Haemodynamic determinants of supine hypertension in patients with classical orthostatic hypotension

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Function
• Hypertension Research

Background:

• The interplay between supine hypertension and classical orthostatic hypotension (cOH) remains poorly understood.
• Investigating the determinants of blood pressure regulation in individuals with cOH is crucial for understanding cardiovascular pathophysiology.

Purpose of the Study:

• To elucidate the relationship between classical orthostatic hypotension (cOH) and supine hypertension.
• To determine the relative contributions of heart rate (HR), stroke volume (SV), and total peripheral resistance (TPR) to supine and upright blood pressure (BP).

Main Methods:

• Retrospective analysis of tilt tests in normotensive controls, hypertensive controls, and cOH patients with (cOH/SH+) and without (cOH/SH-) supine hypertension.
• Linear regression and logratio analysis were employed to assess the contributions of HR, SV, and TPR to BP regulation.
• Hypertension defined as supine systolic blood pressure (SBP) ≥ 140 mmHg; P < 0.003 considered significant.

Main Results:

• High supine SBP was consistently associated with elevated TPR in both patients and controls.
• Orthostatic SBP decrease was more pronounced in cOH patients with higher supine SBP, primarily due to a failure of TPR to increase upon standing in the cOH/SH+ group.
• Stroke volume (SV) contributed less to orthostatic BP changes in cOH/SH- compared to cOH/SH+, while heart rate (HR) contributions were similar across cOH groups.

Conclusions:

• Elevated supine TPR is a key factor in supine hypertension within cOH patients.
• The inability to adequately increase upright TPR significantly contributes to the orthostatic blood pressure fall in cOH.
• While autonomic failure explains the BP drop, the persistent high supine TPR suggests a role for slow-acting vasoconstrictors in maintaining supine hypertension.