Assessment of right ventricular function by tissue Doppler imaging in patients with chronic obstructive pulmonary disease

Background. The evaluation of right ventricular function is clinically useful in patients with chronic obstructive pulmonary disease (COPD because the presence of right ventricular failure has prognostic implications. All invasive and non invasive techniques evaluating right ventricular performance have important limitations due to right ventricular complex geometry. The introduction of Doppler measurement of myocardial wall velocities (tissue Doppler imaging, TDI) and the recently developed strain rate (SR) imaging technique have made possible a more adequate assessment of global and regional systolic and diastolic right ventricular function. Our purpose was: 1) to compare TDI/SR parameters with conventional indices evaluating right ventricular function; 2) to assess the correlation among TDI/SR parameters and respiratory function tests . Methods. Twenty-nine patients (age 5313 years) with chronic obstructive pulmonary disease were included in the study. 15 patients had pulmonary artery pressure >35mmHg (group I), 14 patients had pulmonary artery pressure <35mmHg (group II). Sixteen age- and gender-matched healthy subjects who had normal cardiac findings served as controls (group III). Right ventricular ejection fraction (EF), fractional shortening (FS), and tricuspid flow filling parameters (E/A ratio, DT) were determined. Offline analysis of the myocardial velocity data sets was performed using dedicated software (Aplio, Toshiba Corp.). Velocity and strain traces from right ventricular free wall at 3 levels (basal, mid cavity, and apical) were processed from the same wall site in the apical 4-chamber view. Diastolic TDI values (Ew, Aw), peak systolic strain and systolic and diastolic strain rate values were determined. Echocardiographic parameters were evaluated after the respiratory function tests were performed ( FEV1= forced expiratory volume in one second; FEV1/VC = forced expiratory volume in one second / vital capacity; DLCO = single-breath diffusion capacity of the lung for carbon monoxide; DLCO/VA = carbon monoxide diffusion capacity per unit of alveolar volume ) . Results. Measurements of TDI/SR parameters were rapidly obtained with a low inter- and intra-observer variability. Ew/Aw ratio at apical and mid level was lower in Group I and II than in Group III (p<0.005). Peak systolic strain and systolic and diastolic strain rate at apical and mid level were lower in Group I and II than in Group III (p<0.001). Right ventricular EF, FS, E/A ratio, and DT were not different among the three groups. No correlation was found between EF, FS, E/A ratio, DT, and respiratory function tests. A highly significant relationship was shown between peak systolic strain at mid level and DLCO/VA (r=0.67, p<0.001) and peak systolic strain at mid level and FEV1/VC (r=0.69, p<0.001). Conclusion. Thus in COPD patients TDI/SR parameters can determine right ventricular dysfunction that is not shown by conventional echocardiographic indices and is correlated with respiratory function tests.