The rate of force generation by the myocardium is not influenced by afterload
Braz. j. med. biol. res
;
30(12): 1471-7, Dec. 1997. ilus, tab
Article
Dans Anglais
| LILACS
| ID: lil-212594
ABSTRACT
The influence of afterload on the rate of force generation by the myocardium was investigated using two types of preparations the in situ dog heart (dP/dt) and isolated papillary muscle of rats (dT/dt). Thirteen anesthetized, mechanically ventilated and thoracotomized dogs were submitted to pharmacological autonomic blockade (3.0 mg/kg oxprenolol plus 0.5 mg/kg atropine). A reservoir connected to the left atrium permitted the control of left ventricular end-diastolic pressure (LVEDP). A mechanical constriction of the descending thoracic aorta allowed to increase the systolic pressure in two steps of 20 mmHg (conditions H1 and H2) above control values (condition C). After arterial pressure elevations (systolic pressure C 119 + 8.1; H1 142 + 7.9; H2 166 + 7.7 mmHg; P<0.01), there were no significant differences in heart rate (C 125 + 13.9; H1 125 + 13.5; H2 123 + 14.1 bpm; P>0.05) or LVEDP (C6.2 + 2.48; H1 6.3 + 2.43; H2 6.1 + 2.51 mmHg; P>0.05). The values of dP/dt did not change after each elevation of arterial pressure (C3,068 + 1,057; H1 3,112 + 996; H2 3,086 + 980 mmHg/s; P>0.05). In isolated rat papillary muscle, an afterload corresponding to 50 percent and 75 percent of the maximal developed tension did not alter the values of the maximum rate of tension development (100 percent 78 + 13; 75 percent 80 + 13; 50 percent 79 + 11 g mm-2 s-1, P>0.05). The results show that the rise in afterload per se does not cause changes in dP/dt or dT/dt.
Texte intégral:
Disponible
Indice:
LILAS (Amériques)
Sujet Principal:
Muscles papillaires
/
Fonction ventriculaire gauche
/
Contraction myocardique
/
Myocarde
Limites du sujet:
Animaux
langue:
Anglais
Texte intégral:
Braz. j. med. biol. res
Thème du journal:
Biologie
/
Médicament
Année:
1997
Type:
Article
/
descriptif de projet
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