Assessment of Left Atrial Pressure–Are Relation in Humans by Means of Retrograde Left Atrial Catheterization and Echocardiographic Automatic Boundary Detection: Effects of Dobutamine

Objectives. This study sought to validate and apply new method for obtaining the left atrial (LA) pressure–are relation. Background. In physiologic investigations, the pressure–are relation is the most accurate and representative index of L hemodynamic status. Methods. We applied real-time two-dimensional echocardiographic imaging with automatic boundary detection to estimate L are changes. To obtain L pressure, catheter-tipped micromanometer was introduced retrogradely into the left atrium using steerable cardiac catheter developed at our institution. Twenty-five patients (11 normal subjects, 7 patients with an enlarged left atrium due to heart failure, 7 patients with atrial fibrillation) were studied before and after dobutamine administration. From the L pressure–are relation, the are of the loop (the first counterclockwise loop) and the V loop (the second clockwise loop), the pressure–minimal are relation and the L passive elastic chamber stiffness constant were measured. Results. Normalized pressure–minimal are relation was highly linear and sensitive to changes in inotropic state (normal subjects: from 0.96 to 1.27 mm Hg/cm2, p < 0.01; patients with heart failure: from 0.59 to 0.68 mm Hg/cm2, p = NS; patients with atrial fibrillation: from 0.80 to 1.06 mm Hg/cm2, p < 0.05). The L stroke work index was accurately calculated, and very good correlation was found with L preload. L stroke work index was lower in patients with heart failure (3.9 ± 0.8 cm2·mm Hg, p < 0.001), whereas the L stiffness constant was increased in patients with heart failure (0.801 ± 0.097 cm−2, p < 0.01) and atrial fibrillation (0.796 ± 0.091 cm−2, p < 0.01) compared with normal subjects (stroke work index 7.3 ± 1.9 cm2·mm Hg, stiffness constant 0.623 ± 0.107 cm−2, respectively). In addition, increased inotropic state after dobutamine administration resulted in improved L pump function (stroke work index) in normal subjects (from 10.2 ± 0.9 to 13.8 ± 1.9 cm2·mm Hg, p < 0.001) and patients with heart failure (from 4.3 ± 0.4 to 7.6 ± 0.4 cm2·mm Hg, p < 0.001), as well as in decreased stiffness constant in all groups of patients (normal subjects: from 0.712 ± 0.141 to 0.473 ± 0.089 cm−2; patients with heart failure: from 0.896 ± 0.181 to 0.494 ± 0.093 cm−2; patients with atrial fibrillation: from 0.779 ± 0.145 to 0.467 ± 0.086 cm−2, p < 0.001). Conclusions. The method described here is both safe and reproducible for obtaining the L pressure–are relation. L function is impaired in patients with heart failure and in those with atrial fibrillation and may be acutely improved with inotropic agents in both normal and diseased atria.