Myocardial Fractional Flow Reserve Measurement Using Contrast Media as a First-Line Assessment of Coronary Lesions in Current Practice

Functional Assessment of Coronary Artery Lesions-Old and New Kids on the Block

Angiography is inaccurate in assessing functional significance of coronary lesions, and often stenoses deemed severe on angiographic assessment do not restrict coronary blood flow at rest or with maximal dilatation. Angiography-guided revascularization has not shown improvement in hard clinical outcomes in stable ischemic heart disease (SIHD). Most current guidelines for SIHD recommend invasive functional assessment of lesions to guide revascularization if prior evidence of ischemia is not available. There has been several recent advances and development of novel methods in this arena. Various contemporary clinical trials have been undertaken for validation of these indices. Here we review the physiological basis, tools, techniques, and evidence base for various invasive (resting as well as hyperemic) and noninvasive methods for functional assessment of coronary lesions. Left main stenosis, bifurcation lesions, serial stenosis, and acute coronary syndrome each causes unique disequilibrium that may affect measurements and require special considerations for accurate functional assessment.

Contrast FFR plus intracoronary injection of nitro-glycerine accurately predicts FFR for coronary stenosis functional assessment

BACKGROUND

Fractional flow reserve (FFR) is the "gold standard" for assessing the physiological significance of coronary disease. In the last decade, several alternative adenosine-free indexes have been proposed in order to facilitate the dissemination of the functional evaluation of coronary stenosis. Our aim was to investigate whether radiographic contrast plus intracoronary nitroglycerin (cFFR-NTG) can predict functional assessment of coronary stenosis offering superior diagnostic agreement with FFR compared to non-hyperemic indexes and contrast mediated FFR (cFFR).

METHODS

Three hundred twenty-nine lesions evaluated with pressure wire in 266 patients were prospectively included in this multicenter study.

RESULTS

The ROC curves for cFFR-NTG using an FFR≤0.80 showed a higher accuracy in predicting FFR (AUC=0.97) than resting Pd/Pa (AUC=0.90, P<0.01) and cFFR (AUC=0.93.5, P<0.01). A significant (P<0.01) strong correlation was found between FFR and the four analyzed indexes: Pd/Pa (r=0.78); iFR/RFR (r=0.73); cFFR(r=0.89) and cFFR-NTG (r=0.93). cFFR-NTG showed the closest agreement at Bland-Altman analysis. The cFFR-NTG cut off value >0.84 showed the highest negative predictive value (88%), specificity (91%), sensitivity (94%) and accuracy (92%) of the studied indexes.

CONCLUSIONS

Submaximal hyperemic adenosine-free indexes are an efficient alternative to adenosine for the physiological assessment of epicardial coronary disease. The most accurate index in predicting the functional significance of coronary stenosis using FFR as reference was cFFR-NTG.

Meta-Analysis of Diagnostic Performance of Contrast-Fractional Flow Reserve versus Quantitative Flow Ratio for Functional Assessment of Coronary Stenoses

Background. Use of the fractional flow reserve (FFR) technique is recommended to evaluate coronary stenosis severity and guide revascularization. However, its high cost, time to administer, and the side effects of adenosine reduce its clinical utility. Two novel adenosine-free indices, contrast-FFR (cFFR) and quantitative flow ratio (QFR), can simplify the functional evaluation of coronary stenosis. This study aimed to analyze the diagnostic performance of cFFR and QFR using FFR as a reference index. Methods. We conducted a systematic review and meta-analysis of observational studies in which cFFR or QFR was compared to FFR. A bivariate model was applied to pool diagnostic parameters. Cochran’s Q test and the I2 index were used to assess heterogeneity and identify the potential source of heterogeneity by metaregression and sensitivity analysis. Results. Overall, 2220 and 3000 coronary lesions from 20 studies were evaluated by cFFR and QFR, respectively. The pooled sensitivity and specificity were 0.87 (95% CI: 0.81, 0.91) and 0.92 (95% CI: 0.88, 0.94) for cFFR and 0.87 (95% CI: 0.82, 0.91) and 0.91 (95% CI: 0.87, 0.93) for QFR, respectively. No statistical significance of sensitivity and specificity for cFFR and QFR were observed in the bivariate analysis (P=0.8406 and 0.4397, resp.). The area under summary receiver-operating curve of cFFR and QFR was 0.95 (95% CI: 0.93, 0.97) for cFFR and 0.95 (95% CI: 0.93, 0.97). Conclusion. Both cFFR and QFR have good diagnostic performance in detecting functional severity of coronary arteries and showed similar diagnostic parameters.

The utility of high-sensitivity C-reactive protein levels in patients with moderate coronary lesions and gray-zone fractional flow reserve

OBJECTIVE

It remains controversial whether patients with fractional flow reserve (FFR) values of 0.75-0.80 (gray-zone) should be treated with percutaneous coronary intervention (PCI). This study aimed to evaluate the prediction of high-sensitivity C-reactive protein (hs-CRP) levels to guide treatment selection in gray-zone patients.

METHODS

This prospective interventional trial was conducted between January 2015 and March 2016. A total of 785 patients with stable angina and single-vessel stenosis with moderate coronary lesions were admitted to hospital in this period. After measurement of hs-CRP levels, coronary angiography, and FFR, gray-zone patients (n=308) were included in the study and were divided into four groups on the basis of a cutoff hs-CRP level of 3 mg/L and then on the basis of whether they underwent PCI or not. Patients in groups I (≥3 mg/L, n=70) and III (<3 mg/L, n=84) underwent PCI, whereas those in groups II (≥3 mg/L, n=70) and IV (<3 mg/L, n=84) were administered only drugs. Major adverse clinical events (MACEs) included cardiac death, nonfatal myocardial infarction (MI), target vessel revascularization (TVR), and PCI or coronary artery bypass grafting (CABG). These parameters were also evaluated during follow-up.

RESULTS

The total Kaplan-Meier curves showed macrodistribution differences among the four groups (p<0.05). There was a significantly increased MACE incidence in group II compared with group I or IV (p=0.039 or 0.006, respectively), and an increased incidence in group I compared with group III (p=0.028). However, there were no differences in MACE incidence between groups III and IV (p=0.095) despite the fact that these patients received different treatments.

CONCLUSION

Among FFR gray-zone patients, hs-CRP level was a predictor of MACE and risk stratification could guide treatment selection. Increased hs-CRP levels (≥3 mg/L) are an indication for urgent PCI whereas normal levels (<3 mg/L) are an indication for delayed PCI treatment. Patients with identical FFR values could require different treatment.

Influence of Contrast Media Dose and Osmolality on the Diagnostic Performance of Contrast Fractional Flow Reserve

BACKGROUND

Contrast fractional flow reserve (cFFR) is a method for assessing functional significance of coronary stenoses, which is more accurate than resting indices and does not require adenosine. However, contrast media volume and osmolality may affect the degree of hyperemia and therefore diagnostic performance.

METHODS AND RESULTS

cFFR, instantaneous wave-free ratio, distal pressure/aortic pressure at rest, and FFR were measured in 763 patients from 12 centers. We compared the diagnostic performance of cFFR between patients receiving low or iso-osmolality contrast (n=574 versus 189) and low or high contrast volume (n=341 versus 422) using FFR≤0.80 as a reference standard. The sensitivity, specificity, and overall accuracy of cFFR for the low versus iso-osmolality groups were 73%, 93%, and 85% versus 87%, 90%, and 89%, and for the low versus high contrast volume groups were 69%, 99%, and 83% versus 82%, 93%, and 88%. By receiver operating characteristics (ROC) analysis, cFFR provided better diagnostic performance than resting indices regardless of contrast osmolality and volume (P<0.001 for all groups). There was no significant difference between the area under the curve of cFFR in the low- and iso-osmolality groups (0.938 versus 0.957; P=0.40) and in the low- and high-volume groups (0.939 versus 0.949; P=0.61). Multivariable logistic regression analysis showed that neither contrast osmolality nor volume affected the overall accuracy of cFFR; however, both affected the sensitivity and specificity.

CONCLUSIONS

The overall accuracy of cFFR is greater than instantaneous wave-free ratio and distal pressure/aortic pressure and not significantly affected by contrast volume and osmolality. However, contrast volume and osmolality do affect the sensitivity and specificity of cFFR.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02184117.

Simplifying the assessment of coronary artery stenosis by enhancing instantaneous wave free ratio

Background

Instantaneous wave free ratio (iFR) does not require adenosine, but has a relatively wide intermediate range where functional assessment remains inconclusive. In this pilot study, we sought to enhance iFR through with the use of intracoronary (IC) saline (iFRs) and contrast media (iFRc) and determine whether these techniques correlated well with fractional flow reserve (FFR).

Methods

Patients with coronary artery stenosis (CAS) associated with an iFR in the intermediate zone (≥0.86 and ≤0.93) were prospectively assessed with resting distal coronary pressure/aorta pressure (Pd/Pa), iFR, iFRs, iFRc and FFR.

Results

A total of 40 coronary lesions were studied (40 patients). Pearson correlation coefficients for FFR and iFR, FFR and iFRs, FFR and iFRc were respectively: 0.57 (P=0.0002), 0.80 (P<0.0001) and 0.77 (P<0.0001). Receiver-operating characteristic (ROC) curve analysis showed similar area under the curve (AUC) of iFRs and iFR [0.90 (95% CI: 0.76-1) vs. 0.89 (95% CI: 0.79-0.99), P=0.89]. Youden's index established cut-off values of ≤0.90 for iFR (sensitivity =91%, specificity =74%) and ≤0.78 for iFRs (sensitivity =73%, specificity =100%). In contrast, the AUC of iFRc was superior to the AUC of iFR [0.99 (95% CI: 0.98-1), P=0.049]. iFRc showed excellent accuracy and established cut-off values of ≤0.81 in predicting an FFR value of ≤0.80 (sensitivity =100%, specificity =93%).

Conclusions

When iFR is in the intermediate zone, functional assessment of CAS by iFR is enhanced with the use of contrast media but not saline. This pilot study could be hypothesis generating for further study to enhance iFR specificity and sensibility.

Fractional flow reserve and resting indices for coronary physiologic assessment: Practical guide, tips, and tricks

Physiologic assessment using fractional flow reserve (FFR) to guide percutaneous coronary interventions (PCI) has been demonstrated to improve clinical outcomes, compared to angiography-guided PCI. Recently, resting indices such as resting Pd/Pa, "instantaneous wave-free ratio", and contrast medium induced FFR have been evaluated for the assessment of the functional consequences of coronary lesions. Herein, we review and discuss the use of FFR and other indices for the functional assessment of coronary lesions. This review will cover theoretical aspects, as well as practical points and common pitfalls related to coronary physiological assessment. © 2017 Wiley Periodicals, Inc.

Contrast-induced Hyperemia as an Alternative to Drug-induced Hyperemia in the Evaluation of the Fractional Flow Reserve in Coronary Lesions

Objective Measuring the fractional flow reserve (FFR) requires the induction of coronary hyperemia, usually with adenosine, adenosine triphosphate (ATP), or papaverine. However, adenosine can induce rhythmic complications, and intracoronary boluses of papaverine that prolong the QT interval can cause ventricular tachycardia. Injection of contrast media, which is routinely performed to validate the FFR guidewire placement, also induces hyperemia and may be an alternative method of measuring the FFR. We evaluated the diagnostic accuracy of the FFR after contrast hyperemia (FFRcont) compared to FFR evaluated after intracoronary papaverine (FFRpp). Methods This study included 109 lesions in 93 patients (mean age 70.4±8.7 years) with stable coronary disease. The FFR was measured as follows: 1) baseline pressure value; 2) FFRcont after intracoronary contrast injection (iopamidol, 8 mL for left coronary artery [LCA] or 6 mL for right coronary artery [RCA]); 3) FFRpp after intracoronary injection of papaverine (12 mg for LCA or 8 mg for RCA). Results FFRcont values were strongly correlated with FFRpp (R=0.940, p<0.0001; FFRpp = FFRcont ×1.007-0.032). The best cut-off point in the receiver operator curve analysis for predicting a FFRpp <0.80 was 0.82 (area under the curve =0.980; sensitivity 95.1%, specificity 91.2%, positive predictive value 86.7%, negative predictive value 96.9%). Conclusion FFRcont is highly accurate for predicting FFRpp. An FFRcont threshold value of 0.82 provides excellent sensitivity and a negative predictive value. FFRcont is an alternative method of inducing hyperemia.

Efficacy of coronary fractional flow reserve using contrast medium compared to adenosine

Introduction

Coronary fractional flow reserve (FFR) is recommended as the gold standard method in evaluating intermediate coronary stenoses. However, there are significant debates concerning the agents and the timing of the measurement.

Aim

To compare the contrast medium induced Pd/Pa ratio (CMR) with the FFR.

Material and methods

We enrolled 28 consecutive patients with 34 intermediate lesions who underwent coronary FFR measurement by intracoronary (i.c.) adenosine. After baseline Pd/Pa was calculated, a single contrast medium (Iomeron) injection of 6 ml (3 ml/s) was performed manually. Within 10 s after the contrast medium injection, the CMR was calculated. Bolus injection of i.c. adenosine was performed to induce maximal hyperemia (from 60 µg to 600 µg), and when it was ≤ 0.80, the intermediate lesion was considered as significant.

Results

After bolus i.c. adenosine, 12 lesions of 34 (35.3%) were identified as significant. The CMR value was 0.86 ±0.06 (range: 0.71–0.97). There were no significant differences between FFR and CMR values (p = 0.108). A substantial positive correlation between adenosine and contrast values was detected (0.886 and p < 0.001). Good agreement in Bland-Altman analysis was revealed (mean bias was 0.027, 95% confidence interval 0.038–0.092). Receiver operating characteristics curve analysis showed 90.9% sensitivity and 91.7% specificity for a cut-off value of 0.85 for the CMR compared to FFR (≤ 0.80).

Conclusions

Our study showed that measuring the CMR is a feasible method compared to FFR. The CMR may be used in situations where adenosine cannot be administered.