Patterns of regional ventilation in patients with cardiomegaly or left heart failure.

Patterns of regional ventilation have been examined in 42 patients, the majority of whom had clinical evidence of left-ventricular or left-atrial dysfunction. Regional ventilation was studied with xenon-133 and regional perfusion with Tc-99m human albumin microspheres. The presence of a cardiac defect, seen in 54.8% of the washin images, was related to the depth of lung between the posterior heart border and the posterior lung border, but not to cardiac size. Washout patterns were fairly uniform in those patients (43%) who cleared their lungs within 3 min, but were remarkably variable in those with longer washout times. The presence of râles or clinical signs of a pleural effusion, and radiographic evidence of vascular redistribution or pleural effusion, were significantly associated with prolonged washout times. These observations suggest that the prolonged washout is due to edema in the walls of the smaller bronchioles, leading to airflow obstruction.