Effects of left atrial compliance on left atrial pressure in pure mitral stenosis

In mitral stenosis (MS), left atrial (LA) pressure is commonly elevated bec ause of increased LA afterload. There is a wide spectrum of LA pressure in patients with MS, however, despite a similar mitral valve orifice area. LA compliance is an important determinant of both cardiovascular performance a nd pathological physiology. Few data are available, however, regarding the effects of LA compliance on LA pressure. We hypothesized that LA pressure m ay be higher in patients with decreased LA compliance. We analyzed the righ t heart and transseptal catheterization data in 47 patients (41 female, mea n age 40 +/- 10 years) with pure MS and sinus rhythm. The magnitude of LA a and v waves was measured from transseptal catheterization. Fick's method w as used to determine cardiac output. LA compliance was calculated by dividi ng the systolic rise in LA pressure (DeltaP(LA) = P-LA(v) - P-LA(x)) into t he stroke volume. LA size, mitral valve area (MVA), mean diastolic pressure gradient (MG), left ventricular (LV) end-diastolic and end-systolic dimens ions were obtained by using two-dimensional and Doppler echocardiography. M ultiple regression analysis was performed to identify independent factors d etermining LA pressure. The mean MVA was 0.95 +/- 0.22 cm(2). MG and LA dim ension were 11.2 +/- 5.2 mm Hg and 50.6 +/- 5.2 mm, respectively. The mean LA pressure and cardiac output obtained by cardiac catheterization were 23. 4 +/- 8.4 mm Hg and 4.3 +/- 1.5 L/min, respectively. The calculated LA comp liance was 4.9 +/- 2.8 cm(3)/mm Hg. Univariate analysis showed that factors associated with increased LA pressure were smaller MVA (r = -0.33, P < 0.0 5), higher MG (r = 0.69, P < 0.01) and lower LA compliance (r = -0.55, P < 0.01); among them, MG (beta coefficient 0.59, SE 0.19, P < 0.01) and LA com pliance (beta coefficient -0.26, standard error 0.34, P < 0.05) were the st rongest predictors of LA pressure. In conclusion, LA compliance, along with MG that reflects the severity of MS, is an important contributing factor d etermining LA pressure in patients with pure MS and sinus rhythm. (C) 2001 Wiley-Liss, Inc.