Operators were blinded to genotype and treatment at the time of phenotyping. To assess cardiac size and function, echocardiography was performed using the Vevo 770 system (Visual Sonics, Toronto, Canada) and the RMV 707B scan head. Mice were anaesthetized using 5% v/v isoflurane, 2 L/min oxygen, and then placed on a heated platform. Anesthesia was maintained using 0.5% to 2% v/v isoflurane through oxygen. Measurements were taken from the long axis and the short axis as described previously.23 (link)–25 (link) Following echocardiography, left ventricular and RV catheterization was performed using a closed chest method. Left ventricles and RVs were reached through the right internal carotid artery and the right external jugular vein, respectively, and hemodynamic parameters obtained using Millar 1F catheters (SPR-1030 [right], SPR-1045 [left]; Millar Instruments, Inc, Houston, TX) as described previously.23 (link)–25 (link) Isoflurane-induced anesthesia was maintained throughout the procedure (0.5%–2% v/v isoflurane). Data were recorded using the Lab Chart Pro software (version 7.0; ADInstruments, Oxfordshire, United Kingdom). RV hypertrophy index was calculated by dividing the weight of the RV by the weight of left ventricular free wall plus septum.