MATERIALS and METHODS
Study population
Ninety-eight adult patients screening for high probability of PH by echocardiography were enrolled from the inpatient or outpatient department of the First Affiliated Hospital of Sun Yat-sen University (SYSU) between July 2021 to April 2022. Patients with a peak tricuspid regurgitation velocity (TRV)>3.4m/s by echocardiography, or TRV>2.8m/s with additional echocardiographic signs from at least two categories (the ventricles, the pulmonary artery or inferior vena cava (IVC) and right atrium) suggestive of PH were assigned high probability of PH. Patients with TRV range from 2.8 to 3.4m/s and the absent of other echocardiographic signs, or TR<2.8m/s with the present of echocardiographic signs of PH were suggested Intermediate probability of PH[15]. Subjects with age < 18 years, acute coronary syndrome or cardiac surgery within a period of 1 year, pacemaker rhythm, echocardiography images might interfere accurate 4D auto LAQ measurements were excluded. This was a single-center retrospective study approved by the Ethic Committee of SYSU, complied with the Declaration of Helsinki.
Clinical and Laboratory evaluation
Demographic parameters (age, gender, height and weight) and clinical variables including blood pressure and clinical diagnosis were collected. The body surface area (BSA) and body mass index (BMI) were calculated. Venous blood samples were collected in the morning after an overnight fasting and some laboratory parameters were detected, including serum NT-pro BNP, creatinine, hemoglobin and glycosylated hemoglobin (HbA1c).
Echocardiography
Comprehensive echocardiographic examinations were performed in all patients by trained experience echocardiographers using a Vivid E95 ultrasound system (General Electric Healthcare, Horten, Norway) in keeping with the current guidelines and recommendations[16]. 2D gray-scale images were equipped with a 2.5 MHz matrix array transducer (M5Sc) and acquired at 50–80 frames/s over 3 heart cycles. Data from 3 to 5 beats was averaged in atrial fibrillation cases. Left ventricular ejection fraction (LVEF) was obtained by Simpson method from apical 4-and 2-chamber views. LV mass (LVM) was calculated using the Devereux formula[17]. And the index of the left ventricular diameters at the end of systole and diastole (LVEDI, LVESI) and LV mass (LVMI) were equal to LVED, LVES and LVM divided by BSA respectively. The Doppler imaging were performed to evaluate the peak early (E) and late (A) diastolic velocities of the mitral inflow, the peak early diastolic velocity of the medial mitral annular (e’), the peak systolic velocity of tricuspid annular (S’) and the tricuspid regurgitation peak velocity (TRV). Then, the ratio of E/A and E/e’ were calculated respectively. Tricuspid annular plane systolic excursion (TAPSE) was tracked in the right ventricular focus apical four-chamber view using M-mode echocardiography. Pulmonary artery systolic pressure (PASP) was calculated by the modified Bernoulli formula: PASP =4×TRV2 + estimated right atrial pressure (RAP), while the estimated RAP was based on inferior vena cava diameter and collapsibility index. The PAWP was estimated by (43 - 0.1×TRV- 0.5× LVEF+1.0× RVFAC+0.3× LAVi + 0.7× E/ e’ + 0:9× IVC) × PAMP/100 [4]. PAWP ≤15 mmHg was defined as pre-capillary PH, and PAWP >15 mmHg was defined as post-capillary PH.
The 4D Auto LAQ
4V probe (4Vc) was used for imaging acquisition in the apical chamber view with the image frame rate >30 frames/s, and the parameters of LA 4D volume and strain were acquired by software of 4D Auto LAQ. When 4D Auto LAQ analysis mode were selected, the sub-mode sequentially entered. Firstly, the sampling point was placed at the center of mitral valve annulus level, then the ‘review’ function was selected to obtain the parameters of LA volume and strain (Figure 1 ). The indices of left atrial volume between the various stages, including LAVImax, LAVIpreA, and LAVImin were measured simultaneously. LA longitudinal strain parameters were also evaluated using this technique including LA reservoir strain (LASr), LA conduit strain (LAScd), and LA contraction strain (LASct). Meanwhile, ePLAGS was calculated as TRV/LASr. LA function in different phases, including storage, channel and active systolic function were calculated as following: