Discussion
In our study, we evaluated the relationship between RA pressure, measured by RHC and IVC, CS diameters and their collapse. It is known that IVC diameter and collapse are used to predict RA pressure(11). However, there is no data on the use of CS diameter and collapse to predict RA pressure. There are a number of studies evaluating CS diameter and collapse in PHT, but there is no study evaluating the relationship between invasively measured RAP and CS.
In our study, the patients were divided into two groups as the group with invasively measured RAP values of 10 mmHg and / or above and below 10 mmHg. The group with RAP≥10 mmHg consisted of 57 individuals and the group with RAP <10 mmHg comprised 79 individuals. It was observed that the CSDmax and CSDmin were higher and CSCI was lower in the group with RAP ≥10 mmHg. This difference has reached statistical significance (p<0.001). In addition, we noticed that the results did not change when we indexed CS parameters to BSA. In addition, correlations of invasive RAP and CS parameters were evaluated and a significant correlation was found between them.
We examined the relationship between IVC diameter, collapse index and RAP and it was seen that IVC diameters were higher and IVC collapse indices were low in the group with RAP ≥10 mmHg (p<0.001). Again, the analysis of the data obtained by indexing these parameters to BSA did not change the results. In previous studies comparing invasive RAP and IVC parameters, a moderate correlation was found between the two parameters (r: 0.35-0.76) (10,12). Similar to previous studies, in our study, a significant correlation was found between IVCDmax, IVCDmin and IVCCI parameters and invasive RAP.
In our study, unlike the studies in the literature, the correlations of IVC and CS parameters with each other were evaluated. It was observed that there was a significant correlation in all IVC and CS parameters (maximum and minimum diameter, collapse index). The correlation coefficient for the maximum IVC and CS diameter was 0.554, and the correlation coefficient for the IVC and CS collapse index was 0.608.
In our study, we determined cut-off values predicting RAP to be 10 mm Hg and above using ROC analysis for both IVC and CS. The cut-off values stated in the guidelines and used in estimating RAP are 21 mm for IVC diameter and 50% for IVCCI (10,11). In a study by Kawata et al. In 2017, invasive RAP and echocardiographic IVC parameters were analyzed in 120 patients. The cut-off values, sensitivity and specificity of IVC parameters predicting RAP> 10 mmHg were determined. The cut-off value for IVCDmax was found to be 17 mm, and the cut-off value for IVCCI was found to be 40% (13). When we invastigated the correlation of invasive RAP with IVCDmax and IVCCI, the correlation coefficients in our study were higher. We found the cut-off values for IVCDmax and IVCCI lower than the values in the guidelines (19.6 mm, 46.1% respectively). The cut-off values we obtained for the CSDmax and CSCI were 11 mm and 39.2% respectively. In previous studies, no cut-off value was specified for CS to predict RAP≥10 mmHg. Our study is the first study on this subject.
In a study in the literature, 155 patients included in the study were divided into 3 groups as patients with no PHT, moderate PHT and severe PHT. It was observed that as the systolic PAP value increased, CS dilation increased (p <0.001) and a significant correlation was found between CS and IVC (r: 0.416; p <0.001) (14). The results in our study were similar and the correlation coefficient between IVC and CS was found to be higher (r:0,554, p<0,001).
In our study, the correlation between invasively measured RAP and estimated RAP calculated by IVC was also examined and found to be highly significant (r: 0.765, p <0.001). This high correlation of the estimated RAP with the invasively measured RAP reveals the reliability of the echocardiography examination we have made.
In a study conducted with 215 people, the systolic PAPs of the patients were calculated according to the Bernoulli equation with echocardiography. The patients were divided into two groups as those with systolic PAP above 35 mmHg (n: 109) and those without. CS diameters were higher in the PHT group (p <0.001). At the same time, the estimated RAP values were calculated according to the IVC diameter and collapse of the patients. The correlation of RAP, calculated by IVC, with the maximum diameter of the CS was examined and found to be statistically significant (r = 0.557, P <0.001) (9). In our study, pressures were measured invasively and it was observed that the diameter of the CS was more dilated in patients with high invasive pressures. It was observed that both the estimated RAP calculated by IVC and the invasively measured RAP were correlated with the CS parameters. In addition, differently, maximum diameters, minimum diameters, CS collapse index and their ratio to BSA were evaluated and all of them were found to be statistically significant.
In a study of 43 people conducted by Mahmud et al. in 2001, RA pressures were measured invasively and compared with the minimum CS diameter measured from the parasternal long axis and significant results were obtained (r: 0.59, P <0.001) (15). In our study, IVCDmin was found to be higher in the group with high invasive RAP. In addition, in our study, ROC analyzes were performed for CSDmax, CSDmin, CSDmax/BSA, CSDmin/BSA and CSCI in order to predict RAP ≥10 mmHg and their sensitivity and specificity were calculated and optimal cut-off values were determined. All CS parameters including CSDmin have been shown to be useful for RAP estimation.