Echocardiography
All of the study patients underwent transthoracic echocardiography. Images were obtained via a Philips iE33 machine (Philips Medical Systems, Andover, USA) with a 3,5 MHz transducer with the patient in the left lateral decubitus position, by a single experienced cardiologist who was blinded to the clinical data of the patients. Echocardiograms were performed within 1 hour after HD while patients were at optimal dry weight for patients on HD and at empty abdomen for patients undergoing PD. Electrocardiogram and respiration of the patients were recorded. Echocardiographic images with at least 3 cardiac cycles were recorded at the end of expiration. Measurements were obtained according to the recommendations of American Association of Echocardiography and European Association of Cardiovascular Imaging. 9
The left ventricular end-diastolic diameter (LVDD), left ventricular end-systolic diameter (LVESD), interventricular septum thickness (IVST), posterior wall thickness (PWT) and left ventricular outflow tract (LVOT) diameter were measured in the parasternal long axis view. Left ventricular mass (LVM) was estimated using the anatomically validated formula of Devereux et al. 10 Left ventricular ejection fraction (LVEF) was calculated using Simpson’s biplane method. Left atrial (LA) diameters were measured from the parasternal long axis and apical 4-chamber views. LAV was calculated using the biplane Simpson method. LVM and LAV were adjusted to body surface area (BSA), as were the LVM index (LVMI) and LAV index (LAVI). To evaluate the diastolic function of LV, early mitral inflow velocity (E), late mitral inflow velocity (A) and E/A ratio were recorded. Early diastolic velocity of the lateral mitral annulus (Em) was recorded with tissue Doppler imaging (TDI) and the E/Em ratio was also evaluated.
Right heart diameters were measured from the apical 4-chamber views focused on RV and RA. Maximal tricuspid regurgitation velocity was measured using continuous wave Doppler echocardiography in the apical 4-chamber view. Pulmonary artery systolic pressure (PASP) was calculated as follows: 4 x (tricuspid systolic jet)² + right atrial pressure, as assessed by the inspiratory collapse of the inferior vena cava. Early (E) and late (A) RV inflow velocities were measured with pulsed wave Doppler by placing the sample volume between the tips of the tricuspid valve in the apical 4-chamber view. Pulsed wave TDI was obtained in the apical 4-chamber view by placing a 5 mm to 10 mm sample volume at the lateral side of the tricuspid annulus. Measurements were recorded during end-expiratory apnea. On the TDI images, peak annular systolic velocity (Sa), early diastolic (Ea) and late diastolic (Aa) annular velocities were measured. Ejection time (ET) was measured from right ventricular outflow tract pulse Doppler and tricuspid valve closure and opening time (TCO) was measured from the tricuspid inflow pulse Doppler. The pulsed Doppler derived MPI, as a global estimate of both systolic and diastolic functions of RV, was calculated with the formula RV-MPI = (TCO-ET) / ET. Tricuspid annular plane systolic excursion (TAPSE) was calculated by placing an M-mode cursor through the tricuspid annulus and measuring the longitudinal motion of the annulus at peak systole in the apical 4-chamber view. Fractional area change (FAC) was obtained by tracing the RV endocardium both in end-systole and end-diastole from the annulus, along with the free wall to the apex, and then back to the annulus with the interventricular septum in the apical 4-chamber view focused on RV. RV FAC was calculated using the formula FAC = (end-diastolic area – end-systolic area) / end-diastolic area x 100. All these measurements and calculations were performed according to guidelines for the Echocardiographic Assessment of the Right Heart in Adults.11
We defined a classification indicating RV function of patients by using TAPSE, RV-MPI, FAC and tricuspid lateral annulus Sa velocity values. Patients who had normal values in all these parameters, according to the universally accepted values defined in the guidelines, were considered to have zero point. Those having an abnormality in one of these parameters were assigned one point, two abnormal parameters received two points and three abnormal parameters were assigned three points. Patients with zero point were accepted as having normal RV function, whereas patients with at least one point were accepted as having abnormal RV function.