Non-hyperaemic coronary pressure measurements to guide coronary interventions

Noninvasive and fast method of calculation for instantaneous wave-free ratio based on haemodynamics and deep learning

BACKGROUND AND OBJECTIVES

Instantaneous wave-free ratio (iFR) is a new invasive indicator of myocardial ischaemia, and its diagnostic performance is as good as the "gold standard" of myocardial ischaemia diagnosis: fractional flow reserve (FFR). iFR can be approximated by iFRCT, which is calculated based on noninvasive coronary CT angiography (CTA) images and computational fluid dynamics (CFD). However, the existing methods for calculating iFRCT fail to accurately simulate the resting state of the coronary artery, resulting in low computational accuracy. Furthermore, the use of CFD technology limits its computational efficiency, making it difficult to meet clinical application needs. The role of coronary microcirculatory resistance compensation suggests that microcirculatory resistance can be adaptively reduced to compensate for increases in coronary stenotic resistance, thereby maintaining stable myocardial perfusion in the resting state. It is therefore necessary to consider this compensation mechanism to establish a high-fidelity microcirculation resistance model in the resting state in line with human physiology, and so to achieve accurate calculation of iFRCT.

METHODS

In this study we successfully collected clinical data, such as FFR, in 205 stenotic vessels from 186 patients with coronary heart disease. A neural network model was established to predict coronary artery stenosis resistance. Based on the compensation mechanism of coronary microcirculation resistance, an iterative solution algorithm for microcirculation resistance in the resting state was developed. Combining the two methods, a simplified single-branch model combining coronary stenosis and microcirculation resistance was established, and the noninvasive and rapid numerical calculation of iFRCT was performed.

RESULTS

The results showed that the mean squared error (MSE) between the pressure drop predicted by the neural network value for the coronary artery stenosis model and the ground truth in the test set was 0.053 %, and correlation analysis proved that there was a good correlation between them (r = 0.99, p < 0.001). With reference to clinical diagnosis of myocardial ischaemia (using FFR as the gold standard), the diagnostic accuracy of the iFRCT calculation model for the 205 cases was 88.29 % (r = 0.71, p < 0.001), and the total calculation time was < 8 s.

CONCLUSIONS

The results of this study demonstrate the utility of a simplified single-branch model in an iFRCT calculation method based on haemodynamics and deep learning, which is important for noninvasive and rapid diagnosis of myocardial ischaemia.

Myocardial Blood Flow by Magnetic Resonance in Patients With Suspected Coronary Stenosis: Comparison to PET and Invasive Physiology

BACKGROUND

Despite recent guideline recommendations, quantitative perfusion (QP) estimates of myocardial blood flow from cardiac magnetic resonance (CMR) have only been sparsely validated. Furthermore, the additional diagnostic value of utilizing QP in addition to the traditional visual expert interpretation of stress-perfusion CMR remains unknown. The aim was to investigate the correlation between myocardial blood flow measurements estimated by CMR, positron emission tomography, and invasive coronary thermodilution. The second aim is to investigate the diagnostic performance of CMR-QP to identify obstructive coronary artery disease (CAD).

METHODS

Prospectively enrolled symptomatic patients with >50% diameter stenosis on computed tomography angiography underwent dual-bolus CMR and positron emission tomography with rest and adenosine-stress myocardial blood flow measurements. Subsequently, an invasive coronary angiography (ICA) with fractional flow reserve and thermodilution-based coronary flow reserve was performed. Obstructive CAD was defined as both anatomically severe (>70% diameter stenosis on quantitative coronary angiography) or hemodynamically obstructive (ICA with fractional flow reserve ≤0.80).

RESULTS

About 359 patients completed all investigations. Myocardial blood flow and reserve measurements correlated weakly between estimates from CMR-QP, positron emission tomography, and ICA-coronary flow reserve (r<0.40 for all comparisons). In the diagnosis of anatomically severe CAD, the interpretation of CMR-QP by an expert reader improved the sensitivity in comparison to visual analysis alone (82% versus 88% [P=0.03]) without compromising specificity (77% versus 74% [P=0.28]). In the diagnosis of hemodynamically obstructive CAD, the accuracy was only moderate for a visual expert read and remained unchanged when additional CMR-QP measurements were interpreted.

CONCLUSIONS

CMR-QP correlates weakly to myocardial blood flow measurements by other modalities but improves diagnosis of anatomically severe CAD.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03481712.

Validation of resting full-cycle ratio and diastolic pressure ratio with [15O]H2O positron emission tomography myocardial perfusion

Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are invasive techniques used to evaluate the hemodynamic significance of coronary artery stenosis. These methods have been validated through perfusion imaging and clinical trials. New invasive pressure ratios that do not require hyperemia have recently emerged, and it is essential to confirm their diagnostic efficacy. The aim of this study was to validate the resting full-cycle ratio (RFR) and the diastolic pressure ratio (dPR), against [15O]H2O positron emission tomography (PET) imaging. A total of 129 symptomatic patients with an intermediate risk of coronary artery disease (CAD) were included. All patients underwent cardiac [15O]H2O PET with quantitative assessment of resting and hyperemic myocardial perfusion. Within a 2 week period, coronary angiography was performed. Intracoronary pressure measurements were obtained in 320 vessels and RFR, dPR, and FFR were computed. PET derived regional hyperemic myocardial blood flow (hMBF) and myocardial perfusion reserve (MPR) served as reference standards. In coronary arteries with stenoses (43%, 136 of 320), the overall diagnostic accuracies of RFR, dPR, and FFR did not differ when PET hyperemic MBF < 2.3 ml min-1 (69.9%, 70.6%, and 77.1%, respectively) and PET MPR < 2.5 (70.6%, 71.3%, and 66.9%, respectively) were considered as the reference for myocardial ischemia. Non-significant differences between the areas under the receiver operating characteristic (ROC) curve were found between the different indices. Furthermore, the integration of FFR with RFR (or dPR) does not enhance the diagnostic information already achieved by FFR in the characterization of ischemia via PET perfusion. In conclusion, the novel non-hyperemic pressure ratios, RFR and dPR, have a diagnostic performance comparable to FFR in assessing regional myocardial ischemia. These findings suggest that RFR and dPR may be considered as an FFR alternative for invasively guiding revascularization treatment in symptomatic patients with CAD.

A comprehensive approach to prediction of fractional flow reserve from deep-learning-augmented model

The underuse of invasive fractional flow reserve (FFR) in clinical practice has motivated research towards non-invasive prediction of FFR. Although the non-invasive derivation of FFR (FFRCT) using computational fluid dynamics (CFD) principles has become a common practice, its clinical application has been limited due to the considerable time required for computation of resulting changes in haemodynamic conditions. An alternative to CFD technology is incorporating a neural network into the computational process to reduce the time necessary for running an effective model. In this study we propose a cascade of data-driven and physic-based neural networks (DP-NN) for predicting FFR (DL-FFRCT). The first network of cascade network DP-NN includes geometric features, and the second network includes physical features. We compare the differences between data-driven neural network (D-NN) and DP-NN for predicting FFR. The training and testing datasets were obtained by solving the three-dimensional incompressible Navier-Stokes equations. Coronary flow and geometric features were used as inputs to train D-NN. In DP-NN the training process involves first training a D-NN to output resting ΔP as one input feature to the DP-NN. Secondly, the physics-based microcirculatory resistance as another input feature to the DP-NN. Using clinically measured FFR as the "gold standard", we validated the computational accuracy of DL-FFRCT in 77 patients. Compared to D-NN, DP-NN improved the prediction of ΔP (R2 = 0.87 vs. R2 = 0.92). Statistical analysis demonstrated that the diagnostic accuracy of DL-FFRCT was not inferior to FFRCT (85.71 % vs. 88.3 %) and the computational time was reduced by a factor of approximately 3000 (4.26 s vs. 3.5 h). DP-NN represents a near real-time, interpretable, and highly accurate deep-learning network, which contributes to the development of high-performance computational methods for haemodynamics. We anticipate that DP-NN will enable near real-time prediction of DL-FFRCT in personalized narrow blood vessels and provide guidance for cardiovascular disease treatments.

Hemodynamic Insights into Combined Fractional Flow Reserve and Instantaneous Wave-Free Ratio Assessment Through Quantitative [15O]H2O PET Myocardial Perfusion Imaging

In patients evaluated for obstructive coronary artery disease (CAD), guidelines recommend using either fractional flow reserve (FFR) or instantaneous wave-free ratio (iFR) to guide coronary revascularization decision-making. The hemodynamic significance of lesions with discordant FFR and iFR measurements is debated. This study compared [15O]H2O PET-derived absolute myocardial perfusion between vessels with concordant and discordant FFR and iFR measurements. Methods: We included 197 patients suspected of obstructive CAD who had undergone [15O]H2O PET perfusion imaging and combined FFR/iFR interrogation in 468 vessels. Resting myocardial blood flow (MBF), hyperemic MBF, and coronary flow reserve (CFR) were compared among 4 groups: FFR low/iFR low (n = 79), FFR high/iFR low (n = 22), FFR low/iFR high (n = 22), and FFR high/iFR high (n = 345). Predefined [15O]H2O PET thresholds for ischemia were 2.3 mL·min-1·g-1 or less for hyperemic MBF and 2.5 or less for CFR. Results: Hyperemic MBF was lower in the concordant low (2.09 ± 0.67 mL·min-1·g-1), FFR high/iFR low (2.41 ± 0.80 mL·min-1·g-1), and FFR low/iFR high (2.40 ± 0.69 mL·min-1·g-1) groups compared with the concordant high group (2.91 ± 0.84 mL·min-1·g-1) (P < 0.001, P = 0.004, and P < 0.001, respectively). A lower CFR was observed in the concordant low (2.37 ± 0.76) and FFR high/iFR low (2.64 ± 0.84) groups compared with the concordant high group (3.35 ± 1.07, P < 0.01 for both). However, for vessels with either low FFR or low iFR, quantitative hyperemic MBF and CFR values exceeded the ischemic threshold in 38% and 49%, respectively. In addition, resting MBF exhibited a negative correlation with iFR (P < 0.001) and was associated with FFR low/iFR high discordance compared with concordant low FFR/low iFR measurements, independent of clinical and angiographic characteristics, as well as hyperemic MBF (odds ratio [OR], 0.41; 95% CI, 0.26-0.65; P < 0.001). Conclusion: We found reduced myocardial perfusion in vessels with concordant low and discordant FFR/iFR measurements. However, FFR/iFR combinations often inaccurately classified vessels as either ischemic or nonischemic when compared with hyperemic MBF and CFR. Furthermore, a lower resting MBF was associated with a higher iFR and the occurrence of FFR low/iFR high discordance. Our study showed that although combined FFR/iFR assessment can be useful to estimate the hemodynamic significance of coronary lesions, these pressure-derived indices provide a limited approximation of [15O]H2O PET-derived quantitative myocardial perfusion as the physiologic standard of CAD severity.

Moving toward Precision Medicine in Acute Coronary Syndromes: A Multimodal Assessment of Non-Culprit Lesions

Patients with acute coronary syndrome and multivessel disease experience several recurrent adverse events that lead to poor outcomes. Given the complexity of treating these patients, and the extremely high risk of long-term adverse events, the assessment of non-culprit lesions becomes crucial. Recently, two trials have shown a possible clinical benefit into treat non-culprit lesions using a fraction flow reserve (FFR)-guided approach, compared to culprit-lesion-only PCI. However, the most recent FLOW Evaluation to Guide Revascularization in Multivessel ST-elevation Myocardial Infarction (FLOWER-MI) trial did not show a benefit of the use of FFR-guided PCI compared to an angiography-guided approach. Otherwise, intracoronary imaging using optical coherence tomography (OCT), intravascular ultrasound (IVUS), or near-infrared spectroscopy (NIRS) could provide both quantitative and qualitative assessments of non-culprit lesions. Different studies have shown how the characterization of coronary lesions with intracoronary imaging could lead to clinical benefits in these peculiar group of patients. Moreover, non-invasive evaluations of NCLs have begun to take ground in this context, but more insights through adequately powered and designed studies are needed. The aim of this review is to outline the available techniques, both invasive and non-invasive, for the assessment of multivessel disease in patients with STEMI, and to provide a systematic guidance on the assessment and approach to these patients.

A high-fidelity geometric multiscale hemodynamic model for predicting myocardial ischemia

BACKGROUND AND OBJECTIVES

Coronary computed tomography angiography (CCTA) derived fractional flow reserve (CT-FFR) requires a maximal hyperemic state to be modeled by assuming the total coronary resistance decreased to a constant 0.24 of that under the resting state. However, this assumption neglects the vasodilator capacity of individual patients. Herein, we proposed a high-fidelity geometric multiscale model (HFMM) to characterize coronary pressure and flow under the resting state, seeking to better predict myocardial ischemia by using CCTA-derived instantaneous wave-free ratio (CT-iFR).

METHODS

Fifty-seven patients (62 lesions) who had undergone CCTA and were then referred to invasive FFR were prospectively enrolled. The coronary microcirculation resistance hemodynamic model (RHM) under the resting condition was established on a patient-specific basis. Coupled with a closed-loop geometric multiscale model (CGM) of their individual coronary circulations, the HFMM model was established to non-invasively derive the CT-iFR from CCTA images.

RESULTS

With the invasive FFR being the reference standard, accuracy of the obtained CT-iFR in identifying myocardial ischemia was greater than those of the CCTA and non-invasively derived CT-FFR (90.32% vs. 79.03% vs. 84.3%). The overall computational time of CT-iFR was 61 ± 6 min, faster than that of the CT-FFR (8 h). The sensitivity, specificity, positive predictive value, and negative predictive value of the CT-iFR in discriminating an invasive FFR > 0.8 were 78% (95% CI: 40-97%), 92% (95% CI: 82-98%), 64% (95% CI: 39-83%), and 96% (95% CI:88-99%), respectively.

CONCLUSIONS

A high-fidelity geometric multiscale hemodynamic model was developed for rapid and accurate estimation of CT-iFR. Compared with CT-FFR, CT-iFR is of less computational cost and enables assessment of tandem lesions.

Insufficient adenosine-induced hyperemia is a major determinant of discordance between non-hyperemic pressure ratio and fractional flow reserve

Adenosine occasionally overestimates fractional flow reserve (FFR) values (i.e., insufficient adenosine-induced hyperemia), leading to low non-hyperemic pressure ratios (NHPR)-high FFR discordance. We investigated the impact of insufficient adenosine-induced hyperemia on NHPR-FFR discordance and the reclassification of functional significance. We measured resting distal-to-aortic pressure ratio (Pd/Pa) and FFR by using adenosine (FFR_ADN) and papaverine (FFR_PAP) in 326 patients (326 vessels). FFR_ADN overestimation was calculated as FFR_ADN - FFR_PAP. We explored determinants of low Pd/Pa - high FFR_ADN discordance (Pd/Pa ≤ 0.92 and FFR_ADN > 0.80) versus high Pd/Pa - low FFR_ADN discordance (Pd/Pa > 0.92 and FFR_ADN ≤ 0.80). Reclassification of functional significance was defined as FFR_ADN > 0.80 and FFR_PAP ≤ 0.80. Multivariable analysis identified FFR_ADN overestimation (p = 0.002) and heart rate at baseline (p = 0.048) as independent determinants of the low Pd/Pa-high FFR_ADN discordance. In the low Pd/Pa-high FFR_ADN group (n = 26), papaverine produced a further decline in the FFR value in 21 vessels (81%) compared with FFR_ADN, and the reclassification was observed in 17 vessels (65%). Insufficient adenosine-induced hyperemia is a major determinant of the low resting Pd/Pa-high FFR discordance. Physicians should bear in mind that the presence of low NHPR-high FFR discordance may indicate a false-negative FFR result.

Combined use of hyperemic and non-hyperemic pressure ratios for revascularization decision-making: From the ILIAS registry

OBJECTIVE

The aim of this study is to evaluate the diagnostic and prognostic value of non-hyperaemic Pd/Pa and to determine its additional value when combined with the gold standard hyperaemic pressure ratio (FFR) to guide revascularization.

METHODS

In a large, multi-center, retrospective registry, we included a total of 2141 patients with a clinical indication for coronary angiography providing physiological data in 2726 vessels. A classification was made based on the FFR (cut-off value: 0.80) and non-hyperaemic Pd/Pa (cut-off value: 0.92) values and the primary outcome was target-vessel failure (TVF) at 5-year follow-up.

RESULTS

Mean age was 63 ± 10.0 and 75% of the study population were men. Regression analysis showed an overall good correlation between FFR and non-hyperaemic Pd/Pa (r = 0.73, p < 0.005) and discordance was present in 17% of the vessels. Resting Pd/Pa was independently associated with TVF at 5-year follow-up (HR 0.08, 95%CI: 0.02-0.27; p < 0.005). The risk for TVF was the lowest in vessles with concordant normal pressure ratio's, with the highest risk in vessels with any abnormal pressure ratio in which revascularization was deferred. In these vessels, there was no difference in risk for TVF between the discordant and concordant abnormal values.

CONCLUSION

Abnormal pressure ratios in both non-hyperemic and hyperemic conditions portend important prognostic value. Combined application of FFR and non-hyperemic Pd/Pa efficiently identifies those vessels with concordant normal resting and hyperemic pressure ratios of which long-term clinical outcomes are excellent. These data lead to hypothesize that the decision to defer revascularization should potentially be based on combined non-hyperemic and hyperemic pressure ratios.

CLINICAL TRIAL REGISTRATION

Inclusive Invasive Physiological Assessment in Angina Syndromes Registry (ILIAS Registry), NCT04485234.

Impact of overestimation of fractional flow reserve by adenosine on anatomical-functional mismatch

Adenosine occasionally results in overestimation of fractional flow reserve (FFR) values, compared with other hyperemic stimuli. We aimed to elucidate the association of overestimation of FFR by adenosine with anatomically significant but functionally non-significant lesions (anatomical-functional mismatch) and its influence on reclassification of functional significance. Distal-to-aortic pressure ratio (Pd/Pa) was measured using adenosine (Pd/PaADN) and papaverine (Pd/PaPAP) in 326 patients (326 vessels). The overestimation of FFR was calculated as Pd/PaADN-Pd/PaPAP. The anatomical-functional mismatch was defined as diameter stenosis > 50% and Pd/PaADN > 0.80. Reclassification was indicated by Pd/PaADN > 0.80 and Pd/PaPAP ≤ 0.80. The mismatch (n = 72) had a greater overestimation of FFR than the non-mismatch (n = 99): median 0.02 (interquartile range 0.01-0.05) versus 0.01 (0.00-0.04), p = 0.014. Multivariable analysis identified the overestimation of FFR (p = 0.003), minimal luminal diameter (p = 0.001), and non-left anterior descending artery (LAD) location (p < 0.001) as determinants of the mismatch. Reclassification was indicated in 29% of the mismatch and was more frequent in the LAD than in the non-LAD (52% vs. 20%, p = 0.005). The overestimation of FFR is an independent determinant of anatomical-functional mismatch. Anatomical-functional mismatch, specifically in the LAD, may suggest a false-negative result.

Diagnostic agreement of quantitative flow ratio with fractional flow reserve in a Latin-American population

Quantitative flow ratio (QFR) is a recently proposed angiographic index that allows to assess the pressure loss in coronary arteries in a similar fashion as the fractional flow reserve (FFR). The purpose of this study was to evaluate the diagnostic performance of QFR as compared to FFR, in a Latin-American population of patients with suspected ischaemic heart disease. QFR was retrospectively derived from coronary angiograms. The association, diagnostic performance, and continuous agreement of fixed-flow QFR (fQFR) and contrast-flow QFR (cQFR) with FFR was assessed by continuous and dichotomous methods. 90 vessels form 66 patients were finally included. The study comprised coronary stenoses of intermediate severity, both angiographically (diameter stenosis: 46.6 ± 12.8%) and physiologically [median FFR = 0.83 (quartile 1-3, 0.76-0.89)]. The correlation of FFR with both fQFR [ρ = 0.841, (95% CI 0.767 to 0.893), p < 0.001] and cQFR [ρ = 0.833, (95% CI 0.755 to 0.887), p < 0.001] was strong. The diagnostic performance of cQFR was good [area under the ROC curve of 0.92 (95% CI 0.86 to 0.97, p < 0.001)], with 0.80 as the optimal cQFR cut-off against FFR ≤ 0.80. This 0.80 cQFR cut-off classified correctly 83.3% of total stenoses, with a sensitivity of 85.2% and specificity of 80.6%. QFR was strongly associated with FFR and exhibited a high diagnostic performance in this Latin-American population.

The quantitative relationship between coronary microcirculatory resistance and myocardial ischemia in patients with coronary artery disease

It was hypothesized that the microcirculatory resistance of resting state (R_m-res) might be a good predictor for ischemia. In this study, the quantitative relationship between R_m-res and myocardial ischemia in different stenosed degrees was explored and verified through retrospective analysis, and the diagnostic performance was evaluated. 136 patients were screened and divided into a training set (90 patients) and a validation set (46 patients). In the training set, R_m-res was calculated, and thresholds were determined by exploring the relationship between R_m-res and myocardial ischemia in different stenosed degrees. In the validation set, the diagnostic performance of the thresholds was verified. It was found that the 90 data mean difference (95%CI) of R_m-res between the ischemic group and the non-ischemic group was 63.03 (95 %CI: 25.72-100.34), p < 0.05. In the training set with stenosed degree 41-60%, 61-70%, 71-80%, and >81%, the average of R_m-res in the ischemic and non-ischemic groups were (80.79, 136.87), (96.41, 172.62), (128.99, 198.94) and (175.95, 310.79) mmHg/s/ml. The R_m-res thresholds were 87.18, 118.96, 142.35, and 177.39 mmHg/s/ml. In the validation set, the overall sensitivity, specificity, PPV, NPV, and accuracy were 73.3%, 77.4%, 61.1%, 85.7%, and 76.1%. In conclusion, R_m-res had a significant predictor on myocardial ischemia. As a smaller R_m-res represents greater myocardial mass perfusion, it is more likely that a stenosis will have a functional impact. Threshold analysis showed that R_m-res of different stenosed degrees was a quantitative predictor of myocardial ischemia, which could assist physicians with clinical treatment strategies.

Linear concentration-response relationship of serum caffeine with adenosine-induced fractional flow reserve overestimation: a comparison with papaverine

BACKGROUND

Caffeine intake from one cup of coffee one hour before adenosine stress tests, corresponding to serum caffeine levels of 3-4 mg/L, is thought to be acceptable for non-invasive imaging.

AIMS

We aimed to elucidate whether serum caffeine is independently associated with adenosine-induced fractional flow reserve (FFR) overestimation and their concentration-response relationship.

METHODS

FFR was measured using adenosine (FFRADN) and papaverine (FFRPAP) in 209 patients. FFRADN overestimation was defined as FFRADN - FFRPAP. The locally weighted scatterplot smoothing (LOWESS) approach was applied to evaluate the relationship between serum caffeine level and FFRADN overestimation. Multiple regression analysis was used to determine independent factors associated with FFRADN overestimation.

RESULTS

Caffeine was ingested at <12 hours in 85 patients, at 12-24 hours in 35 patients, and at >24 hours in 89 patients. Multiple regression analysis identified serum caffeine level as the strongest factor associated with FFRADN overestimation (p<0.001). The LOWESS curve demonstrated that FFRADN overestimation started from just above the lower detection limit of serum caffeine and increased approximately 0.01 FFR unit per 1 mg/L increase in serum caffeine level with a linear relationship. The 90th percentile of serum caffeine levels for the ≤12-hour, the 12-24-hour, and the >24-hour groups corresponded to FFRADN overestimations by 0.06, 0.03, and 0.02, respectively.

CONCLUSIONS

Serum caffeine overestimates FFRADN values in a linear concentration-response manner. FFRADN overestimation occurs at much lower serum caffeine levels than those that were previously believed. Our results highlight that standardised caffeine control is required for reliable adenosine-induced FFR measurements.

Association of Echocardiographic Diastolic Dysfunction with Discordance of Invasive Intracoronary Pressure Indices

Instantaneous wave-free ratio (iFR)-guided coronary revascularization has similar clinical outcomes compared to fractional flow reserve (FFR)-guided revascularization strategy. However, some studies have shown a discordance of around 20% between iFR and FFR. Although various factors have been reported in the literature to affect pressure indices and lead to such discordance, there is a paucity of data regarding the effect of diastolic dysfunction on functional assessment of coronary arteries. Our study aimed to investigate whether there was an association between echocardiographic left ventricular diastolic dysfunction and iFR/FFR discordance. This retrospective observational study evaluated 100 patients with angiographically intermediate coronary stenosis (50-70%) who underwent physiological testing with iFR and FFR. Transthoracic echocardiograms were reviewed to assess echocardiographic indices of diastolic function. The study population was divided into two groups based on diastolic function. iFR and FFR discordance was measured in each group and compared to evaluate the statistical difference. The mean age of the study population was 66.22 ± 10.02 years. Discordance between iFR and FFR was seen in 45.16% of patients with diastolic dysfunction compared to 24.64% of patients with normal diastolic function (p = 0.04). Multivariable logistic regression analysis indicated that echocardiographic E/e' was independently associated with iFR/FFR discordance (p = 0.02). Left ventricular diastolic dysfunction is a significant factor that can lead to discordance between iFR and FFR and should be taken into account during coronary physiological testing.

Physiology-Based Revascularization: A New Approach to Plan and Optimize Percutaneous Coronary Intervention

Coronary physiological assessment using fractional flow reserve or nonhyperemic pressure ratios has become a standard of care for patients with coronary atherosclerotic disease. However, most evidence has focused on the pre-interventional use of physiological assessment to aid revascularization decision-making, whereas post-interventional physiological assessment has not been well established. Although evidence for supporting the role of post-interventional physiological assessment to optimize immediate revascularization results and long-term prognosis has been reported, a more thorough understanding of these data is crucial in incorporating post-interventional physiological assessment into daily practice. Recent scientific efforts have also focused on the potential role of pre-interventional fractional flow reserve or nonhyperemic pressure ratio pullback tracings to characterize patterns of coronary atherosclerotic disease to better predict post-interventional physiological outcomes, and thereby identify the appropriate revascularization target. Pre-interventional pullback tracings with dedicated post-processing methods can provide characterization of focal versus diffuse disease or major gradient versus minor gradient stenosis, which would result in different post-interventional physiological results. This review provides a comprehensive look at the current evidence regarding the evolving role of physiological assessment as a functional optimization tool for the entire process of revascularization, and not merely as a pre-interventional tool for revascularization decision-making.

Optimal Prognostication of Patients with Coronary Stenoses in the Pre- and Post-PCI setting: Comments on TARGET FFR and DEFINE-FLOW Trials Presented at TCT Connect 2020

The body of evidence for the use of coronary physiology assessments to guide percutaneous coronary intervention (PCI) has been growing continuously in recent decades. Two studies presented during TCT Connect 2020 added insights into the prognostic value of coronary physiology measurements in pre- and post-PCI settings. The first study, TARGET FFR, assessed whether a post-PCI fractional flow reserve (FFR)-guided incremental optimisation strategy (PIOS) was superior to angiography-guided PCI. The second study, DEFINE-FLOW, assessed the course of stenoses with fractional and coronary flow reserve (FFR+/CFR-) discordance when treated medically. This article summarises the main results from the TARGET FFR and the DEFINE-FLOW trials and puts them into the context of the existing literature.

Effect of Elevated Left Ventricular End Diastolic Pressure on Instantaneous Wave-Free Ratio and Fractional Flow Reserve Discordance

Background

Instantaneous wave-free ratio (iFR)-guided physiological assessment has been shown to be non-inferior to fractional flow reserve (FFR)-guided assessment for deciding best treatment strategy for angiographically intermediate stenosis. The diagnostic accuracy of iFR compared to FFR reported in various studies is around 80%. Many factors can lead to iFR/FFR discordance, though underlying physiological mechanism of discordance and its associated factors have not been fully evaluated. The effect of left ventricle end diastolic pressure (LVEDP) on iFR/FFR discordance is unknown and needs further evaluation.

Methods

We performed a single center, non-randomized, both retrospective and prospective study. A total of 65 patients with intermediate coronary stenosis undergoing physiological assessment were included in the study. Patients were assigned to two groups (normal LVEDP and high LVEDP group) based on LVEDP cutoff of 15 mm Hg. iFR and FFR were measured for each patient and iFR/FFR results were compared between the two groups.

Results

A significantly large number of patients in elevated LVEDP group had iFR/FFR discordance compared to normal LVEDP group (42.8% vs. 6.7%, P = 0.001). More patients with acute coronary syndrome (ACS) had discordance compared to stale coronary artery disease (CAD) patients (53% vs. 15%, P = 0.003).

Conclusions

Elevated LVEDP can affect iFR and FFR measurements and can lead to discordance. Further studies are required to determine effect of elevated LVEDP on iFR/FFR discordance and whether such discordance is clinically relevant. “Normal range” iFR results should be cautiously interpreted in patients with elevated LVEDP, especially those with ACS.

Physiology-Based Revascularization of Left Main Coronary Artery Disease

It is of critical importance to correctly assess the significance of a left main lesion. Underestimation of significance beholds the risk of inappropriate deferral of revascularization, whereas overestimation may trigger major but unnecessary interventions. This article addresses the invasive physiological assessment of left main disease and its role in deciding upon revascularization. It mainly focuses on the available evidence for fractional flow reserve and instantaneous wave-free ratio, their interpretation, and limitations. We also discuss alternative invasive physiological indices and imaging, as well as the link between physiology, ischemia, and prognosis.