; group B = 2/2
0 pts, 10%; p = .05, OR 5.55 at univariate analysis). At multivariate
analysis mean aortic blood pressure was the only variable discriminati
ng the two groups; the type of fibrosis, although not statistically si
gnificant, maintained a high value of odds-ratio (5.23). In conclusion
, extent of total fibrosis assessed by EMB may range widely in patient
s with DCM, is not correlated with the most important clinical variabl
es, and is not predictive of long-term response to beta-blocker treatm
ent. Otherwise, prevalent perivascular and/or focal replacement fibros
is could be associated with a higher probability of improvement after
long-term beta-blocker treatment.