Coronary Flow Variations Following Percutaneous Coronary Intervention Affect Diastolic Nonhyperemic Pressure Ratios More Than the Whole Cycle Ratios

Abstract

Background Post-percutaneous coronary intervention (PCI) fractional flow reserve ≥0.90 is an accepted marker of procedural success, and a cutoff of ≥0.95 has recently been proposed for post-PCI instantaneous wave-free ratio. However, stability of nonhyperemic pressure ratios (NHPRs) post-PCI is not well characterized, and transient reactive submaximal hyperemia post-PCI may affect their precision. We performed this study to assess stability and reproducibility of NHPRs post-PCI. Methods and Results Fifty-seven patients (age, 63.77±10.67 years; men, 71%) underwent hemodynamic assessment immediately post-PCI and then after a recovery period of 10, 20, and 30 minutes and repeated at 3 months. Manual offline analysis was performed to derive resting and hyperemic pressure indexes (Pd/Pa resting pressure gradient, mathematically derived instantaneous wave-free ratio, resting full cycle ratio, and fractional flow reserve) and microcirculatory resistances (basal microvascular resistance and index of microvascular resistance). Transient submaximal hyperemia occurring post-PCI was demonstrated by longer thermodilution time at 30 minutes compared with immediately post-PCI; mean difference of thermodilution time was 0.17 seconds (95% CI, 0.07-0.26 seconds; P=0.04). Basal microcirculatory resistance was also higher at 30 minutes than immediately post-PCI; mean difference of basal microvascular resistance was 10.89 mm Hg.s (95% CI, 2.25-19.52 mm Hg.s; P=0.04). Despite this, group analysis confirmed no significant differences in the values of resting whole cycle pressure ratios (Pd/Pa and resting full cycle ratio) as well as diastolic pressure ratios (diastolic pressure ratio and mathematically derived instantaneous wave-free ratio). Whole cardiac cycle NHPRs demonstrated the best overall stability post-PCI, and 1 in 5 repeated diastolic NHPRs crossed the clinical decision threshold. Conclusions Whole cycle NHPRs demonstrate better reproducibility and clinical precision post-PCI than diastolic NHPRs, possibly because of less perturbation from predominantly diastolic reactive hyperemia and left ventricular stunning. Registration URL: https://ichgcp.net/clinical-trials-registry/NCT03502083; Unique identifier: NCT03502083 and URL: https://ichgcp.net/clinical-trials-registry/NCT03076476; Unique identifier: NCT03076476.

Keywords: instantaneous wave‐free ratio; nonhyperemic pressure ratios; post–percutaneous coronary intervention coronary physiology; post–percutaneous coronary intervention hyperemia; resting full cycle ratio.

Figures

Figure 1. Serial post–percutaneous coronary intervention (PCI) hemodynamic raw data measured immediately post‐PCI (A) and at +10 minutes (B), at +30 minutes (C), and at +3 months (D) post‐PCI.

Resting pressure gradient (Pd/Pa) is measured at rest (nonhyperemia) ‐ Pd/Pa and hyperemia ‐ fractional flow reserve (FFR). Thermodilution transit time (Tmn) is measured at rest and hyperemia in triplicates to measure coronary flow reserved (CFR) and index of microvascular resistance (IMR).

Figure 2. Schematic diagram of recruitment of patients.

CAD indicates coronary artery disease; GLP‐1, glucagon‐like peptide‐1; LMS, left main stem; and PCI, percutaneous coronary intervention.

Figure 3. Post–percutaneous coronary intervention (PCI) coronary hemodynamic variation.

Post‐PCI changes of coronary transit time (Tmn) (A), coronary flow reserve (CFR) (B), and basal microvascular resistance (BMR) (C) immediately post‐PCI and at 30 minutes post‐PCI. P<0.05 is given in bold.

Figure 4. Stability of nonhyperemic pressure ratios.

Linear regression of post–percutaneous coronary intervention (PCI) pressure ratios compared with their respective retest value at 30 minutes. A, Resting pressure gradient (Pd/Pa). C, Resting full cycle ratio (RFR). E, Mathematically calculated instantaneous wave‐free ratio (iFRmat). G, Average diastolic Pd/Pa (dPR). I, Fractional flow reserve (FFR). R is derived from correlation matrix, whereas R2 is calculated by simple linear regression. Bland‐Altman charts are plotted opposite to report the degree of bias for post‐PCI pressure ratio values vs repeated measurements at 30 minutes post‐PCI for Pd/Pa (B), RFR (D), iFRmat (F), dPR (H), and FFR (J).

Figure 5. Clinical precision of nonhyperemic pressure ratios (NHPRs).

Change in diagnostic category with crossover to >0.95: patients with respective NHPR value 0.95 at 30 minutes, and crossover to 0.95 immediately post‐PCI, which became

Figure 6. Reproducibility of resting pressure gradient (Pd/Pa) (A), resting full cycle ratio (RFR) (B), average diastolic Pd/Pa (dPR) (C), and mathematically calculated instantaneous wave‐free ratio (iFRmat) (D) immediately post–percutaneous coronary intervention (PCI) to 30 minutes post‐PCI.

Whole cycle ratios: Pd/Pa, average ratio of Pd/Pa over whole cardiac cycle; RFR, lowest value of ratio of Pd/Pa over whole cardiac cycle. Diastolic ratios: dPR, average ratio of Pd/Pa over diastole; iFR, average Pd/Pa from 25% into diastole until 5 ms before the end of diastole.