PRESERVATION OF MYOCARDIAL BLOOD-FLOW BY CALCIUM-ANTAGONISTS DOES NOTPREVENT ATTENUATION OF REGIONAL MYOCARDIAL-FUNCTION AFTER REPETITIVE BRIEF PERIODS OF MYOCARDIAL-ISCHEMIA IN THE RAT-HEART

The aim of this study was to assess the effect of two different calciu m channel blockers on myocardial blood flow and function in a rat mode l of myocardial 'stunning' by repeated short episodes of ischaemia ('r epetitive ischaemia'). In an open chest rat model, the left anterior d escending coronary artery was ligated for 10 min followed by 15 min re perfusion. In total, five periods of ischaemia and reperfusion were pe rformed. Myocardial blood flow was assessed by the hydrogen clearance technique and systolic thickening fi action by pulsed Doppler. After f ive episodes of ischaemia, myocardial blood flow and myocardial thicke ning in the ischaemic area were reduced by 60 +/- 8% and 52 +/- 7% (n = 9 ), respectively, as compared to baseline. Continuous intravenous i nfusion of the calcium channel blockers nifedipine (n = 6) and gallopa mil (n = 6), started 20 min prior to onset of ischaemia, attenuated th e ischaemia-induced den ease of myocardial perfusion. Nifedipine was t he mast effective with only 5 +/- 2% reduction in blood flow after fiv e ischaemic episodes, whereas reduction of myocardial blood flow was 3 0 +/- 4% in the presence of gallopamil. However, neither nifedipine no r gallopamil were able to pl event regional ventricular dysfunction in duced by repetitive ischaemia. Despite the preservation of myocardial blood flow following repetitive ischaemia, calcium channel blockers do not pl event ischaemia-induced reduction of myocardial function in th e ischaemic area.