Clinical use of physiological lesion assessment using pressure guidewires: an expert consensus document of the Japanese Association of Cardiovascular Intervention and Therapeutics

Prognostic Values of Fractional Flow Reserve Based on Clinical Outcomes in Patients on Chronic Hemodialysis

The fractional flow reserve (FFR) cut-off values of 0.75 or 0.8 have been widely used; however, whether they apply to patients on hemodialysis remains unknown. We aimed to investigate the cut-off value of FFR associated with clinical outcomes in patients on hemodialysis. Using the Japanese multicenter registry, we analyzed data of patients on hemodialysis with measured FFR between January 2010 and December 2016. Survival classification and regression tree analysis for the composite primary outcome of cardiovascular mortality, myocardial infarction, and target vessel revascularization revealed a threshold FFR of 0.83. Multivariate Cox regression analyses were performed for the clinical outcomes. Additionally, the primary outcome was analyzed using propensity score matching by dividing the patients into complete and incomplete revascularization groups according to the presence of residual lesions with an FFR of ≤0.83 after the intervention. Of the 212 included patients, 112 (52.8%) had lesions with an FFR of ≤0.83. After adjusting for confounders, an FFR of ≤0.83 was associated with a higher risk for the primary outcome (adjusted hazard ratio 2.01, 95% confidence interval 1.11 to 3.66, p = 0.021). Propensity score matching showed that complete revascularization for lesions with an FFR of ≤0.83 was associated with a reduced risk for the primary outcome compared with incomplete revascularization (hazard ratio 0.38, 95% confidence interval 0.20 to 0.71, log-rank p = 0.0016). In conclusion, an FFR of ≤0.83 was an independent predictor of clinical events in patients on hemodialysis. Furthermore, complete revascularization was associated with better clinical outcomes. Thus, this population may require a distinct FFR cut-off value.

Comparison between the diagnostic performance of vessel fractional flow reserve and nonhyperemic pressure ratio for functionally significant coronary stenosis severity as assessed by fractional flow reserve

BACKGROUND

Fractional flow reserve (FFR) and nonhyperemic pressure ratios (NHPRs) have been widely used to assess the functional severity of coronary stenosis. However, their measurement requires using a pressure wire, making their use in all patients difficult. The recently developed vessel fractional flow reserve (vFFR), derived from three-dimensional quantitative coronary angiography, is expected to serve as a surrogate for pressure wire assessment.

METHODS

This retrospective study was conducted on patients with intermediate coronary stenosis who underwent FFR and NHPR measurements. The vFFR and NHPR values were compared for diagnosing coronary stenosis as defined by an FFR of ≤0.80, and the number of patients not requiring wire-based assessment was estimated.

RESULTS

In a total of 90 lesions from 74 patients (median [SD] age 75 [12] years; men 80%), the median FFR was 0.78 (0.72-0.84), and 57% of these lesions (N = 51) exhibited an FFR of ≤0.80. vFFR provided high discrimination for coronary stenosis (area under the curve 0.80, 95% confidence interval 0.70-0.90), which was comparable to that of NHPRs (p = 0.42). High diagnostic accuracy was consistently observed across a variety of clinical presentations (i.e., old age, diabetes, target coronary artery, and left ventricular hypertrophy) (p_interaction  > 0.05). In total, 55 lesions (61%) demonstrated positive or negative likelihood of coronary stenosis when vFFR was <0.73 (specificity 90%) or >0.87 (sensitivity 88%), respectively.

CONCLUSION

vFFR demonstrated excellent diagnostic performance for detecting functionally significant coronary stenosis as evaluated by FFR. vFFR may be used as a surrogate for pressure wire assessment.

Comparative study of fractional flow reserve and diastolic pressure ratio using a guidewire with a sensor for measuring intravascular pressure

PURPOSE

This study aimed to evaluate the correlation and diagnostic agreement between diastolic pressure ratio (dPR) and fractional flow reserve (FFR) in a Japanese real-world setting.

DESIGN

Prospective multicenter observational study.

METHODS

This study included 100 patients with intermediate coronary artery stenosis at 4 Japanese hospitals. For these lesions, FFR and dPR were measured using a guidewire with a sensor and a monitor to measure intravascular pressure. The correlation and diagnostic agreement between FFR and dPR were assessed. When both FFR and dPR were negative or positive, the results were considered to be concordant. When one was positive and the other was negative, the result was regarded as discordant (positive discordance, FFR > 0.80 and dPR ≤ 0.89; negative discordance, FFR ≤ 0.80 and dPR > 0.89).

RESULTS

Overall, the FFR and dPR were well-correlated (R = 0.841). FFR and dPR were concordant in 89% of cases (concordant normal, 43%; concordant abnormal, 46%) and discordant in 11% (positive discordance, 7%; negative discordance, 4%). No significant difference was observed in the rate of concordant results between patients with and without diabetes mellitus. The diagnostic concordance rate was significantly different among the 3 coronary arteries (right coronary artery, 93.3%; left anterior descending artery, 93.2%; and left circumflex artery, 58.3%; P = .001). Additionally, the rate of concordant results tended to be higher when using intravenous administration of adenosine than when using intracoronary bolus injection of nicorandil (adenosine, 95.1%; nicorandil, 84.7%; P = .103).

CONCLUSION

We found that dPR was highly correlated with FFR, and diagnostic discordance was observed in 11% of the lesions. Several factors, including lesion location and medication for hyperemia, may cause the diagnostic discordance between dPR and FFR.

Differential Impact of Renal Function on the Diagnostic Performance of Resting Full-Cycle Ratio in Patients With Renal Dysfunction

Background: Physiological assessments using fractional flow reserve (FFR) and resting full-cycle ratio (RFR) have been recommended for revascularization decision making. Previous studies have shown a 20% rate of discordance between FFR and RFR. In this context, the correlation between RFR and FFR in patients with renal dysfunction remains unclear. This study examined correlations between RFR and FFR according to renal function.

Methods and Results: In all, 263 consecutive patients with 370 intermediate lesions were enrolled in the study. Patients were classified into 3 groups according to renal function: Group 1, estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m²; Group 2, 30 mL/min/1.73 m²≤eGFR<60 mL/min/1.73 m²; Group 3, eGFR <30 mL/min/1.73 m². The discordance between FFR and RFR was assessed using known cut-off values for FFR (≤0.80) and RFR (≤0.89). Of the 370 lesions, functional significance with FFR was observed in 154 (41.6%). RFR was significantly correlated with FFR in all groups (Group 1, R²=0.62 [P<0.001]; Group 2, R²=0.67 [P<0.001]; Group 3, R²=0.46 [P<0.001]). The rate of discordance between RFR and FFR differed significantly among the 3 groups (Group 1, 18.8%; Group 2, 18.5%; Group 3, 42.9%; P=0.02).

Conclusions: The diagnostic performance of RFR differed based on renal function. A better understanding of the clinical factors contributing to FFR/RFR discordance, such as renal function, may facilitate the use of these indices.

Health economics-based verification of functional myocardial ischemia evaluation of stable coronary artery disease in Japan: A long-term longitudinal study using propensity score matching

BACKGROUND

The procedural numbers and medical costs of percutaneous coronary intervention (PCI), mainly elective PCI, have been increasing in Japan. Owing to increased interest in the appropriateness of coronary revascularization, we conducted this medical economics-based evaluation of testing and diagnosis of stable coronary artery disease (CAD).

METHODS AND RESULTS

We reviewed patients' medical insurance data to identify stable CAD patients who underwent coronary computed tomography angiography, cardiac single-photon emission computed tomography, coronary angiography, or fractional flow reserve. Subjects were divided into anatomical and functional evaluation groups according to the modality of testing, and background factors were matched by propensity score. The endpoints were major adverse cardiovascular events (MACE), life years (LYs), medical costs, and cost-effectiveness analysis (CEA). The observations were performed for 36 months. MACE, medical costs, and CEA of the functional group in the overall category were trending to be better than the anatomical group (MACE, P = .051; medical costs: 3,105 US$ vs 4,430 US$, P = .007; CEA: 2,431 US$/LY vs 2,902 US$/LY, P = .043).

CONCLUSIONS

The functional evaluation approach improved long-term clinical outcomes and reduced cumulative medical costs. As a result, the modality composition of functional myocardial ischemia evaluation was demonstrated to offer superior cost-effectiveness in stable CAD.

Resistive reserve ratio and microvascular resistance reserve in patients with coronary vasospastic angina

Patients with epicardial coronary vasospastic angina (VSA) may be likely to have coronary microvascular dysfunction, although mixed results have been reported. The aim of this study was to evaluate coronary microvascular function in detail using novel invasive physiologic indices, such as resistive reserve ratio (RRR) and microvascular resistance reserve (MRR). A total of 45 patients undergoing intracoronary acetylcholine (ACh) provocation test and invasive coronary circulatory evaluation using a thermodilution method were prospectively included. VSA was diagnosed as angiographic vasospasm accompanied by chest pain and/or ischemic electrocardiographic changes by intracoronary injection of ACh. Coronary circulation was assessed with physiologic indices including fractional flow reserve, resting and hyperemic mean transit time (Tmn), coronary flow reserve (CFR), basal resistance index, index of microcirculatory resistance (IMR), RRR, and MRR. Of 45 patients, 23 (51.1%) were diagnosed as having VSA. Patients with positive ACh test had longer resting Tmn (slower coronary flow velocity), higher basal resistance index, and greater RRR and MRR than those without, while fractional flow reserve, CFR, and IMR did not differ significantly between the two groups. In conclusion, although conventional measures such as CFR and IMR failed to show significant differences, RRR and MRR, novel invasive coronary physiologic indices, provided counterintuitive insights that coronary microvascular dilation function was better preserved in patients with VSA than those without.

Clinical Efficacy of Intracoronary Papaverine After Nicorandil Administration for Safe and Optimal Fractional Flow Reserve Measurement

Fractional flow reserve (FFR) is considered the standard for assessment of the physiological significance of coronary artery stenosis. Intracoronary papaverine (PAP) is the most potent vasodilator used for the achievement of maximal hyperemia. However, its use can provoke ventricular tachycardia (VT) due to excessive QT prolongation. We evaluated the clinical efficacy and safety of the administration of PAP after nicorandil (NIC), a potassium channel opener that prevents VT, for optimal FFR measurement.A total of 127 patients with 178 stenoses were enrolled. The FFR values were measured using NIC (NIC-FFR) and PAP (PAP-FFR). We administered PAP following NIC (NIC-PAP). Changes in the FFR and electrogram parameters (baseline versus NIC versus PAP) were assessed and the incidence of arrhythmias after PAP was evaluated. In addition, we analyzed another 41 patients with 51 stenoses by assessing the FFR using PAP before NIC (PAP-NIC). After propensity score matching, the electrogram parameters between 2 groups were compared.The mean PAP-FFR was significantly lower than the mean NIC-FFR (0.82 ± 0.11 versus 0.81 ± 0.11, P < 0.05). The mean baseline-QTc, NIC-QTc, and PAP-QTc values were 425 ± 37 ms^1/2, 424 ± 41 ms^1/2, and 483 ± 54 ms^1/2, respectively. VT occurred in only 1 patient (0.6%). Although PAP induced QTc prolongation (P < 0.05), the PAP-QTc duration was significantly shorter in NIC-PAP compared to PAP-NIC (P < 0.05).The administration of PAP with NIC may induce sufficient hyperemia and prevent fatal arrhythmia through reductions in the PAP-induced QTc prolongation during FFR measurement.

Independent predictors of discordance between the resting full-cycle ratio and fractional flow reserve

The resting full-cycle ratio (RFR), a novel resting index, is well correlated with and shows good diagnostic accuracy to the fractional flow reserve (FFR). However, discordance results between the RFR and FFR have been observed to occur in about 20% of cases. This study aimed to clarify the prevalence and factors of discordant results between the RFR and FFR through a direct comparison of these values in daily clinical practice. A total of 220 intermediate coronary lesions of 156 consecutive patients with RFR and FFR measurements were allocated to four groups according to RFR and FFR cutoff values. We compared the angiographic, clinical, and hemodynamic variables among the groups. Discordant results between the RFR and FFR were observed in 19.6% of vessels, and the proportion of discordant results was significantly higher in the left main trunk and left anterior descending artery (LM + LAD) than in non-LAD vessels (25.2% vs. 12.3%, p = 0.006). In the multivariable regression analysis, LM + LAD location, hemodialysis, and peripheral artery disease were associated with a low RFR among patients with a high FFR. Conversely, the absence of diabetes mellitus and the presence of higher hemoglobin levels were associated with a higher RFR among patients with a low FFR. Specific angiographic and clinical characteristics such as LM + LAD location, hemodialysis, peripheral artery disease, and absence of diabetes mellitus and anemia can be independent predictors of physiologic discordance between the RFR and FFR.

Clinical implications and debates on the ISCHEMIA trial

The ISCHEMIA was eagerly awaited study in the field of ischemic heart disease. Following the presentation and publication of ISCHEMIA, multiple opinions and viewpoints get complicated. The ongoing debates have been including the relevance of coronary revascularization, non-invasive diagnostic methods, and invasive ischemic testing in patients with stable ischemic heart disease (SIHD). Prior to ISCHEMIA, observational studies indicated the potential of coronary revascularization for improving clinical outcomes, while the randomized COURAGE trial did not support the plausible concept. Although the FAME 2 trial implied the superiority of percutaneous coronary intervention over medical therapy alone, the clinical relevance of coronary revascularization to improve outcomes and quality of life has been questioned. As a consequence, the ISCHEMIA trial did not demonstrate clear benefits in reducing clinical events but showed antianginal effects of revascularization. This landmark trial also suggested the difficulties of non-invasive ischemia testing rather than computed tomography angiography. Despite the complex results, the ISCHEMIA trial may simplify the clinical indications of coronary revascularization in patients with SIHD. Future publications from the ISCHEMIA trial and debates on the results will sharpen our thinking and understanding.

Influence of different physiological hemodynamics on fractional flow reserve values in the left coronary artery and right coronary artery

BACKGROUND

Although the left coronary artery (LCA) has a flow profile in that most blood flow occurs during diastole rather than systole, the right coronary artery (RCA) has a flow pattern that is less diastolic dominant. This study assessed whether coronary pressure waveforms distal to stenoses with the same fractional flow reserve (FFR) was the same between the LCA and RCA.

METHODS

A total of 347 vessels from 318 patients who underwent FFR measurements were included. Conventional FFR was calculated as the ratio of the mean coronary distal pressure (Pd) to the mean aortic pressure (Pa) at maximal hyperemia. The pressure drop ratios in systole (PDR_systole) and diastole (PDR_diastole) were calculated as the sum of (Pa minus Pd) divided by the sum of Pa at the intracoronary diastolic and systolic pressure phases, respectively.

RESULTS

Analysis of covariance of the regression line of correlation between conventional FFR and PDR_systole revealed that the slope was significantly greater in the RCA than in the left anterior descending artery (LAD) and left circumflex artery (LCX) (-0.765, -0.578, and -0.589, p < 0.001). On the other hand, the regression line of correlation between conventional FFR and PDR_diastole found that the slope was significantly greater in the LAD and LCX than in the RCA (-1.349, -1.318, and -1.223, p < 0.001).

CONCLUSIONS

The pressure waveform distal to the stenosis differs between the LCA and RCA. In the LCA, the decrease in diastolic pressure mainly contributed to the drop in FFR, whereas in the RCA, it was the decrease in systolic pressure.

Mechanisms of gradual pressure drop in angiographically normal left anterior descending and right coronary artery: Insights from wave intensity analysis

BACKGROUND

This study evaluated the mechanism of decline in coronary pressure from the proximal to the distal part of the coronary arteries in the left anterior descending (LAD) versus the right coronary artery (RCA) from the insight of coronary hemodynamics using wave intensity analysis (WIA).

METHODS

Twelve patients with angiographically normal LAD and RCA were prospectively enrolled. Distal coronary pressure, mean aortic pressure, and average peak velocity were measured at 4 different positions: 9, 6, 3, and 0 cm distal from each coronary ostium.

RESULTS

The distal-to-proximal coronary pressure ratio during maximum hyperemia gradually decreased in proportion to the distance from the ostium (0.92±0.03 and 0.98±0.03 at 9 cm distal to the LAD and RCA ostium). WIA showed the dominant forward-traveling compression wave gradually decreased and the backward-traveling suction wave gradually decreased in proportion to the decrease in coronary pressure through the length of the non-diseased LAD but not the RCA.

CONCLUSIONS

The pushing wave and suction wave intensities on WIA were diminished in proportion to the distance from the ostium of the LAD despite the wave intensity not changing across the length of the RCA, which may lead to gradual intracoronary pressure drop in the angiographically normal LAD.

Insufficient recovery of fractional flow reserve even after optimal implantation of drug-eluting stents: 3-year outcomes from the FUJI study

BACKGROUND

Adequate improvement in fractional flow reserve (FFR) is not necessarily achieved in some cases of drug-eluting stent (DES) implantation, even when imaging confirms successful placement. We hypothesized that post-stent FFR may be associated with advanced diffuse atherosclerotic condition. We explored the relationships between FFR values after DES implantation (post-stent FFR).

METHODS

A total of 218 patients were included in this prospective, multicenter study and were divided into two groups: adequate FFR group (post-stent FFR >0.80, n=176) and inadequate FFR group (post-stent FFR ≤0.80, n=42). The primary endpoint was a major adverse cardiovascular event (MACE) including cardiac death, non-fatal myocardial infarction (MI), unplanned coronary revascularization, and hospitalization for heart failure. The secondary endpoints were event rate of all-cause death, non-fatal MI, unplanned coronary revascularization, non-fatal stroke, and hospitalization for heart failure.

RESULTS

During follow-up of 31.4±8.7 months, 34 patients (16%) had cardiovascular events. Inadequate FFR group was significantly associated with higher risk of MACE (hazard ratio: 3.86; 95% confidence interval: 1.17-12.76, p=0.026; log-rank p=0.027). In particular, the incidence of unplanned coronary revascularization on non-target lesions was significantly higher in the inadequate FFR group (log-rank p=0.031).

CONCLUSIONS

Post-stent FFR ≤0.80 was associated with a high incidence of non-target lesion revascularization and could be a surrogate marker for advanced atherosclerotic condition in the vessels of the entire coronary artery.

Functional assessment of intermediate coronary artery stenosis with 4-Fr catheters

The 4-Fr catheter system is not recommended for invasive functional assessment of coronary artery stenosis, because it tends to distort the aortic waveform. This study aimed to identify the incidence of aortic waveform distortion and a feasible method for correct diagnosis of coronary artery stenosis with a 4-Fr catheter. We retrospectively investigated 178 lesions with intermediate coronary artery stenosis. Non-hyperemic distal coronary artery pressure (Pd) and aortic pressure (Pa) were measured with a 4-Fr diagnostic or 6-Fr guiding catheter before and after saline flush. The mean Pd/mean Pa (Pd/Pa) and instantaneous wave-free ratio (iFR) were calculated before and after flushing. We compared the effect of flushing on the changes in Pd/Pa and iFR between the 4-Fr diagnostic and 6-Fr guiding catheters. Using the 4-Fr diagnostic catheter, there was a significant decrease in incidence of aortic waveform distortion from 42.0% (47 lesions) before flushing to 1.8% (2 lesions) after flushing (p < 0.001); the incidence was only 3.0% before saline flush and decreased to 0% after saline flush when using the 6-Fr guiding catheter. The presence of aortic waveform distortion influenced the iFR when the 4-Fr system was used. Functional measurements with the 4-Fr diagnostic catheter require adequate saline flush to remove the influence of aortic waveform distortion.

Predictors of discordance between fractional flow reserve and resting full-cycle ratio in patients with coronary artery disease: Evidence from clinical practice

BACKGROUND

Fractional flow reserve (FFR) is an established method for assessing functional myocardial ischemia. Recently, the resting full-cycle ratio (RFR) has been introduced as a non-hyperemic index of functional coronary stenosis. However, the effects of clinical characteristics on discordance between RFR and FFR have not been fully evaluated. We aimed to identify clinical characteristics that influence FFR-RFR concordance.

METHODS

We included 410 patients with 573 intermediate coronary lesions who underwent clinically indicated invasive coronary angiography, as well as assessments of FFR and RFR. Receiver-operating characteristic (ROC) curves were created to assess the optimal cut-off values of RFR for predicting FFR ≤0.80.

RESULTS

RFR exhibited a strong correlation with FFR (r = 0.66, p < 0.0001). ROC analysis identified an optimal RFR cut-off value of 0.92 for categorization based on an FFR cut-off value of 0.8. The discordance of FFR >0.8 and RFR ≤0.92 (high FFR/low RFR) was observed in 112 lesions (20.9%), whereas the discordance of FFR ≤0.8 and RFR >0.92 (low FFR/high RFR) was observed in 35 lesions (6.5%). Higher rate of hemodialysis and lower hemoglobin levels were observed in the high FFR/low RFR group. Multivariate analyses identified female sex, left anterior descending artery (LAD) lesions, and hemodialysis as significant predictors of high FFR/low RFR. Conversely, body surface area and non-LAD lesions were significantly associated with low FFR/high RFR. Hemodialysis [odds ratio (OR): 2.41, 95% confidence interval (CI) 1.31-4.41; p = 0.005] and LAD lesions (OR: 1.86, 95% CI: 1.25-2.79; p = 0.002) were identified as independent predictors of overall FFR-RFR discordance.

CONCLUSIONS

RFR exhibited good diagnostic performance in the identification of functionally significant stenosis. However, RFR may overestimate functional severity in patients undergoing hemodialysis or in those with LAD lesions. Further prospective trials are required to demonstrate the non-inferiority of RFR to FFR.

Two-Year Outcomes of Asymptomatic vs. Symptomatic Patients After Deferral of Revascularization Based on Fractional Flow Reserve - Insights From the J-CONFIRM Registry

Background: The effect of symptoms on clinical outcomes after deferral of revascularization based on fractional flow reserve (FFR) remains poorly understood. Methods and Results: From the J-CONFIRM (Long-Term Outcomes of Japanese Patients With Deferral of Coronary Intervention Based on Fractional Flow Reserve in Multicenter) Registry, this study evaluated 1,215 patients with stable coronary artery disease, including symptomatic and asymptomatic patients (n=571 and 644, respectively). The primary endpoint was the cumulative 2-year incidence of target vessel failure (TVF), including cardiac death, target vessel-related myocardial infarction (TVMI), and clinically driven target vessel revascularization (CDTVR). An inverse probability weighted analysis was performed to adjust for the differences in baseline clinical characteristics between the 2 groups. At 2 years, the TVF rate did not differ significantly between symptomatic and asymptomatic patients (6.5% vs. 4.9%, respectively; P=0.15) or between symptomatic and asymptomatic patients with lesions with an FFR ≤0.80 (8.0% vs. 12.3%, respectively; P=0.20). Conversely, symptomatic patients showed significantly higher rates of TVF (6.2% vs. 3.3%; P=0.01) and CDTVR (6.2% vs. 3.1%; P=0.009) than asymptomatic patients, regardless of negative FFR values (>0.80). Conclusions: Despite negative FFR values, symptomatic patients were at higher risk of TVF than asymptomatic patients, driven primarily by a higher rate of CDTVR. Conversely, those with a positive FFR were likely to develop TVF regardless of their symptoms.

A novel fiber-optic based 0.014″ pressure wire: Designs of the OptoWire™, development phases, and the O2 first-in-man results

OBJECTIVES

To review the technical limitations of available pressure-wires, present the design evolution of a nitinol fiber-optic pressure wire and to summarize the First-in-Man (FIM) O2 pilot study results.

BACKGROUND

Despite increasing use of physiology assessment of coronary lesions, several technical limitations persist. We present technical details, design evolution and early clinical results with a novel 0.014" nitinol fiber-optic based pressure-wire.

METHODS AND RESULTS

The 0.014' OptoWire™ (Opsens Medical, Quebec, Canada) was designed to combine improved handling properties compared to standard pressure-wires and to offer extremely reliable pressure recording and transmission due to fiber-optic properties compared to piezo-electric sensors and electrical wires. In vitro assessment showed that OptoWire™ steerability, pushability and torquability properties were closer to regular PCI wires than standard electrical pressure wires. In the First-in-Man O2 study, 60 patients were recruited at 2 centers in Canada. A total of 103 lesions were assessed with the OptoWire™ and OptoMonitor™, 75 lesions at baseline and 28 lesions post-PCI (without disconnection). In all crossed lesions (n = 100, 97%), mean Pd/Pa and FFR could be adequately measured. In 11 cases assessed successively with OptoWire™ and Aegis™ (Abbott Vascular, USA) bland-Altman analysis showed a mean difference of 0.002 ± 0.052 mmHg (p = .91) for Pd/Pa and 0.01 ± 0.06 for FFR calculation (p = .45). There was no device-related complication. Upon these initial results, several design changes aimed to improve overall performance including torquability, stiffness, resistance to kink and pressure drift were completed.

CONCLUSION

The novel 0.014" fiber-optic OptoWire™ provides superior wire handling with reduced risk of pressure drift allowing reliable pre- and post-PCI physiology assessment.

Effect of QTU prolongation on hyperemic instantaneous wave-free ratio value: a prospective single-center study

We hypothesized that in patients with QT prolongation, resistance might not decrease in the wave-free period, because QTU prolongation cannot be detected by instantaneous wave-free ratio (iFR) analysis software. We investigated whether corrected QTU (QTUc) prolongation affects the hyperemic iFR value. Forty-two consecutive patients with intermediate stenosis (≥ 50%) in the left anterior descending coronary artery (LAD) were analyzed. Fractional flow reserve (FFR) and hyperemic iFR were simultaneously and continuously recorded with intravenous adenosine triphosphate (ATP) and papaverine infusions. In 17 patients with stenosis in the proximal LAD, coronary flow was measured. Patients were divided into two groups according to the median absolute deviation of the QTUc by ATP administration/QTUc by papaverine administration. FFR, hyperemic iFR, and flow data were compared between each stimulus and group. Moreover, influences of pressure and electrocardiogram parameters on differences in iFR values under ATP and papaverine administration were compared between the following two groups (group 1: the absolute difference of hyperemic iFR values between ATP and papaverine administration is ≤ 0.05; group 2: that is > 0.05). The paired t test and t test were used in analysis. Hyperemic iFR values of patients under the use of papaverine were lower than those of patients under the use of ATP when QTUc was more prolonged by papaverine administration than by ATP administration (ATP 0.74 ± 0.14, papaverine 0.71 ± 0.15, P = 0.025). No significant differences were observed in the FFR value and flow data between the groups. Regarding QTU, QTUc, and QTUc by ATP/QTUc by papaverine, significant differences were observed between group 1 and group 2. Pressure parameters did not induce significant differences. QTUc prolongation induced by papaverine was associated with lower hyperemic iFR values. An iFR-based assessment might lead to inappropriate treatment of patients with QTUc prolongation.

Influence of caffeine intake on intravenous adenosine-induced fractional flow reserve

BACKGROUND

This study evaluated whether caffeine abstention is required before fractional flow reserve (FFR) measurement by intravenous adenosine triphosphate (ATP) administration in Japanese patients.

METHODS

This study was a subanalysis of a previously published study and a total of 208 intermediate lesions that underwent FFR measurements were enrolled for this analysis. Hyperemia was induced by continuous intravenous ATP infusion at 150 μg/kg/min (IVATP150) and 210 μg/kg/min (IVATP210), and by intracoronary administration of nicorandil 2 mg (ICNIC2mg) as a reference standard.

RESULTS

The degree of change in the FFR value after ICNIC2mg and IVATP210 was similar between the caffeine and non-caffeine groups (0.00 ± 0.02 vs. 0.01 ± 0.02). In patients who consumed caffeine before the FFR measurement, the degree of FFR change was independent of the time interval (<12 h, 12-24 h, and 24-48 h) between caffeine intake and catheterization both after IVATP150 and ICNIC2mg and after IVATP210 and ICNIC2mg.

CONCLUSION

When compared with the FFR value after ICNIC2mg, the degree of change in the FFR value after IVATP210 were similar regardless of caffeine intake. Strict caffeine abstention before intravenous ATP-induced FFR measurement may not be required in clinical practice.

Clinical feasibility of resting full-cycle ratio as a unique non-hyperemic index of invasive functional lesion assessment

The resting full-cycle ratio (RFR) is a new physiologic index to assess myocardial ischemia. RFR and fractional flow reserve (FFR), the conventionally used index, have not been directly compared in evaluating the entire cardiac cycle. Accordingly, we aimed to compare the diagnostic performance of RFR directly with FFR and clarify the clinical feasibility of RFR as a unique non-hyperemic index in evaluating the cardiac cycle. The diagnostic performance of RFR was compared with FFR using an automated online calculation software. A total of 156 consecutive patients with 220 intermediate lesions were enrolled. RFR showed significant correlation with FFR (r = 0.774, p < 0.001). RFR systole and RFR diastole did also with FFR (r = 0.918, p < 0.001, and r = 0.733, p < 0.001, respectively). With FFR < 0.80 as a reference standard, RFR showed good diagnostic accuracy (DA: 80.5%), similar DA between RFR systole and RFR diastole (79.6% and 87.5%, p = 0.58, respectively), and good DA in any lesion locations, especially in non-left anterior descending coronary artery (LAD) lesions (73.7% and 87.6% for LAD vs. non-LAD, p < 0.05, respectively). RFR is a feasible and reliable non-hyperemic index regardless of the difference in cardiac cycle in evaluating physiological lesion severity in daily practice.

Clinical expert consensus document on quantitative coronary angiography from the Japanese Association of Cardiovascular Intervention and Therapeutics

Quantitative coronary angiography (QCA) remains to play an important role in clinical trials and post-marketing surveillance related to the safety and efficacy of new PCI devices. In this document, the current standard methodology of QCA is summarized. In addition, its history, recent development and future perspectives are also reviewed.

How Do PET Myocardial Blood Flow Reserve and FFR Differ?

PURPOSE OF REVIEW

This review discusses similarities and differences between cardiac positron emission tomography (PET), absolute myocardial blood flow, and flow reserve with invasive fractional flow reserve (FFR).

RECENT FINDINGS

Fundamentally, cardiac PET measures absolute myocardial blood flow whereas FFR provides a relative flow reserve. Cardiac PET offers a non-invasive and therefore lower risk alternative, able to image the entire left ventricle regardless of coronary anatomy. While cardiac PET can provide unique information about the subendocardium, FFR pullbacks offer unparalleled spatial resolution. Both diagnostic tests provide a highly repeatable and technically successful index of coronary hemodynamics that accounts for the amount of distal myocardial mass, albeit only indirectly with FFR. The randomized evidence base for FFR and its associated cost effectiveness remains unsurpassed. Cardiac PET and FFR have been intertwined since the very development of FFR over 25 years ago. Recent work has emphasized the ability of both techniques to guide revascularization decisions by high-quality physiology. In the past few years, cardiac PET has expanded its evidence base regarding clinical outcomes, whereas FFR has solidified its position in randomized studies as the invasive reference standard.

Update on Antithrombotic Therapy after Percutaneous Coronary Intervention

Percutaneous coronary intervention (PCI) has become a standard-of-care procedure in the setting of angina or acute coronary syndrome. Antithrombotic therapy is the cornerstone of pharmacological treatment aimed at preventing ischemic events following PCI. Dual antiplatelet therapy as the combination of aspirin and P2Y₁₂ inhibitor has been proven to decrease stent-related thrombotic risks. However, the optimal duration of dual antiplatelet therapy, an appropriate P2Y₁₂ inhibitor, and the choice of aspirin versus P2Y₁₂ inhibitor as single antiplatelet therapy remain controversial. Furthermore, the combined use of oral anticoagulation in addition to antiplatelet therapy is a complex issue in clinical practice, such as in patients with atrial fibrillation. The key challenge concerning the optimal antithrombotic regimen is ensuring a balance between protection against thrombotic events and against excessive increases in bleeding risk. In this review article, we summarize the current evidence concerning antithrombotic therapy in patients with coronary artery disease undergoing PCI.

Diabetes mellitus and other cardiovascular risk factors in lower-extremity peripheral artery disease versus coronary artery disease: an analysis of 1,121,359 cases from the nationwide databases

BACKGROUND

Lower-extremity peripheral artery disease (LE-PAD) and coronary artery disease (CAD) are both pathologically rooted in atherosclerosis, and their shared clinical features regarding the exposure to cardiovascular risk factors have been emphasized. However, comparative data of the two cardiovascular diseases (CVDs) were so far lacking. The purpose of this study was to directly compare the clinical profile between cases undergoing endovascular therapy (EVT) for LE-PAD and those undergoing percutaneous coronary intervention (PCI).

METHODS

Data were extracted from the nationwide procedural databases of EVT and PCI in Japan (J-EVT and J-PCI) between 2012 and 2017. A total of 1,121,359 cases (103,887 EVT cases for critical limb ischemia [CLI] or intermittent claudication and 1,017,472 PCI cases for acute coronary syndrome [ACS] or stable angina) were analyzed. Heterogeneity in clinical profile between CVDs was evaluated using the C statistic of the logistic regression model for which dependent variable was one CVD versus another, and explanatory variables were clinical profile. When two CVDs were completely discriminated from each other by the developed model, the C statistic (discrimination ability) of the model would be equal to 1, indicating that the two CVDs were completely different in clinical profile. On the other hand, when two CVDs were identical in clinical profile, the developed model would not discriminate them at all, with the C statistic equal to 0.5.

RESULTS

Mean age was 73.5 ± 9.3 years in LE-PAD patients versus 70.0 ± 11.2 years in CAD patients (P < 0.001). The prevalence of diabetes mellitus and end-stage renal disease was 1.96- and 6.39-times higher in LE-PAD patients than in CAD patients (both P < 0.001). The higher prevalence was observed irrespective of age group. The exposure to other cardiovascular risk factors and the likelihood of cardiovascular risk clustering also varied between the diseases. The between-disease heterogeneity in patient profile was particularly evident between CLI and ACS, with the C statistic equal to 0.833 (95% CI 0.831-0.836).

CONCLUSIONS

The current study, an analysis based on nationwide procedural databases, confirmed that patient profiles were not identical but rather considerably different between clinically significant LE-PAD and CAD warranting revascularization.

Utility and Validity of Intracoronary Administration of Nicorandil Alone for the Measurement of Fractional Flow Reserve in Patients With Intermediate Coronary Stenosis

BACKGROUND

Intracoronary (IC) administration of nicorandil has been proposed as an alternative choice of hyperemic agent for fractional flow reserve (FFR) measurements. This study evaluated the utility and validity of IC nicorandil administration alone to induce maximal hyperemia.Methods and Results:Two-hundred-seven patients with coronary artery disease listed for coronary angiography with FFR were prospectively enrolled. FFR was measured after (1) IC administration of nicorandil 2 mg (ICNIC2 mg); (2) continuous intravenous (IV) adenosine triphosphatase (ATP) infusion at 150 μg/kg/min (IVATP150); (3) IV ATP infusion at 210 μg/kg/min (IVATP210); (4) IC administration of 0.5 mg nicorandil during IVATP150 (ICNIC0.5 mg+IVATP150); (5) IC administration of 1 mg nicorandil during IVATP150 (ICNIC1 mg+IVATP150); and (6) IC administration of 2 mg nicorandil during IVATP150 (ICNIC2 mg+IVATP150). The average FFR values and the rate of achieving maximum hyperemia after ICNIC2 mg, IVATP150, IVATP210, ICNIC0.5 mg+IVATP150, ICNIC1 mg+IVATP150, and ICNIC2 mg+IVATP150 were 0.85±0.08, 0.89±0.08, 0.85±0.09, 0.84±0.08, 0.83±0.08, 0.83±0.08 (P<0.01), and 92%, 54%, 91%, 96%, 99%, 99% (P<0.01), respectively. The incidence of systolic aortic pressure drop, chest discomfort, and transient atrioventricular block increased in a dose-dependent manner after IV ATP infusion, but almost no adverse effects were observed after ICNIC2 mg.

CONCLUSIONS

ICNIC2 mg produced a more pronounced hyperemia than continuous IV ATP, and might be the preferred method for assessment of FFR.