Personalized Pressure Conditions and Calibration for a Predictive Computational Model of Coronary and Myocardial Blood Flow

Predictive modeling of hyperemic coronary and myocardial blood flow (MBF) greatly supports diagnosis and prognostic stratification of patients suffering from coronary artery disease (CAD). In this work, we propose a novel strategy, using only readily available clinical data, to build personalized inlet conditions for coronary and MBF models and to achieve an effective calibration for their predictive application to real clinical cases. Experimental data are used to build personalized pressure waveforms at the aortic root, representative of the hyperemic state and adapted to surrogate the systolic contraction, to be used in computational fluid-dynamics analyses. Model calibration to simulate hyperemic flow is performed in a "blinded" way, not requiring any additional exam. Coronary and myocardial flow simulations are performed in eight patients with different clinical conditions to predict FFR and MBF. Realistic pressure waveforms are recovered for all the patients. Consistent pressure distribution, blood velocities in the large arteries, and distribution of MBF in the healthy myocardium are obtained. FFR results show great accuracy with a per-vessel sensitivity and specificity of 100% according to clinical threshold values. Mean MBF shows good agreement with values from stress-CTP, with lower values in patients with diagnosed perfusion defects. The proposed methodology allows us to quantitatively predict FFR and MBF, by the exclusive use of standard measures easily obtainable in a clinical context. This represents a fundamental step to avoid catheter-based exams and stress tests in CAD diagnosis.

Physiological Assessment with iFR prior to FFR Measurement in Left Main Disease

Despite guideline-based recommendation of the interchangeable use of instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) to guide revascularization decision-making, iFR/FFR could demonstrate different physiological or clinical outcomes in some specific patient or lesion subsets. Therefore, we sought to investigate the impact of difference between iFR and FFR-guided revascularization decision-making on clinical outcomes in patients with left main disease (LMD). In this international multicenter registry of LMD with physiological interrogation, we identified 275 patients in whom physiological assessment was performed with both iFR/FFR. Major adverse cardiovascular event (MACE) was defined as a composite of death, non-fatal myocardial infarction, and ischemia-driven target lesion revascularization. The receiver-operating characteristic analysis was performed for both iFR/FFR to predict MACE in respective patients in whom revascularization was deferred and performed. In 153 patients of revascularization deferral, MACE occurred in 17.0% patients. The optimal cut-off values of iFR and FFR to predict MACE were 0.88 (specificity:0.74; sensitivity:0.65) and 0.76 (specificity:0.81; sensitivity:0.46), respectively. The area under the curve (AUC) was significantly higher for iFR than FFR (0.74; 95%CI 0.62-0.85 vs. 0.62; 95%CI 0.48-0.75; p = 0.012). In 122 patients of coronary revascularization, MACE occurred in 13.1% patients. The optimal cut-off values of iFR and FFR were 0.92 (specificity:0.93; sensitivity:0.25) and 0.81 (specificity:0.047; sensitivity:1.00), respectively. The AUCs were not significantly different between iFR and FFR (0.57; 95%CI 0.40-0.73 vs. 0.46; 95%CI 0.31-0.61; p = 0.43). While neither baseline iFR nor FFR was predictive of MACE in patients in whom revascularization was performed, iFR-guided deferral seemed to be safer than FFR-guided deferral.

Timing of fractional flow reserve-guided complete revascularization in patients with ST-segment elevation myocardial infarction with multivessel disease: Rationale and design of the OPTION-STEMI trial

BACKGROUND

Current guidelines recommend complete revascularization (CR) in hemodynamically stable patients with ST-segment elevation myocardial infarction (STEMI) and multivessel coronary artery disease (MVD). With regard to the timing of percutaneous coronary intervention (PCI) for non-infarct-related artery (non-IRA), recent randomized clinical trials have revealed that immediate CR was non-inferior to staged CR. However, the optimal timing of CR remains uncertain. The OPTION-STEMI trial compared immediate CR and in-hospital staged CR guided by fractional flow reserve (FFR) for intermediate stenosis of the non-IRA.

METHODS

The OPTION-STEMI is a multicenter, investigator-initiated, prospective, open-label, non-inferiority randomized clinical trial. The study included patients with at least one non-IRA lesion with ≥50% stenosis by visual estimation. Patients fulfilling the inclusion criteria were randomized into two groups at a 1:1 ratio: immediate CR (i.e., PCI for the non-IRA performed during primary angioplasty) or in-hospital staged CR. In the in-hospital staged CR group, PCI for non-IRA lesions was performed on another day during the index hospitalization. Non-IRA lesions with 50-69% stenosis by visual estimation were evaluated by FFR, whereas those with ≥70% stenosis were revascularized without FFR. The primary endpoint was the composite of all-cause death, non-fatal myocardial infarction, and all unplanned revascularization at 1 year after randomization. Enrolment began in December 2019 and was completed in January 2024. The follow-up for the primary endpoint will be completed in January 2025, and primary results will be available in the middle of 2025.

CONCLUSIONS

The OPTION-STEMI is a multicenter, non-inferiority, randomized trial that evaluated the timing of in-hospital CR with the aid of FFR in patients with STEMI and MVD.

TRIAL REGISTRATION

URL: https://www.

CLINICALTRIALS

gov. Unique identifier: NCT04626882; and URL: https://cris.nih.go.kr. Unique identifier: KCT0004457.

Lesion Eccentricity Plays a Key Role in Determining the Pressure Gradient of Serial Stenotic Lesions: Results from a Computational Hemodynamics Study

PURPOSE

In arterial disease, the presence of two or more serial stenotic lesions is common. For mild lesions, it is difficult to predict whether their combined effect is hemodynamically significant. This study assessed the hemodynamic significance of idealized serial stenotic lesions by simulating their hemodynamic interaction in a computational flow model.

MATERIALS AND METHODS

Flow was simulated with SimVascular software in 34 serial lesions, using moderate (15 mL/s) and high (30 mL/s) flow rates. Combinations of one concentric and two eccentric lesions, all 50% area reduction, were designed with variations in interstenotic distance and in relative direction of eccentricity. Fluid and fluid-structure simulations were performed to quantify the combined pressure gradient.

RESULTS

At a moderate flow rate, the combined pressure gradient of two lesions ranged from 3.8 to 7.7 mmHg, which increased to a range of 12.5-24.3 mmHg for a high flow rate. Eccentricity caused an up to two-fold increase in pressure gradient relative to concentric lesions. At a high flow rate, the combined pressure gradient for serial eccentric lesions often exceeded the sum of the individual lesions. The relative direction of eccentricity altered the pressure gradient by 15-25%. The impact of flow pulsatility and wall deformability was minor.

CONCLUSION

This flow simulation study revealed that lesion eccentricity is an adverse factor in the hemodynamic significance of isolated stenotic lesions and in serial stenotic lesions. Two 50% lesions that are individually non-significant can combine more often than thought to hemodynamic significance in hyperemic conditions.

Triglyceride to high-density lipoprotein cholesterol ratio associated with long-term adverse clinical outcomes in patients deferred revascularization following fractional flow reserve

BACKGROUND

Guidelines on coronary intermediate lesions strongly recommend deferred revascularization after detecting a normal fractional flow reserve (FFR). Researches about triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) on cardiovascular diseases has also been well conducted. However, the association of TG/HDL-C and long-term adverse clinical outcomes remains unknown for patients deferred revascularization following FFR.

METHODS

This study retrospectively included 374 coronary artery disease (CAD) patients with non-significant coronary lesions diagnosed by coronary angiography (CAG) and FFR. The main outcome measure was the combination of major adverse cardiovascular and cerebrovascular events (MACCEs). All patients were categorized into three subgroups in terms of TG/HDL-C tertiles (T1 < 0.96, 0.96 ≤ T2 < 1.58, T3 ≥ 1.58). Three different Cox regression models were utilized to reveal the association between TG/HDL-C and prevalence of MACCEs.

RESULTS

47 MACCEs were recorded throughout a median monitoring period of 6.6 years. The Kaplan-Meier survival curves showed a higher MACCEs rate occurred in the higher TG/HDL-C group (5.6% vs. 12.9% vs. 19.4%, log-rank P < 0.01). After adjustment, patients in T3 suffered a 2.6-fold risk compared to the T1 group (T3 vs. T1: HR 2.55, 95% CI 1.05-6.21, P = 0.038; T2 vs. T1: HR 1.71, 95% CI 0.65-4.49, P = 0.075; P for trend = 0.001). The restricted cubic spline (RCS) analysis demonstrated that the HR for MACCEs rose as TG/HDL-C increased. Both the receiver operating characteristic (ROC) and time-dependent ROC proved the excellent predictive ability of TG/HDL-C.

CONCLUSION

The study illustrates that TG/HDL-C correlates with the risk of MACCEs in CAD patients deferred revascularization following FFR. TG/HDL-C could serve as a dependable predictor of cardiovascular events over the long term in this population.

Clinical effects of physiologic lesion testing in influencing treatment strategy for multi-vessel coronary artery disease

Background

The application of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) in multivessel coronary artery disease (CAD) patients has not been definitively explored. We herein assessed how treatment strategies were decided based on FFR/iFR values in vessels selected clinically. Specifically, we sought to determine whether treatment selection was based on whether the vessel tested was the clinical target stenosis.

Methods

270 consecutive patients with angiographically determined multivessel disease who underwent FFR/iFR testing were included. Patients were classified initially based on their angiographic findings, then re-evaluated from FFR/iFR results (normal or abnormal). Tested lesions were classified into target or non-target lesions based on clinical and non-invasive evaluations.

Results

Abnormal FFR/iFR values were demonstrated in 51.9 % of patients, in whom 51.4 % received coronary stenting (PCI) and 44.3 % had bypass surgery (CABG). With two-vessel CAD patients, medical therapy was preferred when the target lesion was normal (72.6 %), while PCI was preferred when it was abnormal (78.4 %). In non-target lesions, PCI was preferred regardless of FFR/iFR results (78.0 %). With three-vessel CAD patients, CABG was preferred when the target lesion was abnormal (68.5 %), and there was no difference in the selected modality when it was normal. Furthermore, the incidence of tested lesions was higher in the left anterior descending (LAD) compared to other coronary arteries, and two-vessel CAD patients with LAD stenoses were more frequently treated by PCI.

Conclusion

The use of invasive physiologic testing in multivessel CAD patients may alter the preferred treatment strategy, leading to an overall increase in PCI selection.

Diagnostic performance of ultrasonic flow ratio versus quantitative flow ratio for assessment of coronary stenosis

BACKGROUND

Ultrasonic flow ratio (UFR) is a novel intravascular ultrasound (IVUS)-derived modality for fast computation of fractional flow reserve (FFR) without pressure wires and adenosine.

AIMS

This study was sought to compare the diagnostic performance of UFR and quantitative flow ratio (QFR), using FFR as the reference standard.

METHODS

This is a retrospective study enrolling consecutive patients with intermediate coronary artery lesions (diameter stenosis of 30%-90% by visual estimation) for IVUS and FFR measurement. UFR and QFR were performed offline in a core-lab by independent analysts blinded to FFR.

RESULTS

From December 2022 to May 2023, a total of 78 eligible patients were enrolled. IVUS and FFR measurements were successfully conducted in 104 vessels, finally 98 vessels with both FFR, UFR and QFR evaluation were analyzed. Mean FFR was 0.79 ± 0.12. UFR showed a strong correlation with FFR similar to QFR (r = 0.83 vs. 0.82, p = 0.795). Diagnostic accuracy of UFR was non-inferior to QFR (94% [89%-97%] versus 90% [84%-94%], p = 0.113). Sensitivity and specificity in identifying hemodynamically significant stenosis were comparable between UFR and QFR (sensitivity: 89% [79%-96%] versus 85% [74%-92%], p = 0.453; specificity: 97% [91%-99%] versus 95% [88%-99%], p = 0.625). The area under curve for UFR was 0.95 [0.90-0.98], non-inferior to QFR (difference = 0.021, p = 0.293), and significantly higher than minimum lumen area (MLA; difference = 0.13, p < 0.001). Diagnostic accuracy of UFR and QFR was not statically different in bifurcation nor non-bifurcation lesions.

CONCLUSIONS

UFR showed excellent concordance with FFR, non-inferior to QFR, superior to MLA. UFR provides a potentiality for the integration of physiological assessment and intravascular imaging in clinical practice.

Utilization of coronary computed tomography angiography and computed tomography-derived fractional flow reserve in a critical limb-threatening ischemia cohort

Objective

Patients with peripheral arterial disease (PAD) have a significant risk of myocardial infarction and death secondary to concomitant coronary artery disease (CAD). This is particularly true in patients with critical limb-threatening ischemia (CLTI) who exceed a 20% mortality rate at 6 months despite standard treatment with risk factor modification. Although systematic preoperative coronary testing is not recommended for patients with PAD without cardiac symptoms, the clinical manifestations of CAD are often muted in patients with CLTI due to poor mobility and activity intolerance. Thus, the true incidence and impact of "silent" CAD in a CLTI cohort is unknown. This study aims to determine the prevalence of ischemia-producing coronary artery stenosis in a CLTI cohort using coronary computed tomography angiography (cCTA) and computed tomography (CT)-derived fractional flow reserve (FFRCT), a noninvasive imaging modality that has shown significant correlation to cardiac catheterization in the detection of clinically relevant coronary ischemia.

Methods

Patients presenting with newly diagnosed CLTI at our institution from May 2020 to April 2021 were screened for underlying CAD. Included subjects had no known history of CAD, no cardiac symptoms, and no anginal equivalent complaints at presentation. Patients underwent cCTA and FFRCT evaluation and were classified by the anatomic location and severity of CAD. Significant coronary ischemia was defined as FFRCT ≤0.80 distal to a >30% coronary stenosis, and severe coronary ischemia was documented at FFRCT ≤0.75, consistent with established guidelines.

Results

A total of 170 patients with CLTI were screened; 65 patients (38.2%) had no coronary symptoms and met all inclusion/exclusion criteria. Twenty-four patients (31.2%) completed cCTA and FFRCT evaluation. Forty-one patients have yet to complete testing secondary to socioeconomic factors (insurance denial, transportation inaccessibility, testing availability, etc). The mean age of included subjects was 65.4 ± 7.0 years, and 15 (62.5%) were male. Patients presented with ischemic rest pain (n = 7; 29.1%), minor tissue loss (n = 14; 58.3%) or major tissue loss (n = 3; 12.5%). Significant (≥50%) coronary artery stenosis was noted on cCTA in 19 of 24 patients (79%). Significant left main coronary artery stenosis was identified in two patients (10%). When analyzed with FFRCT, 17 patients (71%) had hemodynamically significant coronary ischemia (FFRCT ≤0.8), and 54% (n = 13) had lesion-specific severe coronary ischemia (FFRCT ≤0.75). The mean FFRCT in patients with coronary ischemia was 0.70 ± 0.07. Multi-vessel disease pattern was present in 53% (n = 9) of patients with significant coronary stenosis.

Conclusions

The use of cCTA-derived fractional flow reserve demonstrates a significant percentage of patients with CLTI have silent (asymptomatic) coronary ischemia. More than one-half of these patients have lesion-specific severe ischemia, which may be associated with increased mortality when treated solely with risk factor modification. cCTA and FFRCT diagnosis of significant coronary ischemia has the potential to improve cardiac care, perioperative morbidity, and long-term survival curves of patients with CLTI. Systemic improvements in access to care will be needed to allow for broad application of these imaging assessments should they prove universally valuable. Additional study is required to determine the benefit of selective coronary revascularization in patients with CLTI.

Combined Assessment of Fractional Flow Reserve and Coronary Flow Velocity Reserve after Drug-Eluting Stent Implantation

BACKGROUND

Coronary flow velocity reserve (CFVR) can be measured noninvasively using stress transthoracic Doppler echocardiography (S-TDE). The prognostic significance of S-TDE-derived CFVR after percutaneous coronary intervention (PCI) remains unknown. The aim of this study was to investigate the prognostic value of post-PCI CFVR and its additional efficacy to fractional flow reserve (FFR) in patients undergoing elective PCI.

METHODS

A retrospective study was conducted involving 187 consecutive patients with chronic coronary syndrome who underwent elective PCI guided by FFR for the left anterior descending coronary artery. Pre- and post-PCI wire-based FFR and CFVR assessments of the left anterior descending coronary artery using S-TDE were performed in all patients. The association between post-PCI clinical and physiologic parameters and major adverse cardiac events (MACE), defined as a composite of cardiac death, myocardial infarction, heart failure, and unplanned remote target vessel revascularization, was evaluated.

RESULTS

Three-quarters of patients exhibited CFVR increase after PCI, while all patients showed FFR improvement. During a median follow-up period of 1.5 years, MACE occurred in 21 patients (11.2%). Among clinical demographics, patients with MACE had higher levels of N-terminal pro-brain natriuretic peptide compared with those without MACE (median, 615 pg/mL [interquartile range, 245-1,500 pg/mL] vs 180 pg/mL [interquartile range, 70-559 pg/mL]; P = .010). Post-PCI S-TDE-derived CFVR was lower in patients with MACE, while post-PCI FFR showed a nonsignificant tendency to be lower in patients with MACE. In a multivariable analysis, higher NT-proBNP (adjusted hazard ratio, 1.33; 95% CI, 1.02-1.74; P = .038), post-PCI CFVR ≤ 2.0 (adjusted hazard ratio, 2.93; 95% CI, 1.16-7.40; P = .023), and post-PCI FFR ≤ 0.82 (adjusted hazard ratio, 3.93; 95% CI, 1.52-10.18; P = .005) were independently associated with MACE.

CONCLUSIONS

In patients with chronic coronary syndrome who underwent successful elective PCI for left anterior descending coronary artery, the combined assessment of S-TDE-derived post-PCI CFVR and post-PCI FFR provided a significant association with the occurrence of MACE.

Comparison among various physiology and angiography-guided strategies for deferring percutaneous coronary intervention: A network meta-analysis

BACKGROUND/PURPOSE

It is unclear whether coronary physiology or coronary angiography (CA)-guided strategy is the more preferable approach for deferring percutaneous coronary intervention (PCI). We sought to evaluate the clinical efficacy of various PCI strategies through a network meta-analysis of randomized controlled trials (RCTs).

METHODS/MATERIALS

We searched multiple databases for RCTs investigating the impact of the following strategies for the purpose of determining whether or not to defer PCI: fractional flow reserve, instantaneous wave-free ratio, quantitative flow ratio (QFR), and CA. We conducted a network meta-analysis for trial-defined major adverse cardiovascular events (MACE), all-cause death, cardiovascular death, myocardial infarction (MI), target lesion revascularization (TLR), and stent thrombosis. We performed a subgroup analysis for those with acute coronary syndrome (ACS).

RESULTS

Our search identified 12 eligible RCTs including a total of 13,177 patients. QFR-guided PCI was associated with reduced MACE, MI, and TLR compared with CA-guided PCI (relative risk (RR) 0.68; 95 % confidence interval (CI] [0.49 to 0.94], RR 0.58; 95 % CI [0.36 to 0.96], and RR 0.58; 95 % CI [0.38 to 0.91], respectively). There were no significant differences in any pairs for all-cause death, cardiovascular death, or stent thrombosis. QFR was ranked the best in most outcomes. In the subgroup analysis of the ACS cohort, there were no significant differences in MACE between any comparisons.

CONCLUSIONS

QFR was associated with reduced MACE, MI, and TLR compared with CA, and ranked the best in most outcomes. However, this was not applied in the ACS cohort.

Fluid-filled versus sensor-tipped pressure guidewires for FFR and Pd/Pa measurement; PW-COMPARE study

BACKGROUND

Fluid-filled pressure guidewires are unaffected by the previously inevitable hydrostatic pressure gradient (HPG). This study aimed to compare simultaneous pressure measurements with fluid-filled and sensor-tipped pressure guidewires.

METHODS

Fifty patients underwent fractional flow reserve (FFR) and Pd/Pa measurement with a fluid-filled and a sensor-tipped pressure guidewire simultaneously. To assess maneuverability, patients were randomized with respect to which pressure guidewire was used to cross the lesion first. Lateral fluoroscopy was used to estimate height difference between catheter tip and distal wire position (and thus HPG). Agreement between pressure measurements was studied.

RESULTS

Measurements were performed in LM (4% (n = 2)), LAD (44% (n = 22)), LCX (26% (n = 13)), and RCA (26% (n = 13)). Simultaneous pressure measurements showed excellent agreement (mean FFR difference - 0.01 ± 0.03 (r = 0.959, p < 0.001), mean Pd/Pa difference - 0.01 ± 0.04 (r = 0.929, p < 0.001)). FFR was ≤0.80 in 42.6% (n = 20) with fluid-filled FFR measurements versus 46.8% (n = 22) by sensor-tipped FFR measurements. Mean height difference was 15 ± 34 mm, and strongly dependent on the coronary artery (LAD 45 ± 10 mm, LCX -23 ± 16 mm, RCA -13 ± 17 mm). There was a strong correlation between height difference and difference in pressure ratios between sensor-tipped and fluid-filled pressure guidewires (FFR r = -0.850, p < 0.001; Pd/Par = -0.641, p < 0.001). Largest FFR differences were present in the LAD (-0.04 ± 0.02). After HPG correction, mean difference between HPG-corrected sensor-tipped FFR and fluid-filled FFR was 0.00 ± 0.02, mean Pd/Pa difference was 0.01 ± 0.03.

CONCLUSIONS

This study shows excellent overall correlation between FFR and Pd/Pa measurements with both pressure guidewires. Differences measured with fluid-filled and sensor-tipped pressure guidewires are vessel-specific and attributable to hydrostatic pressure gradients (NCT04802681).

Diagnostic accuracy of Murray law-based quantitative flow ratio in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement

BACKGROUND

Murray law-based quantitative flow ratio (μQFR) is a novel computational method that enables accurate estimation of fractional flow reserve (FFR) using a single angiographic projection. However, its diagnostic value in patients with severe aortic stenosis (AS) remains unclear.

METHOD

We included 25 consecutive patients who underwent transcatheter aortic valve replacement (TAVR) for severe AS with intermediate or greater (30-90%) coronary artery disease (CAD). Pre- and post-TAVR μQFR, QFR, instantaneous flow reserve (iFR), and post-TAVR invasive FFR values were measured. We evaluated the diagnostic performance of pre-TAVR μQFR, QFR, and iFR using post-TAVR FFR ≤ 0.80 as a reference standard of ischemia.

RESULT

Pre-TAVR μQFR was significantly correlated with post-TAVR FFR (r = 0.73, p < 0.0001). The area under the curve of pre-TAVR μQFR on post-TAVR FFR ≤ 0.8 was 0.91 (95% confidence interval [CI] 0.77-0.98), comparable to that of pre-TAVR iFR (0.86 [95% CI 0.71-0.98], p = 0.97). The accuracy, sensitivity, specificity, and positive and negative predictive values of pre-TAVR μQFR on post-TAVR FFR ≤ 0.8 were 84.2% (95% CI 68.7-93.4), 61.6% (95% CI 31.6-86.1), 96.0% (95% CI 79.6-99.9), 88.9% (95% CI 52.9-98.3), and 82.8% (95% CI 70.6-90.6), respectively. For pre-TAVR iFR, these values were 76.5% (95% CI 58.8-89.3), 90.9% (95% CI 58.7-99.8), 69.6% (95% CI 47.1-86.8), 58.8% (95% CI 42.8-73.1), and 94.1% (95% CI 70.8-99.1), respectively.

CONCLUSION

μQFR could be useful for the physiological evaluation of patients with severe AS with concomitant CAD.

Lesion of slit-like stenosis underestimated by fractional flow reserve based on computed tomography images

This case report discusses a 74-year-old man presenting with angina pectoris. Coronary computed tomography angiography suggested only mild stenosis in the mid left anterior descending artery (LAD), with fractional flow reserve based on computed tomography images (FFRct) value of 0.87. However, coronary angiography revealed slit-like stenosis in the mid LAD, and the invasive fractional flow reserve (FFR) was measured at 0.72, demonstrating a deviation from the FFRct value.

Intra-individual comparison of coronary CT angiography-based FFR between energy-integrating and photon-counting detector CT systems

BACKGROUND

Coronary computed tomography angiography (CCTA)-based fractional flow reserve (CT-FFR) allows for noninvasive determination of the functional severity of anatomic lesions in patients with coronary artery disease. The aim of this study was to intra-individually compare CT-FFR between photon-counting detector (PCD) and conventional energy-integrating detector (EID) CT systems.

METHODS

In this single-center prospective study, subjects who underwent clinically indicated CCTA on an EID-CT system were recruited for a research CCTA on PCD-CT within 30 days. Image reconstruction settings were matched as closely as possible between EID-CT (Bv36 kernel, iterative reconstruction strength level 3, slice thickness 0.5 mm) and PCD-CT (Bv36 kernel, quantum iterative reconstruction level 3, virtual monoenergetic level 55 keV, slice thickness 0.6 mm). CT-FFR was measured semi-automatically using a prototype on-site machine learning algorithm by two readers. CT-FFR analysis was performed per-patient and per-vessel, and a CT-FFR ≤ 0.75 was considered hemodynamically significant.

RESULTS

A total of 22 patients (63.3 ± 9.2 years; 7 women) were included. Median time between EID-CT and PCD-CT was 5.5 days. Comparison of CT-FFR values showed no significant difference and strong agreement between EID-CT and PCD-CT in the per-vessel analysis (0.88 [0.74-0.94] vs. 0.87 [0.76-0.93], P = 0.096, mean bias 0.02, limits of agreement [LoA] -0.14/0.19, r = 0.83, ICC = 0.92), and in the per-patient analysis (0.81 [0.60-0.86] vs. 0.76 [0.64-0.86], P = 0.768, mean bias 0.02, LoA -0.15/0.19, r = 0.90, ICC = 0.93). All included patients were classified into the same category (CT-FFR > 0.75 vs ≤0.75) with both CT systems.

CONCLUSIONS

CT-FFR evaluation is feasible with PCD-CT and it shows a strong agreement with EID-CT-based evaluation when images are similarly reconstructed.

Hemodynamic Impairments of Evaluating Symptomatic Intracranial Atherosclerotic Stenosis using Quantitative Flow Ratio on Digital Subtraction Angiography : A Comparison with Computed Tomography Perfusion, MRI and Fractional Flow Reserve

PURPOSE

Cerebral hemodynamics are important for the management of intracranial atherosclerotic stenosis (ICAS). The quantitative flow ratio (QFR) is a novel angiography-derived index for assessing the functional relevance of ICAS without pressure wires and adenosine. Good diagnostic yield with the hyperemic fractional flow reserve (FFR) have been reported, while data on the comparison of QFR to FFR are scarce.

METHODS

In this prospective study 56 patients with anterior circulation symptomatic ICAS who received endovascular treatment were included. The new method of computing QFR from a single angiographic view, i.e., the Murray law-based QFR (μQFR), was applied to the examined vessels. An artificial intelligence algorithm was developed to realize the automatic delineation of vascular contour. Pressure gradients were measured before and after treatment within the lesion vessel using a pressure guidewire and the FFR was calculated.

RESULTS

There was a good correlation between μQFR and FFR. Preoperative FFR predicted DWI watershed infarction (FFR optimal cut-off level: 0.755). Preoperative μQFR predicted DWI watershed infarction (μQFR optimal cut-off level: 0.51). Preoperative FFR predicted CTP hypoperfusion (FFR best predictive value: 0.62). Preoperative μQFR predicted CTP hypoperfusion (μQFR best predictive value: 0.375).

CONCLUSION

The μQFR based on DSA images can be used as an indicator to assess the functional status of the lesion in patients with ICAS.

A high level of uric acid is associated with long-term adverse cardiovascular outcomes in patients who received fractional flow reserve with coronary intermediate stenosis

BACKGROUND AND AIMS

The role of fractional flow reserve (FFR) in coronary intermediate lesions is widely recommended by guidelines. The effect of uric acid (UA) on cardiovascular events is also well known. However, the relationship between UA and long-term cardiovascular outcomes in patients who received FFR with intermediate lesions remains unknown.

METHODS AND RESULTS

We retrospectively included 428 patients who underwent both coronary angiography (CAG) and FFR. Participants were stratified into two groups based on the median UA. The primary endpoint was the composite of major adverse cardiovascular and cerebrovascular events (MACCEs), including repeat revascularization, nonfatal stroke, nonfatal myocardial infarction, and all-cause death. A Cox proportional hazards model was utilized to analyze the association between UA and the prevalence of MACCEs. During a median follow-up of 5.8 years, a higher MACCEs rate occurred in the high UA group compared to the low UA group (16.8% vs. 5.1%, p log-rank<0.01). Elevated UA was independently linked to a higher incidence of MACCEs, whether UA was treated as a categorical or continuous variable (hazard ratio [HR] 2.76, 95% confidence interval [CI] 1.27-6.03 or HR 1.01, 95% CI 1.01-1.02). The restricted cubic spline (RCS) analysis illustrated that the HR for MACCEs increased with increasing UA.

CONCLUSION

The present study demonstrates that UA is associated with MACCEs risk and suggests that UA is a reliable predictor of long-term cardiovascular events in coronary intermediate stenosis patients.

In-vitro validation of coronary physiology assessment with 5 French guiding catheters

BACKGROUND

The trans-radial approach for cardiac catheterization led to an increasing adoption of 5 French (F) catheters. We aim to evaluate reliability and reproducibility of coronary physiology assessment performed with 5F guiding catheter (GC).

METHODS

Physiological measurements were performed in a coronary flow simulator, which provides two pulsatile flows, the baseline and hyperaemic flows. Two screws, positioned proximally and distally to the distal sensor of a pressure-temperature guidewire, were used to determine various combinations of stenoses and distal obstructions, simulating different pathophysiological conditions. For each setting, 5 measurements of fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microvascular resistance (IMR) were performed with 6F and 5F GCs.

RESULTS

A total amount of 190 measurements were performed, 95 with 6F GC and 95 with 5F GC. Minimal differences between 6F and 5F GCs were detected for FFR [0.91 (IQR: 0.87-0.94) and 0.87 (IQR: 0.82-0.92) respectively, p < 0.001] and IMR (16.5 ± 8.8 and 15.4 ± 8.3 respectively, p = 0.001). Mean CFR was comparable between 6F and 5F GCs (3.6 ± 1.1 and 3.5 ± 0.7 respectively, p = 0.38). Misclassification rates were 1.0 %, 1.0 % and 0 % for FFR, CFR and IMR, respectively. According to Passing-Bablok analysis, an excellent agreement between 6F and 5F GCs was demonstrated for FFR and IMR, and a modest agreement for CFR. All measurements with 5F GC showed high reproducibility.

CONCLUSIONS

In our in-vitro model, a complete physiological assessment including FFR, CFR and IMR resulted substantially comparable between 6F and 5F GCs. Further in-vivo analysis is required to support these findings.

Investigation of the predictive value of a novel algorithm based on coronary CT angiography regarding fractional flow reserve and revascularization in patients with stable coronary artery disease

Fractional flow reserve (FFR) has been established as a gold standard for functional coronary ischemia. At present, the FFR can be calculated from coronary computed tomography angiography (CCTA) images (CT-FFR). Previous studies have suggested that CT-FFR outperforms CCTA and invasive coronary angiography (ICA) in determining hemodynamic significance of stenoses. Recently, a novel automatical algorithm of CT-FFR called RuiXin-FFR has been developed. The present study is designed to investigate the predictive value of this algorithm and its value in therapeutic decision making. The present study retrospectively included 166 patients with stable coronary artery disease (CAD) who underwent CCTA screening and diagnostic ICA examination at Peking University People's Hospital, in 73 of whom wire-derived FFR was also measured. CT-FFR analyses were performed with a dedicated software. All patients were followed up for at least 1 year. We validated the accuracy of RuiXin-FFR with invasive FFR as the standard of reference, and investigated the role of RuiXin-FFR in predicting treatment strategy and long-term prognosis. The mean age of the patients was 63.3 years with 63.9% male. The CT-FFR showed a moderate correlation with wire-derived FFR (r = 0.542, p < 0.0001) and diagnostic accuracy of 87.6% to predict myocardial ischemia (AUC: 0.839, 95% CI 0.728-0.950), which was significantly higher than CCTA and ICA. In the multivariate logistic regression analysis, CT-FFR ≤ 0.80 was an independent predictor of undergoing coronary revascularization (OR: 45.54, 95% CI 12.03-172.38, p < 0.0001), whereas CT-FFR > 0.80 was an independent predictor of non-obstructive CAD (OR: 14.67, 95% CI 5.42-39.72, p < 0.0001). Reserving ICA and revascularization for vessels with positive CT-FFR could have reduced the rate of ICA by 29.6%, lowered the rate of ICA in vessels without stenosis > 50% by 11.7%, and increased the rate of revascularization in patients receiving ICA by 21.2%. The average follow-up was 23.7 months, and major adverse cardiovascular events (MACE) occurred in 11 patients. The rate of MACE was significantly lower in patients with CT-FFR > 0.80. The new algorithm of CT-FFR can be used to predict the invasive FFR. The RuiXin-FFR can also provide useful information for the screening of patients in whom further ICA is indeed needed and prognosis evaluation.

Optimal diagnostic approach for using CT-derived quantitative flow ratio in patients with stenosis on coronary computed tomography angiography

BACKGROUND

Coronary computed tomography angiography (CCTA)-derived quantitative flow ratio (CT-QFR) is an on-site non-invasive technique estimating invasive fractional flow reserve (FFR). This study assesses the diagnostic performance of using most distal CT-QFR versus lesion-specific CT-QFR approach for identifying hemodynamically obstructive coronary artery disease (CAD).

METHODS

Prospectively enrolled de novo chest pain patients (n ​= ​445) with ≥50 ​% visual diameter stenosis on CCTA were referred for invasive evaluation. On-site CT-QFR was analyzed post-hoc blinded to angiographic data and obtained as both most distal (MD-QFR) and lesion-specific CT-QFR (LS-QFR). Abnormal CT-QFR was defined as ≤0.80. Hemodynamically obstructive CAD was defined as invasive FFR ≤0.80 or ≥70 ​% diameter stenosis by 3D-quantitative coronary angiography.

RESULTS

In total 404/445 patients had paired CT-QFR and invasive analyses of whom 149/404 (37 ​%) had hemodynamically obstructive CAD. MD-QFR and LS-QFR classified 188 (47 ​%) and 165 (41 ​%) patients as abnormal, respectively. Areas under the receiver-operating characteristic curve for MD-QFR was 0.83 vs. 0.85 for LS-QFR, p ​= ​0.01. Sensitivities for MD-QFR and LS-QFR were 80 ​% (95%CI: 73-86) vs. 77 ​% (95%CI: 69-83), p ​= ​0.03, respectively, and specificities were 73 ​% (95%CI: 67-78) vs. 80 ​% (95%CI: 75-85), p ​< ​0.01, respectively. Positive predictive values for MD-QFR and LS-QFR were 63 ​% vs. 69 ​%, p ​< ​0.01, respectively, and negative predictive values for MD-QFR and LS-QFR were 86 ​% vs. 85 ​%, p ​= ​0.39, respectively).

CONCLUSION

Using a lesion-specific CT-QFR approach has superior discrimination of hemodynamically obstructive CAD compared to a most distal CT-QFR approach. CT-QFR identified most cases of hemodynamically obstructive CAD while a normal CT-QFR excluded hemodynamically obstructive CAD in the majority of patients.

Imaging biomarkers in cardiac CT: moving beyond simple coronary anatomical assessment

Cardiac computed tomography angiography (CCTA) is considered the standard non-invasive tool to rule-out obstructive coronary artery disease (CAD). Moreover, several imaging biomarkers have been developed on cardiac-CT imaging to assess global CAD severity and atherosclerotic burden, including coronary calcium scoring, the segment involvement score, segment stenosis score and the Leaman-score. Myocardial perfusion imaging enables the diagnosis of myocardial ischemia and microvascular damage, and the CT-based fractional flow reserve quantification allows to evaluate non-invasively hemodynamic impact of the coronary stenosis. The texture and density of the epicardial and perivascular adipose tissue, the hypodense plaque burden, the radiomic phenotyping of coronary plaques or the fat radiomic profile are novel CT imaging features emerging as biomarkers of inflammation and plaque instability, which may implement the risk stratification strategies. The ability to perform myocardial tissue characterization by extracellular volume fraction and radiomic features appears promising in predicting arrhythmogenic risk and cardiovascular events. New imaging biomarkers are expanding the potential of cardiac CT for phenotyping the individual profile of CAD involvement and opening new frontiers for the practice of more personalized medicine.

Systematic review and meta-analysis of randomized and nonrandomized studies on fractional flow reserve-guided revascularization

INTRODUCTION AND OBJECTIVES

Several studies have investigated the effectiveness of fractional flow reserve (FFR) guidance in improving clinical outcomes after myocardial revascularization, yielding conflicting results. The aim of this study was to compare clinical outcomes in patients with coronary artery disease following FFR-guided or angiography-guided revascularization.

METHODS

Both randomized controlled trials (RCTs) and nonrandomized intervention studies were included. Coprimary endpoints were all-cause death, myocardial infarction, and major adverse cardiovascular events (MACE). The study is registered with PROSPERO (CRD42022344765).

RESULTS

A total of 30 studies enrolling 393 588 patients were included. FFR-guided revascularization was associated with significantly lower rates of all-cause death (OR, 0.63; 95%CI, 0.53-0.73), myocardial infarction (OR, 0.70; 95%CI, 0.59-0.84), and MACE (OR, 0.77; 95%CI, 0.70-0.85). When only RCTs were considered, no significant difference between the 2 strategies was observed for any endpoints. However, the use of FFR was associated with reduced rates of revascularizations and treated lesions. Metaregression suggested that the higher the rate of revascularized patients the lower the benefit of FFR guidance on MACE reduction compared with angiography guidance (P = .012). Similarly, higher rates of patients with acute coronary syndromes were associated with a lower benefit of FFR-guided revascularization (P = .039).

CONCLUSIONS

FFR-guided revascularization was associated with lower rates of all-cause death, myocardial infarction and MACE compared with angiographic guidance, with RCTs and nonrandomized intervention studies yielding conflicting data. The benefits of FFR-guidance seem to be less evident in studies with high revascularization rates and with a high prevalence of patients with acute coronary syndrome.

Co-registered optical coherence tomography and X-ray angiography for the prediction of fractional flow reserve

Cardiovascular disease (CVD) stands as the leading global cause of mortality, and coronary artery disease (CAD) has the highest prevalence, contributing to 42% of these fatalities. Recognizing the constraints inherent in the anatomical assessment of CAD, Fractional Flow Reserve (FFR) has emerged as a pivotal functional diagnostic metric. Herein, we assess the potential of employing an ensemble approach with deep neural networks (DNN) to predict invasively measured Fractional Flow Reserve (FFR) using raw anatomical data extracted from both optical coherence tomography (OCT) and X-ray coronary angiography (XA). In this study, we used a challenging dataset, with 46% of the lesions falling within the FFR range of 0.75 to 0.85. Despite this complexity, our model achieved an accuracy of 84.3%, demonstrating a sensitivity of 87.5% and a specificity of 81.4%. Our results demonstrate that incorporating both OCT and XA signals, co-registered, as inputs for the DNN model leads to an important increase in overall accuracy.

Long-term prognostic implications of CT angiography-derived fractional flow reserve: Results from the DISCOVER-FLOW study

BACKGROUND & OBJECTIVES

The long-term prognostic implications of CT angiography-derived fractional flow reserve (FFRCT) remains unclear. We aimed to explore the long-term outcomes of FFRCT in the first-in-human study of it.

MATERIALS & METHODS

A total of 156 vessels from 102 patients with stable coronary artery disease, who underwent coronary CT angiography (CCTA) and invasive FFR measurement, were followed. The primary endpoint was target vessel failure (TVF), including cardiovascular death, target vessel myocardial infarction, and target vessel revascularization. Outcome analysis with FFRCT was performed on a per-vessel basis using a marginal Cox proportional hazard model.

RESULTS

During median 9.9 years of follow-up, TVF occurred in 20 (12.8%) vessels. FFRCT ​≤0.80 discriminated TVF (hazard ratio [HR] 2.61, 95% confidence interval [CI] 1.06, 6.45). Among 94 vessels with deferral of percutaneous coronary intervention (PCI), TVF risk was inversely correlated with FFRCT ​(HR 0.62 per 0.1 increase, 95% CI 0.44, 0.86), with the cumulative incidence of TVF being 2.6%, 15.2%, and 28.6% for vessels with FFRCT ​>0.90, 0.81-0.90, and ≤0.80, respectively (p-for-trend 0.005). Predictive value for clinical outcomes of FFRCT was similar to that of invasive FFR (c-index 0.79 vs 0.71, P ​= ​0.28). The estimated TVF risk was higher in the deferral of PCI group than the PCI group for vessels with FFRCT ≤0.81.

CONCLUSION

FFRCT showed improved long-term risk stratification and displayed a risk continuum similar to invasive FFR.

CLINICAL TRIAL REGISTRATION

NCT01189331.

Coronary artery disease evaluation during transcatheter aortic valve replacement work-up using photon-counting CT and artificial intelligence

PURPOSE

The purpose of this study was to evaluate the capabilities of photon-counting (PC) CT combined with artificial intelligence-derived coronary computed tomography angiography (PC-CCTA) stenosis quantification and fractional flow reserve prediction (FFRai) for the assessment of coronary artery disease (CAD) in transcatheter aortic valve replacement (TAVR) work-up.

MATERIALS AND METHODS

Consecutive patients with severe symptomatic aortic valve stenosis referred for pre-TAVR work-up between October 2021 and June 2023 were included in this retrospective tertiary single-center study. All patients underwent both PC-CCTA and ICA within three months for reference standard diagnosis. PC-CCTA stenosis quantification (at 50% level) and FFRai (at 0.8 level) were predicted using two deep learning models (CorEx, Spimed-AI). Diagnostic performance for global CAD evaluation (at least one significant stenosis ≥ 50% or FFRai ≤ 0.8) was assessed.

RESULTS

A total of 260 patients (138 men, 122 women) with a mean age of 78.7 ± 8.1 (standard deviation) years (age range: 51-93 years) were evaluated. Significant CAD on ICA was present in 126/260 patients (48.5%). Per-patient sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were 96.0% (95% confidence interval [CI]: 91.0-98.7), 68.7% (95% CI: 60.1-76.4), 74.3 % (95% CI: 69.1-78.8), 94.8% (95% CI: 88.5-97.8), and 81.9% (95% CI: 76.7-86.4) for PC-CCTA, and 96.8% (95% CI: 92.1-99.1), 87.3% (95% CI: 80.5-92.4), 87.8% (95% CI: 82.2-91.8), 96.7% (95% CI: 91.7-98.7), and 91.9% (95% CI: 87.9-94.9) for FFRai. Area under the curve of FFRai was 0.92 (95% CI: 0.88-0.95) compared to 0.82 for PC-CCTA (95% CI: 0.77-0.87) (P < 0.001). FFRai-guidance could have prevented the need for ICA in 121 out of 260 patients (46.5%) vs. 97 out of 260 (37.3%) using PC-CCTA alone (P < 0.001).

CONCLUSION

Deep learning-based photon-counting FFRai evaluation improves the accuracy of PC-CCTA ≥ 50% stenosis detection, reduces the need for ICA, and may be incorporated into the clinical TAVR work-up for the assessment of CAD.

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.

Is Coronary Physiology Assessment Valid in Special Circumstances?: Aortic Stenosis, Atrial Fibrillation, Left Ventricular Hypertrophy, and Other

Fractional flow reserve (FFR) and nonhyperemic pressure ratios (NHPRs) provide an important clinical tool to evaluate the hemodynamic significance of coronary lesions. However, these indices have major limitations. As these indices are meant to be surrogates of coronary flow, clinical scenarios such as aortic stenosis (with increased end-systolic and end-diastolic pressures) or atrial fibrillation (with significant beat-to-beat cardiac output variability) can have significant effect on the accuracy and reliability of these hemodynamic indices. Here, we provide a comprehensive evaluation of the pitfalls, limitations, and strengths of FFR and NHPRs in common clinical scenarios paired with coronary artery disease.

What About All the Recent "Negative" FFR Trials?

During the past 30 years, fractional flow reserve (FFR) has moved from animal models to class IA recommendations in guidelines. However, the FLOWER-MI, RIPCORD-2, FUTURE, and FAME 3 trials in 2021 were "negative"-has FFR exceeded its expiration date? We critically examine these randomized trials in order to draw insights not just about FFR but also about study design and interpretation. Are all randomized trials created equal? No, rather we must focus on discordant decisions between angiography and FFR and highlight clinical endpoints that can be improved by percutaneous coronary intervention instead of medical therapy.

Physiologic Assessment After Percutaneous Coronary Interventions and Functionally Optimized Revascularization

Coronary physiologic assessment has become a standard of care for patients with coronary atherosclerotic disease. While most attention has focused on pre-interventional physiologic assessment to aid in revascularization decision-making, post-interventional physiologic assessment has not been as widely used, despite evidence supporting its role in assessment and optimization of the revascularization procedure. A thorough understanding of such evidence and ongoing studies would be crucial to incorporate post-interventional physiologic assessment into daily practice. Thus, this review provides a comprehensive overview of current evidence regarding the evolving role of physiologic assessment as a functional optimization tool for the entire revascularization process.

Computed Tomography-Derived Physiology Assessment: State-of-the-Art Review

Coronary computed tomography angiography (CCTA) and CCTA-derived fractional flow reserve (FFRCT) are the best non-invasive techniques to assess coronary artery disease (CAD) and myocardial ischemia. Advances in these technologies allow a paradigm shift to the use of CCTA and FFRCT for advanced plaque characterization and planning myocardial revascularization.

Prognostic differences between physiology-guided percutaneous coronary intervention and optimal medical therapy in coronary artery disease: A systematic review and meta-analysis

Background

Intracoronary physiology, particularly fractional flow reserve (FFR), has been used as a guide for revascularization for patients with coronary artery disease (CAD). The optimal treatment in the physiological grey-zone area has been unclear and remains subject to ongoing debate.

Methods

We conducted a systematic review of randomized controlled trials and observational studies comparing the prognostic effect of percutaneous coronary revascularization (PCI) and optimal medical therapy (OMT) in patients with CAD. Studies were identified by medical literature databases. The outcomes of interest were major adverse cardiac events (MACE) and its components, death, myocardial infarction (MI), and repeat revascularization.

Results

A total of 16 studies with 27,451 patients were included. The pooled analysis demonstrated that PCI was associated with a prognostic advantage over OMT in patients with FFR value ≤0.80 (RR: 0.64, 95 % CI: 0.45-0.90, p < 0.01). Patients with an FFR value >0.80 were shown to benefit more from OMT (RR 1.38, 95 % CI 1.24-1.53, p < 0.01). The analysis also showed that there was no significant difference in MACE in the grey-zone area (FFR 0.75-0.80) (RR 0.64, 95 % CI: 0.35-1.16, p = 0.14), but a significant reduction in repeat revascularization (RR 0.54, 95 % CI, 0.31-0.91, p < 0.01) when patients were treated with PCI.

Conclusions

Among patients with CAD and FFR values >0.80, OMT was associated with favorable outcomes over PCI in reducing the risk of MACE. However, among patients with FFR values ≤0.80, revascularization was superior in terms of reducing MACE. The available evidence supports the guideline-recommended use of an FFR cut-off of ≤0.80.

The Role of CCTA-derived Cardiac Structure and Function Analysis in the Prediction of Readmission in Nonischemic Heart Failure

Cardiac function and structure significantly impact nonischemic heart failure (HF) patient outcomes. This study investigated 236 patients (107 nonischemic heart failure, 129 healthy) to assess the relationship between coronary computed tomography angiography (CCTA)-derived parameters and clinical outcomes. Among the nonischemic heart failure patients, 37.3% experienced readmissions. In this group, specific CCTA measurements were identified as significant predictors of readmission: epicardial adipose tissue (CTEAT) at 54.49 cm3 (HR: 1.05; 95% CI: 1.03-1.07; P < 0.001), cardiac muscle mass to lumen volume (CTV/M) at 20% (HR: 0.59; 95% CI: 0.48-0.72; P < 0.001), peri-coronary adipose (CTPCAT) at -64.68 HU (HR: 1.1; 95% CI: 1.03-1.16; P = 0.002) for the right coronary artery, -81.07 HU (HR: 1.3; 95% CI: 1.1-1.53; P = 0.002) for the left anterior descending artery, and -73.42 HU (HR: 1.33; 95% CI: 1.18-1.51; P < 0.001) for the circumflex branch of the left coronary artery. In patients with nonischemic heart failure, increased CTEAT, CTPCAT, and CTV/M independently predicted rehospitalization.

Computed tomography fractional flow reserve discrepancies with invasive angiography and physiology - Case series

BACKGROUND

Computed tomography with fractional flow reserve (CT-FFR) is increasingly common in assessing coronary artery disease.

CASE PRESENTATION

We report five cases of discrepancies that led to changes in treatment.

CONCLUSIONS

This report highlights discordant findings between modalities, which should be considered during the diagnostic assessment of chest pain.

Diagnostic accuracy of CT-FFR with a new coarse-to-fine subpixel algorithm in detecting lesion-specific ischemia: a prospective multicenter study

INTRODUCTION AND OBJECTIVES

A new computed tomography-derived fractional flow reserve (CT-FFR) technique with a "coarse-to-fine subpixel" algorithm has been developed to generate precise lumen contours. The aim of this study was to assess the diagnostic performance of this new CT-FFR algorithm for discriminating lesion-specific ischemia using wire-based FFR ≤ 0.80 as the reference standard in patients with coronary artery disease.

METHODS

This prospective, multicenter study screened 330 patients undergoing coronary CT angiography (CCTA) and invasive FFR (median interval 2 days) from 6 tertiary hospitals. CT-FFR was evaluated in a blinded fashion with a "coarse-to-fine subpixel" algorithm for lumen contour.

RESULTS

Between March 2019 and May 2020, we included 316 patients with 324 vessels. There was a good correlation between CT-FFR and invasive FFR (r=0.76, P<.001). The diagnostic sensitivity, specificity, and accuracy on a per-vessel level were 95.3%, 89.8%, and 92.0% for CT-FFR, and 96.4%, 26.4%, and 53.1% for CCTA>50% stenosis, respectively. CT-FFR showed improved discrimination of ischemia compared with CCTA alone overall (AUC, 0.95 vs 0.74, P<.001) and in intermediate (AUC, 0.96 vs 0.62, P<.001) and "gray zone" lesions (AUC, 0.88 vs 0.61, P<.001). The diagnostic specificity, accuracy, and AUC for CT-FFR (71.9%, 82.8%, and 0.84) outperformed CCTA (9.4%, 48.3%, and 0.66) in patients or in vessels with severe calcification (all P<.05).

CONCLUSIONS

CT-FFR with a new "coarse-to-fine subpixel" algorithm showed high performance in identifying hemodynamically significant stenosis. The diagnostic performance of CT-FFR was superior to that of CCTA in intermediate lesions, "gray zone" lesions, and severely calcified lesions. Clinical Trial Register: NCT04731285.

Blood Flow Energy Identifies Coronary Lesions Culprit of Future Myocardial Infarction

The present study establishes a link between blood flow energy transformations in coronary atherosclerotic lesions and clinical outcomes. The predictive capacity for future myocardial infarction (MI) was compared with that of established quantitative coronary angiography (QCA)-derived predictors. Angiography-based computational fluid dynamics (CFD) simulations were performed on 80 human coronary lesions culprit of MI within 5 years and 108 non-culprit lesions for future MI. Blood flow energy transformations were assessed in the converging flow segment of the lesion as ratios of kinetic and rotational energy values (KER and RER, respectively) at the QCA-identified minimum lumen area and proximal lesion sections. The anatomical and functional lesion severity were evaluated with QCA to derive percentage area stenosis (%AS), vessel fractional flow reserve (vFFR), and translesional vFFR (ΔvFFR). Wall shear stress profiles were investigated in terms of topological shear variation index (TSVI). KER and RER predicted MI at 5 years (AUC = 0.73, 95% CI 0.65-0.80, and AUC = 0.76, 95% CI 0.70-0.83, respectively; p < 0.0001 for both). The predictive capacity for future MI of KER and RER was significantly stronger than vFFR (p = 0.0391 and p = 0.0045, respectively). RER predictive capacity was significantly stronger than %AS and ΔvFFR (p = 0.0041 and p = 0.0059, respectively). The predictive capacity for future MI of KER and RER did not differ significantly from TSVI. Blood flow kinetic and rotational energy transformations were significant predictors for MI at 5 years (p < 0.0001). The findings of this study support the hypothesis of a biomechanical contribution to the process of plaque destabilization/rupture leading to MI.

The ability of contemporary cardiologists to judge the ischemic impact of a coronary lesion visually

BACKGROUND

Landmark trials showed that invasive pressure measurement (Fractional Flow Reserve, FFR) was a better guide to coronary stenting than visual assessment. However, present-day interventionists have benefited from extensive research and personal experience of mapping anatomy to hemodynamics.

AIMS

To determine if visual assessment of the angiogram performs as well as invasive measurement of coronary physiology.

METHODS

25 interventional cardiologists independently visually assessed the single vessel coronary disease of 200 randomized participants in The Objective Randomized Blinded Investigation with optimal medical Therapy of Angioplasty in stable angina trial (ORBITA). They gave a visual prediction of the FFR and Instantaneous Wave-free Ratio (iFR), denoted vFFR and viFR respectively. Each judged each lesion on 2 occasions, so that every lesion had 50 vFFR, and 50 viFR assessments. The group consensus visual estimates (vFFR-group and viFR-group) and individual cardiologists' visual estimates (vFFR-individual and viFR-individual) were tested alongside invasively measured FFR and iFR for their ability to predict the placebo-controlled reduction in stress echo ischemia with stenting.

RESULTS

Placebo-controlled ischemia improvement with stenting was predicted by vFFR-group (p < 0.0001) and viFR-group (p < 0.0001), vFFR-individual (p < 0.0001) and viFR-individual (p < 0.0001). There were no significant differences between the predictive performance of the group visual estimates and their invasive counterparts: p = 0.53 for vFFR vs FFR and p = 0.56 for viFR vs iFR.

CONCLUSION

Visual assessment of the angiogram by contemporary experts, provides significant additional information on the amount of ischaemia which can be relieved by placebo-controlled stenting in single vessel coronary artery disease.

Coronary protection using a pressure wire during transcatheter aortic valve implantation

Coronary obstruction is a rare but life-threatening complication of transcatheter aortic valve implantation (TAVI). This article describes the case of a patient with severe aortic valve stenosis treated with TAVI, during which preventive coronary wiring using a pressure wire was performed for coronary protection. After the deployment of the transcatheter heart valve (THV), the values of the fractional flow reserve (FFR) and resting full-cycle ratio (RFR) remarkably decreased, although the findings of transesophageal echocardiography and coronary angiography did not suggest coronary obstruction. Intravascular ultrasound revealed severe stenosis in the left main trunk due to the displacement of the calcified native leaflets. The decrease in the FFR and RFR values after THV deployment led to a diagnosis of partial coronary obstruction, and percutaneous coronary intervention was successfully performed. In patients at a high risk for coronary obstruction, coronary protection with a pressure wire is useful for the diagnosis and prevention of coronary flow deterioration during TAVI. Functional assessment using a pressure wire before and after TAVI may contribute to the accurate diagnosis of coronary obstruction.

Learning objective

Accurate diagnosis of coronary obstruction during transcatheter aortic valve implantation (TAVI) is important for successful management. In patients at a high risk for coronary obstruction, coronary protection with a pressure wire is useful for the diagnosis and prevention of coronary flow deterioration during TAVI. The remarkable decrease in the fractional flow reserve and resting full-cycle ratio values after the deployment of the transcatheter heart valve may suggest coronary obstruction.

Intra-arterial Fractional Flow Reserve Measurements Provide an Objective Assessment of the Functional Significance of Peripheral Arterial Stenoses

OBJECTIVE

Peripheral arterial stenoses (PAS) are commonly investigated with duplex ultrasound (DUS) and angiography, but these are not functional tests. Fractional flow reserve (FFR), a pressure based index, functionally assesses the ischaemic potential of coronary stenoses, but its utility in PAS is unknown. FFR in the peripheral vasculature in patients with limb ischaemia was investigated.

METHODS

Patients scheduled for angioplasty and or stenting of isolated iliac and superficial femoral artery stenoses were recruited. Resting trans-lesional pressure gradient (Pd/Pa) and FFR were measured after adenosine provoked hyperaemia using an intra-arterial 0.014 inch flow and pressure sensing wire (ComboWire XT, Philips). Prior to revascularisation, exercise ABPI (eABPI) and DUS derived peak systolic velocity ratio (PSVR) of the index lesion were determined. Calf muscle oxygenation was measured using blood oxygenation level dependent cardiovascular magnetic resonance prior to and after revascularisation.

RESULTS

Forty-one patients (32, 78%, male, mean age 65 ± 11 years) with 61 stenoses (iliac 32; femoral 29) were studied. For lesions < 80% stenosis, resting Pd/Pa was not influenced by the degree of stenosis (p = .074); however, FFR was discriminatory, decreasing as the severity of stenosis increased (p = .019). An FFR of < 0.60 was associated with critical limb threatening ischaemia (area under the curve [AUC] 0.87; 95% CI 0.75 - 0.95), in this study performing better than angiographic % stenosis (0.79; 0.63 - 0.89), eABPI (0.72; 0.57 - 0.83), and PSVR (0.65; 0.51 - 0.78). FFR correlated strongly with calf oxygenation (rho, 0.76; p < .001). A greater increase in FFR signalled resolution of symptoms and signs (ΔFFR 0.25 ± 0.15 vs. 0.13 ± 0.09; p = .009) and a post-angioplasty and stenting FFR of > 0.74 predicted successful revascularisation (combined sensitivity and specificity of 95%; AUC 0.98; 0.91 - 1.00).

CONCLUSION

This pilot study demonstrates that FFR can objectively measure the functional significance of PAS that compares favourably with visual and DUS based assessments. Its role as a quality control adjunct that confirms optimal vessel patency after angioplasty and or stenting also merits further investigation.

Normalization of FFRCT after surgical unroofing of a myocardial bridge: a case report

Background

Cardiac computed tomography angiography derived fractional flow reserve (FFRCT) is a diastolic measurement and has emerged as a valuable non-invasive alternative to FFR in patients with stable coronary artery disease. It has, unlike FFR during coronary angiography, not been validated for the physiological evaluation of an isolated myocardial bridge (MB) so far.

Case summary

Our patient, previously known with a long myocardial bridge of the mid-segment of the left anterior descending artery, presented with a non-ST-segment elevation myocardial infarction that was treated by surgical unroofing of the MB. FFRCT after surgery confirms a major amelioration of coronary blood flow.

Discussion

Myocardial bridge may rarely present as a non-ST-segment elevation myocardial infarction. FFRCT has thus far been accepted as a useful diagnostic tool in stable coronary artery disease. Our case report suggests that cardiac computed tomography angiography may be considered a useful technique for anatomical and physiological evaluation of MBs.

Prognostic role of discordance between quantitative flow ratio and visual estimation in revascularization guidance

Aims

Revascularization guided by functional severity has presented improved outcomes compared with visual angiographic guidance. Quantitative flow ratio (QFR) is a reliable angiography-based method for functional assessment. We sought to investigate the prognostic value of discordance between QFR and visual estimation in coronary revascularization guidance.

Methods and results

We performed offline QFR analysis on all-comers undergoing coronary angiography. Vessels with calculated QFR were divided into four groups based on the decision to perform or defer percutaneous coronary intervention (PCI) and on the QFR result, i.e.: Group A (PCI-, QFR > 0.8); Group B (PCI+, QFR ≤ 0.8); Group C (PCI+, QFR > 0.8); Group D (PCI-, QFR ≤ 0.8). Patients with at least one vessel falling within the disagreement groups formed the discordance group, whereas the remaining patients formed the concordance group. The primary endpoint was the composite endpoint of cardiovascular death, myocardial infarction, and ischaemia-driven revascularization. Overall, 546 patients were included in the study. Discordance between QFR and visual estimation was found in 26.2% of patients. After a median follow-up period of 2.5 years, the discordance group had a significantly higher rate of the composite outcome (hazard ratio: 3.34, 95% confidence interval 1.99-5.60, P < 0.001). Both disagreement vessel Groups C and D were associated with increased cardiovascular risk compared with agreement Groups A and B.

Conclusion

Discordance between QFR and visual estimation in revascularization guidance was associated with a worse long-term prognosis. Our results highlight the importance of proper patient selection for intervention and the need to avoid improper stent implantations when not dictated by a comprehensive functional assessment.

Clinical and prognostic incremental value of FFRCT in screening of patients with obstructive coronary artery disease

BACKGROUND

Coronary computed tomography angiography (CCTA) -derived fractional flow reserve (FFRCT) is recommended to evaluate the functional consequences of obstructive coronary artery disease (OCAD). Real-world incremental impacts of FFRCT use still remains under debate.

METHODS

1601 patients with suspected OCAD on CCTA (>50 ​% stenosis), including 808 (50.5 ​%) patients evaluated by FFRCT, were included from a 2013-2021 registry. Propensity adjusted impacts of FFRCT use on rates of invasive coronary angiography (ICA), myocardial revascularization (MR) and post MR major adverse cardiac events (MACE) were reported, including a sensitivity analysis in severe OCAD (>70 ​% stenosis) (n ​= ​450). Accuracy of numerical and comprehensive FFRCT interpretations in selection of patients requiring a MR were also compared.

RESULTS

1160 (72,5 ​%) ICA, 559 (34.9 ​%) MR and 137 (24.5 ​%) post MR MACE occurred at 4.7 ​± ​1.9 years. FFRCT use was independently associated with decreased rate of ICA and MR (OR: 0.66; 95 ​% CI 0.53-0.83, p ​< ​0.001 and OR: 0.71; 95 ​% CI 0.58-0.88, p ​< ​0.01, respectively). Compared to the numerical interpretation, the FFRCT comprehensive assessment increased the ratio of MR per ICA (61.7 ​% vs 50.1 ​%, p ​< ​0.01) and was more accurate in selection of patients requiring MR. FFRCT reduced post MR MACE (OR: 0.64; 95 ​% CI 0.43-0.96, p ​< ​0.05). All these associations were no longer observed in severe OCAD.

CONCLUSION

Implementing FFRCT in OCAD patients reduces ICA use, improves selection of patients requiring MR and reduces post MR MACE. However, these incremental values of FFRCT were no longer observed in severe OCAD.

A multi-dimensional CFD framework for fast patient-specific fractional flow reserve prediction

Fractional flow reserve (FFR) is considered as the gold standard for diagnosing coronary myocardial ischemia. Existing 3D computational fluid dynamics (CFD) methods attempt to predict FFR noninvasively using coronary computed tomography angiography (CTA). However, the accuracy and efficiency of the 3D CFD methods in coronary arteries are considerably limited. In this work, we introduce a multi-dimensional CFD framework that improves the accuracy of FFR prediction by estimating 0D patient-specific boundary conditions, and increases the efficiency by generating 3D initial conditions. The multi-dimensional CFD models contain the 3D vascular model for coronary simulation, the 1D vascular model for iterative optimization, and the 0D vascular model for boundary conditions expression. To improve the accuracy, we utilize clinical parameters to derive 0D patient-specific boundary conditions with an optimization algorithm. To improve the efficiency, we evaluate the convergence state using the 1D vascular model and obtain the convergence parameters to generate appropriate 3D initial conditions. The 0D patient-specific boundary conditions and the 3D initial conditions are used to predict FFR (FFRC). We conducted a retrospective study involving 40 patients (61 diseased vessels) with invasive FFR and their corresponding CTA images. The results demonstrate that the FFRC and the invasive FFR have a strong linear correlation (r = 0.80, p < 0.001) and high consistency (mean difference: 0.014 ±0.071). After applying the cut-off value of FFR (0.8), the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of FFRC were 88.5%, 93.3%, 83.9%, 84.8%, and 92.9%, respectively. Compared with the conventional zero initial conditions method, our method improves prediction efficiency by 71.3% per case. Therefore, our multi-dimensional CFD framework is capable of improving the accuracy and efficiency of FFR prediction significantly.

Murray law-based quantitative flow ratio to assess left main bifurcation stenosis: selecting the angiographic projection matters

Murray law-based quantitative flow ratio (µQFR) assesses fractional flow reserve (FFR) in bifurcation lesions using a single angiographic view, enhancing the feasibility of analysis; however, accuracy may be compromised in suboptimal angiographic projections. FFRCT is a well-validated non-invasive method measuring FFR from coronary computed tomographic angiography (CCTA). We evaluated the feasibility of µQFR in left main (LM) bifurcations, the impact of the optimal/suboptimal fluoroscopic view with respect to CCTA, and its diagnostic concordance with FFRCT. In 300 patients with three-vessel disease, the values of FFRCT and µQFR were compared at distal LM, proximal left anterior descending artery (pLAD) and circumflex artery (pLCX). The optimal viewing angle of LM bifurcation was defined on CCTA by 3-dimensional coordinates and converted into a 2-dimensional fluoroscopic view. The best fluoroscopic projection was considered the closest angulation to the optimal viewing angle on CCTA. µQFR was successfully computed in 805 projections. In the best projections, µQFR sensitivity was 88.2% (95% CI 76.1-95.6) and 84.8% (71.1-93.7), and specificity was 96.8% (93.8-98.6) and 97.2% (94.4-98.9), in pLAD and pLCX, respectively, with regard to FFRCT. The AUC of µQFR for predicting FFRCT ≤ 0.80 tended to be improved using the best versus suboptimal projections (0.94 vs. 0.89 [p = 0.048] in pLAD; 0.94 vs. 0.88 [p = 0.075] in pLCX). Computation of µQFR in LM bifurcations using a single angiographic view showed high feasibility from post-hoc analysis of coronary angiograms obtained for clinical purposes. The fluoroscopic viewing angle influences the diagnostic performance of physiological assessment using a single angiographic view.

Non-invasive fractional flow reserve derived from reduced-order coronary model and machine learning prediction of stenosis flow resistance

BACKGROUND AND OBJECTIVE

Recently, computational fluid dynamics enables the non-invasive calculation of fractional flow reserve (FFR) based on 3D coronary model, but it is time-consuming. Currently, machine learning technique has emerged as an efficient and reliable approach for prediction, which allows saving a lot of analysis time. This study aimed at developing a simplified FFR prediction model for rapid and accurate assessment of functional significance of stenosis.

METHODS

A reduced-order lumped parameter model (LPM) of coronary system and cardiovascular system was constructed for rapidly simulating coronary flow, in which a machine learning model was embedded for accurately predicting stenosis flow resistance at a given flow from anatomical features of stenosis. Importantly, the LPM was personalized in both structures and parameters according to coronary geometries from computed tomography angiography and physiological measurements such as blood pressure and cardiac output for personalized simulations of coronary pressure and flow. Coronary lesions with invasive FFR ≤ 0.80 were defined as hemodynamically significant.

RESULTS

A total of 91 patients (93 lesions) who underwent invasive FFR were involved in FFR derived from machine learning (FFRML) calculation. Of the 93 lesions, 27 lesions (29.0%) showed lesion-specific ischemia. The average time of FFRML simulation was about 10 min. On a per-vessel basis, the FFRML and FFR were significantly correlated (r = 0.86, p < 0.001). The diagnostic accuracy, sensitivity, specificity, positive predictive value and negative predictive value were 91.4%, 92.6%, 90.9%, 80.6% and 96.8%, respectively. The area under the receiver-operating characteristic curve of FFRML was 0.984.

CONCLUSION

In this selected cohort of patients, the FFRML improves the computational efficiency and ensures the accuracy. The favorable performance of FFRML approach greatly facilitates its potential application in detecting hemodynamically significant coronary stenosis in future routine clinical practice.

Assessment of the functional severity of coronary lesions from optical coherence tomography based on ensembled learning

BACKGROUND

Atherosclerosis is one of the most frequent cardiovascular diseases. The dilemma faced by physicians is whether to treat or postpone the revascularization of lesions that fall within the intermediate range given by an invasive fractional flow reserve (FFR) measurement. The paper presents a monocentric study for lesions significance assessment that can potentially cause ischemia on the large coronary arteries.

METHODS

A new dataset is acquired, comprising the optical coherence tomography (OCT) images, clinical parameters, echocardiography and FFR measurements collected from 80 patients with 102 lesions, with stable multivessel coronary artery disease. Having the ground truth given by the invasive FFR measurement, the dataset is challenging because almost 40% of the lesions are in the gray zone, having an FFR value between 0.75 and 0.85. Twenty-six features are extracted from OCT images, clinical characteristics, and echocardiography and the most relevant are identified by examining the models' accuracy. An ensembled learning is performed for solving the binary classification problem of lesion significance considering the leave-one-out cross-validation approach.

RESULTS

Ensemble models are designed from the multi-features voting from 5 features models by prediction aggregation with a maximum accuracy of 81.37% and a maximum area under the curve score (AUC) of 0.856.

CONCLUSIONS

The proposed explainable supervised learning-based lesion classification is a new method that can be improved by training with a larger multicenter dataset for further designing a tool for guiding the decision making of the clinician for the cases outside the gray zone and for the other situation extra clinical information about the lesion is needed.

The influence of flow distribution strategy for the quantification of pressure- and wall shear stress-derived parameters in the coronary artery: A CTA-based computational fluid dynamics analysis

For image-based computational fluid dynamics (CFD) analysis to characterize the local coronary hemodynamic environment, the accuracy depends on the flow rate which is in turn associated with outlet branches' morphology. A good flow distribution strategy is important to mitigate the effect when certain branches cannot be considered. In this study, stenotic coronary arteries from 13 patients were used to analyze the effect of missing branches and different flow distribution strategies. Pressure- and wall shear stress (WSS)-derived parameters around the stenotic region (ROI) were compared, including fractional flow reserve (CT-FFR), instantaneous wave-free ratio (CT-iFR), resting distal to aortic coronary pressure (CT-Pd/Pa), time-averaged WSS, oscillatory shear index (OSI) and relative residence time (RRT). Three flow distribution strategies were the Huo-Kassab model at distal outlets (Type I), flow distribution based on outlet resistances (Type II), and a developed algorithm distributing flow at each bifurcation until the final outlets (Type III). Results showed that Type III strategy for models with truncated branch(es) had a good agreement in both pressure- and WSS-related results (interquatile range less than 0.12% and 4.02%, respectively) with the baseline model around the ROI. The relative difference of pressure- and WSS-related results were correlated with the flow differences in the ROI to the baseline mode. Type III strategy had the best performance in maintaining the flow in intermediate branches. It is recommended for CFD analysis. Removal of branches distal to a stenosis can be undertaken with an improved performance and maintained accuracy, while those proximal to the ROI should be kept.

Changes in microvascular resistance following percutaneous coronary intervention - From the ILIAS global registry

BACKGROUND

Microvascular resistance (MR) has prognostic value in acute and chronic coronary syndromes following percutaneous coronary intervention (PCI), however anatomic and physiologic determinants of the relative changes of MR and its association to target vessel failure (TVF) has not been investigated previously. This study aims to evaluate the association between changes in MR and TVF.

METHODS

This is a sub-study of the Inclusive Invasive Physiological Assessment in Angina Syndromes (ILIAS) registry which is a global multi-centre initiative pooling lesion-level coronary pressure and flow data.

RESULTS

Paired pre-post PCI haemodynamic data were available in n = 295 vessels out of n = 828 PCI treated patients and of these paired data on MR was present in n = 155 vessels. Vessels were divided according to increase vs. decrease % in microvascular resistance following PCI (ΔMR % ≤ 0 vs. ΔMR > 0%). Decreased microvascular resistance ΔMR % ≤ 0 occurred in vessels with lower pre-PCI fractional flow reserve (0.67 ± 0.15 vs. 0.72 ± 0.09 p = 0.051), coronary flow reserve (1.9 ± 0.8 vs. 2.6 ± 1.8 p < 0.0001) and higher hyperemic microvascular resistance (2.76 ± 1.3 vs. 1.62 ± 0.74 p = 0.001) and index of microvascular resistance (24.4 IQ (13.8) vs. 15. 8 IQ (13.2) p = 0.004). There was no difference in angiographic parameters between ΔMR % ≤ 0 vs. ΔMR > 0%. In a cox regression model ΔMR % > 0 was associated with increased rate of TVF (hazard ratio 95% CI 3.6 [1.2; 10.3] p = 0.018).

CONCLUSION

Increased MR post-PCI was associated with lesions of less severe hemodynamic influence at baseline and higher rates of TVF at follow-up.

A simplified coronary model for diagnosis of ischemia-causing coronary stenosis

BACKGROUND AND OBJECTIVE

The functional assessment of the severity of coronary stenosis from coronary computed tomography angiography (CCTA)-derived fractional flow reserve (FFR) has recently attracted interest. However, existing algorithms run at high computational cost. Therefore, this study proposes a fast calculation method of FFR for the diagnosis of ischemia-causing coronary stenosis.

METHODS

We combined CCTA and machine learning to develop a simplified single-vessel coronary model for rapid calculation of FFR. First, a zero-dimensional model of single-vessel coronary was established based on CCTA, and microcirculation resistance was determined through the relationship between coronary pressure and flow. In addition, a coronary stenosis model based on machine learning was introduced to determine stenosis resistance. Computational FFR (cFFR) was then obtained by combining the zero-dimensional model and the stenosis model with inlet boundary conditions for resting (cFFRr) and hyperemic (cFFRh) aortic pressure, respectively. We retrospectively analyzed 75 patients who underwent clinically invasive FFR (iFFR), and verified the model accuracy by comparison of cFFR with iFFR.

RESULTS

The average computing time of cFFR was less than 2 s. The correlations between cFFRr and cFFRh with iFFR were r = 0.89 (p < 0.001) and r = 0.90 (p < 0.001), respectively. Diagnostic accuracy, sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio for cFFRr and cFFRh were 90.7%, 95.0%, 89.1%, 76.0%, 98.0%, 8.7, 0.1 and 92.0%, 95.0%, 90.9%, 79.2%, 98.0%, 10.5, 0.1, respectively.

CONCLUSIONS

The proposed model enables rapid prediction of cFFR and exhibits high diagnostic performance in selected patient cohorts. The model thus provides an accurate and time-efficient computational tool to detect ischemia-causing stenosis and assist with clinical decision-making.

Diagnostic accuracy of diastolic pressure ratio using a pressure microcatheter for intracoronary physiological assessment

Recently, instantaneous wave-free ratio (iFR) has emerged as an alternative to the fractional flow reserve (FFR) for intracoronary physiological assessment. Although all diastolic resting indices are reportedly identical to the iFR, limited data exist on diastolic pressure ratio (dPR) measured using a microcatheter (dPRmicro). This study aimed to evaluate the diagnostic accuracy of dPRmicro compared to FFR measured using a microcatheter (FFRmicro) in real-world practice for intracoronary physiological assessment. This was a single-center, retrospective, observational study. We identified 103 consecutive suspected angina pectoris patients (107 lesions) who underwent dPRmicro and FFRmicro measurement using the Navvus® catheter at Takasaki Heart Hospital from March 2019 to June 2019. A total of 103 lesions in 103 patients were finally included in the study. The mean FFRmicro and dPRmicro values were 0.80 and 0.88, respectively. With an FFRmicro ≤ 0.80, the dPRmicro showed a diagnostic accuracy of 79.6%, sensitivity of 74.6%, specificity of 87.5%, positive predictive value of 90.4%, and negative predictive value of 68.6%. The area under the receiver operating characteristic (ROC) curve was 0.894 (95% confidence interval, 0.833-0.956), and the optimal cut-off value for dPRmicro derived from the ROC analysis was 0.90. dPRmicro and FFRmicro values were discordant in 21/103 cases (20.4%). As a multivariable logistic regression analysis was performed, the male sex (vs. female) had a statistically significant association with a dPRmicro-FFRmicro discordance (OR 4.91; 95% CI, 1.04-23.0; P = 0.044). No other factors were found to be significantly associated with the discordance. In conclusion, dPRmicro measured using a microcatheter had good diagnostic accuracy and correlation with FFRmicro, hence, it can be useful for making revascularization decisions. However, re-studies in larger populations will be needed to better understand the properties of diastolic resting index measured using a microcatheter in clinical settings.