Spr 1000

Mice were anesthetized with a mixture of ketamine and xylazine and analgesic therapy was applied subcutaneously with buprenorphine 0.12 mg/kg body weight. The thorax was opened and a microtip catheter (SPR-1000, Millar Instruments) was inserted into LV chamber. Hemodynamic parameters such as LVSP, LVEDP, heart rate (HR), and LV contractility performance (dP/dt) were continuously registered in a Powerlab 8/30 system with LabChart (v7.3.2) software (both ADInstruments). Systolic and diastolic wall stress were computed accordingly: LVP × LV radius/(2 × wall thickness) (77 (link)). The LV radius and LV wall thickness were assessed by echocardiography.

Blood pressure measurements were made as previously described (22 (link), 23 (link)). Briefly, the right carotid artery was isolated and cannulated with a pressure catheter (SPR-1,000: Millar Instruments, Inc., Houston, TX) and advanced into the ascending aorta to measure aortic pressure (along with simultaneous measurement of aortic blood flow velocity as described below). The aortic pressure and velocity signals were displayed simultaneously, and 2 s segments of both signals were recorded using DFVS system. The catheter was then advanced into the LV. Again, 2 s segments of LV pressure, and systolic (SBP), diastolic (DBP), mean (MBP), pulse pressures (PP), and rate-pressure product (RPP) were calculated from aortic pressure. Peak LV pressure (P_LVP), indices of contractility (+dP/dt_max) and relaxation (−dP/dt_max), relaxation time constant (tau), and LV end-diastolic pressure (LVEDP) were calculated from LV pressure.

Following cardiac MRI, hemodynamic parameters were assessed in vivo. Mice were anesthetized by intraperitoneal injection of a mixture of ketamine (100 mg/kg) and xylazine (4 mg/kg), and analgesic therapy was applied subcutaneously (buprenorphine: 0.12 mg/kg body weight). The thorax was opened and a microtip catheter (SPR-1000, Millar Instruments, Houston, TX, USA) inserted into the left ventricular chamber. Hemodynamic parameters such as left ventricular systolic pressure, left ventricular end-diastolic pressure, heart rate, and left ventricular contractility performance (dP/dt) were continuously registered on Labchart (v7.3.2, Powerlab System (8/30), both AD Instruments, Spechbach, Germany). In addition, both systolic and diastolic wall stress were computed accordingly: LV pressure × LV radius/(2 × wall thickness) [66 (link)]. The LV radius and LV wall thickness were assessed by cardiac MRI.

Animals were anesthetized with 3–4% isoflurane and placed on controlled heating pads. RV systolic pressure (RVSP) was measured by advancing a curved-tip pressure transducer catheter, 2F (SPR-513, Millar Instruments) for rats and 1F (SPR-1000, Millar Instruments) for mice, into the RV via the right jugular vein under 1–2% isofluorane anesthesia. In rats, cardiac output was assessed by advancing a 2F microtipped PV catheter (SPR 838, Millar Instruments) into the left ventricle through the right carotid artery under 1.5–2% isofluorane anesthesia. Cardiac index (CI) was calculated by dividing cardiac output by body weight. Total pulmonary vascular resistance index (TPRI) was estimated by dividing RVSP by CI^{35 (link)}. Heart and lungs were collected en bloc and lungs were perfused with physiological saline via the RV outflow tract to flush the blood cells from the pulmonary circulation. RV hypertrophy was determined by calculating the weight ratio of the RV free wall to the combined left ventricle and septum (Fulton index). Values shown for hemodynamic parameters and Fulton index from rats treated with sildenafil monotherapy are historical data from our laboratory.

Blood pressure was measured as previously described [45 (link)]. Briefly, once a level plane of anesthesia was achieved with isoflurane (Isoflurane florane, Baxter, Deerfield, IL, USA), a pressure catheter (1.0-F, model SPR-1000, Millar Instruments, Houston, TX, USA) was inserted into the right carotid and advanced to the ascending aorta. Systolic and diastolic pressures were recorded using Chart 5 software (ADInstruments, Sydney, Australia). Animals were monitored closely for discomfort or over-sedation.