Background .– Acute increase in right ventricular overload secondary to acute respiratory distress syndrome (ARDS) may result in acute cor pulmonale (ACP). Hypoxemia could be worsened by the increased right-to-left shunting across a patent foramen ovale (PFO).

Objectives .– To assess prevalence of ACP and PFO in ventilated patients with ARDS during the first 48 hours. We secondary aimed to assess transthoracic echocardiography (TTE) feasibility and main measurements compared to transesophageal echocardiography (TEE).

Patients .– This prospective observational study in nine intensive care units enrolled all patients with ARDS (new bilateral pulmonary infiltrates on chest X-ray, PaO2/FiO2 ratio ≤ 200 and no left ventricular pressure overload). TTE and TEE were performed by trained intensivists, digitally recorded and reviewed by two experts. ACP was diagnosed when right ventricle was dilated (end-diastolic right ventricle/left ventricle area (RV/LV) ratio > 0.6 in the four-chamber views) associated with septal dyskinesia [eccentricity index > 1 on the short-axis view (TTE) and the transgastric short axis view (TEE)]. PFO was detected by contrast study on the apical four-chamber view (TTE) and 0° and bicaval views (TTE).

Results .– During 34 months 204 patients were studied. Two hundred patients were analysable. Mean ± SD were: age 56 ± 15 year-old, SAPS II 46 ± 17, PaO2/FiO2 115 ± 39, PEEP 11 ± 3 cm H2O. Day 28 mortality rate was 23% (CI 95% [17–29]). ACP was diagnosed in 45 patients (22.5%; CI 95%[16.9–28.9]) and PFO in 31 (15.5%; CI 95%[10.8–21.3]). Right-to-left interatrial shunting was small in 27 patients, moderate in 4 patients and intermittent in 26 patients. ACP and PFO were associated in nine patients (4.5%; CI 95% [2.1–8.4]). TTE compared to TEE measurements had sensitivity and specificity respectively of 42.1% and 97.7% (PFO) and 30.6% and 90.1% (ACP). RV/LV ratio measurement was 0.7 ± 0.2 (mean ± SD) and systolic eccentricity index was 1.11 ± 0.14 (mean ± SD). TTE allowed measurement of other right ventricular function parameters: tricuspid regurgitation velocity (277 ± 56 cm/s), tissue Doppler-derived tricuspid lateral annular systolic velocity (15.8 ± 6.5 cm/s) and tricuspid annular plane systolic excursion (19.7 ± 5.2 mm) (TAPSE). TEE allowed measurement of right ventricular fractional area change (33 ± 13%). Mean values (Student test) were significantly different for RV/LV ratio ( P = 0.03) and eccentricity index ( P = 0.03) between patients with PFO compared to patients without PFO and for right ventricular fractional area change ( P = 0.0002) and TAPSE ( P = 0.05) between patients with ACP compared to patients without ACP.

Conclusion .– These results in patients with early severe ARDS under protective mechanical ventilation found prevalence of 22.5% of ACP and 15.5% of PFO. Low TTE sensitivity requires TEE for diagnosis of PFO and ACP. PFO was associated with significantly increase of RV/LV ratio and eccentricity index. ACP was associated with significantly decrease of right ventricular fractional area change and TAPSE.

Acknowledgement .– Grant acknowledgement, SRLF 2008.