Adenosine intracoronary bolus dose escalation versus intravenous infusion to induce maximum coronary hyperemia for fractional flow reserve assessment

The Impact of Microvascular Resistance Reserve on the Outcome of Patients With STEMI

BACKGROUND

Microvascular resistance reserve (MRR) can characterize coronary microvascular dysfunction (CMD); however, its prognostic impact in ST-segment elevation myocardial infarction (STEMI) patients remains undefined.

OBJECTIVES

This study sought to investigate the prevalence of CMD in STEMI patients and to elucidate the prognostic performance of MRR.

METHODS

This prospective cohort study enrolled 210 STEMI patients with multivessel disease who underwent successful revascularization and returned at 3 months for coronary physiology assessments with bolus thermodilution. The prevalence of CMD (MRR <3) and the association between MRR and major adverse cardiovascular and cerebrovascular events (MACCEs) at 12 months were investigated.

RESULTS

The median age of patients was 65 years, and 59.5% were men. At the 3-month follow-up, 56 patients (27%) had CMD (MRR <3.0). The number of MACCEs at 12 months was higher in patients with vs without CMD (48.2% vs 11.0%; P < 0.001). MRR was independently associated with 12-month MACCEs (HR: 0.45 per unit increase; 95% CI: 0.31-0.67; P < 0.001) and with stroke, heart failure, and poorer recovery in left ventricular systolic function. The areas under the receiver-operating characteristic curves for predicting MACCEs at 12 months with fractional flow reserve, coronary flow reserve (CFR), the index of microvascular resistance (IMR), and MRR were 0.609, 0.762, 0.781, and 0.743, respectively. The prognostic performance of CFR, IMR, and MRR were all comparable.

CONCLUSIONS

The novel parameter MRR is a prognostic marker of MACCEs in STEMI patients with a comparable performance to CFR and IMR. (Impact of TMAO Serum Levels on Hyperemic IMR in STEMI Patients [TAMIR]; NCT05406297).

Implementation of Microcirculation Examination in Clinical Practice-Insights from the Nationwide POL-MKW Registry

Background and Objectives: The assessment of coronary microcirculation may facilitate risk stratification and treatment adjustment. The aim of this study was to evaluate patients' clinical presentation and treatment following coronary microcirculation assessment, as well as factors associated with an abnormal coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) values. Materials and Results: This retrospective analysis included 223 patients gathered from the national registry of invasive coronary microvascular testing collected between 2018 and 2023. Results: The frequency of coronary microcirculatory assessments in Poland has steadily increased since 2018. Patients with impaired IMR (≥25) were less burdened with comorbidities. Patients with normal IMR underwent revascularisation attempts more frequently (11.9% vs. 29.8%, p = 0.003). After microcirculation testing, calcium channel blockers (CCBs) and angiotensin-converting enzyme inhibitors were added more often for patients with IMR and CFR abnormalities, respectively, as compared to control groups. Moreover, patients with coronary microvascular dysfunction (CMD, defined as CFR and/or IMR abnormality), regardless of treatment choice following microcirculation assessment, were provided with trimetazidine (23.2%) and dihydropyridine CCBs (26.4%) more frequently than those without CMD who were treated conservatively (6.8%) and by revascularisation (4.2% with p = 0.002 and 0% with p < 0.001, respectively). Multivariable analysis revealed no association between angina symptoms and IMR or CFR impairment. Conclusions: The frequency of coronary microcirculatory assessments in Poland has steadily increased. Angina symptoms were not associated with either IMR or CFR impairment. After microcirculation assessment, patients with impaired microcirculation, expressed as either low CFR, high IMR or both, received additional pharmacotherapy treatment more often.

Comparison of Fractional Flow Reserve with Resting Non-Hyperemic Indices in Patients with Coronary Artery Disease

Guidelines recommend using hyperemic (FFR) and non-hyperemic (iFR/RFR) methods of evaluating coronary artery stenoses in patients with coronary artery disease. However, in some cases, achieved results indicating significant ischemia may differ between those methods. Thus, we sought to identify predictors of such a discrepancy. Data were collected on all consecutive patients with chronic coronary syndrome hospitalized between 2020 and 2021. For 279 patients (417 vessels), results for both FFR and iFR/RFR were available. Values of ≤0.80 for FFR and ≤0.89 for iFR/RFR were considered positive for ischemia. Discordant measurements of FFR and iFR/RFR were observed in 80 (19.2%) patients. Atrial fibrillation was the only predictor of the overall FFR and iFR/RFR discordance - OR (95%CI) 1.90 (1.02-3.51); p = 0.040. The chance of positive FFR and negative iFR/RFR decreased independently with age - OR (95%CI) 0.96 (0.93-0.99); p = 0.024. On the contrary, insulin-treated diabetes mellitus was the predictor of negative FFR and positive iFR/RFR discrepancy - OR (95%CI) 4.61 (1.38-15.40); p = 0.013. In everyday clinical practice, iFR/FFR correlates well with FFR. However, discordance between these methods is quite common. Physicians should be aware of the risk of such discordance in patients with atrial fibrillation, advanced age, and insulin-treated diabetes mellitus.

The impact of coronary microvascular dysfunction on the discordance between fractional flow reserve and resting full-cycle ratio in patients with chronic coronary syndromes

Background

Resting full-cycle ratio (RFR) is an alternative to fractional flow reserve (FFR) for the evaluation of borderline coronary artery lesions. Although FFR and RFR results are discordant in some cases, factors associated with the discordance remain unclear. The role of coronary microvascular dysfunction (CMD) is discussed as a potential mechanism to explain these discrepancies.

Aim

The study aimed to assess concordance between RFR and FFR in a real-life cohort from a high-volume center regarding the role of CMD.

Methods

Consecutive patients with borderline coronary lesions undergoing coronary functional testing for chronic coronary syndromes were included in the study. Measurements of RFR and FFR were performed alongside additional coronary flow reserve (CFR), resistance reserve ratio (RRR), and an index of microcirculatory resistance (IMR) measurements. CMD was defined according to the current guideline by either IMR ≥25 or CFR ≤2.0 in vessels with no significant stenosis.

Results

Measurements were performed in 157 coronary arteries, in 101 patients, with a median age of 66 y., 74% male, with prior history of arterial hypertension (96%), dyslipidaemia (91%), and diabetes (40%). The median value of vessel diameter stenosis was 45% according to QCA.

Overall, FFR and RFR values were significantly correlated (r = 0.66, p < 0.001), where positive FFR/negative RFR and negative FFR/positive RFR were observed in 6 (3.8%) and 38 (24.2%) of 157 vessels. The RFR/FFR discrepancy was present in 44 (28%) of measurements. CMD was confirmed in 28 (64%) of vessels with discrepant RFR/FFR and in 46 (41%) of vessels with concordant results (p = 0.01). In discordant RFR/FFR vessels, as compared to concordant ones, significantly lower values of CFR [median 1.95 (IQR: 1.37, 2.30) vs. 2.10 (IQR: 1.50, 3.00), p = 0.030] and RRR [median 2.50 (IQR: 1.60, 3.10) vs. 2.90 IQR (1.90, 3.90), p = 0.048] were observed.

Main predictors of RFR/FFR discrepancy in a univariate regression analysis were: higher age of patients [OR = 1.06 (1.01; 1.10), p = 0.010], presence of CMD [OR = 2.51 (1.23; 5.25), p = 0.012], lower CFR [OR = 1.64 (1.12; 2.56), p = 0.018], and lower RRR values [OR = 1.35 (95% CI: 1.03; 1.83), p = 0.038].

Conclusion

In discrepant RFR/FFR vessels, CMD is more prevalent than in concordant RFR/FFR measurements, which can be driven by lower CFR or RRR values. Further research is needed to confirm this observation.

Quantitative flow ratio for evaluation of borderline coronary lesions in patients with severe aortic stenosis

INTRODUCTION AND OBJECTIVES

Quantitative flow ratio (QFR) is a novel noninvasive method for evaluating coronary physiology. However, data on the QFR in patients with aortic stenosis (AS) and coronary artery disease are scarce. Thus, we compared the diagnostic performance of the QFR with that of the resting distal to aortic coronary pressure (Pd/Pa) ratio, fractional flow reserve (FFR), and instantaneous wave-free ratio (iFR), as well as angiographic indices.

METHODS

A total of 221 AS patients with 416 vessels undergoing FFR/iFR measurements were enrolled in the study.

RESULTS

The mean percent diameter stenosis (%DS) was 58.6%±13.4% and the mean Pd/Pa ratio, FFR, iFR, and QFR were 0.95±0.03, 0.85±0.07, 0.90±0.04, and 0.84±0.07, respectively. A FFR ≤ 0.80 was noted in 26.0% of interrogated vessels, as well as an iFR ≤ 0.89 in 33.2% and QFR ≤ 0.80 in 31.7%. The QFR had better agreement with FFR (intraclass correlation coefficient [ICC], 0.96; 95% confidence interval [95%CI], 0.95-0.96) than with the iFR (ICC, 0.79; 95%CI, 0.75-0.82) and Pd/Pa ratio (ICC, 0.52; 95%CI, 0.44-0.58). In addition, the QFR showed better diagnostic accuracy (98.6% vs 94.2%; P <.001) and discriminant function (area under the curve=0.996 vs 0.988; P <.001) when the iFR was used as the reference instead of FFR.

CONCLUSIONS

In patients with AS, the QFR has good agreement with both FFR and iFR. However, the agreement appears to be even better when the iFR is used as the reference, presumably due to the complex nature of the coronary physiology in the assessment of coronary artery disease in patients with severe AS.

Hyperemic versus non-hyperemic indexes for coronary physiology assessment in patients with severe aortic stenosis

PURPOSE

Recent data suggests that fractional flow reserve (FFR) may underestimate intermediate coronary stenosis in the presence of severe aortic stenosis (AS), whereas instantaneous wave-free ratio (iFR) values may remain similar after treatment of AS, yet the evidence still lacks to use iFR as the reference. We aimed to compare FFR/iFR values in the AS setting.

MATERIALS AND METHODS

The functional significance of 416 coronary lesions in 221 patients with severe AS was investigated with iFR and FFR.

RESULTS

The diagnostic agreement between iFR and FFR has been tested, using the cut-off value of 0.89 for iFR and 0.80 for FFR. The mean diameter stenosis was 58.6 ​± ​13.4% with FFR of 0.85 ​± ​0.07 and iFR of 0.90 ​± ​0.04. FFR ≤0.80 was identified in 26.0% and iFR≤0.89 in 33.2% of interrogated vessels. Good agreement between iFR and FFR was confirmed (Intraclass Correlation Coefficient 0.83 [95%CI 0.79-0.85]). The overall diagnostic accuracy (AUC in ROC analysis) of FFR in detecting iFR≤0.89 was 0.997 (95%CI 0.986 to 1.000; p<0.001) and of iFR in detecting FFR≤0.80 was 0.995 (95%CI 0.983 to 0.999; p<0.001). The optimal cut-off value for FFR to detect iFR≤0.89 was 0.82 with sensitivity, specificity, and accuracy of 97.1%, 98.9%, and 97.7%, respectively, and for IFR to detect FFR≤0.80 was 0.88 with sensitivity, specificity, and accuracy of 99.1%, 95.8%, and 97.4%, respectively.

CONCLUSION

In the presence of AS, FFR has good agreement with iFR. However, the optimal FFR/iFR threshold to identify iFR≤0.89/FFR≤0.80 may be different from the standard thresholds of ischemia.

Borderline coronary lesion assessment with quantitative flow ratio and its relation to the instantaneous wave-free ratio

PURPOSE

Quantitative flow ratio (QFR) is a recently developed image-based index for the assessment of borderline coronary artery disease. We sought to investigate a correlation between QFR and instantaneous wave-free ratio (iFR) for the assessment of intermediate coronary stenoses.

MATERIALS AND METHODS

Patients with borderline coronary lesions (40-90% by visual assessment) undergoing iFR assessment were enrolled. QFR was derived from a modeled hyperemic flow velocity derived from angiography without adenosine-induced hyperemia. Pressure wire-derived iFR served as the reference.

RESULTS

Values of QFR and iFR from 110 vessels with a mean percent diameter stenosis of 44.6 ​± ​12.0% were compared. Mean iFR was 0.90 ​± ​0.07 and 38 (34.5%) had iFR ≤0.89. Mean QFR was 0.81 ​± ​0.10 and 44 (40%) had QFR ≤0.80. A good agreement between QFR and iFR measurements was confirmed with a mean difference of 0.09 (95%CI -0.027 to 0.207) and intraclass correlation coefficient of 0.87 (95%CI 0.81-0.91). The overall diagnostic accuracy (AUC in ROC analysis) of QFR in detecting iFR ≤0.89 was 0.87 (95%CI 0.79-0.93; p ​< ​0.001). Regarding iFR ≤0.89, the optimal cutoff value of QFR was 0.79 with sensitivity, specificity, and accuracy of 76.3%, 83.3%, and 80.0%, respectively. A 100% sensitivity was observed for a QFR cutoff value of 0.88 and a 100% specificity for a QFR cutoff value of 0.69.

CONCLUSIONS

Our study confirmed good QFR diagnostic performance and correlation with iFR for detecting the functional ischemia caused by intermediate lesions in coronary arteries. However, the pressure wire assessment with iFR might be warranted in 2/3 of patients after QFR assessment.

Contrast medium Pd/Pa ratio in comparison to fractional flow reserve, quantitative flow ratio and instantaneous wave-free ratio for evaluation of intermediate coronary lesions

Introduction

Contrast medium Pd/Pa ratio (cFFR) was introduced as an alternative to fractional flow reserve (FFR).

Aim

To assess the accuracy of cFFR in predicting of FFR, quantitative flow ratio (QFR) and instantaneous wave-free ratio (iFR).

Material and methods

Resting Pd/Pa, cFFR, FFR, QFR, and iFR were measured in 110 intermediate coronary lesions. cFFR was obtained after intracoronary injection of contrast medium. FFR was measured after the intravenous administration of adenosine. QFR was derived from fixed empiric hyperemic flow velocity based on coronary angiography. iFR was calculated by measuring the resting pressure gradient across a coronary lesion during diastole.

Results

Forty-four patients with 110 intermediate coronary lesions were enrolled. Mean baseline Pd/Pa was 0.93 ±0.05. Mean cFFR value was similar to FFR value (0.83 ±0.09 vs. 0.81 ±0.09; p = 0.13) and QFR (0.81 ±0.1; p = 0.69) and iFR (0.90 ±0.07; p = 0.1). A total of 46 vessels (41.8%) had FFR ≤ 0.80, 50 (45.5%) vessels had cFFR ≤ 0.83, 44 (40.0%) vessels had QFR ≤ 0.80, and 38 (34.5%) vessels had iFR ≤ 0.89. An excellent agreement between cFFR and resting Pd/Pa, FFR, QFR, and iFR was confirmed (intraclass correlation coefficients of 0.83, 0.99, 0.98, and 0.88, respectively). The optimal cutoff value of cFFR was 0.83 for prediction of FFR ≤ 0.80 with sensitivity, specificity, and accuracy of 96.9%, 97.8%, and 97.3%, respectively. 100% sensitivity was observed for a cutoff value of 0.82 and 100% specificity for a cutoff value of 0.84; AUC = 0.998 (0.995–1.00); p < 0.001.

Conclusions

Contrast medium Pd/Pa ratio seems to be accurate in predicting the functional significance of borderline coronary lesions assessed with FFR, iFR, and QFR.