Abstract Body (Do not enter title and authors here): Background: Double switch operation (DSO) for congenitally corrected transposition of the great arteries with intact ventricular septum (ccTGA) has a high rate of post-DSO LV dysfunction.
Hypothesis: LV pressure-volume area (PVA), a surrogate of myocardial O₂ consumption, is a superior marker of LV preparedness and is associated with adverse outcomes after DSO.
Aims: 1. Derive a mathematical relationship to estimate LV PVA (ePVA) from catheterization (pressure) and imaging (volumetric) data, using directly measured PVA (mPVA) as reference 2. Assess if lower ratio of LV ePVA to RV ePVA (as an internal control) is associated with adverse outcome after DSO.
Methods: Aim 1: Using conductance catheter derived invasive subpulmonary LV PV loops, mPVA was recorded as the sum of stroke work (SW) and potential energy (PE). A mathematical relationship was established with standard catheterization/imaging data to estimate ePVA. Aim 2: In a retrospective cohort, LV:RV ePVA ratio was calculated as above, and along with standard clinical metrics, assessed for relationship with a composite outcome of ≥ moderate LV dysfunction, transplant, or death post-DSO.
Results: Aim 1: In 20 PV loop studies in 18 pre-DSO patients, there was a strong linear correlation between measured and estimated SW and PE (R² > 0.9 and p<0.0001 for both). ePVA yielded high agreement and low bias compared to mPVA (mean bias 0.5±11%). Aim 2: Composite outcome occurred in 6/42 DSO patients (14%). LV:RV ePVA ratio (0.57 [0.49, 0.61] vs 0.90 [0.73, 1.1], p<0.001) and LV:RV pressure ratio (0.80 [0.77, 0.87] vs 1.13 [1.01, 1.23], p<0.001) were lower in those with adverse outcome. There were no differences in other pre-operative parameters. On time to event analysis, lower LV:RV ePVA ratio was the strongest determinant (HR 39, 95% CI 15-100; C Index 0.94), while lower LV:RV pressure ratio was the only other predictor (HR 24, 95% CI 13-42; C Index 0.88). In 8 patients with borderline pressure ratios of 0.77-0.88, ePVA ratio was an excellent discriminator - 3 patients with ePVA ratio of ≥0.67 had good outcomes, whereas 5 patients with ePVA ratio <0.67 had adverse outcomes.
Conclusion: LV:RV ePVA ratio >0.67 is a strong and novel predictor of LV preparedness for DSO in patients with ccTGA.