Pulmonary vasoconstriction induced by mitral valve obstruction in sheep

15 awake sheep instrumented with a Foley balloon catheter to variably obstruct the mitral valve and a Swan-Ganz catheter for hemodynamic measurements

Experimental left atrial hypertension (increases in left atrial pressure of 10 and 20 cmH2O) with and without inhalation of approximately 36 parts per million of nitric oxide; additional experiments with phentolamine, atropine, and ibuprofen

Baseline conditions (prior to left atrial pressure elevation) and without nitric oxide inhalation

Changes in pulmonary vascular resistance (total, upstream, and downstream) and pulmonary arterial pressuresurrogate