Fractional flow reserve in acute coronary syndromes: A review

Adenosine Contrast Correlations in Evaluating Revascularization: The (ACCELERATION) Study

BACKGROUND

Injection of contrast media for rapid measurement of contrast fractional flow reserve (cFFR) obviates the side effects and time requirements of adenosine fractional flow reserve (aFFR) and improves diagnostic performance relative to nonhyperemic pressure ratios. However, studies of cFFR have had variable delivery of contrast. We evaluated the diagnostic performance of cFFR using an automated contrast injector with a standardized volume and rate of delivery of contrast to the reference standard aFFR.

METHODS

The ACCELERATION study (Adenosine Contrast Correlations in Evaluating Revascularization) is an investigator-initiated, multicenter, prospective, single-arm trial conducted in 5 sites across the United States. cFFR and aFFR were measured in patients with stable coronary artery disease and intermediate stenosis (40% to 70%) using the ACIST CVi automated contrast injector (iopamidol; left coronary: rate of 4 mL/s, volume of 10 cm3 and right coronary: rate of 3 mL/s, volume of 6 cm3) and RXi/Navvus FFR microcatheter. The diagnostic performance of cFFR was assessed using a 0.83 cutoff value based on published literature. Optimal cFFR cutoffs were also determined and illustrated using Bland-Altman analysis.

RESULTS

A total of 192 lesions from 178 patients were included in the per-protocol analysis (69 with an aFFR ≤0.80 and 109 with an aFFR >0.80). Using a cFFR cutoff value of ≤0.83, the accuracy, sensitivity, and specificity of cFFR were 0.89 (95% CI, 0.83-0.93), 0.70 (95% CI, 0.58-0.81), and 0.99 (95% CI, 0.95-1.00), respectively. The mean difference between cFFR and aFFR was 0.05 (-0.04 to 0.13). A cFFR threshold of ≤0.85 had the highest accuracy in predicting aFFR ≤0.80 with accuracy, sensitivity, and specificity equaling 0.90 (95% CI, 0.84-0.94), 0.87 (95% CI, 0.77-0.94), and 0.91 (95% CI, 0.84-0.95), respectively.

CONCLUSIONS

cFFR utilizing standardized parameters for contrast delivery leads to clinically acceptable levels of diagnostic performance compared with traditional aFFR to identify physiologically significant intermediate lesions. Future data evaluating the impact on clinical outcomes of cFFR-guided percutaneous coronary intervention are warranted.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03557385.

Long-term outcomes of intermediate coronary stenosis in patients undergoing hemodialysis after deferred revascularization based on fractional flow reserve

OBJECTIVES

This study aimed to assess the long-term outcomes of patients undergoing hemodialysis (HD) after deferred revascularization based on fractional flow reserve (FFR).

BACKGROUND

FFR is a practical technique for assessing the functional severity of intermediate coronary stenosis. Prior research has revealed a satisfactory outcome in patients after the deferral of percutaneous coronary intervention for coronary lesions based on FFR measurement. However, little research has been conducted focusing on patients undergoing HD.

METHODS

The retrospective study comprised 225 consecutive patients with FFR assessment and deferred revascularization between January 2016 and December 2019. Based on a deferral cutoff FFR value of >0.80, we assessed the differences in all-cause death, major adverse cardiac events (MACEs), and target vessel failure (TVF) between the HD (n = 69) and non-HD groups (n = 156) during a mean ± standard deviation routine follow-up of 32.2 ± 13.4 months.

RESULTS

Although the HD group had significantly higher rates of diabetes mellitus than the non-HD group (53.6% vs. 37.2%, p = 0.021), there were no significant differences in sex, left ventricular ejection fraction, or other risk factors between the groups, nor with respect to stenosis diameter or mean FFR. The HD group had a significantly higher incidence of TVF than the non-HD group (34.8% vs. 14.1%, p < 0.001), as well as a significantly higher risk of all-cause death and MACEs.

CONCLUSIONS

The study revealed that deferred revascularization in coronary lesions with an FFR value of >0.80 in patients undergoing HD was associated with poor outcomes. Therefore, it is important to carefully monitor patients with intermediate coronary stenosis undergoing HD.

Prognostic value of post-percutaneous coronary intervention diastolic pressure ratio

Aim

To evaluate the distribution of a generic diastolic pressure ratio (dPR) after angiographically successful percutaneous coronary intervention (PCI) and to assess its association with the 2‑year incidence of target vessel failure (TVF), defined as a composite of cardiac mortality, target vessel revascularisation, target vessel myocardial infarction and stent thrombosis.

Methods

The dPR SEARCH study is a post hoc analysis of the prospective single-centre FFR-SEARCH registry, in which physiological assessment was performed after angiographically successful PCI in a total of 1000 patients, using a dedicated microcatheter. dPR was calculated offline with recently validated software in a subset of 735 patients.

Results

Mean post-PCI dPR was 0.95 ± 0.06. Post-PCI dPR was ≤ 0.89 in 15.2% of the patients. The cumulative incidence of TVF at 2‑year follow-up was 9.4% in patients with a final post-PCI dPR ≤ 0.89 as compared to 6.1% in patients with a post-PCI dPR > 0.89 (adjusted hazard ratio [HR] for dPR ≤ 0.89: 1.53; 95% CI 0.74–3.13; p = 0.249). dPR ≤ 0.89 was associated with significantly higher cardiac mortality at 2 years; adjusted HR 2.40; 95% CI 1.01–5.68; p = 0.047.

Conclusions

In a real-world setting, despite optimal angiographic PCI results, 15.2% of the patients had a final post-PCI dPR of ≤ 0.89, which was associated with a higher incidence of TVF and a significantly higher cardiac mortality rate.

Supplementary Information

The online version of this article (10.1007/s12471-022-01680-0) contains supplementary material, which is available to authorized users.

Patients with Moderate Non-Culprit Coronary Lesions of Recent Acute Coronary Syndrome

Fractional flow reserve (FFR) measurement was compared to dobutamine stress echocardiography (DSE) instable angina (SA) with stable coronary lesion (s) (SCL (s) ) in a few trials; however, similar comparisons in patients with acute coronary syndrome (ACS) with non-culprit lesion (s) (NCL (s) ) are lacking. Our objectives were to prospectively evaluate the diagnostic performance of FFR with two different cutoff values (< 0.80 and < 0.75) relative to DSE in moderate (30%-70% diameter stenosis) NCLs (ACS group) and to compare these observations with those measured in SCLs (SA group). One hundred seventy-five consecutive patients with SA (n = 86) and ACS (n = 89) with 225 coronary lesions (109 SCLs and 116 NCLs) were enrolled. In contrast to the ACS cohort in SA patients, normal DSE was associated with higher FFR values compared to those with abnormal DSE (P = 0.051 versus P = 0.006). In addition, in the SA group, a significant correlation was observed between DSE (regional wall motion score index at peak stress) and FFR (r = -0.290; P = 0.002), whereas a similar association was absent (r = -0.029; P = 0.760) among ACS patients. In the SA group, decreasing the FFR cutoff value (< 0.80 versus < 0.75) improved the concordance of FFR with DSE (70.6% versus 81.7%) without altering its discriminatory power (area under the curve; 0.68 versus 0.63; P = 0.369), whereas in the ACS group, concordance remained similar (69.0% versus 71.6%) and discriminatory power decreased (0.62 versus 0.51; P = 0.049), respectively. In conclusion, lesion-specific FFR assessment may have different relevance in patients with moderate NCLs than in patients with SCLs.

The accuracy of distribution of non-ST elevation electrocardiographic changes in localising the culprit vessel in non-ST elevation myocardial infarction

Introduction

ST-segment elevation distribution on electrocardiogram (ECG) in patients presenting with ST-elevation myocardial infarction (STEMI) accurately localises the culprit vessel. However, the utility of the ECG changes in localising the coronary culprit territory in the setting of non-ST segment elevation myocardial infarction (NSTEMI) is not well established.

Material and methods

This study included patients presenting with NSTEMI, who had dynamic non-ST elevation ischaemic changes in one or more ECG leads and underwent percutaneous coronary intervention (PCI) in a single vessel between October 2011 and November 2017 in a single university hospital institution. The accuracy, sensitivity, and specificity of the distribution of ECG changes in localising the culprit vessel were calculated.

Results

There was a total of 82 patients included in this study, who received PCI to the left anterior descending (LAD), right coronary artery (RCA), and left circumflex (LCX), in 43.9%, 24.4%, and 31.7%, respectively; 51% were male. In this cohort, sensitivity of ECG in localising single-culprit-vessel NSTEMI was 41.5%. The overall accuracy of ECG changes was 50.0%, 72.0%, and 70.0% in LAD, RCA, and LCX distribution, respectively. The sensitivity and specificity were 72.2% and 32.6% in LAD distribution, 20% and 88.7% in RCA distribution, and 15.4% and 82.1% in LCX distributions, respectively.

Conclusions

Ischaemic non-ST elevation ECG changes had modest accuracy in localising the culprit vessel in patients with PCI-treated NSTEMI. These changes were more sensitive in LAD distribution and more specific in RCA and LCX distributions.

Intravascular ultrasound, optical coherence tomography, and fractional flow reserve use in acute myocardial infarction

BACKGROUND

There are limited data on the use of intravascular ultrasound (IVUS), optical coherence tomography (OCT), and fractional flow reserve (FFR) during acute myocardial infarction (AMI).

OBJECTIVES

To assess the temporal trends of IVUS, OCT, and FFR use in AMI.

METHODS

A retrospective cohort study from the National Inpatient Sample (2004-2014) was designed to include AMI admissions that received coronary angiography. Administrative codes were used to identify percutaneous coronary intervention (PCI), IVUS, OCT, and FFR. Outcomes included temporal trends, inhospital mortality and resource utilization stratified by IVUS, OCT, or FFR use.

RESULTS

In 4,419,973 AMI admissions, IVUS, OCT, and FFR were used in 2.6%, 0.1%, and 0.6%, respectively. There was a 22-fold, 118-fold, and 33-fold adjusted increase in IVUS, OCT, and FFR use, respectively, in 2014 compared to the first year of use. Non-ST-elevation AMI presentation, male sex, private insurance coverage, admission to a large urban hospital, and absence of cardiac arrest and cardiogenic shock were associated with higher IVUS, OCT, or FFR use. PCI was performed in 83.2% of the IVUS, OCT, or FFR cohort compared to 64.2% of the control group (p < .001). The cohort with IVUS/OCT/FFR use had lower inhospital mortality (adjusted odds ratio 0.53 [95% confidence interval 0.50-0.56]), more frequent discharges to home (83.7% vs. 76.8%), shorter hospital stays (4.3 ± 4.4 vs. 5.0 ± 5.5 days) and higher hospitalization costs ($90,683 ± 74,093 vs. $74,671 ± 75,841).

CONCLUSIONS

In AMI, the use of IVUS, OCT, and FFR has increased during 2004-2014. Significant patient and hospital-level disparities exist in the use of these technologies.

Advances in coronary physiology

Pressure-wire technology, most typically fractional flow reserve (FFR), has provided interventional cardiologists with a means of determining the physiological importance of a stenosis during angiography. There has been renewed interest in coronary physiology in the light of guideline recognition, ongoing clinical research and new technologies changing the paradigm of how assessment is performed in the catheter laboratory. We reflect on FFR, with regards the potential effects of changing hemodynamics on FFR and the latest evidence with regards to outcomes. We also review the instantaneous wave-free ratio (iFR), a new pressure-only index, measured at rest, that is under active evaluation in several international randomized controlled trials. We review the accumulated evidence and discuss the important physiological concepts between pressure and flow that underlie the approach to using resting indices. Finally we investigate future developments, including physiological mapping with iFR-Pullback and the potential to predict the hemodynamic effect of stenting.

Value of FFR in clinical practice

Fractional flow reserve is an important tool in the cardiac catheterization lab to assess the physiological significance of coronary lesions. This article discusses the basic concepts about FFR and its utility in clinical decision making.