ASSESSMENT OF LEFT ATRIAL PRESSURE-AREA 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 a new method for o btaining the left atrial (LA) pressure-area relation. Background. In p hysiologic investigations, the pressure-area relation is the most accu rate and representative index of LA hemodynamic status. Methods. We ap plied real-time two-dimensional echocardiographic imaging with automat ic boundary detection to estimate LA area changes. To obtain LA pressu re, a catheter-tipped micromanometer was introduced retrogradely into the left atrium using a steerable cardiac catheter developed at our in stitution. Twenty-five patients (11 normal subjects, 7 patients with a n enlarged left atrium due to heart failure, 7 patients with atrial fi brillation) were studied before and after dobutamine administration. F rom the LA pressure-area relation, the area of the A loop (the first c ounterclockwise loop) and the V loop (the second clockwise loop), the pressure-minimal area relation and the LA passive elastic chamber stif fness constant were measured. Results. Normalized pressure-minimal are a relation was highly linear and sensitive to changes in inotropic sta te (normal sub jects: from 0.96 to 1.27 mm Hg/cm(2), p < 0.01; patient s with heart failure: from 0.59 to 0.68 mm Hg/cm(2), p = NS; patients with atrial fibrillation: from 0.80 to 1.06 mm Hg/cm(2), p < 0.05). Th e LA stroke work index was accurately calculated, and a very good corr elation was found with LA preload. LA stroke work index was lower in p atients with heart failure (3.9 +/- 0.8 cm(2) mm Hg, p < 0.001), where as the LA stiffness constant was increased in patients with heart fail ure (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 cm(2) mm Hg, stiffness constant 0.623 +/- 0.107 cm( -2), respectively), In addition, increased inotropic state after dobut amine administration resulted in improved LA pump function (stroke wor k index) in normal subjects (from 10.2 +/- 0.9 to 13.8 +/- 1.9 cm(2).m m Hg, p < 0.001) and patients with heart failure (from 4.3 +/- 0.4 to 7.6 +/- 0.4 cm(2).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 0.373 +/- 0.089 cm(-2); patients with heart failure: from 0.89 6 +/- 0.181 to 0.494 +/- 0.093 cm(-2); patients with heart failure: fr om 0.896 +/- 0.181 to 0.494 +/- 0.093 cm(-2); patients with atrial fib rilliation: from 0.779 +/- 0.145 to 0.086 cm(-2), p < 0.0001). Conclus ions. The method described here is both safe and reproducible for obta ining the LA pressure-area relation. LA function is impaired in patien ts with heart failure and in those with atrial fibrillation and may be acutely improved with inotropic agents in both normal and diseased at ria. (C) 1998 by the American College of Cardiology.