Angiotensin-converting enzyme (ACE) is produced by endothelial cells and is found in particularly high concentrations in the pulmonary vasculature. Circulating ACE levels are thought to represent either sloughing off of, or secretion from, endothelial cells. Pulmonary endothelial injury likely occurs during pulmonary insult, such as an acute thromboembolism, and measurement of serum ACE levels may provide a clinically useful marker of pulmonary injury. We therefore investigated the utility of serum ACE levels in the evaluation of patients with pulmonary embolism (PE).
Patients were evaluated for suspected PE either by cat scan angiography (CTA) or ventilation perfusion (V/Q) scans, results of which were interpreted by an independent radiologist. Serum samples were prospectively collected either at the time of admission or during a radiological procedure. ACE levels were measured by enzyme linked immunosorbant assay (ELISA) in a blinded manner. Patients receiving ACE inhibitors were excluded from the study and serum from healthy volunteers served as controls. ACE levels are expressed as ng/mL (mean +SE) with significance between groups set at p < 0.05 (student’s t-test).
Of the 45 patients evaluated, 19 were diagnosed with acute PE (15 CTA, 2 V/Q scan, 2 by both). Patients with PE tended to be older. At diagnosis, serum ACE levels for patients with pulmonary symptoms were as follows –PE: 312±30 ng/ml; non-PE: 299±24 ng/ml (p=NS). In contrast, ACE levels differed significantly in pulmonary pathology groups vs. normal controls (control ACE levels: 433+32 ng/ml; PE vs control, p=0.03; non-PE vs. control, p=0.006).
Although ACE levels did not significantly differ between PE and non-PE patients, ACE levels were significantly decreased in patients presenting with pulmonary symptoms when compared with controls.
Serum ACE levels can be useful in differentiating patients with pulmonary symptoms from those with non-pulmonary causes. Furthermore, additional studies are needed to determine if ACE can serve as a useful diagnostic marker in patients presenting in early vs. late stage PE and as a monitor of clinical course.
Zothanmawii Khiangte, None.