Modulation of Left Ventricular Diastolic Filling During Exercise in Persons with Cervical Motor Incomplete Spinal Cord Injury
Authors: Aldhahi Monira I , Keyser Randall E , Guccione Andrew , Collins John , Chin Lisa , Woolstenhulme Joshua 
Published: June 2021

Purpose

The impairment of systolic ventricular performance and the risk of cardiovascular diseases have been identified in individuals with different levels of spinal cord injury (SCI). Despite the high prevalence of cardiovascular disease among patients with SCI, limited progress has been made in understanding the pathophysiology of left ventricular (LV) hypokinesia. In particular, little is known about the underlying effects of a higher cervical spinal cord injury on ventricular filling and the cardiac loading impairment that could be precipitated. Therefore, the purpose of the study is to characterize LV diastolic function during exercise in adults with incomplete cervical (C5–C7) SCI.

Methods

In this cross‐sectional study, LV diastolic performance was examined using bioimpedance cardiography (ZCG). A convenience sample of 2 groups participated in the study: 8 males with incomplete cervical spinal cord injury (icSCI: age 39 ± 14 years; BMI 22.70 ± 2.46 kg.m−2) and lesions at levels ranging from C5–7, and 8 non‐injured male controls (CON: age 38 ± 13 years; BMI 24.48 ± 1.60 kg.m−2). The exercise protocol included a 3‐minute unloaded warm‐up and a stepwise increase in resistance of 5–10 Watts·min−1 until volitional exhaustion. The left ventricle diastolic indices including cardiac end‐diastolic volume (EDV), and early diastolic filling ratio (EDFR); thus, left ventricular ejection time (LVET) and stroke volume (SV) were compared between the group relative to % of peak oxygen consumption (VO2%). Analysis of covariance (ANCOVA) was used to determine the significant group differences in diastolic filling measures while controlling for the heart rate (HR) and cardiac inotropicity (dZ/dT2).

Results

Peak workload (CON 60 ± 5 Watts vs icSCI 29 ± 10 Watts, p = 0.001) and peak VO2 (CON 19.15 ± 3.38 ml/kg/min vs. icSCI 11.15 ± 4.03 ml/kg/min, p = 0.008) were significantly higher in CON than icSCI. The observed decline in EDV was evident during exercise in icSCI compared to CON (EDVpeak:131.4 ± 7.3 vs. 188.78 ± 9.4, p < 0.001). In icSCI, the EDFR was significantly lower than CON at peak VO2 (73.23 ± 14% vs. 118.5 ± 11 %, p = 0.006). LV filling during exercise was blunted at 50% of peak VO2. There was no significant difference in the LVET between the groups. Left ventricular stroke volume (SV), which is exactly equal to venous return per cardiac cycle, was significantly lower at peak exercise in icSCI vs. CON (77.1 ± 6.05 mL vs. 108.8 ± 7.10 mL, P < 0.000).

Conclusion

The subjects with icSCI in this study had reduced LV preload and decreased LV filling compared to healthy subjects without SCI. Decreased diastolic filling dynamics occurred with observed declines in venous return and cardiac stroke volume. Overall, these findings support the premise that active venous muscle pump is an essential mechanism for increasing the preloading condition and rapid early diastolic filling during exercise.

Illustration of left ventricular diastolic response to exercise for the icSCI and controls. *p‐value for comparison obtained form ANCOVA.

image

Illustration of left ventricular diastolic response to exercise for the icSCI and controls. *p‐value for comparison obtained form ANCOVA.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.