Fractional Flow Reserve in the Transradial Era: Will Hand Vein Adenosine Infusion Suffice?

Continuous intracoronary versus standard intravenous infusion of adenosine for fractional flow reserve assessment: the HYPEREMIC trial

AIMS

The aim of this study was to evaluate the accuracy of a continuous intracoronary (IC) adenosine infusion, administered through the novel HYPEREM™IC over-the-wire microcatheter, to measure fractional flow reserve (FFR).

METHODS AND RESULTS

The HYPEREMIC trial was a randomised, non-inferiority, crossover study in which patients with intermediate coronary lesions were enrolled for sequential pressure wire studies. FFR was measured using intravenous (IV) (140-180 mcg/kg/min) versus continuous non-weight-adjusted IC (360 mcg/min) adenosine. Patients were randomised and blinded to the order in which they received the adenosine, separated by a washout period. The primary endpoint was the mean hyperaemic FFR. Forty-one patients were enrolled at three UK sites between June and November 2016. The mean (standard deviation) FFR was 0.82 (±0.09) after IC versus 0.84 (±0.09) after IV adenosine. The difference of -0.02 (95% confidence interval [CI]: -0.03 to -0.01) confirmed the non-inferiority (margin <0.05) of IC to IV adenosine. Intracoronary adenosine was associated with a shorter mean time to maximal hyperaemia (difference -44 [95% CI: -59 to -29] seconds; p<0.0001). Chest discomfort was reported in 32/41 (78.0%) patients during IV adenosine versus 12/41 (29.3%) patients during IC adenosine.

CONCLUSIONS

Continuous IC adenosine was a reliable, faster and better tolerated method of achieving maximal hyperaemia compared to IV adenosine.

Comparison of hyperemic efficacy between femoral and antecubital fossa vein adenosine infusion for fractional flow reserve assessment

Introduction

Intravenous infusion of adenosine via the femoral vein is commonly used to achieve maximum hyperemia for fractional flow reserve (FFR) assessment in the catheterization laboratory. In the era of transradial access for coronary interventions, obtaining additional venous access with sheath insertion in the groin is unpractical and may be associated with a higher risk of bleeding complications. In a vast majority of cases, patients scheduled for the catheterization laboratory are already equipped with peripheral vein access in antecubital fossa vein. However, only limited data exist to support non-central vein infusion of adenosine instead of the femoral vein for FFR assessment.

Aim

To compare infusion of adenosine via a central versus a peripheral vein for the assessment of peak FFR.

Material and methods

We enrolled 50 consecutive patients with 125 borderline coronary lesions that were assessed by FFR using adenosine femoral and antecubital vein infusion of 140 µg/kg/min.

Results

Physiological severity assessed with femoral vein adenosine infusion at 140 µg/kg/min was mean 0.82 ±0.09, and with antecubital vein adenosine infusion at 140 µg/kg/min was 0.82 ±0.09. The mean time from initiation of adenosine infusion to maximal stable hyperemia was significantly shorter for 140 µg/kg/min femoral vein infusion as compared to antecubital vein infusion (49 ±19 s vs. 68 ±23 s; p < 0.001). There was a strong correlation between FFR values obtained from 140 µg/kg/min femoral and antecubital vein infusion (r = 0.99; p < 0.001).

Conclusions

Antecubital vein adenosine infusion achieved FFR values are very similar to those obtained using femoral vein adenosine administration. However, time to maximal hyperemia is longer with infusion via the antecubital vein.

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.

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.

Assessment of increasing intravenous adenosine dose in fractional flow reserve

Background

Effects of increased adenosine dose in the assessment of fractional flow reserve (FFR) were studied in relation to FFR results, hemodynamic effects and patient discomfort. FFR require maximal hyperemia mediated by adenosine. Standard dose is 140 μg/kg/min administrated intravenously. Higher doses are commonly used in clinical practice, but an extensive comparison between standard intravenous dose and a high dose (220 μg/kg/min) has previously not been performed.

Methods

Seventy-five patients undergoing FFR received standard dose adenosine, followed by high dose adenosine. FFR, mean arterial pressure (MAP) and heart rate (HR) were analyzed. Patient discomfort measured by Visual Analogue Scale (VAS) was assessed.

Results

No significant difference was found between the doses in FFR value (0.85 [0.79–0.90] vs 0.85 [0.79–0.89], p = 0.24). The two doses correlated well irrespective of lesion severity (r = 0.86, slope = 0.89, p = <0.001). There were no differences in MAP or HR. Patient discomfort was more pronounced using high dose adenosine (8.0 [5.0–9.0]) versus standard dose (5.0 [2.0–7.0]), p = <0.001.

Conclusions

Increased dose adenosine does not improve hyperemia and is associated with increased patient discomfort. Our findings do not support the use of high dose adenosine.

Trial registration

Retrospective Trial registration: Current Controlled Trials ISRCTN14618196. Registered 15 December 2016.

Effect of High (200 μg/kg per Minute) Adenosine Dose Infusion on Fractional Flow Reserve Variability

BACKGROUND

Variations in distal coronary pressure (Pd)/aortic pressure (Pa) ratio during steady-state hyperemia with standard (140 μg/kg per minute) adenosine dose may hamper accurate fractional flow reserve assessment. This study investigated to what extent an increased adenosine dose can overcome Pd/Pa variation.

METHODS AND RESULTS

In a prospective, single-arm study, out of 95 prospectively screened patients, 38 (40.0%) exhibited significant (≥0.05 difference of max Pd/Pa minus min Pd/Pa) variations in Pd/Pa from 15 s post Pd/Pa dip and until the end of a 3-minute adenosine (140 μg/kg per minute) infusion. Thirty patients agreed to participate in a post 5-minute repeat fractional flow reserve assessment using 200 μg/kg per minute 3-minute adenosine infusion. The study's co-primary end point of Pd/Pa coefficient of dispersion was lower for the high versus standard adenosine dose: 1.31 (1.13-2.72) versus 2.76 (2.38-5.60), P=0.002. The study's co-primary end point of ΔPd/Pa was also lower for the high versus standard adenosine dose: 0.065 (0.038-0.10) versus 0.08 (0.06-0.11), P=0.002. This difference was mainly driven by the lowering effect of the high adenosine dose on the maximum Pd/Pa compared to the standard dose: 0.84 (0.81-0.93) versus 0.90 (0.83-0.95), P=0.007, while minimum Pd/Pa remained unaffected. High adenosine dose was adequately tolerated by all patients, without requiring infusion discontinuation in any case.

CONCLUSIONS

Pd/Pa variability is frequently observed during standard adenosine infusion and is significantly decreased following a high (200 μg/kg per minute) adenosine dose. This is achieved without a significant difference in the minimum Pd/Pa.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02350439.

Fractional Flow Reserve: Does a Cut-off Value add Value?

Fractional flow reserve (FFR) has been shown to improve outcomes when used to guide percutaneous coronary intervention (PCI). There have been two proposed cut-off points for FFR. The first was derived by comparing FFR against a series of non-invasive tests, with a value of ≤0.75 shown to predict a positive ischaemia test. It was then shown in the DEFER study that a vessel FFR value of ≥0.75 was associated with safe deferral of PCI. During the validation phase, a 'grey zone' for FFR values of between 0.76 and 0.80 was demonstrated, where a positive non-invasive test may still occur, but sensitivity and specificity were sub-optimal. Clinical judgement was therefore advised for values in this range. The FAME studies then moved the FFR cut-off point to ≤0.80, with a view to predicting outcomes. The ≤0.80 cut-off point has been adopted into clinical practice guidelines, whereas the lower value of ≤0.75 is no longer widely used. Here, the authors discuss the data underpinning these cut-off values and the practical implications for their use when using FFR guidance in PCI.

Efficacy of combined administration of intracoronary papaverine plus intravenous adenosine 5'-triphosphate in assessment of fractional flow reserve

BACKGROUND

Inducing maximal coronary hyperemia is important to measure fractional flow reserve (FFR) accurately. Intravenous adenosine and adenosine 5'-triphosphate (ATP) have been used to achieve maximal hyperemia. However, they may not induce maximal hyperemia in all patients. The present study evaluated the combined effect of intracoronary papaverine and intravenous ATP on FFR measurements.

METHODS

FFR measurements with administration of intracoronary papaverine (12mg in the left coronary artery and 8mg in the right coronary artery), intravenous ATP (140μg/kg/min), and combined administration of intracoronary papaverine and intravenous ATP were performed in 51 patients with 57 intermediate lesions.

RESULTS

The mean FFR after intravenous ATP was higher compared to intracoronary papaverine and intravenous ATP plus intracoronary papaverine (0.76±0.13 vs. 0.75±0.13 vs. 0.75±0.13, p=0.01). FFR-positive lesions (FFR ≤0.80) were observed more frequently with intravenous ATP plus intracoronary papaverine compared to intravenous ATP (64.9% vs. 47.4%, p=0.02). Of 32 and 25 FFR-negative lesions with intravenous ATP and intracoronary papaverine, 11 (34%) and 7 (28%) had positive FFR after administration of intravenous ATP plus intracoronary papaverine. No ventricular tachycardia or ventricular fibrillation was observed after administration of intracoronary papaverine.

CONCLUSIONS

Maximal hyperemia may not be induced with intravenous ATP in all lesions. When sufficient hyperemia is doubtful during intravenous infusion of ATP, additional intracoronary administration of papaverine may be a possible option.

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.