Diagnostic Performance of Angiography-Derived Quantitative Flow Ratio in Complex Coronary Lesions

BACKGROUND

Quantitative flow ratio derived from computed tomography angiography (CT-QFR) and invasive coronary angiography (Murray law-based quantitative flow ratio [μQFR]) are novel approaches enabling rapid computation of fractional flow reserve without the use of pressure guidewires and vasodilators. However, the feasibility and diagnostic performance of both CT-QFR and μQFR in evaluating complex coronary lesions remain unclear.

METHODS

Between September 2014 and September 2021, 240 patients with 30% to 90% coronary diameter stenosis who underwent both coronary computed tomography angiography and invasive coronary angiography with fractional flow reserve within 60 days were retrospectively enrolled. The diagnostic performance of CT-QFR and μQFR in detecting functional ischemia among all lesions, especially complex coronary lesions, was analyzed using fractional flow reserve as the reference standard.

RESULTS

CT-QFR and μQFR analyses were performed on 309 and 289 vessels, respectively. The diagnostic sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for CT-QFR in all lesions at the per-vessel level were 91% (with a 95% CI of 84%-96%), 92% (95% CI, 88%-95%), 83% (95% CI, 75%-90%), 96% (95% CI, 93%-98%), and 92% (95% CI, 88%-95%), with values for μQFR of 90% (95% CI, 81%-95%), 97% (95% CI, 93%-99%), 92% (95% CI, 84%-97%), 96% (95% CI, 92%-98%), and 94% (95% CI, 91%-97%), respectively. Among bifurcation, tandem, and moderate-to-severe calcified lesions, the diagnostic values of CT-QFR and μQFR showed great correlation and agreement with those of invasive fractional flow reserve, achieving an area under the receiver operating characteristic curve exceeding 0.9 for each complex lesion at the vessel level. Furthermore, the accuracies of CT-QFR and μQFR in the gray zone were 85% and 84%, respectively.

CONCLUSIONS

Angiography-derived quantitative flow ratio (CT-QFR and μQFR) demonstrated remarkable diagnostic performance in complex coronary lesions, indicating its pivotal role in the management of patients with coronary artery disease.

Nonhyperemic Pressure Ratios-All the Same or Nuanced Differences?

Fractional flow reserve (FFR) has become the gold standard for invasively assessing the functional significance of coronary artery disease (CAD) to guide revascularization. The amount of evidence supporting the role of FFR in the cardiac catheterization laboratory is large and still growing. However, FFR uptake in the daily practice is limited by a variety of factors such as invasive instrumentation of the coronary artery that requires extra time and need for vasodilator medications for hyperemia. In this review, we describe the details of wire-based alternatives to FFR, providing insights as to their development, clinical evidence, and limitations.

Practical Application of Coronary Physiologic Assessment: Asia-Pacific Expert Consensus Document: Part 1

Coronary physiologic assessment is performed to measure coronary pressure, flow, and resistance or their surrogates to enable the selection of appropriate management strategy and its optimization for patients with coronary artery disease. The value of physiologic assessment is supported by a large body of evidence that has led to major recommendations in clinical practice guidelines. This expert consensus document aims to convey practical and balanced recommendations and future perspectives for coronary physiologic assessment for physicians and patients in the Asia-Pacific region based on updated information in the field that including both wire- and image-based physiologic assessment. This is Part 1 of the whole consensus document, which describes the general concept of coronary physiology, as well as practical information on the clinical application of physiologic indices and novel image-based physiologic assessment.

Nonhyperemic Pressure Ratios-All the Same or Nuanced Differences?

Fractional flow reserve (FFR) has become the gold standard for invasively assessing the functional significance of coronary artery disease (CAD) to guide revascularization. The amount of evidence supporting the role of FFR in the cardiac catheterization laboratory is large and still growing. However, FFR uptake in the daily practice is limited by a variety of factors such as invasive instrumentation of the coronary artery that requires extra time and need for vasodilator medications for hyperemia. In this review, we describe the details of wire-based alternatives to FFR, providing insights as to their development, clinical evidence, and limitations.

Reliability of Fractional Flow Reserve and Instantaneous Wave-Free Ratio in Assessing Intermediate Coronary Stenosis in Patients With Atrial Fibrillation

Despite the current use of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) for guiding revascularization in atrial fibrillation (AF), there is a lack of studies evaluating their reliability in this particular population. This retrospective study aimed to investigate the reliability of FFR and iFR in patients with AF. This retrospective study included all patients with AF undergoing FFR measurements (n = 45 vessels from 36 patients) at Brugmann University Hospital, Brussels, Belgium, between 2012 and 2020 or iFR (n = 18 vessels from 13 patients) and a corresponding number of patients with sinus rhythm (SR) randomly selected from the same period, benefiting from iFR (n = 20 vessels from 17 patients) or FFR (n = 50 vessels from 37 patients). Our main findings indicate that there is an increased beat-to-beat variability of individual iFR measures in patients with AF, compared with SR. In addition, the reproducibility of iFR on test-retest is low in patients with AF, leading to increased lesion reclassification (53.8% of lesions reclassified on 2 consecutive iFR measurements in AF vs 6.6% lesions reclassified in SR, p <0.05). In contrast, FFR seems to be more robust in evaluating coronary lesions in AF in terms of equivalent variability, reproducibility, and lesion reclassification observed in the SR population. In conclusion, this is the first study to evaluate the reliability of iFR and FFR in AF. Our findings raise caution in using iFR to guide revascularization in patients with AF, whereas FFR seems to be more robust in this population.

Fractional Flow Reserve: Patient Selection and Perspectives

The aim of this review was to discuss the current practice and patient selection for invasive FFR, new techniques to estimate invasive FFR and future of coronary physiology tests. We elaborate on the indication and application of FFR and on the contraindications and concerns in certain patient populations.

Invasive and non-invasive assessment of ischaemia in chronic coronary syndromes: translating pathophysiology to clinical practice

Intracoronary physiology testing has emerged as a valuable diagnostic approach in the management of patients with chronic coronary syndrome, circumventing limitations like inferring coronary function from anatomical assessment and low spatial resolution associated with angiography or non-invasive tests. The value of hyperaemic translesional pressure ratios to estimate the functional relevance of coronary stenoses is supported by a wealth of prognostic data. The continuing drive to further simplify this approach led to the development of non-hyperaemic pressure-based indices. Recent attention has focussed on estimating physiology without even measuring coronary pressure. However, the reduction in procedural time and ease of accessibility afforded by these simplifications needs to be counterbalanced against the increasing burden of physiological assumptions, which may impact on the ability to reliably identify an ischaemic substrate, the ultimate goal during catheter laboratory assessment. In that regard, measurement of both coronary pressure and flow enables comprehensive physiological evaluation of both epicardial and microcirculatory components of the vasculature, although widespread adoption has been hampered by perceived technical complexity and, in general, an underappreciation of the role of the microvasculature. In parallel, entirely non-invasive tools have matured, with the utilization of various techniques including computational fluid dynamic and quantitative perfusion analysis. This review article appraises the strengths and limitations for each test in investigating myocardial ischaemia and discusses a comprehensive algorithm that could be used to obtain a diagnosis in all patients with angina scheduled for coronary angiography, including those who are not found to have obstructive epicardial coronary disease.

Novel Indices of Coronary Physiology

Fractional flow reserve is the current invasive gold standard for assessing the ischemic potential of an angiographically intermediate coronary stenosis. Procedural cost and time, the need for coronary vessel instrumentation, and the need to administer adenosine to achieve maximal hyperemia remain integral components of invasive fractional flow reserve. The number of new alternatives to fractional flow reserve has proliferated over the last ten years using techniques ranging from alternative pressure wire metrics to anatomic simulation via angiography or intravascular imaging. This review article provides a critical description of the currently available or under-development alternatives to fractional flow reserve with a special focus on the available evidence, pros, and cons for each with a view towards their clinical application in the near future for the functional assessment of coronary artery disease.

Instantaneous wave-free ratio cutoff values for nonculprit stenosis classification in patients with ST-segment elevation myocardial infarction (an iSTEMI substudy)

OBJECTIVES

The instantaneous wave-free ratio cutoff value of <0.90 for hemodynamic significance of coronary stenoses has been validated in stable patients. We examined different cutoff values in the evaluation of nonculprit stenoses in patients with ST-segment elevation myocardial infarction.

METHODS

We measured instantaneous wave-free ratio across nonculprit stenoses in the acute setting and at follow-up in 120 patients with ST-segment elevation myocardial infarction and 157 nonculprit stenoses, of which, 113 patients with 147 nonculprit stenoses completed follow-up.

METHODS

The prevalence of nonculprit stenosis hemodynamic significance was 52% in the acute setting and 41% at follow-up. With follow-up, instantaneous wave-free ratio as reference, acute instantaneous wave-free ratio >0.90 had a negative predictive value of 89%. Acute instantaneous wave-free ratio <0.90 had a positive predictive value of 68%. Acute instantaneous wave-free ratio >0.93 had a negative predictive value of 100%. Acute instantaneous wave-free ratio <0.86 and <0.83 had positive predictive values of 71 and 77%. Using acute instantaneous wave-free ratio <0.90 as cutoff for hemodynamic significance yielded the highest degree of classification agreement between acute and follow-up instantaneous wave-free ratio.

CONCLUSIONS

In patients with ST-segment elevation myocardial infarction, acute instantaneous wave-free ratio with the cutoff values <0.90 for hemodynamic significance appears optimal in the evaluation of nonculprit stenoses and has a high negative predictive value and a moderate positive predictive value.

Diastolic-systolic velocity ratio to detect coronary stenoses under physiological resting conditions: a mechanistic study

Objective

Diastolic-systolic velocity ratio (DSVR) is a resting index to assess stenoses in the left anterior descending artery (LAD). DSVR can be measured by echocardiographic or intracoronary Doppler flow velocity. The objective of this cohort study was to elucidate the fundamental rationale underlying the decreased DSVR in coronary stenoses.

Methods

In cohort 1, simultaneous measurements of intracoronary Doppler flow velocity and pressure were acquired in the LAD of 228 stable patients. Phasic stenosis resistance, microvascular resistance and total vascular resistance (defined as stenosis and microvascular resistance combined) were studied during physiological resting conditions. Stenoses were classified according to severity by strata of 0.10 fractional flow reserve (FFR) units.

Results

DSVR was decreased in stenoses with lower FFR. Stenosis resistance was equal in systole and diastole for every FFR stratum. Microvascular resistance was consistently higher during systole than diastole. In lower FFR strata, stenosis resistance as a percentage of the total vascular resistance increases both during systole and diastole. The difference between the stenosis resistance as a percentage of total vascular resistance during systole and diastole increases for lower FFR strata, with an accompanying rise in diastolic-systolic resistance ratio. A significant inverse correlation was observed between DSVR and the diastolic-systolic resistance ratio (r=0.91, p<0.001). In cohort 2 (n=23), DSVR was measured both invasively and non-invasively by transthoracic echocardiography, yielding a good correlation (r=0.82, p<0.001).

Conclusions

The rationale by which DSVR is decreased distal to coronary stenoses is dependent on a comparatively higher influence of the increased stenosis resistance on total vascular resistance during diastole than systole.