Refining the assessment of pulmonary regurgitation in adults after tetralogy of Fallot repair: should we be measuring regurgitant fraction or regurgitant volume?

CLINICAL RESEARCH European Heart Journal (2009) 30, 356–361 doi:10.1093/eurheartj/ehn595 Valvular and congenital heart disease Refining the assessment of pulmonary regurgitation in adults after tetralogy of Fallot repair: should we be measuring regurgitant fraction or regurgitant volume? 1 Department of Cardiology, Toronto Congenital Cardiac Centre for Adults, Peter Munk Cardiac Centre, University Health Network, Toronto General Hospital, North Wing, 5N-517, 585 University Avenue, Toronto, Ontario, Canada M5G 2C4; and 2Department of Medical Imaging, Toronto Congenital Cardiac Centre for Adults, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada Received 26 February 2008; revised 6 November 2008; accepted 17 December 2008; online publish-ahead-of-print 22 January 2009 Aims Pulmonary regurgitation (PR) is an important determinant of outcome after tetralogy of Fallot (TOF) repair. The physiologic impact of PR on the right ventricle remains incompletely understood. We hypothesized that a volumetric expression of PR would be a better measure of ventricular preload and a more accurate reflection of degree of insufficiency. ..................................................................................................................................................................................... Methods Patients (n ¼ 64) with magnetic resonance imaging after TOF repair were identified. PR was quantified using: (i) phase contrast (PC) analysis of main pulmonary artery flow and (ii) differential right and left ventricular stroke volumes. PR and results was expressed as a volume (PRvolume) and percentage of total forward flow (PRfraction). The median PCPR volume was 19 mL/m2 (range 0–63 mL/m2) and PCPR fraction was 29% (range 0–58%). PRfraction was found to be highly variable in terms of absolute PRvolume. In those with significant PR, PRvolume was better than PRfraction for the identification of severe RV dilation (receiver-operator curve area: 0.83 vs. 0.71, P ¼ 0.003). PRvolume using PC analysis was better at differentiating moderate from severe RV dilation (P ¼ 0.005) as compared with PRfraction (P ¼ 0.064). ..................................................................................................................................................................................... Conclusion PRvolume and PRfraction are not interchangeable. PRvolume may be a more accurate reflection of RV preload and may better represent physiologically significant PR as compared with PRfraction. ----------------------------------------------------------------------------------------------------------------------------------------------------------Keywords MRI † Tetralogy of Fallot † Pulmonary regurgitation Introduction Pulmonary regurgitation (PR) is now recognized as an important determinant of late outcome after tetralogy of Fallot (TOF) repair.1 A common finding after right ventricular (RV) outflow tract surgery, pulmonary insufficiency may result in a cascade of haemodynamic sequelae that can include RV dilation, RV dysfunction, and ultimate deterioration in clinical status.2 Impaired exercise tolerance, ventricular arrhythmia, and sudden death have all been associated with the secondary effects of chronic PR.1,3 – 5 With the growing population of adult patients with TOF who have residual PR, determining the optimal method of PR assessment is of increasing importance. Owing to the accuracy and reproducibility of its measurements, cardiac magnetic resonance (CMR) imaging is accepted as the imaging modality of choice for the quantification of PR and assessment of RV size and systolic function.6 – 8 For these reasons, CMR evaluation is recommended during the routine follow-up of patients after TOF repair.8,9 However, despite the importance of PR in this population, PR measurement and the assessment of its physiological impact remain incompletely understood. The expression of the * Corresponding author. Tel: þ1 416 340 5502, Fax: þ1 416 340 5014, Email: Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2009. For permissions please email: . Rachel M. Wald 1*, Andrew N. Redington 1, Andre Pereira2, Yves L. Provost 2, Narinder S. Paul 2, Erwin N. Oechslin 1, and Candice K. Silversides1 357 Refining the assessment of PR in adults after TOF repair regurgitant burden as a fraction of forward pulmonary flow is commonplace and is beginning to form the basis of recommendations for treatment. Because PR fraction (PRfraction) may be highly variable in terms of absolute volumes (PRvolume), we speculated that a volumetric measurement of PR may be a better measure of ventricular preload and therefore the more accurate measure of the degree of insufficiency. We therefore sought to evaluate the optimal method of PR quantification in patients after repair of TOF. Methods Subjects Patient data Clinical data were retrospectively abstracted from hospital medical records including date of birth, gender, anatomic diagnoses, age and type of each surgical procedure, and age at CMR evaluation. Transthoracic echocardiographic data within 1 year of the CMR study were reviewed, particularly for assessment of valvular regurgitation and identification of residual shunt lesions, and the results were recorded. Statistical analysis Data analyses were performed using SPSS statistical software (Version 11.5, 2002). Descriptive data were expressed as medians with interquartile ranges (IQRs), unless otherwise specified. Mann– Whitney and x2 tests were used to compare groups, as appropriate. Comparisons of PRvolume or PRfraction between patients with mild, moderate, and severe RV dilation were performed using the Kruskal – Wallis test. Correlations were examined using the Spearman correlation co-efficient. Statistical significance was set at a P-value ,0.05 (twosided). In the subset of patients with significant PR (at least moderate insufficiency defined as regurgitation fraction 20%), receiveroperator curves (ROC) were constructed to examine the ability of the differing expressions of PR (PRvolume and PRfraction) as well as differing techniques for PR quantification (PC vs. SV differentials) to detect significant RV dilation, defined as indexed RV end-diastolic volume (RVEDVi) 170 mL/m2. This cut-point was used because prior studies from our centre and others have suggested that RVEDVi . 160 – 170 mL/m2 may be an appropriate threshold whereby pulmonary valve replacement should be considered in the presence of significant PR in the asymptomatic patient with repaired TOF.11,15,16 Agreement between methods for PR quantification (PC vs. SV differentials) and intra- and inter-observer variabilities were evaluated using intra-class correlation co-efficients. Cardiac magnetic resonance The CMR protocols and technical aquisition parameters utilized at our institution for the evaluation of global ventricular systolic function, ve (...truncated)