Marked reduction in the ratio of main right ventricular chamber to outflow tract function in patients with proximal bilateral acute pulmonary embolism

Right ventricular (RV) function is an important prognostic determinant in patients with acute pulmonary embolism (aPE) and chronic pulmonary hypertension (cPH) [1,2]. Furthermore, echocardiography has been proven useful in identifying the extent of RV involvement and magnitude of RV strain in these patients [3,4]. However, the routine use of echocardiography in aPE not only has been limited to hemodynamically unstable patients unable to be transported or when a multidetector CT is not available, but also has been excluded from currently used diagnostic aPE algorithms for lack of consistent objective echocardiographic measures [5]. Even though the McConnell's sign has been proposed as a useful echocardiographic marker in identifying aPE [6], this sign was found to lack sensitivity [7]. Furthermore, distinction between aPE and cPH can become problematic as both conditions might share similar RV echocardiographic abnormalities. Since our laboratory has previously suggested that a global rather than a regional abnormality in RV function is present in aPE [8], this study intended to determine if the ratio betweenmain chamber RV fractional area change (mcRVFAC) to RVoutflow tract (RVOT) systolic excursion not onlymight be useful in identifying aPE, but also discriminative in differentiating aPE from cPH. In this retrospective study, echocardiographic data from 15 patients (58±12 years) with confirmed aPE (group I) by chest computed tomography demonstrating proximal bilateral pulmonary artery embolismwas analyzed and compared to similar data obtained from stable outpatients with documented cPH (group II:30 patients (57±12 years)) and 15 patients (52±16 years) with normal pulmonary pressures (group III). All echocardiograms included pulsed Doppler spectral signals across the RVOT, discernible tricuspid regurgitation signal, and good endocardial border resolution for tracingof end-systole and end-diastole, aswell as M-mode of the lateral mitral and tricuspid annuli. Finally, all patients were in normal sinus rhythm and had normal LV systolic function. Echocardiograms from aPE patients were done within 24 h of their diagnostic chest scan. The University of Pittsburgh Institutional Review Board approved this study (IRB # PRO10110456). Standard measures used in the assessment of left ventricular function as recommended by both the American Society of Echocardiography and European Association of Echocardiography were used [9]. Similarly, assessment of RV areas as well as RVOT diameters and systolic function, RVOT velocity time integrals, estimates of pulmonary vascular resistance (PVR), ratios between each respective end-diastolic as well as systolic RV to left ventricular diameters and estimates of pulmonary artery systolic pressure were calculated as previously described [6–8,10]. For the purpose of this study, a global assessment of RV systolic functionwas determinedbycalculating the ratio between mcRVFAC to RVOT systolic excursion. All continuous data are presented as mean±SD. Categorical data are presented as frequencies or percentages. Univariate analysis was performed when appropriate. Analysis of variance (ANOVA) with repeated measures was used to test statistical significance of the studied variables. When ANOVA showed statistically significant differences among groups, post hoc analysis with the Student-Newman–Keuls test was then performed to assess differences among the groups. A stepwise multiple linear regression analysis was then performed to determine the independent relationship between all significant echocardiographic and Doppler variables that will help differentiate aPE from cPH. Receiver operating characteristic curves andareas under the curveswere examined and compared to determine cut-off values. p-Values of less than .05 were considered to be statistically significant. In this study, all echocardiographic measurements were feasible. Pulmonary artery systolic pressures in aPE patients (50±16 mmHg; pb0.05) not only ranged between pressures of both cPH and controls (85±26 mmHgvs. 29±7 mmHg; pb0.001), but alsowere statistically different when compared to cPH patients. In contrast, PVR was lowest among control patients (0.11±0.03 WU; pb0.001) and incrementally higher in cPH (0.33±0.16 WU) and aPE (0.49±0.23 WU; pb0.05) patients. In addition, not only was mcRVFAC lowest among aPE patients (25±8%; pb0.001) when compared to cPH (34±16%) and control (66±7%) patients, but also, TAPSE values (1.3±0.4 cm, 1.8±0.4 cm, and 2.7±0.5 cm; pb0.001, respectively). Even though there was no difference among end-diastolic RVOT length measurements (3.4±0.6 cm for control patients, 3.6±0.5 cm for cPHpatients and 3.8±0.5 cm for aPE patients), incremental differences in endsystolic RVOT length measurements were noted (1.2±0.5 cm for control patients, 2.3±0.6 cm for cPH patients and 3.2±0.5 cm for aPE patients; pb0.001). Consequently, RVOT FAC was different being 65±10% for control patients, 37±12% for cPH patients and 17±5% for aPE patients; pb0.001. On a stepwise multiple regression analysis, even though TAPSE was useful to differentiate aPE from cPH, the ratio ofmcRVFAC to RVOTsystolic excursionwas the best echocardiographic variable to distinguish aPE from