Orthostatic hypotension and complaints: not a clear-cut relation

Previous research regarding the association between blood pressure (BP) fall and symptoms yielded inconsistent results in classical orthostatic hypotension (cOH), with some studies proposing specific cut-off values and others reporting only weak or absent correlations. This study examined clinical cOH symptoms in relation to changes in BP and the haemodynamic parameters determining BP.

We retrospectively analysed 77 tilt test records showing cOH and selected 40 with and 37 without complaint recognition during the test. We compared absolute values of haemodynamic parameters as well as the differences and ratios compared to supine baseline at three different times during tilt. We also explored relationships between relative haemodynamic changes and symptoms with the log-ratio method.

There was a larger blood pressure fall in the group with complaint recognition compared (49.2 vs 37.3, p = 0.043). The log-ratio analysis showed less total peripheral resistance increase and a larger blood pressure decrease in the symptomatic group.

Recognised complaints were related to a larger BP fall, while in previous studies complaints were either not related to BP or to minimum BP. These contrasts suggest that the pathophysiology of orthostatic complaints is complex. The chain of events from low BP to awareness of complaints contains multiple links, of which cerebral perfusion is probably a critical one. We suggest that the pathway contains so much variability that we should not expect the relation between low blood pressure and complaints in cOH to be simple.