Effects of Preload on Atrial and Ventricular Volumes and Function

Background: Serial assessment with magnetic resonance imaging (MRI) is routinely used for volumetric assessments of cardiac chambers in congenital heart disease (including Tetralogy of Fallot) and cardiomyopathies. While the intraobserver and interobserver reproducibilities of these measurements are established the effects of preload are unknown.

Methods: 13 healthy adult volunteers (7 male, mean age 37 yrs) underwent MRI ventricular volumetry three times in the same setting: A) after an overnight fast, B) after a 10 ml/kg i.v. bolus of normal saline, and C) after a second bolus similar to B). Atrial and ventricular volumes were assessed from a stack of axial cine images. The primary reader was blinded to subject’s identity, age, and gender as well as the volume status (A, B, or C). For intra- and interobserver variability one MRI study from each individual was randomly selected and recontoured by the same and a second reader, respectedly.

Results: The end-diastolic left and right atrial and ventricular volumes increased significantly between A), B), and C). These changes exceeded the inter- and intraobserver variations in the same cohort. Right and left ventricular stroke volumes increased significantly, while ejection fractions remained unchanged.

Conclusions: Atrial and ventricular volumes vary significantly with hydration. In clinical practice, these differences add to the known intraobserver, interobserver, and interstudy variability and must be considered when small changes (<10%) in volumes are observed in the follow-up of patients with congenital and acquired heart disease.