Data collection and echocardiography in Tromsø7 and KYH
Transthoracic echocardiography was performed in the left lateral decubitus position using commercially available GE Healthcare systems, in Tromsø7 using a high-end Vivid E9 ultrasound system with a single crystal matrix sector probe of 1.5–4.6 MHz, while the KYH was performed on a Vivid Q machine with a 1.5–3.6 MHz sector matrix transducer. Conventional acquisitions, including two-dimensional (2D) grayscale images and M-mode pulsed, continuous, and color Doppler data, were performed in the parasternal and apical views. 2D-images were obtained at a frame rate of at least 50 Hz. In both countries, experienced readers utilized similar EchoPAC workstations (v.113; GE-Vingmed AS, Horten, Norway). The offline analysis in Norway utilized one ECHO reader (MS), while in Russia it was conducted by three ECHO specialists (S.M., An.R. and V.G.). Intra- and inter-observer variability for conventional echocardiographic measures was regularly assessed within both the Tromsø7 and KYH reading laboratories and compared between laboratories. Conventional echocardiography included LV systolic and diastolic volumes (LV ESV and LV EDV, respectively) and LV outflow tract (LVOT) Doppler-derived stroke volume (SV). EF and LA volumes were calculated using the 2D Simpson biplane method. The Doppler-derived measurements included mitral valve (MV) E and A, E/A ratio, and deceleration time (MV DT). The M-mode was used to calculate the myocardial mass and LVOT diameter for the SV calculation. SV, myocardial mass, and LA volume were indexed using body surface area (BSA). Conventional readings were performed by two reading laboratories in Norway and Russia, and LA volume was estimated using a single reader (M.K.).