Diagnosis and Significance of Pulmonary Microvascular Disease in Diabetes

To determine whether pulmonary microvascular disease is detectable in subjects with diabetes and associated with diminished exercise capacity using a novel echocardiographic marker quantifying the pulmonary transit of agitated contrast bubbles (PTAC).

Sixty participants (40 with diabetes and 20 control subjects) performed cardiopulmonary (maximal oxygen consumption [VO₂peak]) and semisupine bicycle echocardiography exercise tests within a 1-week period. Pulmonary microvascular disease was assessed using PTAC (the number of bubbles traversing the pulmonary circulation to reach the left ventricle, categorized as low PTAC or high PTAC). Echocardiographic measures of cardiac output, pulmonary artery pressures, and biventricular function were obtained during exercise.

Subjects with diabetes and control subjects were of similar age (44 ± 13 vs. 43 ± 13 years, P = 0.87) and sex composition (70% vs. 65% male, P = 0.7). At peak exercise, low PTAC was present in more participants with diabetes than control subjects (41% vs. 12.5%, χ²P = 0.041) and, in particular, in more subjects with diabetes with microvascular complications compared with both those without complications and control subjects (55% vs. 26% vs. 13%, χ²P = 0.02). When compared with high PTAC, low PTAC was associated with a 24% lower VO₂peak (P = 0.006), reduced right ventricular function (P = 0.015), and greater pulmonary artery pressures during exercise (P = 0.02).

PTAC is reduced in diabetes, particularly in the presence of microvascular pathology in other vascular beds, suggesting that it may be a meaningful indicator of pulmonary microvascular disease with important consequences for cardiovascular function and exercise capacity.