Cardiovascular responses to physical exercise and tyramine infusion in hypertensive and normotensive subjects

The aim of our investigation was to assess blood pressure and heart rate variations in 20 essential hypertensive male in-patients (WHO class I and II) and in 20 normotensive healthy volunteers submitted to three provocation tests: isometric handgrip (IHG), bicycle ergometric exercise (BEE) and tyramine infusion (TI) given as i.v. boluses alternating with saline in a single-blind fashion. According to our data IHG induced a comparable rise of systolic BP, diastolic BP and heart rate both in hypertensive and normotensive subjects. BEE, compared with IHG, caused a more significant (P less than 0.01) rise in SBP and heart rate in both groups. By contrast, DBP during BEE was significantly increased in hypertensive (P less than 0.01), but slightly decreased in normotensive subjects (P = NS). TI caused a dose dependent SBP rise in both groups studied, while DBP and HR were unaffected. BP elevation was, however, more marked in hypertensive subjects. Confirming this finding significantly lower tyramine doses were required to produce the same SBP increase in hypertensives than in the normotensive volunteers. In short, SBP rise during TI and DBP rise during BEE may be the markers of an enhanced cardiovascular reactivity of hypertensive subjects. Our study suggests that BP reactivity to stress may be different according to the laboratory stress employed and also that BEE and TI are more useful than IHG for the assessment of an enhanced cardiovascular response to stress in hypertensive subjects.