[Diastolic behavior during postischemic hypercontraction phase in rabbit stunned myocardium].

UNLABELLED

The objective was to determine whether "hypercontraction" (HC) that occurs at the beginning of reperfusion (R) in stunned myocardium is accompanied by diastolic alterations and determine if the R with low Ca2+. Ringer's solution modifies these alterations. Isolated isovolumic rabbit hearts were divided into 2 groups. Group 1 (G1, n = 11) was perfused with Ringer's solution ([Ca2+] = 2 mM) and subjected to 15 min of global ischemia and 30 min of R. Group 2 (G2, n = 10) was R during the first 10 min with ([Ca2+] = 1 mM), which was increased to 1.5 mM and 2 mM in the perfusate at 30 min of R. The left ventricular +dP/dtmax, left ventricular end diastolic pressure (LVEDP) (stiffness index), and relaxation rate (t 1/2 and +P/-P ratio) were measured, from the beginning of R every 10 sec for 2 min, and then at 5 and 30min. At 60 sec of R the +dP/dtmax in G1 was increased (76.88 +/- 5.37% vs preischemic value) and was attenuated in G2 (48.22 +/- 3.40%; P < 0.05 vs G1). The LVEDP in G1 was increased early in the R, although it was negatively correlated with HC degree (r = .0.7477; p = 0.008). This increase was attenuated in G2 (P < 0.05 vs G1) at 60 sec R. There was a dealy in the relaxation at 60 secR in both group (G1 vs G2, NS).

IN CONCLUSION

HC is accompanied by diastolic alterations. The improvement of HC is inversely related with LVEDP. During R the stiffness during the relaxation rate was normal. The R with low Ca2+ attenuated the HC and the diastolic stiffness.