Blood pressure (BP) is centrally regulated by baroreflex mechanism where a change in BP would provoke vagal and sympathetic responses to counteract the moment by moment perturbations in BP. This study investigated the integrity of central regulation of BP in patients with hypertension (HTN) in response to known and standard autonomic tests.
Beat-by-beat measurement of arterial BPs (mmHg);systolic, diastolic and mean (M), heart rate (HR) (beats/min) and indices of brainstem responses; cardiac vagal tone (CVT; arbitrary units) and cardiac sensitivity to baroreflex (CSB; ms/mmHg) were continuously monitored and recorded using the Neuroscope system (Medifit instruments Ltd, UK). Statistical analysis was performed using two tail student’s t test.
The study included total of 23 subjects; 12 hypertensive males (mean±SD; 45±14.4 years) and 11 (3 females, 8 males) controls (35.6±9.7 y). Their age difference was not significant. The table describes the cardiovascular and brainstem responses during: baseline, supine, before and to the following autonomic tests: deep breathing (DB), sitting up, standing up, isometric handgrip (IHG) and phase IIe of valsalva’s maneouvre (Val-IIe), in addition to P values for control subjects.
In conclusion, brainstem mechanism is intact in patients with HTN, however, there were variable responses during deep breathing and sitting up tests. The baseline measurement showed improper BP control and hence continuous measurement showed more reliability than office discrete readings to ensure effective BP monitoring. The adjustment of brainstem responses to antihypertensive therapy is suggested to be used as an index to monitor treatment effect.