Maximal Hyperemia in the Assessment of Fractional Flow Reserve

Development of machine learning models for fractional flow reserve prediction in angiographically intermediate coronary lesions

BACKGROUND

Fractional flow reserve (FFR) represents the gold standard in guiding the decision to proceed or not with coronary revascularization of angiographically intermediate coronary lesion (AICL). Optical coherence tomography (OCT) allows to carefully characterize coronary plaque morphology and lumen dimensions.

OBJECTIVES

We sought to develop machine learning (ML) models based on clinical, angiographic and OCT variables for predicting FFR.

METHODS

Data from a multicenter, international, pooled analysis of individual patient's level data from published studies assessing FFR and OCT on the same target AICL were collected through a dedicated database to train (n = 351) and validate (n = 151) six two-class supervised ML models employing 25 clinical, angiographic and OCT variables.

RESULTS

A total of 502 coronary lesions in 489 patients were included. The AUC of the six ML models ranged from 0.71 to 0.78, whereas the measured F1 score was from 0.70 to 0.75. The ML algorithms showed moderate sensitivity (range: 0.68-0.77) and specificity (range: 0.59-0.69) in detecting patients with a positive or negative FFR. In the sensitivity analysis, using 0.75 as FFR cut-off, we found a higher AUC (0.78-0.86) and a similar F1 score (range: 0.63-0.76). Specifically, the six ML models showed a higher specificity (0.71-0.84), with a similar sensitivity (0.58-0.80) with respect to 0.80 cut-off.

CONCLUSIONS

ML algorithms derived from clinical, angiographic, and OCT parameters can identify patients with a positive or negative FFR.

Optical Coherence Tomography Measures Predicting Fractional Flow Reserve: The OMEF Study

Background

Optical coherence tomography (OCT) allows to carefully characterize coronary plaque morphology and lumen dimensions. We sought to evaluate the value of OCT in predicting fractional flow reserve (FFR).

Methods

We performed a multicenter, international, pooled analysis of individual patient-level data from published studies assessing FFR and OCT on the same vessel. Data from stable or unstable patients who underwent both FFR and OCT of the same coronary artery were collected through a dedicated database. Predefined OCT parameters were minimum lumen area (MLA), percentage area stenosis (%AS), and presence of thrombus or plaque rupture. Primary end point was FFR ≤0.80. Secondary outcome was the incidence of major adverse cardiac events in patients not undergoing revascularization based on negative FFR (>0.80).

Results

A total of 502 coronary lesions in 489 patients were included. A significant correlation was observed between OCT-MLA and FFR values (R = 0.525; P < .001), and between OCT-%AS and FFR values (R = -0.482; P < .001). In Receiver operating characteristic analysis, MLA <2.0 mm2 showed a good discriminative power to predict an FFR ≤0.80 (AUC, 0.80), whereas %AS >73% showed a moderate discriminative power (AUC, 0.73). When considering proximal coronary segments, the best OCT cutoff values predicting an FFR ≤0.80 were MLA <3.1 mm2 (AUC, 0.82), and %AS >61% (AUC, 0.84). In patients with a negative FFR not revascularized, the combination of lower MLA and higher %AS had a trend toward worse outcome (which was statistically significant in the analysis restricted to proximal vessels).

Conclusions

OCT lumen measures (MLA, %AS) may predict FFR, and different cutoffs are needed for proximal vessels.

Diagnostic performance of a novel automated CT-derived FFR technology in detecting hemodynamically significant coronary artery stenoses: A multicenter trial in China

BACKGROUND AND AIMS

Computed tomography-derived fractional flow reserve (CT-derived FFR) algorithms have emerged as promising noninvasive methods for identifying hemodynamically significant coronary artery disease (CAD). However, its broad adaption is limited by the complex workflow, slow processing, and supercomputer requirement. Therefore, CT-derived FFR solutions capable of producing fast and accurate results could help deliver time-sensitive results rapidly and potentially alter patient management. The current study aimed to determine the diagnostic performance of a novel CT-derived FFR algorithm, esFFR, on patients with CAD was evaluated.

METHODS

329 patients from 6 medical centers in China were included in this prospective study. CT-derived FFR calculations were performed on 350 vessels using the esFFR algorithm using patients' presenting coronary computed tomography angiography (CCTA) images, and results and processing speed were recorded. Using invasive FFR measurements from direct coronary angiography as the reference standard, the diagnostic performance of esFFR and CCTA in detecting hemodynamically significant lesions were compared. Post-hoc analyses were performed for patients with calcified lesions or stenoses within the CT-derived FFR diagnostic "gray zone."

RESULTS

The esFFR values correlated well with invasive FFR. The sensitivity, specificity, accuracy, positive and negative predictive value for esFFR were all above 90%. The overall performance of esFFR was superior to CCTA. Coronary calcification had minimal effects on esFFR's diagnostic performance. It also maintained 85% of diagnostic accuracy for "gray zone" lesions, which historically was <50%. The average esFFR processing speed was 4.6 ± 1.3 minutes.

CONCLUSIONS

The current study demonstrated esFFR had high diagnostic efficacy and fast processing speed in identifying hemodynamically significant CAD.

Safety and effectiveness of post percutaneous coronary intervention physiological assessment: Retrospective data from the post-revascularization optimization and physiological evaluation of intermediate lesions using fractional flow reserve registry

Background

While the importance of invasive physiological assessment (IPA) to choose coronary lesions to be treated is ascertained, its role after PCI is less established. We evaluated feasibility and efficacy of Physiology-guided PCI in the everyday practice in a retrospective registry performed in a single high-volume and “physiology-believer” center.

Materials and methods

The PROPHET-FFR study (NCT05056662) patients undergoing an IPA in 2015–2020 were retrospectively enrolled in three groups: Control group comprising patients for whom PCI was deferred based on a IPA; Angiography-Guided PCI group comprising patients undergoing PCI based on an IPA but without a post-PCI IPA; Physiology-guided PCI group comprising patients undergoing PCI based on an IPA and an IPA after PCI, followed by a physiology-guided optimization, if indicated. Optimal result was defined by an FFR value ≥ 0.90.

Results

A total of 1,322 patients with 1,591 lesions were available for the analysis. 893 patients (67.5%) in Control Group, 249 patients (18.8%) in Angiography-guided PCI Group and 180 patients (13.6%) in Physiology-guided PCI group. In 89 patients a suboptimal functional result was achieved that was optimized in 22 cases leading to a “Final FFR” value of 0.90 ± 0.04 in Angiography-Guided PCI group. Procedural time, costs, and rate of complications were similar. At follow up the rate of MACEs for the Physiology-guided PCI group was similar to the Control Group (7.2% vs. 8.2%, p = 0.765) and significantly lower than the Angiography-guided PCI Group (14.9%, p < 0.001), mainly driven by a reduction in TVRs.

Conclusion

“Physiology-guided PCI” is a feasible strategy with a favorable impact on mid-term prognosis. Prospective studies using a standardized IPA are warrant to confirm these data.

Comparative efficacy and safety of adenosine and regadenoson for assessment of fractional flow reserve: A systematic review and meta-analysis

BACKGROUND

Adenosine is a coronary hyperemic agent used to measure invasive fractional flow reserve (FFR) of intermediate severity coronary stenosis.

AIM

To compare FFR assessment using adenosine with an alternate hyperemic agent, regadenoson.

METHODS

PubMed, Google Scholar, CINAHL and Cochrane databases were queried for studies comparing adenosine and regadenoson for assessment of FFR. Data on FFR, correlation coefficient and adverse events from the selected studies were extracted and analyzed by means of random effects model. Two tailed P-value less than 0.05 was considered significant. Heterogeneity was assessed using I² test.

RESULTS

Five studies with 248 patients were included in the final analysis. All included patients and coronary lesions underwent FFR assessment using both adenosine and regadenoson. There was no significant mean difference between FFR measurement by the two agents [odds ratio (OR) = -0.00; 95% confidence interval (CI): (-0.02)-0.01, P = 0.88]. The cumulative correlation coefficient was 0.98 (0.96-0.99, P < 0.01). Three of five studies reported time to FFR with cumulative results favoring regadenoson (mean difference 34.31 s; 25.14-43.48 s, P < 0.01). Risk of adverse events was higher with adenosine compared to regadenoson (OR = 2.39; 95%CI: 1.22-4.67, P = 0.01), which most commonly included bradycardia and hypotension. Vast majority of the adverse events associated with both agents were transient.

CONCLUSION

The performance of regadenoson in inducing maximal hyperemia was comparable to that of adenosine. There was excellent correlation between the FFR measurements by both the agents. The use of adenosine, was however associated with higher risk of adverse events and longer time to FFR compared to regadenoson.

Comparison of efficacy and safety of intracoronary nicardipine and adenosine for fractional flow reserve assessment of coronary stenosis

BACKGROUND

Administration of intracoronary (IC) adenosine allows an easily feasible, inexpensive, and more rapid alternative method for fractional flow reserve (FFR). It is common practice in many centers worldwide. Nicardipine is a strong coronary vasodilator but its efficacy and safety for assessing FFR is not established. The purpose of present study was to compare the efficacy and safety of IC nicardipine and adenosine for assessing FFR.

METHODS

One hundred and fifty-nine patients with a total of 193 vessels undergoing clinically indicated FFR assessment of intermediate coronary stenoses were included. For the initial assessment of FFR, hyperemia was induced by an IC adenosine. After a washout period of 3 min, FFR was reassessed using 200 μg of IC nicardipine.

RESULTS

Hyperemic efficacy among two different stimuli was compared. The mean FFR with IC adenosine was 0.83 ± 0.09 and that with an IC nicardipine was 0.84 ± 0.09. The median FFR with an IC adenosine was 0.83 (0.78-0.91) and that with an IC nicardipine was 0.85 (0.79-0.91) (p-value 0.246). Both FFR values showed an excellent correlation (R² = 0.982, p < 0.001). Nicardipine produced fewer changes in heart rate, less chest pain and less flushing than adenosine. Transient atrioventricular block occurred in 29 patients with IC adenosine and none with IC nicardipine.

CONCLUSIONS

IC bolus injection of nicardipine could be introduced as a safe and practical alternative method of inducing hyperemia during FFR measurements. Compared to IC adenosine, IC nicardipine has a similar hyperemic efficacy and excellent side-effect profile.

Coronary angiography-derived contrast fractional flow reserve

BACKGROUND

Based on coronary angiography and mean aortic pressure, a specially designed computational flow dynamics (CFD) method is proposed to determine contrast fractional flow reserve (cFFR) without using invasive pressure wire. This substudy assessed diagnostic performance of coronary angiography-derived cFFR in catheterization laboratory, based on a previous multicenter trial for online assessment of coronary angiography-derived FFR (caFFR).

METHODS

Patients with diagnosis of stable angina pectoris or unstable angina pectoris were enrolled in six centers. Wire-based FFR was measured in coronary arteries with 30-90% diameter stenosis. Offline angiography-derived cFFR was computed in blinded fashion against the wire-based FFR and caFFR at an independent core laboratory.

RESULTS

A total of 330 patients were enrolled to fulfill inclusion/exclusion criteria from June 26 to December 18, 2018. Offline angiography-derived cFFR and wire-based FFR results were compared in 328 interrogated vessels. The statistical analysis showed the highest diagnostic accuracy of 89.0 and 86.6% for angiography-derived cFFR with a cutoff value of 0.94 and 0.93 against the wire-based FFR with a cutoff value of 0.80 and 0.75, respectively. The corresponding sensitivity and specificity were 92.2 and 87.3% for the cutoff value of 0.94 and 80.0 and 88.4% for the cutoff value of 0.93, which are similar to those against the caFFR. The receiver-operating curve has area under the curve of 0.951 and 0.972 for the wire-based FFR with the cutoff value of 0.80 and 0.75, respectively.

CONCLUSIONS

Coronary angiography-derived cFFR showed higher accuracy, sensitivity, and specificity against wired-based FFR and caFFR. Hence, angiography-derived cFFR could enhance the hemodynamic assessment of coronary lesions.

Coronary Angiography-Derived Diastolic Pressure Ratio

Aims

Based on the aortic pressure waveform, a specially designed computational fluid dynamic (CFD) method was proposed to determine coronary angiography-derived diastolic pressure ratio (caDPR) without using invasive pressure wire. The aim of the study is to retrospectively assess diagnostic performance of the caDPR in the catheterization laboratory, based on a previous multicenter trial for online assessment of coronary angiography-derived FFR (caFFR).

Methods and Results

Patients with diagnosis of stable or unstable angina pectoris were enrolled in six centers. Wire-derived FFR was measured in coronary arteries with 30–90% diameter stenosis. Offline caDPR was assessed in blinded fashion against wire-derived FFR at an independent core laboratory. A total of 330 patients who met the inclusion/exclusion criteria were enrolled from June 26 to December 18, 2018. Offline computed caDPR and wire-derived FFR were compared in 328 interrogated vessels. The caDPR with a cutoff value of 0.89 shows diagnostic accuracy of 87.7%, sensitivity of 89.5%, specificity of 86.8%, and AUC of 0.940 against the wire-derived FFR with a cutoff value of 0.80.

Conclusions

Using wired-based FFR as the standard reference, there is good diagnostic performance of the novel-CFD-design caDPR. Hence, caDPR could enhance the hemodynamic assessment of coronary lesions.

High dose escalation of intracoronary adenosine in the assessment of fractional flow reserve: A retrospective cohort study

Maximal hyperaemia for fractional flow reserve (FFR) may not be achieved with the current recommended doses of intracoronary adenosine. Higher doses (up to 720 μg) have been reported to optimize hyperaemic stimuli in small dose-response studies. Real-world data from a large cohort of patients is needed to evaluate FFR results and the safety of high-dose escalation. This is a retrospective study aimed to evaluate the safety and frequency of FFR ≤0.8 after high-dose escalation of intracoronary adenosine. Data were extracted from the medical databases of two university hospitals. Increasing doses (100, 200, 400, 600, and 800 μg) of adenosine were administered as intracoronary boluses until FFR ≤0.8 was achieved or heart block developed. The percentage of FFR ≤0.8 after higher-dose escalation was compared with those at conventional doses, and the predictors for FFR ≤0.8 after higher doses were analysed. In the 1163 vessels of 878 patients, 402 vessels (34.6%) achieved FFR ≤0.8 at conventional doses and 623 vessels (53.6%) received high-dose escalation. An additional 84 vessels (13.5%) achieved FFR ≤0.8 after high-dose escalation. No major complications developed during high-dose escalation. Borderline FFR (0.81-0.85) at the conventional dose, stenosis >60%, and triple-vessel disease increased the likelihood of FFR ≤0.8 after high-dose escalation, but chronic kidney disease decreased it. For vessels of borderline FFR at conventional doses, 46% achieved FFR ≤0.8 after high-dose escalation. In conclusion, High-dose escalation of intracoronary adenosine increases the frequency of FFR ≤0.8 without major complications. It could be especially feasible for borderline FFR values near the 0.8 diagnostic threshold.

Relationship between adenosine A2a receptor polymorphism rs5751876 and fractional flow reserve during percutaneous coronary intervention

Fractional flow reserve (FFR) assessed during adenosine-induced maximal hyperemia has emerged as a useful tool for the guidance of percutaneous coronary interventions (PCI). However, interindividual variability in the response to adenosine has been claimed as a major limitation to the use of adenosine for the measurement of FFR, carrying the risk of underestimating the severity of coronary stenoses, with potential negative prognostic consequences. Genetic variants of the adenosine receptor A2a (ADORA2A gene), located in the coronary circulation, have been involved in the modulation of the hyperemic response to adenosine. However, no study has so far evaluated the impact of the single nucleotide polymorphism rs5751876 of ADORA2A on the measurement of FFR in patients undergoing percutaneous coronary intervention that was, therefore, the aim of our study. We included patients undergoing coronary angiography and FFR assessment for intermediate (40-70%) coronary lesions. FFR measurement was performed by pressure-recording guidewire (Prime Wire, Volcano), after induction of hyperemia with intracoronary boli of adenosine (from 60 to 1440 μg, with dose doubling at each step). Restriction fragment length polymorphism (RFLP) analysis was performed to assess the presence of rs5751876 C>T polymorphism of ADORA2a receptor. We included 204 patients undergoing FFR measurement of 231 coronary lesions. A total of 134 patients carried the polymorphism (T allele), of whom 41 (30.6%) in homozygosis (T/T).Main clinical and angiographic features did not differ according to ADORA2A genotype. The rs5751876 C>T polymorphism did not affect mean FFR values (p = 0.91), the percentage of positive FFR (p = 0.54) and the duration of maximal hyperemia. However, the time to recovery to baseline FFR values was more prolonged among the T-allele carriers as compared to wild-type patients (p = 0.04). Based on these results, in patients with intermediate coronary stenoses undergoing FFR assessment with adenosine, the polymorphism rs5751876 of ADORA2A does not affect the peak hyperemic response to adenosine and the results of FFR. However, a more prolonged effect of adenosine was observed in T-carriers.

Individual Lesion-Level Meta-Analysis Comparing Various Doses of Intracoronary Bolus Injection of Adenosine With Intravenous Administration of Adenosine for Fractional Flow Reserve Assessment

BACKGROUND

Intravenous infusion of adenosine is considered standard practice for fractional flow reserve (FFR) assessment but is associated with adverse side-effects and is time-consuming. Intracoronary bolus injection of adenosine is better tolerated by patients, cheaper, and less time-consuming. However, current literature remains fragmented and modestly sized regarding the equivalence of intracoronary versus intravenous adenosine. We aim to investigate the relationship between intracoronary adenosine and intravenous adenosine to determine FFR.

METHODS

We performed a lesion-level meta-analysis to compare intracoronary adenosine with intravenous adenosine (140 µg/kg per minute) for FFR assessment. The search was conducted in accordance to the Preferred Reporting for Systematic Reviews and Meta-Analysis statement. Lesion-level data were obtained by contacting the respective authors or by digitization of scatterplots using custom-made software. Intracoronary adenosine dose was defined as; low: <40 µg, intermediate: 40 to 99 µg, and high: ≥100 µg.

RESULTS

We collected 1972 FFR measurements (1413 lesions) comparing intracoronary with intravenous adenosine from 16 studies. There was a strong correlation (correlation coefficient =0.915; P<0.001) between intracoronary-FFR and intravenous-FFR. Mean FFR was 0.81±0.11 for intracoronary adenosine and 0.81±0.11 for intravenous adenosine (P<0.001). We documented a nonclinically relevant mean difference of 0.006 (limits of agreement: -0.066 to 0.078) between the methods. When stratified by the intracoronary adenosine dose, mean differences between intracoronary and intravenous-FFR amounted to 0.004, 0.011, or 0.000 FFR units for low-dose, intermediate-dose, and high-dose intracoronary adenosine, respectively.

CONCLUSIONS

The present study documents clinically irrelevant differences in FFR values obtained with intracoronary versus intravenous adenosine. Intracoronary adenosine hence confers a practical and patient-friendly alternative for intravenous adenosine for FFR assessment.

[Echocardiographic Stress Test with Adenosine Triphosphate: Optimization of the Algorithm]

PURPOSE

To: 1) optimize algorithm of stress echocardiography (s-Echo) with intravenous adenosine triphosphate (ATP) infusion taking into account pharmacokinetics and pharmacodynamics of ATP in human body, 2) test new algorithm in patients with coronary and other heart diseases.

MATERIALS AND METHODS

In order to determine spectrum of factors influencing the results of stress test with ATP we inspected main scientific data bases and found 48 publications on ATP application for diagnostic purposes. Analysis of these publications allowed us to optimize algorithm of ATP s-Echo. Optimized algorithm was tested on 26 subjects, who underwent ATP 4D strain-stress-echocardiography of the left ventricle.

RESULTS AND DISCUSSION

Optimized algorithm has three stages: registration of Echo data sets before, at the time of ATP infusion, and after 5 min of ATP infusion termination. Registration of Echo parameters at the second stage must begin not earlier than 3 min after the onset of ATP infusion and only in the presence of signs of coronary vasodilation. We think that the main indirect criterion of submaximal coronary vasodilation is 5 mm Hg or more decrease in systolic blood pressure (SBP), but not below SBP level of 90 mm Hg. Initial dose of ATP is 140 µg/kg/min. If after 2 min of infusion SBP do not diminish we increase the infusion rate at first to 175 and then to 210 µg/kg/min. While testing new algorithm in all cases we have achieved criteria of effective vasodilation. Mean SBP decrease was 16.4±13.7 mm Hg, heart rate increase - 12.7±8.1 bpm. In all patients we obtained interpretable 4D LV Echo data sets for visual analysis of local contractility and automatic strain analysis.

CONCLUSION

Optimization of ATP s-Echo algorithm was performed. Safety and efficacy of optimized algorythm for registration of echo data was demonstrated. New ATP infusion algorithm can also be recommended for testing with other cardiac imaging modalities in evaluation of myocardial perfusion and contractility (SPECT, CT, MRI, PET).

Accuracy of computational pressure-fluid dynamics applied to coronary angiography to derive fractional flow reserve: FLASH FFR

Aims

Conventional fractional flow reserve (FFR) is measured invasively using a coronary guidewire equipped with a pressure sensor. A non-invasive derived FFR would eliminate risk of coronary injury, minimize technical limitations, and potentially increase adoption. We aimed to evaluate the diagnostic performance of a computational pressure-flow dynamics derived FFR (caFFR), applied to coronary angiography, compared to invasive FFR.

Methods and results

The FLASH FFR study was a prospective, multicentre, single-arm study conducted at six centres in China. Eligible patients had native coronary artery target lesions with visually estimated diameter stenosis of 30–90% and diagnosis of stable or unstable angina pectoris. Using computational pressure-fluid dynamics, in conjunction with thrombolysis in myocardial infarction (TIMI) frame count, applied to coronary angiography, caFFR was measured online in real-time and compared blind to conventional invasive FFR by an independent core laboratory. The primary endpoint was the agreement between caFFR and FFR, with a pre-specified performance goal of 84%. Between June and December 2018, matched caFFR and FFR measurements were performed in 328 coronary arteries. Total operational time for caFFR was 4.54 ± 1.48 min. caFFR was highly correlated to FFR (R = 0.89, P = 0.76) with a mean bias of −0.002 ± 0.049 (95% limits of agreement −0.098 to 0.093). The diagnostic performance of caFFR vs. FFR was diagnostic accuracy 95.7%, sensitivity 90.4%, specificity 98.6%, positive predictive value 97.2%, negative predictive value 95.0%, and area under the receiver operating characteristic curve of 0.979.

Conclusions

Using wire-based FFR as the reference, caFFR has high accuracy, sensitivity, and specificity. caFFR could eliminate the need of a pressure wire, technical error and potentially increase adoption of physiological assessment of coronary artery stenosis severity.

Clinical Trial Registration

URL: http://www.chictr.org.cn Unique Identifier: ChiCTR1800019522.

Comparison of intracoronary versus intravenous adenosine-induced maximal hyperemia for fractional flow reserve measurement: A systematic review and meta-analysis

OBJECTIVE

We sought to perform a systematic review and meta-analysis of the available literature comparing fractional flow reserve (FFR) measurements after administration of adenosine using intracoronary (IC) bolus versus standard continuous intravenous (IV) infusion.

BACKGROUND

FFR is considered the gold standard for invasive assessment of coronary lesions of intermediate severity. IV adenosine is recommended to induce hyperemia; however, IC adenosine is widely used for convenience. The difference between IV and IC administration in lesions assessment is not well studied.

METHODS

We systematically searched MEDLINE and relevant databases for studies comparing IV with IC adenosine administration for FFR measurement. We reviewed data pertaining to adenosine doses, side effects, and FFR values.

RESULTS

Eight studies addressing the primary question were identified. Dose of IC adenosine varied between 36 and 600 μg. Compared to IV adenosine infusion, the sensitivity of IC administration is 0.805 (95% confidence interval [95% CI]: 0.664-0.896; p < .001), specificity is 0.965 (95% CI: 0.932-0.983; p < .001), positive likelihood ratio is 24.218 (95% CI: 12,263-47.830; p < .001), negative likelihood ratio is 0.117 (95% CI: 0.033-0.411; p < .01), and diagnostic odds ratio is 274.225 [95% CI: 92.731-810.946; p < .001]. Overall, hemodynamic side effects and symptoms were reported more frequently with IV adenosine.

CONCLUSIONS

The available literature suggests that IC adenosine is well tolerated and may provide equivalent diagnostic accuracy compared to IV administration. However, variability in dosing regimens does not allow definitive conclusions regarding noninferiority of IC approach compared to IV administration.

Safety and efficacy of intracoronary sodium nitroprusside for the assessment of coronary fractional flow reserve

Background

Coronary fractional flow reserve (FFR) determination is a valuable tool for the assessment of stenosis significance in intermediate coronary obstructions. Maximal hyperemia is mandatory for this determination. Although intravenous (IV) Adenosine is the standard agent used, its use carries an elevated incidence of side effects. Intracoronary sodium nitroprusside (IC NTP) is a very well-known coronary vasodilator, but it is not routinely used for FFR determinations.

Objectives

The purpose of the present study was to compare FFR determinations and side effect profile of IC NTP with IV Adenosine.

Methods

We prospectively assessed FFR determinations in a total of 20 intermediate coronary artery stenotic lesions in 18 consecutive patients with the administration of IV Adenosine (140 μg/kg/min) and IC NTP (100 μg). The appearance of side effects was registered.

Results

The mean age was 55.5 ± 7.5 years. Fifteen (83%) of the patients were male. Mean FFR values with IC NTP were similar to those obtained with IV Adenosine (0.82 ± 0.07 vs 0.82 ± 0.06, respectively, r = 0.775, p < 0.0001). Intravenous Adenosine induced side effects in 45% of patients (shortness of breath 30%, flushing 5%, headache 5%, angina pectoris 5%, and transient conduction disturbances 10%). No side effects were reported with IC NTP.

Conclusions

IC NTP at a dose of 100 μg is as effective as IV Adenosine for FFR assessment. Besides, it is better tolerated and should be consider as a vasodilator agent in the assessment of FFR.

Intracoronary versus intravenous adenosine to assess fractional flow reserve: a systematic review and meta-analysis

AIMS

Intravenous infusion of adenosine is the reference method to measure fractional flow reserve (FFR). Intracoronary boluses are often used because of time and convenience, but their effectiveness has yet to be assessed.

METHODS

We conducted a systematic review and meta-analysis of prospective studies directly comparing intravenous and intracoronary adenosine administration for FFR measurement. FFR values and prevalence of functionally critical lesions obtained with the different methods of adenosine administration were compared.

RESULTS

Twelve studies evaluating 781 lesions from 731 patients were included (63.7 years, 25.5% women, median FFR 0.82). FFR values were significantly lower with intravenous adenosine than with intracoronary adenosine [mean difference 0.01, 95% confidence interval (CI) 0.00-0.02, P = 0.005], even if no significant differences were observed when only high doses of intracoronary adenosine (≥150 μg) were considered. The prevalence of functionally critical lesions did not significantly differ between intracoronary and intravenous adenosine. Concerning the use of different doses of intracoronary adenosine, low doses (≤60 μg) were associated with higher FFR values (mean difference 0.02, 95% CI 0.01-0.03, P < 0.001) and fewer functionally critical lesions (OR 0.57, 95% CI 0.40-0.81, P = 0.002) compared with high doses. Meta-regression analysis did not show any significant interaction between the way of adenosine administration and main clinical features. Intracoronary adenosine was associated with a higher incidence of atrioventricular blocks, whereas angina and/or systemic symptoms were more frequent with intravenous adenosine.

CONCLUSION

Intracoronary adenosine might be as effective as intravenous adenosine to measure FFR, provided that adequate doses are used. Intracoronary adenosine represents a valuable alternative to intravenous adenosine whenever appropriately administered.

Saline-induced Pd/Pa ratio predicts functional significance of coronary stenosis assessed using fractional flow reserve

AIMS

Fractional flow reserve (FFR), assessed using distal coronary pressure/aortic pressure (Pd)/(Pa) ratio, functionally evaluates coronary stenosis. An assessment method without vasodilators would be helpful. A single intracoronary bolus of saline decreases Pd because of the speculated low-viscosity effect. We hypothesised that saline-induced Pd/Pa ratio (SPR) could functionally evaluate coronary stenosis. This study aimed to test the accuracy and utility of SPR for predicting FFR ≤0.80.

METHODS AND RESULTS

In 137 coronary lesions with over 50% angiographic diameter stenosis, SPR was assessed using an intracoronary bolus of saline (2 mL/s) for five heartbeats (SPR-5) and three heartbeats (SPR-3). FFR was obtained after intravenous adenosine infusion (140 µg/kg/min). There was a strong correlation between FFR and SPR-5 or SPR-3 (R=0.941 and R=0.933, respectively). Receiver operating characteristic (ROC) curve analysis demonstrated good accuracy (86.3%) for SPR-5, with a cut-off of ≤0.84 for predicting FFR ≤0.80 (area under ROC curve 0.96, specificity 94.3, sensitivity 79.9). Thirty-three lesions (24%) were located in the "grey zone" (SPR 0.83-0.88). No complications were observed in 673 SPR measurements.

CONCLUSIONS

SPR may accurately predict FFR and can limit adenosine use to one in four lesions. Further studies are needed to confirm the validity of SPR.

Comparison of sodium nitroprusside and adenosine for fractional flow reserve assessment: a systematic review and meta-analysis

BACKGROUND

Fractional flow reserve (FFR) has become a useful tool in the assessment of physiological significance of coronary artery stenosis (CAS), and Adenosine (ADE) is associated with a high incidence of transient side effects. Sodium nitroprusside (NPS) has been proposed as an alternative vasodilator agent. A meta-analysis of studies comparing ADE and NPS for FFR assessment in the same coronary lesions was performed.

METHODS

Authors searched for articles comparing NPS and ADE for FFR assessment in intermediate coronary lesions published through January 2018. The following keywords were used: 'fractional flow reserve' AND 'nitroprusside'. Data were summarized using weighted mean differences for paired data.

RESULTS

Seven studies were identified comprising 342 patients and 401 lesions. Four studies evaluated intravenous ADE and 3 studies intracoronary ADE administration. Weighted means FFR values obtained with ADE and NPS were 0.8411 and 0.8445, respectively (weighted mean difference: 0.00, 95% confidence interval (CI) -0.01 to 0.01, p = 0,548). Adverse events were significantly reduced with IC NPS (RR = 0.08, 95%CI 0.02-0.30, P < 0.0001).

CONCLUSIONS

NPS produces similar FFR measurements compared to ADE with a significant reduction in adverse effects. These results may support its use as a suitable alternative to ADE for FFR assessment.

Correlation between frequency-domain optical coherence tomography and fractional flow reserve in angiographically-intermediate coronary lesions

BACKGROUND

The decision-making process of patients with angiographically-intermediate coronary lesions (ICL) is clinically challenging and may benefit from adjunctive invasive techniques. Fractional-flow-reserve (FFR) represents the gold standard to evaluate ICL but frequency-domain optical-coherence-tomography (OCT) is a novel, promising, high resolution coronary imaging technique, which allows physiopathologic assessment of coronary plaque. We investigated the possible relation between OCT and FFR in selected ICL patients.

METHODS

Stable or unstable patients with ICL who underwent both FFR and OCT assessment at two large tertiary centers were retrospectively enrolled. FFR was performed according to standard methodology. OCT images were (on blind to clinical and FFR results) analyzed to assess minimal lumen area (MLA), percentage area stenosis (AS), thrombus and plaque ulceration.

RESULTS

Forty patients were identified (62±10years, 93% symptomatic, 35% acute presentation, 93% left-anterior-descending artery ICL). Percentage diameter stenosis at quantitative coronary angiography was 40±12% and FFR was 0.85±0.07. MLA (p=0.009), AS (p<0.001) and plaque ulceration (p=0.02) were significantly associated with FFR values. An integrated assessment of AS (≥ or <70%), MLA (≥ or <2.5mm²) and presence or absence of thrombus and plaque ulceration was found to have the potential to accurately (sensitivity 91%, specificity 93%) predict FFR results.

CONCLUSION

In patients with ICL, a combination of different OCT parameters may help predict FFR results. These findings suggest that only a comprehensive assessment of lesion features by OCT can allow an accurate prediction of lesion severity assessed by FFR.

Instantaneous Wave-Free Ratio for the Assessment of Intermediate Coronary Artery Stenosis in Patients With Severe Aortic Valve Stenosis: Comparison With Myocardial Perfusion Scintigraphy

OBJECTIVES

This study investigated the diagnostic performance of instantaneous wave-free ratio (iFR) in patients with aortic valve stenosis (AS).

BACKGROUND

The iFR was introduced as a new, nonpharmacologic stress index of coronary stenosis severity. However, the diagnostic performance of iFR has not been sufficiently explored in patients with severe AS.

METHODS

We analyzed 95 consecutive patients with AS (57 women) demonstrating intermediate coronary artery stenosis (116 vessels), and compared the iFR values with fractional flow reserve (FFR) values and with adenosine-stress myocardial perfusion imaging as indicators of myocardial ischemia.

RESULTS

The median value and interquartile range (first quartile [Q1], third quartile [Q3]) of the iFR was 0.86 (Q1 to Q3 range, 0.76 to 0.93), and that of the FFR was 0.84 (Q1 to Q3 range, 0.76 to 0.91). The iFR values correlated well with the FFR values (R = 0.854; p < 0.0001). A receiver operating characteristic analysis demonstrated an optimal cutoff of 0.82 for the iFR to indicate an FFR ≤0.75, with an area under the curve of 0.92. The optimal iFR cutoff value indicating myocardial ischemia on perfusion scintigraphy was 0.82 (area under the curve: 0.84).

CONCLUSIONS

In patients with severe AS, a good correlation exists between iFR and FFR. Both the iFR and FFR values exhibit good correlation with perfusion scintigraphy-identified myocardial ischemia. The iFR could be a safe diagnostic tool for patients with severe AS. (The Impact of FFR and iFR in Patients with Severe Aortic Stenosis; UMIN000024479).

Fractional flow reserve (FFR) as a guide to treat coronary artery disease

INTRODUCTION

The presence and extent of myocardial ischemia are the major determinants of prognosis in patients with coronary artery disease (CAD). Unlike coronary angiography alone, fractional flow reserve (FFR) has enabled interventional cardiologists to accurately determine whether coronary atherosclerotic plaques are responsible for myocardial ischemia, and therefore deserve to be revascularized. Areas covered: An overview on the role of FFR in the diagnosis and treatment of coronary artery disease, as well as the potential related controversies is provided. Authors describe the coronary physiology underneath this technique and all the procedural aspects in the catheterization laboratory. The landmark trials and the current applications in different coronary lesions and syndromes are also described and potential future research involving FFR and comparisons with other methodologies for the evaluation of coronary physiology are introduced. Expert commentary: FFR is still unsurpassed in diagnostic performance when compared to non-hyperemic indices and noninvasive techniques, and remains the gold standard for the detection of ischemia-inducing coronary stenoses. FFR-guided PCI has been demonstrated superior to an angiography-guided PCI and over medical therapy alone, and ongoing investigation will clarify whether it could perform better, or at least equalize the results of cardiac surgery in patients with severe multivessel disease.

Meta-Analysis of Head-to-Head Comparison of Intracoronary Versus Intravenous Adenosine for the Assessment of Fractional Flow Reserve

Intravenous (IV) infusion of adenosine represents the gold standard for measuring fractional flow reserve (FFR). However, IV adenosine is more expensive and time-consuming compared with intracoronary (IC) boluses of adenosine. We conducted a meta-analysis of studies comparing IC with IV adenosine for FFR assessment in the same coronary lesions. We searched for studies comparing IC with IV adenosine and reporting absolute FFR values or rate of abnormal FFR for both routes. Prespecified subgroup analysis was performed to appraise studies using low-dose (<100 μg) or high-dose IC adenosine (≥100 μg). We retrieved 11 studies amounting to 587 patients and 621 lesions. Six studies evaluated low-dose IC boluses (15 to 80 μg) and 5 studies high-dose boluses (120 to 600 μg). Absolute FFR values were slightly, yet significantly lower with IV adenosine compared with IC adenosine (mean difference 0.02, 95% confidence interval [CI] 0.00 to 0.03, p = 0.02). This difference, however, did not translate into a significant difference in the rate of abnormal FFR between IC and IV adenosine (hazard ratio 0.93, 95% CI 0.76 to 1.13, p = 0.57); moreover, no statistically significant difference was observed between low-dose and high-dose IC adenosine subgroups. Adverse events were less frequent with IC adenosine compared with IV adenosine (risk ratio 0.17, 95% CI 0.07 to 0.43, p <0.001). In conclusion, IC administration of adenosine, although inducing a slightly lower amount of hyperemia compared with IV infusion of adenosine, yields a similar diagnostic accuracy in identifying hemodynamically significant coronary stenosis and is better tolerated by the patients.

Comparison of regadenoson and nitroprusside to adenosine for measurement of fractional flow reserve: A systematic review and meta-analysis

BACKGROUND

FFR is useful in defining the physiological significance of intermediate coronary stenosis and requires induction of maximal hyperemia and measurement of pressure proximal and distal to the stenosis. Hyperemia normally is induced by either IV or IC adenosine, a medication associated with short-term side effects. IV regadenoson and IC nitroprusside have been suggested as viable alternatives. This meta-analysis aims to identify all studies comparing use of intravenous (IV) regadenoson or intracoronary (IC) nitroprusside with IV adenosine to determine differences related to the agent utilized for assessment of fractional flow reserve (FFR).

METHODS

We searched PubMed, EMBASE, Web of Science, SCOPUS, ClinicalTrials.gov and the Cochrane Library databases for studies comparing IV regadenoson or IC nitroprusside to IV adenosine for FFR assessment. The main outcome was difference in mean FFR measurement. The main secondary outcomes were composite side-effect profile and reclassification of lesions.

RESULTS

Seven studies were included in the analysis, with a total of 375 patients. Compared to IV adenosine, there was no difference in the mean FFR derived from IV regadenoson (p=1.0) or IC nitroprusside (p=0.48). IV regadenoson was associated with 53% lower risk of pooled side effects compared to IV adenosine (p=0.05). IC nitroprusside was associated with 97% lower risk of pooled side effects compared to IV adenosine (p<0.001).

CONCLUSIONS

IV regadenoson and IC nitroprusside produce similar pressure-derived FFR measurements compared to IV adenosine and have a favorable side effect profile. Both can be considered as alternative agents to IV adenosine for FFR measurement. Further clinical validation is warranted.

Standardization of Fractional Flow Reserve Measurements

Pressure wire-based fractional flow reserve is considered the standard of reference for evaluation of the ischemic potential of coronary stenoses and the expected benefit from revascularization. Accordingly, its application in daily practice or for research purposes has to be as standardized as possible to avoid technical or operator-related artifacts in pressure recordings. This document proposes a standardized way of acquiring, recording, interpreting, and archiving the pressure tracings for daily practice and for the purpose of clinical research involving a core laboratory. Proposed standardized steps enhance the uniformity of clinical practices and data interpretation.

Evaluation of intermediate coronary stenoses in acute coronary syndromes using pressure guidewire

Fractional flow reserve (FFR) is increasingly used to guide myocardial revascularisation. However, supporting evidence regarding its use originates from studies that have enrolled mainly patients with stable angina, while patients with acute coronary syndromes (ACS) have not been included. Notably, multifactorial microvascular dysfunction and an increased sympathetic tone in patients with ACS may lead to blunted response to adenosine and false-negative results of FFR due to submaximal hyperaemia. This may raise the possibility of deferring treatment of stenosis that instead would have needed dilatation, thus leaving a residual risk of preventable cardiac events. In this literature review, we aim at summarising laboratory and clinical investigations concerning the use of FFR in culprit and non-culprit lesions in ACS. Furthermore, we will report recent data on instantaneous wave-free ratio, an adenosine-free index of functional stenosis severity, in stable coronary artery disease and in patients with ACS.

Identification of the State of Maximal Hyperemia in the Assessment of Coronary Fractional Flow Reserve Using Non-Invasive Electrical Velocimetry

Previous research revealed that, in patients with coronary pressure-derived fractional flow reserve (FFR) in the 'grey zone' (0.75-0.85), repeated FFR assessments sometimes yield conflicting results. One of the causes of the fluctuations in FFR values around the grey zone may be imprecise identification of the point where maximal hyperemia is achieved. Identification of the state of maximal hyperemia during assessment of FFR can be challenging. This study aimed to determine whether non-invasive electrical velocimetry (EV) can be used to identify the state of maximal hyperemia.Stroke volume (SV), SV variation (SVV), and systemic vascular resistance index (SVRI) were determined by EV in 15 patients who underwent FFR assessment. Time intervals from initiation of adenosine infusion to achieving maximal hyperemia (time^mFRR), as well as to achieving maximal cardiac output (CO), SV, SVV, and SVRI (time^mCO, time^mSV, time^mSVV, and time^mSVRI, respectively), were determined. Time^mCO and time^mSVV were closer to time^mFRR than other values (time^mSVV/time^mFRR versus time^mSVRI/time^mFRR = 1.03 ± 0.2 versus 1.36 ± 0.4, P < 0.05). The maximum of SV was difficult to determine owing to considerable variations, but the maximum of SVV was clearly recognized. Time^mCO and time^mSVV were significantly correlated with time^mFFR, with time^mSVV showing a stronger correlation than time^mSV (time^mSVV: r = 0.92, P < 0.01; time^mCO: r = 0.80, P < 0.01).Maximal SVV is reached close to maximal hyperemia. Monitoring of SVV with non-invasive EV during FFR assessment can help identify the state of maximal hyperemia.

Temporal dissociation between the minimal distal-to-aortic pressure ratio and peak hyperemia during intravenous adenosine infusion

The present study sought to compare the temporal relation between maximal coronary flow (peak hyperemia) and minimal coronary-to-aortic pressure ratio (Pd/Pa) for intracoronary (IC) and intravenous (IV) adenosine administration. Peak hyperemia is assumed to coincide with the minimal Pd/Pa value. However, this has not been confirmed for systemic hemodynamic variations during IV adenosine infusion. Hemodynamic responses to IV and IC adenosine administration were obtained in 12 patients (14 lesions) using combined IC pressure and flow velocity measurements. A fluid dynamic model was used to predict the change in Pd/Pa for different stenosis severities and varying Pa. Hemodynamic variability during IV adenosine hyperemia was greater than during IC adenosine, as assessed by the coefficient of variation. During IV adenosine, flow velocity peaked 28 ± 4 (SE) s after the onset of hyperemia, while Pd/Pa reached a minimum (0.82 ± 0.01) 22 ± 7 s later ( P < 0.05), when Pa had declined by 6.1% and hyperemic velocity by 4.5% ( P < 0.01). Model outcomes corroborated the role of variable Pa in this dissociation. In contrast, maximal flow and minimal Pd/Pa coincided for IC adenosine, with IV-equivalent peak velocities and a higher Pd/Pa ratio (0.86 ± 0.01, P < 0.01). Hemodynamic variability during continuous IV adenosine infusion can lead to temporal dissociation of minimal Pd/Pa and peak hyperemia, in contrast to IC adenosine injection, where maximal velocity and minimal Pd/Pa coincide. Despite this variability, stenosis hemodynamics remained stable with both ways of adenosine administration. Our findings suggest advantages of IC over IV adenosine to identify maximal hyperemia from pressure-only measurements.

NEW & NOTEWORTHY Systemic hemodynamic variability during intravenous adenosine infusion produces substantial temporal dissociation between peak hyperemia appraised by coronary flow velocity and the minimal distal-to-aortic pressure ratio commonly used to determine functional stenosis severity. This dissociation was absent for intracoronary adenosine administration and tended to be mitigated in patients receiving Ca2+ antagonists.

Efficacy of intravenous nicorandil for fractional flow reserve assessment: study protocol for a crossover randomised trial

INTRODUCTION

Nicorandil has vasodilatory effects on both the epicardial coronary arteries and the coronary microvasculature, thereby increasing coronary blood flow. Intravenous administration of nicorandil can be applicable for fractional flow reserve (FFR) measurement as a hyperaemic agent and a possible alternative to adenosine. However, the effectiveness of intravenous nicorandil infusion for FFR measurement is largely unclear.

METHODS AND ANALYSIS

This crossover randomised study is being performed to investigate the efficacy of intravenous administration of nicorandil for FFR measurement. Patients with an intermediate coronary artery stenosis who satisfy the eligibility criteria undergo FFR measurement with a consecutive randomised order of patient-blind infusions of continuous intravenous administration of adenosine and a single bolus intravenous administration of nicorandil. The primary end point of the study is the agreement between the FFR values obtained by the intravenous nicorandil and those obtained by the intravenous adenosine. Recruitment of this trial started in November 2015 and will end in March 2017, or until a total of 50 participants have been recruited.

ETHICS AND DISSEMINATION

The protocol was approved by the Institutional Review Board at Chiba University Hospital. Study findings will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

UMIN000019309; Pre-results.

Intracoronary adenosine-induced ventricular arrhythmias during fractional flow reserve (FFR) measurement: case series and literature review

Fractional flow reserve (FFR) is a standardized and well-established method frequently used in clinical practice to evaluate the hemodynamic significance of epicardial coronary stenosis identified by coronary angiography. It is based on the change in the pressure gradient across the stenosis after the achievement of maximal hyperemia of the coronary circulation which is commonly induced by intravenous (IV) or intracoronary (IC) administration of adenosine. Here, we have described three cases of IC adenosine-induced ventricular arrhythmias during FFR measurement from our institution, and after literature review we found that all the cases of ventricular arrhythmias induced by adenosine during FFR measurement were observed where it was administered via IC route. Although a causal relationship between the use of IC adenosine during FFR measurement and the induction of ventricular arrhythmias is not yet established, we suggest using IV adenosine as the preferred route of administration until we better understand the incidence and mechanism underlying this phenomenon.

Computed Tomography Fractional Flow Reserve Can Identify Culprit Lesions in Aortoiliac Occlusive Disease Using Minimally Invasive Techniques

BACKGROUND

Currently, the gold standard diagnostic examination for significant aortoiliac lesions is angiography. Fractional flow reserve (FFR) has a growing body of literature in coronary artery disease as a minimally invasive diagnostic procedure. Improvements in numerical hemodynamics have allowed for an accurate and minimally invasive approach to estimating FFR, utilizing cross-sectional imaging. We aim to demonstrate a similar approach to aortoiliac occlusive disease (AIOD).

METHODS

A retrospective review evaluated 7 patients with claudication and cross-sectional imaging showing AIOD. FFR was subsequently measured during conventional angiogram with pull-back pressures in a retrograde fashion. To estimate computed tomography (CT) FFR, CT angiography (CTA) image data were analyzed using the SimVascular software suite to create a computational fluid dynamics model of the aortoiliac system. Inlet flow conditions were derived based on cardiac output, while 3-element Windkessel outlet boundary conditions were optimized to match the expected systolic and diastolic pressures, with outlet resistance distributed based on Murray's law. The data were evaluated with a Student's t-test and receiver operating characteristic curve.

RESULTS

All patients had evidence of AIOD on CT and FFR was successfully measured during angiography. The modeled data were found to have high sensitivity and specificity between the measured and CT FFR (P = 0.986, area under the curve = 1). The average difference between the measured and calculated FFRs was 0.136, with a range from 0.03 to 0.30.

CONCLUSIONS

CT FFR successfully identified aortoiliac lesions with significant pressure drops that were identified with angiographically measured FFR. CT FFR has the potential to provide a minimally invasive approach to identify flow-limiting stenosis for AIOD.

Fractional Flow Reserve Assessment of a Significant Coronary Stenosis Masked by a Downstream Serial Lesion

Fractional flow reserve (FFR) has been recognized as an effective tool to determine functional significance in intermediate coronary lesions and FFR-guided percutaneous coronary intervention (PCI) improves clinical outcomes. However, hemodynamic interaction between serial stenoses within one coronary artery complicates the assessment of functional severity of each individual lesion. We present a case in which FFR measurement by intracoronary bolus injection of adenosine helps to make appropriate revascularization decision in serial stenoses when the procedures are performed systemically and properly.

Comparison of fractional flow reserve measurements using intracoronary adenosine versus intracoronary sodium nitroprusside infusions in moderately stenotic coronary artery lesions

INTRODUCTION

The aim of this study was to investigate the efficacy and safety of intracoronary (IC) sodium nitroprusside infusion in comparison to IC adenosine for fractional flow reserve (FFR) measurement in moderately diseased coronary artery lesions for functional assessment.

METHODS

During a nine month period, a consecutive of 98 patients with suspected or known coronary artery disease with moderate stenosis found during angiography (40% to 70% stenosis), were enrolled in this study. Hyperemia was induced by bolus doses of IC adenosine followed by sodium nitroprusside for FFR measurement.

RESULTS

Both IC adenosine and IC sodium nitroprusside induced similar and significant reduction in FFR. There was no statistically difference in FFR values between adenosine vs sodium nitroprusside infusions (mean FFR 84.3±6.3 vs 85.7±6.2, p=0.1) respectively. Furthermore, comparing different FFR cut-off points between the groups (FFR<0.75, 0.75-0.8 and >0.8) showed no significant differences (p value=0.7).

CONCLUSION

An IC bolus of sodium nitroprusside (0.6μg/kg) infusion induces a similar degree of hyperemia to IC bolus of 100-300μg of adenosine. Therefore, IC sodium nitroprusside could be considered as an alternative drug to adenosine for FFR measurement with lower side effect profile.

Fractional flow reserve based on computed tomography: an overview

Computed tomography coronary angiography (CTCA) is a technique proved to provide high sensitivity and negative predictive value for the identification of anatomically significant coronary artery disease (CAD) when compared with invasive X-ray coronary angiography. While the CTCA limitation of a ionizing radiation dose delivered to patients is substantially overcome by recent technical innovations, a relevant limitation remains the only anatomical assessment of coronary stenoses in the absence of evaluation of their functional haemodynamic significance. This limitation is highly important for those stenosis graded as intermediate at the anatomical assessment. Recently, non-invasive methods based on computational fluid dynamics were developed to calculate vessel-specific fractional flow reserve (FFR) using data routinely acquired by CTCA [computed tomographic fractional flow reserve (CT-FFR)]. Here we summarize methods for CT-FFR and review the evidence available in the literature up to June 26, 2016, including 16 original articles and one meta-analysis. The perspective of CT-FFR may greatly impact on CAD diagnosis, prognostic evaluation, and treatment decision-making. The aim of this review is to describe technical characteristics and clinical applications of CT-FFR, also in comparison with catheter-based invasive FFR, in order to make a cost-benefit balance in terms of clinical management and patient's health.

Limitations and Pitfalls of Fractional Flow Reserve Measurements and Adenosine-Induced Hyperemia

Coronary hemodynamic measurements provide a critical tool to assess the ischemic potential of coronary stenoses. Fractional flow reserve (FFR) is a reliable method to relate translesional coronary pressures to hyperemic myocardial blood flow. Although a basic understanding in FFR can be quickly achieved, many of the nuances and potential pitfalls require special attention. The authors discuss the practical setup of coronary pressure measurement, the most common pitfalls in technique and ways to avoid them, and the limitations of available pharmacologic hyperemic methods.

Measuring Procedure and Maximal Hyperemia in the Assessment of Fractional Flow Reserve for Superficial Femoral Artery Disease

AIM

The optimal fractional flow reserve (FFR) measurement method for superficial femoral artery (SFA) lesions remains to be established. We clarified the optimal measuring procedure for FFR for SFA lesions and investigated the necessary dose of papaverine for inducing maximal hyperemia in SFA lesions.

METHODS

Forty-eight patients with SFA lesions who underwent measurement of peripheral FFR (pFFR: distal mean pressure divided by proximal mean pressure) after endovascular treatment by the contralateral femoral crossover approach were prospectively enrolled. In the pFFR measurement, a guide sheath was placed on top of the common iliac bifurcation and pressure equalization was performed. After advancing the pressure wire distal to the SFA lesion, sequential papaverine administration selectively to the affected common iliac artery was performed.

RESULTS

There were no symptoms, electrocardiogram changes, and significant pressure drops at the guide sheath tip with increasing papaverine dose. pFFR changes following 20, 30, and 40 mg of papaverine were 0.87±0.10, 0.84±0.10, and 0.84±0.10, respectively (P＜0.001). Although not significantly different, pFFR decreased more in several patients at 30 mg of papaverine than at 20 mg. The pFFR at 40 mg of papaverine was almost similar to that at 30 mg of papaverine. The necessary papaverine dose was not changed according to sex and number of run-off vessels.

CONCLUSIONS

The contralateral femoral crossover approach is useful in FFR measurement for SFA lesions, and maximal hyperemia is induced by 30 mg of papaverine.

Incremental diagnostic value of epicardial adipose tissue for the detection of functionally relevant coronary artery disease

BACKGROUND AND AIM

To determine the incremental diagnostic value of epicardial adipose tissue (EAT) volume in addition to the coronary artery calcium (CAC) score for detecting hemodynamic significant coronary artery disease (CAD).

METHODS AND RESULTS

122 patients (mean age 61 ± 10 years, 61% male) without a previous cardiac history underwent a non-contrast CT scan for calcium scoring and EAT volume measurements. Subsequently all patients underwent invasive coronary angiography (ICA) in conjunction with fractional flow reserve (FFR) measurements. A stenosis >90% and/or a FFR ≤0.80 were considered significant. Mean EAT volume and CACscore were 128 ± 51 cm(3) and 418 ± 704, respectively. The correlation between EAT volume and the CACscore was poor (r = 0.11, p = 0.24). Male gender (odds ratio [OR] 2.86, p = 0.01), CACscore ([cut-off value 100] OR 3.31, p = 0.003, and EAT volume ([cut-off value 92 cm(3)] OR 4.28, p = 0.01) were associated with flow-limiting disease. The multivariate model revealed that only male gender (OR 2.50, p = 0.045), CAC score (OR 3.60, p = 0.005), and EAT volume (OR 4.95, p = 0.02) were independent predictors of myocardial ischemia. Using the cut-off values of 100 (CAC score) and 92 cm(3) (EAT volume), sensitivity, specificity, negative predictive value, positive predictive value, and accuracy for detecting functionally relevant CAD as indicated by FFR were 71, 57, 77, 50 and 63% and 91, 29, 85, 44 and 52% for the CACscore and EAT volume, respectively. Adding EAT volume to the CAC score and cardiovascular risk factors did not enhance diagnostic performance for the detection of significant CAD (p = 0.57).

CONCLUSION

EAT volume measurements have no diagnostic value beyond calcium scoring and cardiovascular risk factors in the detection of hemodynamic significant CAD.

Ventricular Fibrillation Precipitated by Intracoronary Adenosine During Fractional Flow Reserve Assessment - A Cautionary Tale

Fractional flow reserve (FFR) measurement is the current benchmark for assessing the physiologic significance of a coronary stenosis. Intravenous / intra-coronary adenosine is a commonly used agent to induce hyperaemia, required for FFR measurement. In our institute, we have observed three cases of ventricular fibrillation (VF) after intra-coronary adenosine injection. Volume of the injections appeared to be the responsible mechanism, supported by evidence from optical coherence tomography (OCT) experience. Since doubling the concentration of adenosine to reduce the volume of injection by half, no further incidence of VF has been noted.

Comprehensive assessment of coronary fractional flow reserve

Fractional flow reserve (FFR) is considered nowadays as the gold standard for invasive assessment of physiologic stenosis significance and an indispensable tool for decision-making in coronary revascularization. Robust studies have shown that FFR is more effective in accurately identifying which lesions should be stented, and revascularization guided by FFR improves the outcome of coronary artery disease in patients. Therefore, FFR has been upgraded to a class A recommendation in current guidelines when the ischemic potential for specific target lesions is controversial. This article reviews the laboratory practice, functional evaluation of FFR as a gold standard and its emerging clinical application. In addition, novel noninvasive technologies of FFR measurement are discussed in depth.