A series of 4-(substituted)-3,4-dihydropyrimidinone derivatives have been synthesized by heating 1,3 dicarbonyl compounds, urea, and aromatic aldehydes in acetic acid under microwave irradiation conditions. The cardiovascular effects of 3,4-dihydropyrimidinones were studied on isolated perfused frog heart at different dose levels and compared with the activity of digoxin. The interaction of 3,4-dihydropyrimidinones with beta-blocker and calcium channel blocker was also investigated. Compound 4d emerged as the most interesting compound in this series with potential cardiotonic activity.