P194: Cardiovascular Responses to Increased Pressure During Healthy Pregnancy

Abstract

A long-standing question is whether pregnant females, who bear an increased biological stress, experience exacerbated cardiovascular responses during physiological challenge. At rest, pregnant females have reduced blood pressure, increased cardiac output, heart rate and stroke volume (1), with reported reductions in cardiac contraction and relaxation (2). Increased cardiac work may potentially exasperate impairments in function observed at rest. The aim of this study was to investigate the cardiovascular responses to an isolated increase in pressure in healthy nulliparous non-pregnant, primiparous pregnant (22–26 weeks gestation; n = 14) and primiparous postpartum (12–16 weeks after delivery; n = 13) females.

The pressure challenge was elicited through a sustained isometric hold for approximately 5 minutes at 30% of maximum using an externally loaded handgrip dynamometer. Echocardiographic images were collected to measure cardiac volumes and mechanics. Blood pressure was monitored continuously using finger photoplethysmography. Analyses of covariance, with baseline measures as covariate, were completed to determine differences between groups (P = <0.05). Post hoc analyses were performed with a Bonferroni adjustment.

There were no significant differences between groups in cardiac volumes or blood pressure during the challenge however; pregnant females had a greater heart rate (68 ± 2 versus 62 ± 2 beats min⁻¹) and longitudinal strain (−20.6 ± 1.0% versus −17.1 ± 0.7%) than non-pregnant females.

Increased longitudinal strain and heart rate are likely result of increased contractility mediated by greater myocardial sympathetic innervation (3). In healthy pregnant females, increased pressure does not result in impaired cardiovascular function, however dysfunctional responses may predict hypertensive disorders of pregnancy.