Using coronary sinus diameter and collapse index to estimate right atrial pressure for echocardiographic systolic pulmonary arterial pressure measurement

Introduction and Purpose: With the use of Doppler echocardiography, pulmonary artery pressure has become predictable by noninvasive methods. Transthoracic echocardiography is an easily accessible, noninvasive method used in the screening, diagnosis and follow-up of patients with suspected pulmonary hypertension. Echocardiographic systolic pulmonary artery pressure is calculated according to the Bernoulli equation. According to this equation; systolic pulmonary artery pressure: 4 × (tricuspid regurgitation flow rate) ² + estimated right atrium pressure (RAP). Estimated RAP is estimated by inferior vena cava (IVC) diameter and collapse index. There are several studies evaluating RAP according to IVC as well as some studies showing the relationship between estimated systolic pulmonary artery pressure, calculated RAP and coronary sinus (CS) evaluation. However, there is no study comparing invasively measured RAP with CS diameter and collapse In this study, our aim is to investigate the usability of CS diameter and collapse in RAP estimation. Patients and Methods: Our study was a single-center prospective study. The study included 136 patients who were admitted to the Akdeniz University Hospital Cardiology Policlinics between March 2017 and March 2018, who were planned to be performed right heart catheterization for any reason, who did not have exclusion criteria and were older than 18 years. Detailed echocardiography was performed before the right heart catheterization Findings: 77 (56.6%) of the patients were female and 59 (43.4%) were male. The mean age of the patients was 57.67±13.36 and the mean RAP was 9.84±5.39 mmHg. Patients were divided into two groups as RAP ≥10 mmHg (n: 57) and RAP <10 mmHg (n: 79). In the group with RAP ≥10 mmHg, maximum IVC and CS diameters were higher than the RAP <10 mmHg group, IVC and CS collapse index were significantly lower (p <0.001). Optimal cut-off values were determined for all IVC and CS parameters predicting for RAP ≥10 mmHg. Optimal cut-off value of the maximum IVC diameter was 19.6 mm (sensitivity, 63.2%, specificity, 87.3%), optimal cut-off value of the IVC collapse index was 46.1 (sensitivity, 75,4 %, specificity, 79,7 %), optimal cut-off value of maximum CS diameter was 11 mm (sensitivity, 64.9%, specificity, 77,3 %), optimal cut-off value of CS collapse index was 39.2 (sensitivity, 75.4%, specificity, 88,6%). We also assessed correlations between invasively measured RAP and IVC and CS parameters in our study. There was a high correlation between the invasive RAP and maximum IVC diameter and IVC collapse index (r: 0,615 p <0,001; r: -0,683 p <0,001 respectively). There was also a moderate correlation between invasively measured RAP and maximum CS diameter and CS collapse index (r: 0,478 p <0,001; r: -0,674 p <0,001 respectively). Correlation between invasively measured RAP and RAP estimated via IVC was also found to be highly significant (r: 0,765 p <0.001). At the same time, correlations between CS and IVC parameters were evaluated and correlations of all parameters were statistically significant (p <0.001). Conclusion: In our study, there was a significant relationship between invasively measured RAP and maximum IVC diameter, IVC collapse index and maximum CS diameter, CS collapse index. The results of the IVC parameters were similar to those of the previous studies. Significant results of the CS parameters as well as the results of the IVC parameters indicate that CS can also be used estimating RAP. High level of significance in majority of the correlations reinforces this idea. In addition, cut-off values for CS parameters are determined in our study and they will be an example for further studies. Key words: Pulmonary hypertension, Inferior vena cava, Coronary sinus, Right atrial pressure