HEMODYNAMIC AND NEUROHUMORAL CHANGES IN SPONTANEOUSLY HYPERTENSIVE RATS WITH AORTOCAVAL FISTULAS

1. Our aim was to evaluate the effects of an aortocaval fistula (1 mm) on cardiorenal haemodynamics, cardiac hypertrophy and neurohumoral fa ctors in spontaneously hypertensive rats and to compare the results wi th those observed in Wistar rats at 2 weeks after fistulae placement. Sham-operated spontaneously hypertensive rats and Wistar rats served a s controls. 2. Heart weight was significantly increased in spontaneous ly hypertensive rats (34%) and in Wistar rats (43%) at 2 weeks after f istula creation. Left ventricular systolic pressure and dp/dt(max), we re significantly decreased (both P<0.01) in spontaneously hypertensive rats with fistulae which had higher left ventricular end-diastolic pr essure than Wistar rats with fistulae (P<0.01). Signs of circulatory c ongestion (ascites, tachypnoea, prostration) were observed only in the overloaded spontaneously hypertensive rats (45%). Cardiac index was c omparably increased in both fistulae groups due to an increase in stro ke index, since heart rate was not increased. 3. Fistulae placement de creased renal blood flow and kidney weight, and increased blood urea n itrogen to a greater degree in spontaneously hypertensive rats (all P< 0.05); serum creatinine levels were unaltered. Plasma noradrenaline co ncentration was increased in spontaneously hypertensive rats with fist ulae (P<0.05), whereas plasma renin activity was not changed. 4. Thus, spontaneously hypertensive rats with fistulae developed overt haemody namic signs of high-output heart failure with frequent ascites and dys pnoea, whereas most of these findings were milder or absent in Wistar rats. This model provides an opportunity to evaluate the pathophysiolo gical and pharmacological responses in high-output heart failure.