Systolic blood pressure does not reliably identify vasoactive status in chronic heart failure

Background In chronic heart failure (CHF), titration of vasodilating medications is often guided by monitoring of systolic blood pressure (BP). However, systolic BP may not indicate the patient’s true vasoactive status—best approximated by systemic vascular resistance—because cardiac output is also a contributing factor. Impedance cardiography (ICG) is a validated noninvasive method of measuring cardiac output and systemic vascular resistance. Methods To evaluate the relationship between systolic BP and systemic vascular resistance index (SVRI) in patients with CHF, we retrospectively evaluated the systolic BP and SVRI from 71 consecutive patients during 615 CHF clinic visits. Measurement of systolic BP was through the oscillometric method and SVRI through ICG (BioZ ICG Monitor, CardioDynamics, San Diego, CA). Absolute values and relative changes in systolic BP and SVRI were compared and characterized by systolic BP grouping. Results The 71 patients were an average of 69.3 ± 12.2 years, New York Heart Association functional class 2.52 ± 0.6, 46.5% men, and 47.8% ischemic etiology. Frequency by systolic BP grouping was: <100 mm Hg in 67 subjects (10.9%), 100 to 119 mm Hg in 245 subjects (39.8%), and ≥120 mm Hg in 303 subjects (49.3%). The correlation (R2 value) of systolic BP to SVRI was 0.21 (N = 615), and change in systolic BP to change in SVRI from previous visit was 0.27 (N = 547). In 138 visits in which systolic BP did not change by 5 mm Hg or more, SVRI changed by 20% or more in 41 (29.7%). In the 67 visits in which systolic BP was below 100, only 6 (9.0%) had low SVRI and 57 (85.1%) had normal SVRI. In the 245 visits with systolic BP 100 to 119, 58 (23.7%) had high SVRI. Conclusions Measurement of systolic BP alone does not reliably indicate the degree of vasoconstriction or vasodilation that exists in patients with CHF. Measurement of SVRI by ICG may help guide determination of need and tolerance for vasodilating medications in CHF.