Comparison Between the Performance of Quantitative Flow Ratio and Perfusion Imaging for Diagnosing Myocardial Ischemia

Exercise electrocardiogram combined with cadmium zinc tellurium (CZT) cardiac-dedicated single photon emission computed tomography (SPECT) predicts coronary artery disease

AIM

Coronary artery disease (CAD) is a primary cause of mortality, prompting ongoing research into noninvasive diagnostic modalities. This study aimed to evaluate the diagnostic efficacy of exercise electrocardiography testing (EET) combined with cadmium zinc tellurium cardiac-dedicated single photon emission computed tomography (CZT-SPECT) imaging for CAD.

MATERIALS AND METHODS

CZT-SPECT and EET were examined in 124 patients aged 20-85 years, followed by coronary angiography to evaluate the sensitivity, specificity, positive predictive value, and negative predictive value of EET/CZT-SPECT alone and in combination. CAD was defined as the presence of > 50% stenosis at the time of coronary angiography.

RESULTS

The sensitivity of the EET test alone was 31.58%, the specificity was 80%, the positive predictive value (PPV) was 22.22%, and the negative predictive value (NPV) was 86.6%. The corresponding values of CZT-SPECT alone were 36.07%, 92.06%, 81.48% and 59.79%, respectively. The combined results showed that the sensitivity, specificity, PPV, and NPV were 60.00%, 90.57%, 54.55%, and 92.31%, respectively. In this study, the positive likelihood ratio (PLR) diagnosed with EET alone was 1.58, the PLR diagnosed with CZT-SPECT alone was 4.54, and the PLR diagnosed with combination was 6.36.

CONCLUSION

The combination of CZT-SPECT and EET showed significantly improved CAD diagnostic accuracy compared with either approach alone.

Evaluation and clinical applicability of angiography-derived assessment of coronary microcirculatory resistance: a [15O]H2O PET study

The introduction of wire-free microcirculatory resistance index from functional angiography (angio-IMR) promises swift detection of coronary microvascular dysfunction, however it has not been properly validated. We sought to validate angio-IMR against invasive IMR and PET derived microvascular resistance (MVR). Moreover, we studied if angio-IMR could aid in the detection of ischemia with non-obstructive coronary arteries (INOCA). In this investigator-initiated study symptomatic patients underwent [15O]H2O positron emission tomography (PET) and invasive angiography with 3-vessel fractional flow reserve (FFR). Invasive IMR was measured in 40 patients. Angio-IMR and QFR were computed retrospectively. MVR was defined as the ratio of mean distal coronary pressure to PET derived coronary flow. PET and QFR/angio-IMR analyses were performed by blinded core labs. The right coronary artery was excluded. A total of 211 patients (mean age 61 ± 9, 148 (70%) male) with 312 vessels with successful angio-IMR analyses were included. Angio-IMR correlated moderately with invasive IMR (r = 0.48, p < 0.01), whereas no correlation was found between angio-IMR and MVR (r=-0.07, p = 0.25). Angio-IMR did not differ for vessels without obstructive coronary artery disease (CAD) (FFR-) but with reduced stress perfusion (PET+) compared to vessels without obstructive CAD (FFR-) with normal stress perfusion (PET-) (median 28.19 IQR 20.42-38.99 vs. 31.67 IQR 23.47-40.63, p = 0.40). Angio-IMR correlated moderately with invasively measured IMR, whereas angio-IMR did not correlate with PET derived MVR. Moreover, angio-IMR did not reliably identify patients with INOCA.

Correlation and Agreement of Quantitative Flow Ratio With Fractional Flow Reserve in Saphenous Vein Grafts

BACKGROUND

The applicability of quantitative flow ratio (QFR), a nonhyperemic, invasive coronary angiography-derived computation of fractional flow reserve (FFR), has not been studied in coronary artery bypass grafts. We sought to explore the correlation and diagnostic agreement between QFR and FFR in saphenous vein grafts (SVGs).

METHODS AND RESULTS

A total of 129 prospectively included patients (mean age 73±8 years, 84% male) with prior coronary artery bypass grafting underwent invasive coronary angiography and pressure-derived functional assessment in 150 nonoccluded SVGs. QFR dedicated angiography images of the SVGs were acquired and used for offline QFR computation. The diagnostic performance of QFR was compared with 2-dimensional quantitative coronary angiography, using FFR as a reference. A threshold of ≤0.80 was used to define functional significance. QFR was successfully computed in 140 (93%) SVGs. We found a significant correlation between QFR and FFR (r=0.72, P<0.001). FFR indicated significant disease in 43 (31%) SVGs, whereas QFR analysis showed significant lesions in 53 (38%) bypass grafts. QFR exhibited a higher sensitivity and diagnostic accuracy compared with angiographic lesion assessment (84% versus 63%, P=0.030 and 83% versus 74%, P=0.036, respectively), whereas specificity did not differ (82% versus 79%, P=0.466). Lastly, QFR demonstrated a higher area under the receiver operating curve than quantitative coronary angiography (0.90 versus 0.82, P=0.008) for the detection of FFR-defined significant vein graft disease.

CONCLUSIONS

This study shows the potential applicability of contemporary QFR computation in venous bypass grafts with a moderate correlation and good diagnostic accuracy compared with functional assessment using FFR.

Non-invasive fractional flow reserve estimation in coronary arteries using angiographic images

Coronary artery disease is the leading global cause of mortality and Fractional Flow Reserve (FFR) is widely regarded as the gold standard for assessing coronary artery stenosis severity. However, due to the limitations of invasive FFR measurements, there is a pressing need for a highly accurate virtual FFR calculation framework. Additionally, it's essential to consider local haemodynamic factors such as time-averaged wall shear stress (TAWSS), which play a critical role in advancement of atherosclerosis. This study introduces an innovative FFR computation method that involves creating five patient-specific geometries from two-dimensional coronary angiography images and conducting numerical simulations using computational fluid dynamics with a three-element Windkessel model boundary condition at the outlet to predict haemodynamic distribution. Furthermore, four distinct boundary condition methodologies are applied to each geometry for comprehensive analysis. Several haemodynamic features, including velocity, pressure, TAWSS, and oscillatory shear index are investigated and compared for each case. Results show that models with average boundary conditions can predict FFR values accurately and observed errors between invasive FFR and virtual FFR are found to be less than 5%.

Diagnostic Value of 99mTc-MIBI Myocardial Perfusion Imaging in Detecting Myocardial Ischemia of Children with Kawasaki Disease and Coronary Artery Lesions

Pediatric patients with coronary artery lesions (CALs) after Kawasaki disease (KD) may be complicated with myocardial ischemia. Although previous studies in adults have proven the diagnostic value of 99mTc-MIBI myocardial perfusion imaging (MPI) for ischemic heart disease, its feasibility and accuracy in this pediatric population remain uncertain. In this retrospective study, we collected data of 177 pediatric patients (Age range: 6 months to 14 years) who had undergone MPI and coronary artery angiography (CAG) between July 2019 and February 2023. Using the positive result of CAG as the reference standard of myocardial ischemia, we compared the results of 99mTc-MIBI MPI with other non-invasive examinations, including cardiac magnetic resonance imaging (CMRI), echocardiogram, and comprehensive electrocardiogram-related examinations. All patients finished adenosine triphosphate stress MPI without major side effects. The sensitivity of MPI was 79.17%, which was greater than CMRI and echocardiogram (P < 0.05). The negative predictive value and the accuracy of MPI were 89.9% and 71.75%, indicating the advantages over others. Composite monitoring strategy of MPI and CMRI effectively improved the diagnostic performance (P < 0.001). In 4 cases diagnosed with myocardial ischemia by "MPI + CMRI," despite the absence of significant stenosis, multiple giant coronary artery aneurysms (GCAA) were all observed in CAG. 99mTc-MIBI MPI is the preferred non-invasive examination for detecting myocardial ischemia in pediatric patients with CAL after KD. When combined with CMRI, it can enhance diagnostic accuracy. Multiple GCAAs without stenosis may be an isolated risk factor of myocardial ischemia.

Comprehensive Angiography-Derived Functional Assessment of Epicardial and Microvascular Coronary Disease. Correlation With Non-invasive Myocardial Stress Imaging

Coronary angiography (CA) is poorly correlated with non-invasive myocardial stress imaging (NSI) and myocardial ischemia is often observed in patients with unobstructed coronary arteries. Moreover, the diagnostic performance of combined epicardial and microcirculatory angiography-derived physiological assessment and its correlation with NSI remains unknown. A total of 917 coronary vessels in 319 patients who underwent both CA and NSI were included in this multicenter observational retrospective analysis. Quantitative flow ratio (QFR) and angiography-derived index of microcirculatory resistance (IMRangio) analyses were performed to estimate coronary epicardial and microcirculatory function respectively. NSI demonstrated evidence of myocardial ischemia in 76% of the cases. IMRangio (36 [22 to 50] vs 29 [21 to 41], p <0.001) was significantly higher and QFR (0.92 [0.78 to 0.99] vs 0.97 [0.91 to 0.99], p <0.001) was significantly lower in vessels subtending ischemic territories. Overall, the diagnostic accuracy of QFR was moderate (area under the curve of receiver operating characteristic [AUCROC] 0.632 [95% confidence interval [CI] 0.589 to 0.674], p <0.0001) but it was higher in patients with normal microcirculatory function (AUCROC = 0.726 [95% CI 0.669 to 0.784], p <0.0001, p Value for AUCROC comparison = 0.009). Combined QFR/IMRangio assessment provided incremental diagnostic performance compared with the evaluation of epicardial or microcirculatory districts in isolation (p Value for AUC comparison <0.0001) and it was able to identify the predominant mechanism of myocardial ischemia in 77% of the patients with positive NSI. Our study suggests the value of a combined angiography-derived assessment of epicardial and microvascular function for the definition of the predominant mechanism of myocardial ischemia in patients with suspected coronary artery disease.

Concordance between vessel-specific and vascular territory coronary functional assessment: A comparison of quantitative flow ratio and myocardial perfusion scintigraphy

BACKGROUND

Quantitative flow ratio (QFR) and myocardial perfusion scintigraphy (MPS) are utilized for assessing coronary artery disease (CAD) significance. We aimed to analyze their concordance and prognostic impact.

AIMS

We aimed to analyze the concordance between QFR and MPS and their risk stratification.

METHODS

Patients with invasive coronary angiography and MPS were categorized as concordant if QFR ≤ 0.80 and summed difference score (SDS) ≥ 4 or if QFR > 0.80 and SDS < 4; otherwise, they were discordant. Concordance was classified by coronary territory involvement: total (three territories), partial (two territories), poor (one territory), and total discordance (zero territories). Leaman score assessed coronary atherosclerotic burden.

RESULTS

2010 coronary territories (670 patients) underwent joint QFR and MPS analysis. MPS area under the curve for QFR ≤ 0.80 was 0.637. Concordance rates were total (52.5%), partial (29.1%), poor (15.8%), and total discordance (2.6%). Most concordance occurred in patients without significant CAD or with single-vessel disease (89.5%), particularly without MPS perfusion defects (91.5%). Leaman score (odds ratio [OR]: 0.839, 95% confidence interval [CI]: 0.805-0.875, p < 0.001) and MPS perfusion defect (summed stress score [SSS] ≥ 4) (OR: 0.355, 95% CI: 0.211-0.596, p < 0.001) were independent predictors for discordance. After 1400 days, no significant difference in death/myocardial infarction was observed based on MPS assessment, but Leaman score, functional Leaman score, and average QFR identified higher risk patients.

CONCLUSIONS

MPS showed good overall accuracy in assessing QFR significance but substantial discordance existed. Predictors for discordance included higher atherosclerotic burden and MPS perfusion defects (SSS ≥ 4). Leaman score, QFR-based functional Leaman score, and average QFR provided better risk stratification for all-cause death and myocardial infarction than MPS.

The diagnostic performance of quantitative flow ratio and perfusion imaging in patients with prior coronary artery disease

AIMS

In chronic coronary syndrome (CCS) patients with documented coronary artery disease (CAD), ischaemia detection by myocardial perfusion imaging (MPI) and an invasive approach are viable diagnostic strategies. We compared the diagnostic performance of quantitative flow ratio (QFR) with single-photon emission computed tomography (SPECT), positron emission tomography (PET), and cardiac magnetic resonance imaging (CMR) in patients with prior CAD [previous percutaneous coronary intervention (PCI) and/or myocardial infarction (MI)].

METHODS AND RESULTS

This PACIFIC-2 sub-study evaluated 189 CCS patients with prior CAD for inclusion. Patients underwent SPECT, PET, and CMR followed by invasive coronary angiography with fractional flow reserve (FFR) measurements of all major coronary arteries (N = 567), except for vessels with a sub-total or chronic total occlusion. Quantitative flow ratio computation was attempted in 488 (86%) vessels with measured FFR available (FFR ≤0.80 defined haemodynamically significant CAD). Quantitative flow ratio analysis was successful in 334 (68%) vessels among 166 patients and demonstrated a higher accuracy (84%) and sensitivity (72%) compared with SPECT (66%, P < 0.001 and 46%, P = 0.001), PET (65%, P < 0.001 and 58%, P = 0.032), and CMR (72%, P < 0.001 and 33%, P < 0.001). The specificity of QFR (87%) was similar to that of CMR (83%, P = 0.123) but higher than that of SPECT (71%, P < 0.001) and PET (67%, P < 0.001). Lastly, QFR exhibited a higher area under the receiver operating characteristic curve (0.89) than SPECT (0.57, P < 0.001), PET (0.66, P < 0.001), and CMR (0.60, P < 0.001).

CONCLUSION

QFR correlated better with FFR in patients with prior CAD than MPI, as reflected in the higher diagnostic performance measures for detecting FFR-defined, vessel-specific, significant CAD.

Triglyceride-glucose index is associated with quantitative flow ratio in patients with acute ST-elevation myocardial infarction after percutaneous coronary intervention

Background

The triglyceride-glucose (TyG) index is a novel marker representing the degree of insulin resistance (IR) and is closely related to cardiovascular diseases. However, the association between the TyG index and vascular function in patients with acute ST-elevation myocardial infarction (STEMI) after percutaneous coronary intervention (PCI) remains unknown.

Materials and methods

This study was a post hoc analysis of a multicenter, prospective cohort study. In this study, patients with STEMI who underwent PCI were included, and coronary angiography data were analyzed by Quantitative coronary angiography (QCA) and quantitative flow ratio (QFR). In addition, the TyG index was calculated as follows: Ln [fasting triglyceride (mg/dl) × fasting blood glucose (mg/dl) × 1/2]. According to the post-PCI QFR, patients were divided into two groups: post-PCI QFR ≤ 0.92 group and post-PCI QFR > 0.92 group. Construction of logistic regression model to explore the relationship between the TyG index and post-PCI QFR.

Results

A total of 241 STEMI patients were included in this study. Compared with patients in the post-PCI QFR > 0.92 group, the TyG index was higher in the post-PCI QFR ≤ 0.92 group. Logistic regression model showed that after adjusting for other confounding factors, the TyG index was positively correlated with the risk of post-PCI QFR ≤ 0.92 (OR = 1.697, 95% CI 1.171–2.460, P = 0.005). Restricted cubic splines showed the cutoff value of TyG index associated with post-PCI QFR ≤ 0.92 risk was 9.75.

Conclusion

The TyG index was associated with the risk of post-PCI QFR ≤ 0.92 in STEMI patients. The risk of post-PCI QFR ≤ 0.92 increased when the TyG index exceeded 9.75.

Residual Quantitative Flow Ratio to Estimate Post-Percutaneous Coronary Intervention Fractional Flow Reserve

Objectives

Quantitative flow ratio (QFR) computes fractional flow reserve (FFR) based on invasive coronary angiography (ICA). Residual QFR estimates post‐percutaneous coronary intervention (PCI) FFR. This study sought to assess the relationship of residual QFR with post-PCI FFR.

Methods

Residual QFR analysis, using pre-PCI ICA, was attempted in 159 vessels with post-PCI FFR. QFR lesion location was matched with the PCI location to simulate the performed intervention and allow computation of residual QFR. A post-PCI FFR < 0.90 was used to define a suboptimal PCI result.

Results

Residual QFR computation was successful in 128 (81%) vessels. Median residual QFR was higher than post-PCI FFR (0.96 Q1–Q3: 0.91–0.99 vs. 0.91 Q1–Q3: 0.86–0.96, p < 0.001). A significant correlation and agreement were observed between residual QFR and post-PCI FFR (R = 0.56 and intraclass correlation coefficient = 0.47, p < 0.001 for both). Following PCI, an FFR < 0.90 was observed in 54 (42%) vessels. Specificity, positive predictive value, sensitivity, and negative predictive value of residual QFR for assessment of the PCI result were 96% (95% confidence interval (CI): 87–99%), 89% (95% CI: 72–96%), 44% (95% CI: 31–59%), and 70% (95% CI: 65–75%), respectively. Residual QFR had an accuracy of 74% (95% CI: 66–82%) and an area under the receiver operating characteristic curve of 0.79 (95% CI: 0.71–0.86).

Conclusions

A significant correlation and agreement between residual QFR and post-PCI FFR were observed. Residual QFR ≥ 0.90 did not necessarily commensurate with a satisfactory PCI (post-PCI FFR ≥ 0.90). In contrast, residual QFR exhibited a high specificity for prediction of a suboptimal PCI result.

Angiography-based estimation of coronary physiology: A frame is worth a thousand words

Cumulative evidence has shown that coronary revascularization should be guided by functional significance of coronary lesions. Fractional flow reserve (FFR) is the gold standard for assessment of hemodynamic significance of coronary stenosis and FFR-guided percutaneous coronary intervention has improved clinical outcomes in patients with coronary artery disease. However, limitations of FFR such as increased operational time and cost, requirement of pressure wire and adenosine and technical difficulties have led to significant underutilization of the method in clinical practice. In the last few years, several methods of FFR estimation based on coronary angiography images have emerged to overcome invasive FFR limitations. The common elements of the novel indices include a 3D anatomical reconstruction of coronary vessels by angiographic projections and various approaches to fluid dynamics computation. Angiography-derived FFR methods have shown high diagnostic accuracy compared to invasive FFR. Although there are promising results regarding their prognostic role, large randomized trials evaluating clinical outcomes are lacking. The aim of this review is to present currently available angiography-derived FFR indices and highlight their differences, advantages, disadvantages and potential clinical implications.

Diagnostic Performance of CMR, SPECT, and PET Imaging for the Identification of Coronary Artery Disease: A Meta-Analysis

Background: Myocardial perfusion imaging modalities, such as cardiac magnetic resonance (CMR), single-photon emission computed tomography (SPECT), and positron emission tomography (PET), are well-established non-invasive diagnostic methods to detect hemodynamically significant coronary artery disease (CAD). The aim of this meta-analysis is to compare CMR, SPECT, and PET in the diagnosis of CAD and to provide evidence for further research and clinical decision-making.

Methods: PubMed, Web of Science, EMBASE, and Cochrane Library were searched. Studies that used CMR, SPECT, and/or PET for the diagnosis of CAD were included. Pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio with their respective 95% confidence interval, and the area under the summary receiver operating characteristic (SROC) curve were calculated.

Results: A total of 203 articles were identified for inclusion in this meta-analysis. The pooled sensitivity values of CMR, SPECT, and PET were 0.86, 0.83, and 0.85, respectively. Their respective overall specificity values were 0.83, 0.77, and 0.86. Results in subgroup analysis of the performance of SPECT with ²⁰¹Tl showed the highest pooled sensitivity [0.85 (0.82, 0.88)] and specificity [0.80 (0.75, 0.83)]. ^99mTc-tetrofosmin had the lowest sensitivity [0.76 (0.67, 0.82)]. In the subgroup analysis of PET tracers, results indicated that ¹³N had the lowest pooled sensitivity [0.83 (0.74, 0.89)], and the specificity was the highest [0.91 (0.81, 0.96)].

Conclusion: Our meta-analysis indicates that CMR and PET present better diagnostic performance for the detection of CAD as compared with SPECT.

Coronary computed tomography angiography and [15O]H2O positron emission tomography perfusion imaging for the assessment of coronary artery disease

Determining the anatomic severity and extent of coronary artery disease (CAD) by means of coronary computed tomography angiography (CCTA) and its effect on perfusion using myocardial perfusion imaging (MPI) form the pillars of the non-invasive imaging assessment of CAD. This review will 1) focus on CCTA and [¹⁵O]H₂O positron emission tomography MPI as stand-alone imaging modalities and their combined use for detecting CAD, 2) highlight some of the lessons learned from the PACIFIC trial (Comparison of Coronary CT Angiography, SPECT, PET, and Hybrid Imaging for Diagnosis of Ischemic Heart Disease Determined by Fractional Flow Reserve (FFR) (NCT01521468)), and 3) discuss the use of [¹⁵O]H₂O PET MPI in the clinical work-up of patients with a chronic coronary total occlusion (CTO).