Context: The renin-angiotensin system is activated in patients with acute severe heart failure, and increased levels of angiotensin II could contribute to microcirculatory defects in these patients.
Objective: To evaluate the microcirculatory effects of angiotensin II antagonists in critically ill patients with severe heart failure.
Methods: After Ethics Committee approval and signed consent, we conducted a prospective observational study using sidestream darkfield (SDF) imaging to evaluate changes in the sublingual microcirculation of 25 adult patients with severe heart failure (ejection fraction < 40% or cardiac index < 2.5 L/min.m2) who received angiotensin inhibitors during their ICU stay. SDF images and global hemodynamic data were obtained immediately before and 4 h, 24 h, and 48 h after the first administration of the drug.
Results: Already 4 h after administration, there was a significant improvement in the proportion of perfused small (<20 μm) vessels (PPV) (from 78 [72-84] to 89 [82-94]%, P < 0.05) and the microvascular flow index (MFI) (from 2.25 [1.95-2.50] to 2.80 [2.39-2.95] points, P < 0.05), which persisted over subsequent hours. Large vessel perfusion remained constant. There was no correlation between changes in the PPV and changes in the mean arterial pressure (R2 0.02, P = 0.50), cardiac output (R2 0.004, P = 0.85), or central or mixed venous oxygen saturation (R2 0.03, P = 0.53).
Conclusions: In patients with severe heart failure, introduction of angiotensin antagonist therapy was associated with an early improvement in the microcirculation that persisted over subsequent hours. The microcirculatory effects were independent of global hemodynamic variables. The improvement in microcirculatory perfusion observed with angiotensin inhibitors in patients with severe heart failure may partially explain the beneficial clinical effects of this intervention in such patients.