[MRI for therapy control in patients with tetralogy of Fallot]

Volumetric measurements in patients with corrected tetralogy of Fallot: comparison of short-axis versus axial cardiac MRI and echocardiography

BACKGROUND

Patients with corrected tetralogy of Fallot (cToF) are prone to develop pulmonary regurgitation and right ventricular enlargement resulting in long-term complications, thus correct right ventricular volumetric monitoring is crucial. However, it remains controversial which cardiovascular magnetic resonance imaging (CMRI) slice orientation is most appropriate in cToF for the analysis of the right ventricular volume.

PURPOSE

To investigate which slice orientation is most suited for right ventricular volumetry in cToF we compared short-axis and axial slices, and furthermore we compared right ventricular data between CMRI and echocardiography.

MATERIAL AND METHODS

Thirty CMRI examinations of 27 patients with cToF were included retrospectively. Right ventricular end-diastolic (EDV) and end-systolic volume (ESV) were derived from short-axis and axial cine CMRI planes. Furthermore, pulmonary trunk forward flow in phase-contrast CMRI and right ventricular inner diastolic diameter in echocardiography (R VIDdiast) were measured. By Bland-Altman and variance analysis intra- and inter-observer agreement were assessed for cine CMRI data. By Pearson correlation CMRI cine and phase-contrast data and CMRI cine and echocardiographic data were compared.

RESULTS

Intra- and inter-observer variability for right ventricular EDV were significantly lower in axial slices (P = 0.016, P = 0.010). For right ventricular ESV a trend towards a lower intra- and inter-observer variability in axial slices was found (P = 0.063, P = 0.138). Right ventricular stroke volume in short-axis (r = 0.872, P < 0.001) and in axial (r = 0.914, P < 0.001) planes correlated highly, respectively very highly with pulmonary trunk forward flow in phase-contrast CMRI. R VIDdiast correlated highly with right ventricular EDV assessed by short-axis and axial CMRI (P < 0.001, P < 0.001).

CONCLUSION

Due to lower intra- and inter-observer variability, axial slices are recommended for right ventricular volumetry in cToF.

[Minimally invasive pulmonary valve replacement in pediatric patients: importance of imaging]

CLINICAL/METHODICAL ISSUE

Right ventricular outflow tract (RVOT) dysfunction with pulmonary regurgitation or obstruction is a common postsurgical consequence in congenital heart disease.

STANDARD RADIOLOGICAL METHODS

Magnetic resonance imaging (MRI) is widely accepted as standard method of imaging in congenital heart disease. It provides anatomical and functional information without radiation exposure and is therefore well suited for serial examinations.

METHODICAL INNOVATIONS

Percutaneous pulmonary valve implantation (PPVI) has been shown to be a safe and effective treatment option for patients with pulmonary valve insufficiency or stenosis. Correct patient selection for PPVI is crucial. It is important to be familiar with the indications and anatomical requirements for stent placement and to tailor imaging protocols.

PERFORMANCE

Imaging the RVOT, assessment of right ventricular volumes and function and calculation of pulmonary flow and regurgitation are core elements of the MRI examination prior to PPVI. Low interobserver and intraobserver variation allows even small changes to be detected.

ACHIEVEMENTS

Imaging provides relevant information for correct patient selection for PPVI and is part of postinterventional follow-up. Imaging is an important tool for documentation of success and for detection of complications.

PRACTICAL RECOMMENDATIONS

Several imaging modalities are used for evaluation of RVOTs; however, MRI can provide answers to most questions without radiation exposure.