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Published on: February 10, 2013
Effects of beta-adrenergic blocking therapy on left ventricular diastolic relaxation properties in patients with
1University of Michigan and Veterans Affairs Medical Centers, Ann Arbor, MI 48105, USA.
Background:
The hemodynamic mechanism for the improvement in left ventricle (LV) end-diastolic pressure in cardiomyopathy patients treated with beta-adrenergic blocking agents is controversial. We hypothesized that the salutary effect of this kind of therapy on LV end-diastolic pressure would be indicative of an improvement in late, passive diastolic relaxation properties.
Methods And Results:
We studied 14 cardiomyopathy patients in normal sinus rhythm with no arteriographic evidence of coronary artery disease and an LV ejection fraction of =40% by radionuclide angiography both before and after 6 months of metoprolol therapy with simultaneous micromanometry and biplane cineventriculography. Four comparable patients who were not treated with metoprolol were studied in a similar fashion and served as control subjects. In those receiving metoprolol, LV end-diastolic pressure decreased (P=0.001). The isovolumic relaxation index, tau(ln), shortened (P=0.03). In a similar fashion, the LV chamber stiffness constant, kappa, decreased (P=0.02), LV volume elastance improved (P=0.04), and the myocardial stiffness constant, kappa(e), decreased (P=0.02). A multiple regression analysis revealed that the decrease in LV end-diastolic pressure was indicative of significant improvements in tau(ln) and kappa(e) with the relationship: LV end-diastolic pressure=-4.73+0.27 tau(ln)+0.54 kappa(e) (r=0.81, P<0.0001). These LV diastolic relaxation properties did not change or worsened in the control cardiomyopathy patients.
Conclusions:
We conclude that the decrease in LV end-diastolic pressure in cardiomyopathy patients treated with metoprolol is an indicator of improvement in LV diastolic properties resulting from more complete myocardial relaxation.
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