Impact of cardiac rhythm on mitral valve area calculated by the pressure half time method in patients with moderate or severe mitral stenosis.
BACKGROUND
The pressure half-time (PHT) method has been widely used to estimate mitral valve area (MVA) in patients with mitral stenosis (MS), in the belief that this simple method provides reliable information on true MVA. However, its limitation has been repeatedly recognized under different circumstances. The aim of this study was to evaluate the effect of cardiac rhythm on PHT-derived MVA calculation in relation to net atrioventricular compliance (C(n)).


METHODS
Patients (n = 41) with rheumatic pure moderate or severe MS were consecutively recruited. Eighteen patients with sinus rhythm were allocated to group 1 and the remaining patients with chronic atrial fibrillation to group 2. MVA was obtained using the PHT method and by planimetry (considered the gold standard in this study). C(n) was calculated with a previously validated equation.


RESULTS
There were no differences between the 2 groups in terms of age, gender, left ventricular dimensions or ejection fraction, or transmitral pressure gradient. Left atrial volume index (134.6 +/- 106.7 vs 79.2 +/- 16.8 mL; P = .003) and C(n) (6.6 +/- 1.5 vs 4.7 +/- 1.2 mL/mm Hg; P < .001) were higher in group 2 than in group 1. Disagreement of MVA estimation by PHT compared with that by 2-dimensional planimetry was 8.0 +/- 19.2% for group 1 and -24.9 +/- 13.9% for group 2 (P = .002). In addition, the extent of disagreement of PHT-derived MVA compared with that by 2-dimensional planimetry was significantly correlated with C(n) (r(2) = 0.71, P < .001). MVA by the PHT method was estimated to be substantially higher in patients with C(n) values < 4 mL/mm Hg, most of whom were in sinus rhythm. Multivariate analysis confirmed the independent association of cardiac rhythm with discrepancy of PHT-derived MVA compared with that by planimetry.


CONCLUSIONS
Changes in cardiac rhythm with associated modifications of C(n) can alter the accuracy of the PHT method for estimating MVA. Given the limitation described here, 2-dimensional planimetry, not the PHT method, should be used as a primary echocardiographic tool for MVA calculation.
Kim
Hyung-Kwan
HK
Department of Internal Medicine, Seoul National University College of Medicine, Cardiovascular Center, Seoul National University Hospital, Chongno-Gu, Seoul, Korea.
Kim
Yong-Jin
YJ
Chang
Sung-A
SA
Kim
Dae-Hee
DH
Sohn
Dae-Won
DW
Oh
Byung-Hee
BH
Park
Young-Bae
YB
D000328:Adult; D000368:Aged; D000465:Algorithms; D019412:Anatomy, Cross-Sectional / Q000379:methods*; D001794:Blood Pressure; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D008946:Mitral Valve Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008955:Models, Cardiovascular; D012720:Severity of Illness Index; D014463:Ultrasonography