Increased Airway Pressure and Simulated Branch Pulmonary Artery Stenosis Increase Pulmonary Regurgitation After Repair of Tetralogy of Fallot

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Abstract
Background Pulmonary regurgitation (PR) is an important determinant of outcome after repair of tetralogy of Fallot. Baseline PR was measured by magnetic resonance (MR) phase velocity mapping and from real-time right ventricular pressure-volume loops with a conductance catheter. Subsequently, the impact of two loading maneuvers (increased airway pressure, simulated branch pulmonary artery stenosis) on PR was assessed by the conductance catheter method. Methods and Results Thirteen patients, 3 to 35 years after tetralogy of Fallot repair or pulmonary valvotomy, had PR measured by MR phase velocity mapping while breathing spontaneously. During catheterization under general anesthesia, PR was estimated from right ventricular pressure-volume loops generated by conductance and microtip pressure catheters. The effect of increased airway pressure (continuous positive airway pressure, 20 cm H2O; n=12) and simulated branch pulmonary artery stenosis (transient balloon occlusion of a branch pulmonary artery, n=7) was measured. Basal PR fraction derived by MR and from right ventricular pressure-volume loops had a correlation coefficient of .76 and mean of differences of 2.0±18.2% (95% limits of agreement). Increased airway pressure increased PR (16.3±11.4% to 25.7±17.3%, P<.01). Simulated branch pulmonary artery stenosis increased right ventricular end-systolic pressure (69.1±21.4 to 78.7±23.1 mm Hg, P<.05) and PR (27.5±11.3% to 36.9±12.8%, P<.05). Conclusions There was reasonable agreement between MR phase velocity–derived PR fraction and that obtained from right ventricular pressure-volume loops generated by use of conductance and pressure-microtip catheters. Exacerbation of PR by increased airway pressure and branch pulmonary stenosis may be relevant to the acute postoperative and long-term management, respectively, of patients after repair of tetralogy of Fallot.