Delineation of epicardial stenosis in patients with microvascular disease using pressure drop coefficient: A pilot outcome study

Abstract

AIMTo investigate the patient-outcomes of newly developed pressure drop coefficient (CDP) in diagnosing epicardial stenosis (ES) in the presence of concomitant microvascular disease (MVD).METHODSPatients from our clinical trial were divided into two subgroups with: (1) cut-off of coronary flow reserve (CFR) < 2.0; and (2) diabetes. First, correlations were performed for both subgroups between CDP and hyperemic microvascular resistance (HMR), a diagnostic parameter for assessing the severity of MVD. Linear regression analysis was used for these correlations. Further, in each of the subgroups, comparisons were made between fractional flow reserve (FFR) < 0.75 and CDP > 27.9 groups for assessing major adverse cardiac events (MACE: Primary outcome). Comparisons were also made between the survival curves for FFR < 0.75 and CDP > 27.9 groups. Two tailed chi-squared and Fischer’s exact tests were performed for comparison of the primary outcomes, and the log-rank test was used to compare the Kaplan-Meier survival curves. P < 0.05 for all tests was considered statistically significant.RESULTSSignificant linear correlations were observed between CDP and HMR for both CFR < 2.0 (r = 0.58, P < 0.001) and diabetic (r = 0.61, P < 0.001) patients. In the CFR < 2.0 subgroup, the %MACE (primary outcomes) for CDP > 27.9 group (7.7%, 2/26) was lower than FFR < 0.75 group (3/14, 21.4%); P = 0.21. Similarly, in the diabetic subgroup, the %MACE for CDP > 27.9 group (12.5%, 2/16) was lower than FFR < 0.75 group (18.2%, 2/11); P = 0.69. Survival analysis for CFR < 2.0 subgroup indicated better event-free survival for CDP > 27.9 group (n = 26) when compared with FFR < 0.75 group (n = 14); P = 0.10. Similarly, for the diabetic subgroup, CDP > 27.9 group (n = 16) showed higher survival times compared to FFR group (n = 11); P = 0.58.CONCLUSIONCDP correlated significantly with HMR and resulted in better %MACE as well as survival rates in comparison to FFR. These positive trends demonstrate that CDP could be a potential diagnostic endpoint for delineating MVD with or without ES.

Comparison Between 5- and 1-Year Outcomes Using Cutoff Values of Pressure Drop Coefficient and Fractional Flow Reserve for Diagnosing Coronary Artery Diseases

“…The results were similar for a FFR cutoff of 0.80 and associated CDP cutoff of 25.4. The MVD sub-group analysis (Hebbar et al, 2017) for %MACE and survival analysis showed similar trends in favor of CDP for both CFR < 2.0 and diabetic sub-groups. Both of these sub-groups were correlated with possible MVD in literature (Feigl, 1983;Muller et al, 1996;Miura et al, 2003;Bagi et al, 2004;Pijls et al, 2007;Picchi et al, 2010;Johnson et al, 2012).…”

“…where P = P a -P d is the pressure drop across the stenosis, P a and P d are the mean pressures measured proximal and distal to the stenosis at hyperemia, respectively, and the distal dynamic pressure is the product of blood density (ρ) and the square of the average peak flow velocity (APV) distal to the stenosis at hyperemia at a constant value of 0.5. The ρ was assumed to be a constant (1.05 g/cm 3 ), as it does not change significantly during the hyperemic (high shear) condition (Banerjee et al, 2009;Effat et al, 2016;Hebbar et al, 2017). Therefore, CDP represents the ratio between the total pressure drop (viscous loss plus loss due to momentum change with pressure recovery) and the dynamic pressure during blood flow.…”

“…It also highlights the overlap of the diabetic and CFR < 2.0 subgroups. The 1-year outcomes of the same 86-patient cohort group (Effat et al, 2016) and sub-groups (Hebbar et al, 2017) were previously published.…”

“…The CDP was tested in vitro (Sinha Roy et al, 2008;Peelukhana et al, 2009) as well as in vivo in animal studies (Banerjee et al, 2009;Kolli et al, 2011Kolli et al, , 2012Peelukhana et al, 2012Peelukhana et al, , 2014b and was able to differentiate between stenosis and MVD. Subsequently, we tested them in single-and two-center cohort patient groups (Kolli et al, 2014a(Kolli et al, ,b, 2016Peelukhana et al, 2014aPeelukhana et al, , 2015Peelukhana et al, , 2018Effat et al, 2016;Hebbar et al, 2017) using prospective trials. In line with our studies, the importance of a combined approach of assessing both coronary pressure and flow has been reported by others as basis for the understanding of coronary physiology (van de Hoef et al, 2012;Shlofmitz and Jeremias, 2017;Gould, 2018;Stegehuis et al, 2018).…”

“…The objective of the current study is to compare (a) the 5-year outcome (%MACE and survival) between the CDP > 27.9 and FFR < 0.75 groups and (b) the outcomes between 1 year (Effat et al, 2016) and 5 years for the complete patient group. Extending our earlier 1-year (Hebbar et al, 2017) MVD sub-group analysis, this study also compares (a) the 5-year outcomes between the CDP > 27.9 and FFR < 0.75 for CFR < 2.0 and the diabetic patient sub-groups and extracted from the complete patient data (Effat et al, 2016) analyzed previously and (b) outcomes between 1-and 5-year patient sub-groups. All comparisons were also repeated for the FFR cutoff of 0.80 and CDP cutoff of 25.4.…”