(D-146) Correlation of CDP with Hyperemic stenosis and microvascular INDICES using a multi-center ilias registry

Introduction:: Coronary artery disease (CAD) results from narrowing or blockage of coronary arteries that supply blood to the heart muscle. The narrowing can be caused by epicardial stenosis (ES) or microvascular disease (MVD). Evaluating the relative contributions of these resistances is important in guiding clinical decision-making for selection of most effective treatment protocol.

Current clinical practice for assessing intermediate coronary stenosis with or without MVD relies on fractional flow reserve (FFR) and coronary flow reserve (CFR). Neither FFR nor CFR can distinguish between the hemodynamic condition of concomitant ES and MVD. To overcome aforementioned limitation, parameters were proposed based on simultaneous measurements of pressure-drop and velocity.

Hyperemic microvascular resistance index (HMR) is a ratio of mean distal pressure and velocity during hyperemia [1], whereas hyperemic stenosis resistance index (HSR) is a ratio of pressure-drop across the stenosis to distal velocity during hyperemia [2]. HSR is primarily developed for assessing ES whereas HMR is expected to detect MVD. FFR and CFR are ratios without units, whereas HSR and HMR are dimensions with units of mm Hg/cm/s. We developed a non-dimensional parameter, the pressure drop coefficient (CDP), based on fundamental principles of fluid dynamics. The CDP combines pressure and flow measurements to simultaneously detect ES and MVD [3, 4].

The objective of this study is to determine the correlation of CDP with HSR and HMR using data from the multicenter international ILIAS (Inclusive Invasive Physiological Assessment in Angina Syndromes) registry. We hypothesize that CDP will correlate significantly with both (HSR and HMR) combined.


Materials and Methods:: The ILIAS registry was used to collect the data. The registry comprises 20 well-known medical institutions, where data were prospectively recorded according to specific protocols for each trial. The registry includes 2,322 patients and 3,046 assessed vessels.

All study participants provided informed consent and underwent exercise testing and myocardial perfusion scans based on inclusion and exclusion criteria. Intracoronary pressure and average peak velocity (APV) measurements were obtained using standard catheterization techniques across the ES. Doppler flow velocity measurement was used to analyze 1,050 arteries, while patients undergoing coronary thermodilution were excluded from the present analysis as velocity data was not available to calculate the CDP.

HSR is the ratio of mean trans-stenotic pressure-drop (Δp) to the mean distal APV measured at hyperemia (Eq. 1).

HSR = Δp/APV (where Δp = p_a - p_d) (1)


HMR is the ratio of mean distal pressure (p_d) to the mean distal APV measured at hyperemia (Eq. 2).

HMR = p_d/APV (2)

CDP is the ratio of trans stenotic pressure-drop (Δp = p_a - p_d) to distal dynamic pressure, which is the product of blood density (ρ), the square of APV at hyperemia, and a constant value of 0.5 (Eq. 3).

CDP = (Δp) / (0.5 x ρ x APV²) (where Δp = p_a - p_d) (3)

CDP was correlated with HSR and HMR with the help of R Markdown software (RStudio Team (2022); RStudio: Integrated Development Environment for R. RStudio, PBC, Boston, MA; https://www.rstudio.com/). For p < 0.05, the results were considered statistically significant.







Results, Conclusions, and Discussions:: RESULTS


Figure 1 shows the linear correlation of log-transformed CDP with log-transformed HSR and log-transformed HMR. The log-transformed CDP was found to have a linearly significant correlation with the logarithmic of HSR (r = 0.98, p < 0.001), as shown in Figure 1A. Log-transformed CDP, when correlated with log-transformed HMR, had a linear correlation (r = 0.49, p < 0.001), as shown in Figure 1B.

The log-transformed CDP, when correlated simultaneously with log-transformed HSR and log-transformed HMR, was found to have a significant and improved correlation (r = 0.99, p < 0.001; Figure 2).



DISCUSSION

The CDP is a non-dimensional parameter developed using fundamental principles of fluid dynamics. It considers the correlation between pressure drop and flow across coronary artery dysfunction. The CDP correlation improved significantly by combining HSR and HMR as compared individually with either HSR (Figure 1A) or HMR (Figure 1B). A significant correlation between CDP, HSR, and HMR is expected due to the incorporation of both pressure drop and flow measurements in these indices. HSR is predominantly developed for assessing ES while HMR detects MVD. Whereas CDP can diagnose and distinguish between concomitant ES and MVD as it accounts for the effects of the velocity by “APV²”[4]. Considering this is a cohort study a randomized trial is needed with a cutoff analysis.



CONCLUSION

CDP correlated significantly with both HSR and HMR and can be a futuristic and improved diagnostic parameter for the diagnosis of CAD.




Acknowledgements (Optional): :

References (Optional): : REFERENCES



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