A short IV dose of the peptide hexarelin raises growth hormone levels in people with severe heart failure, and it can temporarily improve heart pumping ability in those whose heart disease is caused by blocked arteries, but it doesn’t help those with a dilated heart. The heart boost seems to come from a direct effect on the heart muscle, not just the hormone rise.

To investigate acute cardiotropic activities of hexarelin in patients with severe left ventricular dysfunction due to ischemic (iCMP) and dilated cardiomyopathy (dCMP). We studied the effect of intravenous hexarelin administration on growth hormone (GH) levels and left ventricular ejection fraction (LVEF) evaluated by radionuclide angiography in eight patients with dCMP (age 53.0+/-2.8, LVEF 16.7+/-2.1%) and five patients with iCMP (age 52.0+/-2.8 years, LVEF 22.6+/-2.1). Results were compared with a group of seven normal subjects (age 37.4+/-3.4 years, LVEF 64.0+/-1.5%) and seven patients with severe growth-hormone deficiency (GHD; age 42.0+/-4.4 years, LVEF 50.0+/-1.9%) previously studied with the same methodology. In dCMP and iCMP patients hexarelin induced a similar significant (P<0.05) increase in GH levels. In iCMP patients hexarelin induced a LVEF increase (peak LVEF 26.2+/-2.5%, P<0.05) as observed in normals and GHD, while in dCMP LVEF was unchanged (peak LVEF 17.7+/-1.7, P=NS). In all groups other hemodynamic parameters were unchanged. Acute hexarelin administration increases LVEF in iCMP patients (as in normals and GHD) but not in dCMP patients in spite of a similar GH releasing effect and basal LVEF. A possible explanation of the positive inotropic effect of hexarelin in iCMP could be a direct stimulation on viable myocardium or myocardial contractile reserve.