The effect of blood volume and volume loading on left ventricular diastolic function in individuals with spinal cord injury
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STUDY DESIGN: Cohort Study (Prospective Observational Study). OBJECTIVES: The objectives of the study were (i) to examine left ventricular (LV) diastolic function at rest and during rapid saline infusion in those with spinal cord injury (SCI) and (ii) to determine the contribution of blood volume on the purported diastolic impairments in individuals with SCI. SETTINGS: St Catharines, ON, Canada. METHODS: Thirteen SCI (AIS:A-D; C4-T6; age: 41±8.5; 10 males, 3 females) and 12 able-bodied (AB) individuals (age: 40±8.5; 9 males, 3 females) without a history of cardiovascular disease participated in the study. LV structure and diastolic function were assessed via conventional echocardiography. The carbon monoxide rebreathe test was used to measure the blood volume. LV diastolic function was assessed once more following rapid saline infusion (dose: 15 ml kg-1; rate: 100 ml min-1). RESULTS: Compared with the AB group, individuals with SCI had a smaller LV internal diameter (SCI: 4.5±0.3 cm vs AB: 5.1±0.7 cm; P=0.01), lower blood volume (SCI: 3.9±0.6 l vs AB: 5.0±1.2 l; P=0.02) and end-diastolic volume (SCI: 97.2±29.4 ml vs AB: 128.6±38.3 ml; P=0.03). There were no between-group differences in baseline diastolic parameters; however, when LV internal diameter was adjusted for individuals with SCI demonstrated lower early to late transmitral velocity ratio (SCI: 1.9±0.5 vs AB: 2.2±0.7; P=0.03). There was no between-group difference in diastolic responses to the saline infusion, as both groups showed similar diastolic changes following volume loading. CONCLUSION: Individuals with SCI have preserved LV diastolic function despite having lower preload. Preserved diastolic function may be mediated by the cardiac atrophy that occurs following SCI. Individuals with SCI also demonstrate normal diastolic responses to increased volume loading, suggesting compliant ventricles.
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