Left atrial (LA) adaptation during the development of left ventricular
(LV) dysfunction is not fully understood. We performed echocardiographic
assessment of LA volumes simultaneously with recordings of pulmonary
wedge pressures in 60 patients. Twenty patients had no structural or
functional LV abnormalities, 20 had a recent myocardial infarction with
LV dysfunction, and 20 suffered from congestive heart failure (CHF).
Pressure-volume loops were obtained at baseline and during increases in
in LA pressure produced by normal saline infusion. LA afterload was
estimated by the effective LV elastance (E-LV). Atrioventricular
coupling was calculated by the E-LV/E-es ratio (where E-es is the
end-systolic elastance). E-es increased in patients with myocardial
infarction (0.80 +/- 0.09 mm Hg/ml, p <0.001); whereas it decreased in
patients with CHF (0.22 +/- 0.05 mm Hg/ml, p <0.001) compared with
controls (0.61 +/- 0.07 mm Hg/ml). Similarly, stroke workload increased
in patients with myocardial infarction (60.7 +/- 7.3 mm Hg.ml, p
<0.001), whereas it decreased in patients with CHF (25.4 +/- 2.2 mm
Hg.ml, p <0.001) compared with controls (44.8 +/- 5.5 mm Hg.ml). In all
patients LA stiffness (slope of the relation of the filling portion of
the pressure-volume loop) was increased compared with controls
(controls: 0.13 +/- 0.04, patients with myocardial infarction: 0.22 +/-
0.05, and patients with CHF: 0.27 +/- 0.05 mm Hg/ml, p <0.001 for both
comparisons). Moreover, the E-LV/E-es ratio increased gradually as LV
function deteriorated (controls: 1.06 +/- 0.10, patients with myocardial
infarction: 1.35 +/- 0.16, and patients with CHF: 6.90 +/- 0.84, p
<0.001). Thus, early in heart failure, LA pump function is augmented but
LA stiffness increases and work mismatch occurs. With further
progression of LV dysfunction, LA pump function decreases as a result of
increased afterload imposed on the LA myocardium. (C) 1998 by Excerpta
Medica, Inc