Abstract
Cardiac magnetic resonance (CMR) parameters are used to decide optical timing of pulmonary valve replacement (PVR) in repaired tetralogy of Fallot (rTOF). Recently, CMR measured RVEF and RV longitudinal strain (RV-LS) were revealed as predictors of outcome in rTOF. This study explores the changes in RV-LS in relation to CMR volumetric data in rTOF. Retrospective review of CMRs of 33 patients with rTOF with greater than mild pulmonary regurgitation and no pulmonary stenosis (PG < 20 mmHg) were analyzed using in-house semi-automatic tracking software to measure RV-LS, systolic strain rate (RV-LSR), and early diastolic strain rate (RV-LSRe). Indexed volumetric parameters (RVEDV, RVESV, RVEF), regurgitation volume and regurgitation fraction (RF) were collected. Patients who underwent pulmonary valve replacement (PVR, n=17) were compared to those who did not (no-PVR, n=16) using unpaired t-tests (p < 0.05). A subset of 15 rTOF who underwent serial CMR prior to PVR were compared to 6 patients with post-PVR serial CMR data. There were 17 patients who underwent PVR at a mean age of 15 ± 6.4 years. Patients who underwent PVR had larger RVEDV (160 vs 127 ml/m2, p< 0.001), RVESV (84 vs. 64 ml/m2, p= 0.001), regurgitant volume (34 vs 21 ml/m2, p= 0.002) and RF (49 vs 37%, p= 0.018) compared to no-PVR. However, there were no differences between PVR vs no-PVR for; RV-LS (-18.9 vs -19.8%, p= 0.30), RV-LSR (-0.90 vs -0.95 s-1, p= 0.34), RV-LSRe (1.05 vs 0.93 s-1, p= 0.24) and RVEF (47 vs 50%, p= 0.13). In patients who underwent serial CMR, the serial change in RV-GLS improved 3-6 years after PVR (ΔRV-LS= -3%) compared to the ΔRV-LS prior to PVR (ΔRV-LS= +1.17 %, p= 0.037). Despite the larger RV volumes in a young population undergoing PVR there were no functional or RV strain differences compared to those who did not undergo PVR. RV-LS and SR may provide additional information regarding the timing of PVR and caution against intervening too early in younger patients. This novel insight suggests future research into the utility of serial CMR strain in the decision for PVR in rTOF.
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