Relationship Between Left Ventricular Ejection Fraction Variation and Systemic Vascular Resistance: A Prospective Cardiovascular Magnetic Resonance Study

Abstract

Introduction: This cardiovascular magnetic resonance (CMR) study aims to determine whether changes in systemic vascular resistance (SVR), obtained from CMR flow sequences, might explain the significant long-term changes in left ventricular (LV) ejection fraction (EF) observed in subjects with no cardiac disease history. Methods: Cohort subjects without any known cardiac disease but with high rates of hypertension and obesity, underwent CMR with phase-contrast sequences both at baseline and at a median follow-up of 5.2 years. Longitudinal changes in EF were analyzed for any concomitant changes in blood pressure and vascular function, notably the indexed SVR given by the formula: mean brachial blood pressure / cardiac output x body surface area. Results: A total of 118 subjects (53 ± 12 years, 52% women) were included, 26% had hypertension, and 52% were obese. Eighteen (15%) had significant EF variations between baseline and follow-up (7 increased EF and 11 decreased EF). Longitudinal changes in EF were inversely related to concomitant changes in mean and diastolic blood pressures (p = 0.030 and p = 0.027, respectively) and much more significantly to SVR (p < 0.001). On average, these SVR changes were -8.08 ± 9.21 and +8.14 ± 8.28 mmHg.min.m2.L-1, respectively, in subjects with significant increases and decreases in EF, and 3.32 ± 7.53 mmHg.min.m2.L-1 in subjects with a stable EF (overall p < 0.001). Conclusions: Significant EF variations are not uncommon during the long-term CMR follow-up of populations with no evident health issues except for uncomplicated hypertension and obesity. However, most of these variations are linked to SVR changes and may therefore be unrelated to any intrinsic change in LV contractility. This underscores the benefits of specifically assessing LV afterload when EF is monitored in populations at risk of vascular dysfunction. Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT01716819 and NCT02430805.

Keywords: cardiovascular magnetic resonance; ejection fraction; flow-encoding sequence; hypertension; obesity; systemic vascular resistance.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2021 Mandry, Girerd, Lamiral, Huttin, Filippetti, Micard, Beaumont, Ncho Mottoh, Pace, Zannad, Rossignol and Marie.

Figures

Figure 1

Correlations between baseline-to-follow-up differences in: (i) left ventricular ejection fraction (EF changes) and (ii) systemic vascular resistance (SVR changes). It may additionally be observed that many EF changes are outside of the −8% to +8% interval (red dashed lines) and may thus be considered significant.

Figure 2

Mean values (±SD) for baseline (black columns) and follow-up (white columns) levels of systemic vascular resistance (SVR, upper panel) and for the mean difference in SVR between baseline and follow-up (gray columns, median panel) in subjects categorized in 3 groups based on baseline-to-follow-up variations in LV ejection fraction -i.e., significant decrease (EF↓), significant increase (EF↑) and stable EF (EF→). *p < 0.05 for paired comparisons between baseline and 6 months.

Figure 3

Graph of the correlation between EF-changes and SVR-changes with the regressions computed with the equation from Table 3 for three baseline EF levels: close to the mean (60%), one SD above the mean (66%), and one SD below the mean (54%). The slope of EF- and SVR-changes for the 3 baseline FE levels are identical. However, the intercept corresponding to an absence of any SVR variation are different, with a predicted absolute decrease in EF of ~3% for the 66% EF baseline, an increase of about 3% for the 54% EF baseline and an insignificant predicted change for the 60% EF baseline.