A Comparison of Right Ventricular Function in the Apical 4 Chamber and Subcostal 4 Chamber TTE Views in the Perioperative Setting: A Prospective Clinical Study

Measuring right ventricular function is difficult on account of the ventricles shape, position, and mode of contraction. In transthoracic echocardiography a number of measures are endorsed by current guidelines, including: tricuspid annular plane systolic excursion (TAPSE), tricuspid annular plane velocities (S'), the right ventricular myocardial performance index (MPI), and fractional area change (FAC). Clinically, assessment is usually limited to measuring TAPSE by M-Mode or S' by tissue Doppler imaging, both of which are angle dependent technologies, but unlike the RV MPI or FAC are quick and easy to measure.

In the perioperative period, however, transthoracic echocardiography may be challenging for a number of reasons. First, obtaining usable apical 4-chamber (AP4C) images - the view used to measure TAPSE and S' - may be difficult in ventilated or post-surgical patients; subcostal 4-chamber views (SC4C), however, are generally obtainable. Secondly, gold standard images of the RV function are generally measured in the left lateral decubitus position, rather than supine, as is usually the case perioperative.

Newer technologies - such as speckle-tracking and 3D imaging - may partially overcome these difficulties as these technologies are considered to be relatively angle independent. For example, speckle-tracking can also measure TAPSE and S' and 3D imaging has been shown to correlated very well with MRI, the gold-standard for volume measurements.

This study aims at examining the bias, precision, and reproducibility of speckle-tracking based TAPSE and S' (TAPSESTE and S'STE) measured in the SC4C with measurements of TAPSE by M-Mode and S' TDI (TAPSEM-MODE and S'TDI) in the left lateral decubitus position. Secondly, the investigators will compare measures of RV function made in the supine position to those in the left lateral decubitus position to ascertain the relevance of positioning in the perioperative setting. Patients will have measurements made before and after induction of anaesthesia.

The investigators hypothesize that TAPSE measured by STE in the SC4C with the patient in supine position(TAPSE STE, SC4C, Supine) will be sufficiently similar to TAPSE measured by M-MODE in the AP4C with the patient in the left lateral decubitus position (TAPSE MMODE, AP4C, LLD). A similar hypothesis holds for S' (S' STE, SC4C, Supine and S' TDI, AP4C, LLD).