On admission, her BP was 130/108 mm Hg, pulse rate was 148
beats/min, and respiration rate was 26 breaths/min. The examination was
significant for a right ventricular S3 gallop, and left basilar rales.
The chest radiograph showed a small left pleural effusion and oligemia
of the right upper lung field. An arterial blood gas analysis, drawn
while breathing room air, showed pH 7.46,
Paco2 of 27 mm Hg, and
Pao2 of 50 mm Hg. ECG revealed sinus
tachycardia, left ventricular hypertrophy, and lateral ST-segment
depression. An emergency transthoracic echocardiogram in the emergency
department was technically limited, and showed normal left ventricular
function and normal right ventricular size. The patient was started on
IV heparin for suspected PE. The oxygen saturation was 95% while
breathing 100% oxygen. A ventilation/perfusion scan (Fig 1
) showed absent perfusion of the right lung with normal ventilation,
consistent with a high probability of PE.