Exercise Renography in Untreated Subjects with Essential Hypertension

Exercise induced renal dysfunction is reported to occur in treated hypertensive patients but not seen normotensive subjects. It is unclear if this phenomenon is related to the disease or to treatment. Methods: Four normal volunteers and 15 hypertensive subjects (antihypertensive medications were discontinued for more than 4 wk) were studied with upright radionuclide renography at rest and during bicycle exercise. The amount of exercise was sufficient to increase the heart rate at least 20 bpm above the resting value. All subjects were healthy, without evidence of left ventricular hypertrophy renal disease or hypertensive retinal disease. BUN, serum creatinine concentration and urinalysis were normal in all subjects. Renograms were performed for 12-15 min after injection of either 1 mCi [¹²³|]orthoiodohippurate (OIH) or 2-7 mCi ^99mTc-mercaptoacetyltriglycine (MAG3). Visual analysis and mean transit time calculation were performed on the rest and exercise studies. Results: Seven of 14 hypertensive subjects and none of the normal volunteers demonstrated abnormal prolongation in renal transit during exercise which was not seen on the resting renogram. Four of these seven subjects had a history of hypertension for 2 yr or less. Conclusion: About 50% of individuals with mild-to-moderate hypertension and normal renal function may have abnormal renal transit of renal excretion agents during exercise, although their baseline studies are normal. This finding is unassociated with therapy and appears to be related directly to the pathophysiology of essential hypertension.