Female-specific echocardiography-derived cardiac responses to the cold pressor test

We previously demonstrated heterogeneous vascular resistance (VR) responses to the cold pressor test (CPT) in females. Since cardiac output (CO) is a key determinant of the pressor response, we prospectively examined cardiac contributions to the CPT, hypothesizing that females would exhibit heterogeneous cardiac and vascular responses to the CPT. Nineteen healthy females (24 ± 3 yr, body mass index 22.9 ± 1.9 kg/m²) and a comparator group of nine males (23 ± 3 yr, 24.8 ± 1.6 kg/m²) completed a 3-min CPT including continuous measurements of mean arterial pressure (MAP; finger photoplethysmography), CO [stroke volume (SV) (echocardiogram) heart rate (HR) (3-lead electrocardiogram)], and femoral VR [FVR; MAP/femoral blood flow (duplex ultrasound)]. The magnitudes of CPT-induced changes (D) in MAP (P ¼ 0.96), HR (P ¼ 0.59), CO (P ¼ 0.09), and %FVR (P ¼ 0.46) were not different between sexes; DSV was smaller in females (1.0 ± 5.0 vs. 5.0 ± 3.0 mL, P ¼ 0.03). DSV responses were distinctly heterogeneous in female participants; females demonstrating positive DSV (SV_INC; n ¼ 10) and negative DSV (SV_DEC; n ¼ 9) were subdivided for subsequent analyses. SV_INC had higher DSV (5.0 ± 3.0 vs. 3.0 ± 2.0 mL; P < 0.001; by design) and DCO (1.11 ± 0.48 vs. 0.47 ± 0.43 L/min; P ¼ 0.01) but lower Dtotal peripheral resistance (TPR) (median: 2 [interquartile range (IQR): 3] vs. 1 [2] mmHg/L/min; P ¼ 0.008). %FVR (P ¼ 0.87), DHR (P ¼ 0.13), and DMAP (P ¼ 0.85) did not differ between subgroups. Among all females, DSV was positively associated with DCO and negatively associated with DTPR but not DFVR, DHR, or DMAP, indicating that heterogeneous SV responses in females may be offset by systemic vascular resistance responses and do not impact the overall magnitude of the pressor response to the CPT.