High and low renin subgroups of essential hypertension: differences and similarities in their renin and sympathetic responses to neural and nonneural stimuli

Plasma renin activity in the emergency department and its independent association with acute myocardial infarction

Elevated plasma renin activity (PRA) is associated with increased risk of future myocardial infarction (MI) in ambulatory hypertensive patients. The present study evaluated the relationship of PRA to the diagnosis of acute MI in patients presenting to an emergency department with suspected acute MI. PRA was measured upon entry to the emergency department, before any acute treatment, as part of the standard evaluation of 349 consecutive patients who were hospitalized for suspected MI. Diagnosis of acute MI was confirmed in 73 patients, and ruled out in 276. They did not differ in age (65.9 +/- 2 v 66.1 +/- 1 years), systolic (143 +/- 4 v 140 +/- 2 mm Hg), or diastolic (81 +/- 2 v 81 +/- 1 mm Hg) pressures. Median PRA was 2.7-fold higher in acute MI (0.89 v 0.33 ng/L/s; P < .001). In a multivariate analysis controlling for other cardiac risk factors and prior drug therapy, PRA as a continuous variable was the predominant independent factor associated with acute MI (P < .0001), followed by white race (P = .002) and history of hypertension (P = .047). The height of the PRA level upon entry to the emergency department was directly and independently associated with the diagnosis of acute MI. These new findings extend earlier reports because they encompass acute MI patients, include both hypertensive and normotensive patients, and control for potentially confounding variables. Based on these observations, a randomized clinical trial is warranted to determine whether measurement of PRA in acute MI could refine the process by which treatments are applied.

Supine and standing plasma catecholamines in essential hypertensive patients with different renin levels

In this study we measured plasma renin activity (PRA), plasma norepinephrine (NE) and epinephrine (E), heart rate (HR) and blood pressure (BP) in 89 supine (sup) essential hypertensive patients (pts), WHO I-II, after 3-5 days of fixed normal sodium and potassium intake; the same measurements were repeated after 30' of active standing (stand) in 44/89 pts. In the whole population NE was directly related to PRA, both in sup and in stand position (p less than 0.01). NE was above the upper limits of normotensive controls in 2/34 (6%) pts with low PRA, in 6/40 (17%) pts with normal PRA and in 6/15 (40%) pts with high PRA. In respect to normal PRA pts, HR was significantly lower in low PRA pts and higher in high PRA pts, both in sup and in stand position (p less than 0.05). Sup and stand NE and E were similar in low and normal PRA pts, while they were significantly higher in high PRA pts (p less than 0.05). These results suggest an increased adrenergic tone at least in some high PRA pts, and blunted responsiveness of renal and cardiac beta adrenergic receptors to adrenergic stimuli in low PRA pts.