Use of regadenoson for measurement of fractional flow reserve

Coronary functional assessment in non-obstructive coronary artery disease: Present situation and future direction

Non-obstructive coronary artery disease (CAD), which is defined as coronary stenosis <50%, has been increasingly recognized as an emerging entity in clinical practice. Vasomotion abnormality and coronary microvascular dysfunction are two major mechanisms contributing to the occur of angina with non-obstructive CAD. Although routine coronary functional assessment is limited due to several disadvantages, functional evaluation can help to understand the pathophysiological mechanism and/or to exclude specific etiologies. In this review, we summarized the potential mechanisms involved in ischemia with non-obstructive coronary arteries (INOCA) and myocardial infarction with non-obstructive coronary arteries (MINOCA), the two major form of non-obstructive CAD. Additionally, we reviewed currently available functional assessment indices and their use in non-obstructive CAD. Furthermore, we speculated that novel technique combined anatomic and physiologic parameters might provide more individualized therapeutic choice for patients with non-obstructive CAD.

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.

Quantitative myocardial perfusion response to adenosine and regadenoson in patients with suspected coronary artery disease

BACKGROUND

The aim of the present study was to compare the quantitative flow responses of regadenoson against adenosine using cardiac 15O-water PET imaging in patients with suspected or known coronary artery disease (CAD).

METHODS

Hyperemic myocardial blood flow (MBF) after adenosine and regadenoson was compared using correlation and Bland-Altman analysis in 21 patients who underwent rest and adenosine 15O-water PET scans followed by rest and regadenoson 15O-water PET scans.

RESULTS

Global mean (± SD) MBF values at rest and stress were 0.92 ± 0.27 and 2.68 ± 0.80 mL·g·min for the adenosine study and 0.95 ± 0.29 and 2.76 ± 0.79 mL·g·min for the regadenoson study (P = 0.55 and P = 0.49). The correlations between global and regional adenosine- and regadenoson-based stress MBF were strong (r = 0.80 and r = 0.77). The biases were small for both global and regional MBF comparisons (0.08 and 0.09 mL·min·g), but the limits of agreement were wide for stress MBF.

CONCLUSION

The correlation between regadenoson- and adenosine-induced hyperemic MBF was strong but the agreement was only moderate indicating that established cut-off values for 150-water PET should be used cautiously if using regadenoson as vasodilator.

Myocardial Stress Perfusion MRI Using Regadenoson: A Weight-based Approach in Infants and Young Children

Purpose

To determine the safety and feasibility of stress cardiac MRI by using weight-based dosing of regadenoson in patients less than 40 kg and whether stress cardiac MRI affects patient management.

Materials and Methods

All patients less than 40 kg undergoing stress cardiac MRI by using weight-based dosing (8 μg/kg) of regadenoson were included in this retrospective single-center study. Hemodynamic response, adverse events, and cardiac MRI abnormalities in myocardial perfusion, wall motion, and delayed enhancement were evaluated. Patient management based on the results of the stress cardiac MRI were evaluated.

Results

Forty-six consecutive stress cardiac MRI examinations were performed in 36 patients (median age, 9.0 years; age range, 2 months to 13.9 years) with congenital and acquired heart disease. Thirty-one of 46 (67.4%) studies were performed with the use of sedation. A myocardial perfusion defect was present in 20 of 46 (43.5%) studies, five with inducible defects only, and the remaining 15 with fixed or irreversible defects. In the 46 total studies, there were no major adverse events and nine (19.6%) minor adverse events including emesis (n = 1) and transient hypotension requiring pharmacologic intervention in eight patients who were all sedated. Sedation was an independent predictor for hypotension (P =.040). Twenty-six negative studies had no coronary interventions performed, and of the 20 positive studies, 15 were referred for catheterization, eight of which underwent coronary interventions.

Conclusion

Weight-based dosing of regadenoson for stress cardiac MRI was safe and feasible in infants and young children and played an integral role in the outcome and treatment decisions for children with coronary artery disease.© RSNA, 2019.

Aldosterone impairs coronary adenosine-mediated vasodilation via reduced functional expression of Ca2+-activated K+ channels

Elevated plasma aldosterone (Aldo) levels are associated with greater risk of cardiac ischemic events and cardiovascular mortality. Adenosine-mediated coronary vasodilation is a critical cardioprotective mechanism during ischemia; however, whether this response is impaired by increased Aldo is unclear. We hypothesized that chronic Aldo impairs coronary adenosine-mediated vasodilation via downregulation of vascular K⁺ channels. Male C57BL/6J mice were treated with vehicle (Con) or subpressor Aldo for 4 wk. Coronary artery function, assessed by wire myography, revealed Aldo-induced reductions in vasodilation to adenosine and the endothelium-dependent vasodilator acetylcholine but not to the nitric oxide donor sodium nitroprusside. Coronary vasoconstriction to endothelin-1 and the thromboxane A₂ mimetic U-46619 was unchanged by Aldo. Additional mechanistic studies revealed impaired adenosine A_2A, not A_2B, receptor-dependent vasodilation by Aldo with a tendency for Aldo-induced reduction of coronary A_2A gene expression. Adenylate cyclase inhibition attenuated coronary adenosine dilation but did not eliminate group differences, and adenosine-stimulated vascular cAMP production was similar between Con and Aldo mice. Similarly, blockade of inward rectifier K⁺ channels reduced but did not eliminate group differences in adenosine dilation whereas group differences were eliminated by blockade of Ca²⁺-activated K⁺ (K_Ca) channels that blunted and abrogated adenosine and A_2A-dependent dilation, respectively. Gene expression of several coronary K_Ca channels was reduced by Aldo. Together, these data demonstrate Aldo-induced impairment of adenosine-mediated coronary vasodilation involving blunted A_2A-K_Ca-dependent vasodilation, independent of blood pressure, providing important insights into the link between plasma Aldo and cardiac mortality and rationale for aldosterone antagonist use to preserve coronary microvascular function.NEW & NOTEWORTHY Increased plasma aldosterone levels are associated with worsened cardiac outcomes in diverse patient groups by unclear mechanisms. We identified that, in male mice, elevated aldosterone impairs coronary adenosine-mediated vasodilation, an important cardioprotective mechanism. This aldosterone-induced impairment involves reduced adenosine A_2A, not A_2B, receptor-dependent vasodilation associated with downregulation of coronary K_Ca channels and does not involve altered adenylate cyclase/cAMP signaling. Importantly, this effect of aldosterone occurred independent of changes in coronary vasoconstrictor responsiveness and blood pressure.

Intravenous regadenoson with aminophylline reversal is safe and equivalent to intravenous adenosine infusion for fractional flow reserve measurements

BACKGROUND

Small studies have shown that adenosine is equivalent to regadenoson when obtaining coronary fractional flow reserve (FFR) measurements. A study that also evaluates time and safety of aminophylline reversal of regadenoson effects has not been presented.

HYPOTHESIS

Reversal of regadenoson with aminophylline is safe and equivalent to adenosine for FFR measurements.

METHODS

Forty-six consecutive patients who underwent clinically indicated FFRs at the time of coronary angiography were enrolled between 4/2012 and 5/2014. Each patient had FFR measured using adenosine 140 mcg/kg/min IV, and following return to baseline, FFR was measured using regadenoson 400 mcg IV, which then was reversed with aminophylline 150 mg IV. Time to baseline hemodynamics was measured. Agreement between the two assessments was compared using linear regression.

RESULTS

FFR results were similar with both agents (R² = 0.935, P < 0.0001). Also, using the 0.80 cutoff for significantly depressed FFR, there was no divergence regarding studies' significance. After aminophylline reversal of regadenoson, hemodynamics returned to baseline in 111 ± 71 seconds. There were no unexpected side effects or complications.

CONCLUSIONS

For FFR measurement, regadenoson and adenosine are equivalent hyperemic agents. Regadenoson with aminophylline reversal may be considered as an alternative to adenosine for FFR measurements.

Fractional flow reserve in 2017: current data and everyday practice

INTRODUCTION

Fractional flow reserve (FFR) is an objective physiological index utilized in coronary angiography. It expresses the blood flow in the presence of a coronary artery stenosis as a fraction of the normal blood flow and gives information regarding the functional significance of the lesion. FFR guided percutaneous coronary intervention (PCI) has been shown to be superior to angiography guided PCI in several trials and registries. In addition, it appears that the use of FFR may also be preferable from an economic perspective. Areas covered: This article will cover the physiological principles underpinning FFR, the landmark clinical trials that have established its diagnostic utility and the current recommendations for the use of the procedure in daily practice. We will also examine potential future directions for the technology and try to predict how its use will evolve in the next five years. Expert commentary: We see FFR as an essential diagnostic tool in the modern catheterization laboratory, enabling physicians to make optimal decisions regarding percutaneous coronary intervention for an individual patient. It must be stated however that FFR is an adjunctive invasive functional tool that must be used in conjunction with sensible clinical history and exam findings pertaining to the individual patient. We expect that the results of FAME3 will further establish the role of FFR in risk stratifying patients with 3 vessel disease by utilizing a functional SYNTAX score.

Performing and Interpreting Fractional Flow Reserve Measurements in Clinical Practice: An Expert Consensus Document

Fractional flow reserve (FFR) measurements can determine the haemodynamic relevance of coronary artery stenoses. Current guidelines recommend their use in lesions in the absence of non-invasive proof of ischaemia. The prognostic impact of FFR has been evaluated in randomised trials, and it has been shown that revascularisation can be safely deferred if FFR is >0.80, while revascularisation of stenoses with FFR values ≤0.80 results in significantly lower event rates compared to medical treatment. Left main stenoses, aorto-ostial lesions, as well as patients with left ventricular hypertrophy and severely-impaired ejection fraction, have been excluded from large, randomised trials. While FFR measurements are relatively straightforward to perform, uncertainty about procedural logistics, as well as data acquisition and interpretation in specific situations, could explain why they are not widely used in clinical practice. We summarise the clinical data in support of FFR measurements, and provide recommendations for performing and interpreting the procedure.

Single bolus intravenous regadenoson injection versus central venous infusion of adenosine for maximum coronary hyperaemia in fractional flow reserve measurement

AIMS

The aim of this study was to compare the hyperaemic effect of a single bolus regadenoson injection to a central venous adenosine infusion for inducing hyperaemia in the measurement of fractional flow reserve (FFR).

METHODS AND RESULTS

One hundred patients scheduled for FFR measurement were enrolled. FFR was first measured by IV adenosine (140 µg/kg/min), thereafter by IV bolus regadenoson injection (400 µg), followed by another measurement by IV adenosine and bolus injection of regadenoson. The regadenoson injections were randomised to central or peripheral intravenous. Hyperaemic response and duration of steady state maximum hyperaemia were studied, central versus peripheral venous regadenoson injections were compared, and safety and reproducibility of repeated injections were investigated. Mean age was 66±8 years, 75% of the patients were male. The target stenosis was located in the LM, LAD, LCX, and RCA in 7%, 54%, 20% and 19%, respectively. There was no difference in FFR measured by adenosine or by regadenoson (ΔFFR=0.00±0.01, r=0.994, p<0.001). Duration of maximum hyperaemia after regadenoson was variable (10-600 s). No serious side effects of either drug were observed.

CONCLUSIONS

Maximum coronary hyperaemia can be achieved easily, rapidly, and safely by one single intravenous bolus of regadenoson administered either centrally or peripherally. Repeated regadenoson injections are safe. The hyperaemic plateau is variable. Clinical Trial Registration: http://clinicaltrials.gov/ct2/ show/study/NCT01809743?term=NCT01809743&rank=1 (ClinicalTrials.gov Identifier: NCT01809743).

Physiologic Assessment of Coronary Artery Disease: Focus on Fractional Flow Reserve

The presence of myocardial ischemia is the most important prognostic factor in patients with ischemic heart disease. Fractional flow reserve (FFR) is a gold standard invasive method used to detect the stenosis-specific myocardial ischemia. FFR-guided revascularization strategy is superior to angiography-guided strategy. The recently developed hyperemia-free index, instantaneous wave free ratio is being actively investigated. A non-invasive FFR derived from coronary CT angiography is now used in clinical practice. Due to rapid expansion of invasive and non-invasive physiologic assessment, comprehensive understanding of the role and potential pitfalls of each modality are required for its application. In this review, we focus on the basic and clinical aspects of physiologic assessment in ischemic heart disease.

Pooled comparison of regadenoson versus adenosine for measuring fractional flow reserve and coronary flow in the catheterization laboratory

BACKGROUND

Adenosine is the gold standard for augmenting coronary flow during fractional flow reserve (FFR) testing of intermediate coronary stenoses. However, intravenous infusion is time-consuming and intracoronary injection is subject to variability. Regadenoson is a newer adenosine alternative administered as a single intravenous bolus during nuclear stress testing, but its efficacy and safety during FFR testing have been evaluated only in small, single-center studies.

METHODS

We pooled data from 5 academic hospitals, in which patients undergoing clinically-indicated FFR prospectively underwent comparison of intravenous adenosine infusion (140-175mcg/kg/min) versus regadenoson bolus (400mcg). Hemodynamics and symptoms with adenosine were recorded until maximal hyperemia occurred, and after returning to baseline hemodynamics, regadenoson was administered and monitoring was repeated. In a subset of patients with coronary flow data, average peak velocity (APV) at the distal flow sensor was recorded.

RESULTS

Of 149 patients enrolled, mean age was 59±9years, 76% were male, and 54% underwent testing of the left anterior descending artery. Mean adenosine-FFR and regadenoson-FFR were identical (0.82±0.10) with excellent correlation of individual values (r=0.96, p<0.001) and no difference in patient-reported symptoms. Four patients (2.6%) had discrepancies between the 2 drugs for the clinical decision-making cutoff of FFR≤0.80. Coronary flow responses to adenosine and regadenoson were similar (APV at maximal hyperemia 36cm/s for both, p=0.81).

CONCLUSIONS

Regadenoson single-bolus administration has comparable FFR, symptoms, and coronary flow augmentation when compared with standard intravenous adenosine infusion. With its greater ease of administration, regadenoson may be a more "user-friendly" option for invasive ischemic testing.

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.

Regadenoson versus dipyridamole hyperemia for cardiac PET imaging

OBJECTIVES

The goal of this study was to compare regadenoson and dipyridamole hyperemia for quantitative myocardial perfusion imaging.

BACKGROUND

Regadenoson is commonly used for stress perfusion imaging. However, no study in nuclear cardiology has employed a paired design to compare quantitative hyperemic flow from regadenoson to more traditional agents such as dipyridamole. Additionally, the timing of regadenoson bolus relative to tracer administration can be expected to affect quantitative flow.

METHODS

Subjects underwent 2 rest/stress cardiac positron emission tomography scans using an Rb-82 generator. Each scan employed dipyridamole and a second drug in random sequence, either regadenoson according to 5 timing sequences or repeated dipyridamole. A validated retention model quantified absolute flow and coronary flow reserve.

RESULTS

A total of 176 pairs compared regadenoson (126 pairs, split unevenly among 5 timing sequences) or repeated dipyridamole (50 pairs). The cohort largely had few symptoms, only risk factors, and nearly normal relative uptake images, with 8% typical angina or dyspnea, 20% manifest coronary artery disease, and a minimum quadrant average of 80% (interquartile range: 76% to 83%) on dipyridamole scans. Hyperemic flow varied among regadenoson timing sequences but showed consistently lower stress flow and coronary flow reserve compared with dipyridamole. A timing sequence most similar to the regadenoson package insert achieved about 80% of dipyridamole hyperemia, whereas further delaying radiotracer injection reached approximately 90% of dipyridamole hyperemia. Because of the small numbers of pairs for each regadenoson timing protocol and a paucity of moderate or large perfusion defects, we did not observe a difference in relative uptake.

CONCLUSIONS

With the standard timing protocol from the package insert, regadenoson achieved only 80% of dipyridamole hyperemia quantitatively imaged by cardiac positron emission tomography using Rb-82. A nonstandard protocol using a more delayed radionuclide injection after the regadenoson bolus improved its effect to 90% of dipyridamole hyperemia.