Hemodynamic Phenotypes of Hypertension Based on Cardiac Output and Systemic Vascular Resistance

Abstract

Background: Blood pressure is a physiologic measure that reflects cardiac output and systemic vascular resistance. Classification by these components could be useful in characterizing subtypes of hypertension, which may have a role in selecting treatment strategies. However, hemodynamic phenotypes of a large, stable, outpatient population with hypertension remain unknown.

Methods: We included 34,238 people with systolic blood pressure of ≥130 mm Hg, who underwent impedance cardiography at 51 sites of iKang Health Checkup Centers throughout China between 2012 and 2018. Hemodynamic parameters measured included stroke volume, stroke volume index, heart rate, cardiac output, cardiac index, systemic vascular resistance, and systemic vascular resistance index. We characterized these by systolic blood pressure categories and assessed patient characteristics associated with the ratio of cardiac index to systemic vascular resistance index.

Results: Among the study cohort (n = 33,414; mean age 52 ± 13 years; 36.6% female), 49%, 40%, and 11% had systolic blood pressure130-139, 140-159, and ≥160 mm Hg, respectively. Among patients with systolic blood pressure 140-159 mm Hg, 9353 (70%) had high systemic vascular resistance index but normal/low cardiac index, 1949 (15%) had high cardiac index but low/normal systemic vascular resistance index, and 2053 (15%) had low/normal cardiac index and systemic vascular resistance index. Using multivariable analysis, we found that cardiac index to systemic vascular resistance index ratio was negatively associated with age and body mass index (all P <0.05; R-square 0.16, 0.12, and 0.09 for systolic blood pressure 130-139, 140-159 and ≥160 mm Hg, respectively).

Conclusions: Different hemodynamic blood pressure phenotypes were identified across all hypertensive blood pressure categories. Although individual characteristics were associated with the cardiac index to systemic vascular resistance index ratio, they only weakly explained the variation.

Keywords: Cardiac output; Hemodynamics; Hypertension; Impedance cardiography; Vascular resistance.