[Influence of afterload on the rate of variation of developed pressure (dT/dt). Study in isolated cardiac muscle].
OBJECTIVE
To evaluate the effects of afterload on peak rate of tension rise (dT/dt) in the isolated muscle.


METHODS
Left ventricular papillary muscles from Wistar rats were studied in isometric and isotonic afterloaded contractions. Muscles were analised in Krebs-Henseleit solution with calcium concentration of 2.52mM at 28 degrees C. The resting muscle length (preload) was maintained constant. The peak isometric developed tension (DT) and dT/dt were measured during increases of afterload (25, 50, 75 and 100% from DT).


RESULTS
A rise in afterload corresponding to 50, 75 and 100% of DT, did not cause an increase in dT/dt values (p > 0.05). The dT/dt value decreased (p < 0.05) when afterload was changed from 75% to 25% of DT.


CONCLUSIONS
The data suggest that an increase in the afterload from 50% of the DT did not promote changes in the dT/dt.
Okoshi
M P
MP
Faculdade de Medicina de Botucatu, Unesp.
Ferreira Tucci
P J
PJ
Okoshi
K
K
Padovani
C R
CR
Cicogna
A C
AC
D000818:Animals; D002302:Cardiac Output / Q000502:physiology*; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D010210:Papillary Muscles / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
Influência da pós-carga sobre a taxa de variação da tensão desenvolvida (dT/dt). Estudo em músculo cardíaco isolado.