ObjectiveTo evaluate the clinical characteristics of increased extravascular lung water (EVLW) in patients with low pulmonary artery occlusion pressure (PAOP) in the early phase of acute myocardial infarction.DesignConsecutive sample for descriptions of the clinical features of medical disorders.SettingA general medicine group practice in a university hospital.PatientsSixteen patients with low PAOP (>18 mm Hg) on the initial measurement obtained within 12 hr of chest pain onset.Measurements and Main ResultsEVLW was measured by the thermal indocyanine green dye double-indicator dilution method. QRS score was obtained on hospital day 7 from the Selvester's QRS Scoring System. Eleven (69%) patients had increased EVLW >7 mL/kg despite low PAOP. EVLW had no significant correlation with PAOP and the difference between plasma colloid osmotic pressure and PAOP, but did have a significant correlation with pulmonary vascular resistance index (r2= .31,p< .05), and QRS score (r2= .45,p< .005).ConclusionLarger infarcts led to increased EVLW even with low PAOP, and the accumulation of increased EVLW around the small arterioles might have led to increased pulmonary vascular resistance. (Crit Care Med 1991; 19:21)