Cardiac effects of postconditioning depend critically on the duration of reperfusion and reocclusion episodes.
OBJECTIVE
The objective of the present study was to evaluate the effects of ischemic postconditioning on left ventricular function in isolated rat hearts.


METHODS
The hearts of 24 Wistar rats were were isolated, perfused immediately, and distributed into 3 groups: GI, control (n = 8); GII, three 10-second cycles of postconditioning (n = 8); and GIII, three 30-second cycles of postconditioning (n = 8). After a 15-minute stabilization period, all hearts underwent 20 minutes of global ischemia following 20 minutes of reperfusion. At times t0 (control), t5, t10, t15, and t20 (0, 5, 10, 15, and 20 minutes of reperfusion, respectively), we recorded the heart rate, coronary flow, systolic pressure, +(dP/dt)max (maximum speed of increase in the left ventricular pressure), and -(dP/dt)max (maximum speed of decrease in the left ventricular pressure). Data were analyzed by a 1-way analysis of variance, followed by the Tukey test; a P value <.05 was considered statistically significant.


RESULTS
There were no significant differences among the analyzed groups with respect to heart rate, coronary flow, systolic pressure, and -(dP/dt)max (P > .05); however, statistically significant differences in +(dP/dt)max between GII and GI and between GII and GIII occurred at t20 (GI, 1409.0 +/- 415.1 mm Hg/s; GII, 1917.3 +/- 403.0 mm Hg/s; GIII, 1344.8 +/- 355.8 mm Hg/s) (GII versus GI, P = .04; GII versus GIII, P = .02).


CONCLUSIONS
Ischemic postconditioning with three 10-second cycles of reperfusion/reocclusion was demonstrated effective for preserving +(dP/dt)max in isolated rat hearts that underwent 20 minutes of ischemia following 20 minutes of reperfusion.
Department of Cardiovascular Surgery, Clinicord, Goiânia, Brazil. bruno.pinheiro@sbccv.org.br
Bruno Botelho
BB
Pinheiro
Alfredo Inácio
AI
Fiorelli
Otoni Moreira
OM
Gomes
Borut
B
Gersak
D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D008297:Male; D017202:Myocardial Ischemia / Q000150:complications / Q000503:physiopathology* / Q000628:therapy*; D015425:Myocardial Reperfusion / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*