Hemodynamic effects of different calcium antagonists in the heart-lung preparation of the guinea pig

The present study was performed with the aim to demonstrate and quantify the influence of several different calcium antagonists (CA) on hemodynamic parameters in the guinea pig heart lung preparation (HLP). In paced HLP the following parameters were recorded: dp/dt max; cardiac output (CO); left ventricular pressure (LVP), and aortic pressure (AoP). In separate experiments the influence of the CA on heart rate (HR) was established in spontaneously performing HLP. All CA studied reduced or depressed dp/dt max, CO, LVP, AoP and HR. Nifedipine and verapamil showed the strongest depressant influence on dp/dt max and CO, whereas diltiazem caused a moderate reduction of these parameters. Lidoflazine, flunarizine and bepridil proved considerably less potent than nifedipine, verapamil and diltiazem. Bepridil proved least potent with respect to the influence on LVP and AoP. The strongest reduction on HR was caused by nifedipine greater than verapamil greater than diltiazem, and to a lesser degree by lidoflazine. Bepridil and flunarizine only caused a mild reduction of HR. From the calculated ratio EC20(HR)/EC20(dp/dt max) it is obvious that nifedipine, verapamil and bepridil display a much stronger influence on contractility than on HR. dp/dt max proved the most sensitive indicator for contractility in the HLP as used in our experiments.