Abstract 2460: Loss of NOS3 Worsens Cardiovascular Outcomes Following Cardiac Arrest
OBJECTIVE: To determine the critical role of NOS3 in determining return of spontaneous circulation (ROSC) and short-term survival following cardiac arrest using genetically-modified mice.
METHODS: Adult female wild-type (WT, n=21) and NOS3−/− (n=17) mice were anesthetized, intubated, and instrumented with left-ventricular pressure-volume catheters. Cardiac arrest was induced with intravenous KCl. After 8 min of untreated arrest, chest compression and ventilations were performed. Hemodynamics were monitored for up to 120 min following return of spontaneous circulation (ROSC). Temperature was maintained at 37°C throughout. Electron paramagnetic resonance spectroscopy was used to measure nitrosylhemoglobin (HbNO) in whole blood samples from separate animals (WT and NOS3−/−, n=4 per time point) sacrificed at: baseline, following 8 (CA8) or 20 (CA20) min of untreated arrest and at 60 (R60) or 120 (R120) min following ROSC. Heart tissue total-NOS3 and phospho-NOS3 were assayed by Western blot.
RESULTS: Prior to arrest, NOS3−/− animals exhibited higher maximum left-ventricular pressure (LVPmax, [111.3±14.6 vs. 90.1±12.8 mmHg, p<0.05]) and contractility (dP/dtmax, [5.9±1.1 vs. 5.1±0.8 mmHg/ms, p<0.05]) than WT. Despite similar CPR quality indices, WT animals displayed higher ROSC (82.4% 14/17 vs. 47.6% 10/21, p<0.05) and 120 minute post-ROSC survival (70.6% 12/17 vs. 19.0% 4/21, p<0.05) rates than NOS3−/−. Post-ROSC cardiovascular collapse leading to death within 120 min occurred more often in NOS3−/− than in WT (60.0% 6/10 vs. 14.3% 2/14, p<0.05). At baseline, HbNO concentrations were similar in WT and NOS3−/− (0.75±0.10 μM vs. 0.86±0.11 μM, p=0.46). In WT, HbNO concentrations increased during untreated arrest at CA20 (1.42±0.19 μM, p<0.05) and following resuscitation at R120 (1.66±0.25 μM, p<0.05) relative to baseline. HbNO concentrations were lower in NOS3−/− as compared to WT at all time points following cardiac arrest (p<0.05). Heart tissue from WT displayed increased levels of heart tissue total-NOS3 and phospho-NOS3 at R60 relative to baseline.
CONCLUSIONS: Cardiac arrest and resuscitation alters expression and phosphorylation of cardiac NOS3. Loss of NOS3 worsens ROSC rate and cardiovascular outcomes following ROSC.