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- Open Access
Designing pulmonary arterial hypertension trials for detecting change in right ventricular function using cardiovascular magnetic resonance: what is the appropriate sample size?
© Addetia et al; licensee BioMed Central Ltd. 2013
- Published: 30 January 2013
- Right Ventricular
- Cardiovascular Magnetic Resonance
- Pulmonary Arterial Hypertension
- Right Ventricular Function
- Pulmonary Arterial Hypertension Patient
Right ventricular (RV) failure is a major complication of pulmonary arterial hypertension (PAH). Cardiovascular magnetic resonance (CMR) can accurately quantify RV volume and function. Short-term changes in CMR measurements of RV size and function in PAH patients on individualized therapy have not been extensively studied; therefore, the required sample size for detecting a certain change in RV size and function in response to therapy is unknown. This study was designed to (1) assess changes in RV size and function in patients on individualized PAH treatment, and (2) to estimate sample sizes needed to detect a change in RV function in future PAH drug trials without discontinuing standard therapy.
Nineteen patients with category I PAH were prospectively recruited. Patients were imaged using a 1.5-T scanner at baseline and after 6 months. Retrospectively gated steady-state free precession short axis cines were used to measure RV end-diastolic volume index (RVEDVI) and ejection fraction (EF) by Simpson's method of disks. Both sets of CMR data were analyzed by 2 independent observers, whose measurements were averaged. Paired, 2-sided t-tests were performed to compare end-diastolic volumes and EFs at baseline and follow up. Sample size calculations to detect changes in RVEDVI and EF over time were performed using Stata software.
Age (years): average ±SD (range) % Female Body surface area(m2): average ±SD
52±11 (28-67) 95% 1.8±0.2
WHO functional class
I (%) II (%) III (%) Unknown (%)
32% 37% 26% 5%
Past medical history
None Hypothyroidism Atrial fibrillation Other (hypertension, stroke, asthma)
10 (53%) 6 (32%) 1 (5%) 5 (26%)
Etiology of pulmonary hypertension
Idiopathic Congenital Connective tissue disease/scleroderma Other (HIV, anorexigen use)
7 (37%) 4 (21%) 3 (16%) 5 (26%)
Therapy for pulmonary hypertension
No therapy Single-therapy Multi-therapy (2 or more agents)
2 (11%) 6 (32%) 11 (58%)
Baseline right ventricular size and function measurements (means)
RVEF (%) RVEDVI (ml/m2) RVESVI (ml/m2)
35±12 136±41 91±38
CMR can be used to detect the effects of new PAH therapies on RV volume and function with relatively small groups of patients.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.