We describe the synthesis and positive inotropic evaluation of a series of 2-(4-substitutedbenzyl-1,4-diazepan-1-yl)-N-(4,5-dihydro-1-phenyl-[1,2,4]triazolo[4,3-a]quinolin-7-yl)acetamides by measuring left atrial stroke volume in preparations of isolated rabbit-heart. Several compounds were developed from, and showed favorable activities compared with the standard drug milrinone. Compound 5o was the most potent with an increased stroke volume of 9.17 ± 0.14% (milrinone 2.47 ± 0.08%) at 3 × 10⁻⁵ M in our in-vitro study. The chronotropic effects of those compounds having inotropic effects were also evaluated.