Influência da elevação sustentada da pressão arterial sobre a dP/dt do ventrículo esquerdo mantendo-se constante a pressão diastólica do ventriículo esquerdo / Influence of Sustained Elevations of Arterial Pressure on the Left Ventricular dP/dt Keeping Constant the Left Ventricular end Diastolic Pressure

ABSTRACT

PURPOSE: To evaluate the influence of sustained elevations of arterial pressure on dP/dt values, while the left ventricular end diastolic pressure was kept constant. METHODS: Thirteen anesthetized dogs, mechanically ventilated and submitted to thoracotomy and pharmacological autonomic block (atropine-0.5 mg/kg i.v. + oxprenolol-3 mg/kg i.v.) were studied. The arterial pressure elevation was obtained by mechanical constriction of the descending thoracic aorta. Analyses were made in control (C) situation and after two successive increments of arterial pressure, sustained for 10 min, called hypertension 1 (H1) and hypertension 2 (H2), respectively. The end diastolic left ventricular pressure was kept constant by utilization of a perfusion system connected to the left atria. RESULTS: Heart rate did not change (C 125 +/- 13.9 bpm; H1 125 +/- 13.5 bpm; H2 123 +/- 14.1 bpm; p > 0.05); the LVSP increased (C 119 +/- 8.1 mmHg; H1 142 +/- 7.9 mmHg; H2 166 +/- 7.7 mmHg; p < 0.01); the AoDP increased (C 89 +/- 11.6 mmHg; H1 99 +/- 9.5 mmHg; H2 120 +/- 11.8 mmHg; p < 0.01); the LVEDP (C 6.2 +/- 2.48 mmHg; H1 6.3 +/- 2.43 mmHg; H26.1 +/- 2.51 mmHg; p > 0.05) and the dP/dt (C 3068 +/- 1057.1 mmHg/s; H1 3112 +/- 995.7 mmHg/s; H2 3086 +/- 979.5 mmHg/s; p > 0.05) did not change. CONCLUSION: dP/dt values are not influenced by a sustained elevation of arterial pressure, when the end diastolic left ventricular pressure is kept constant.