Coronary Pressure Wire Research Articles

Diabetes does not impact the diagnostic performance of contrast-based fractional flow reserve: insights from the CONTRAST study

BackgroundAdenosine-free coronary pressure wire metrics have been proposed to test the functional significance of coronary artery lesions, but it is unexplored whether their diagnostic performance might be altered in patients with diabetes.MethodsWe performed a post-hoc analysis of the CONTRAST study, which prospectively enrolled an international cohort of patients undergoing routine fractional flow reserve (FFR) assessment for standard indications. Paired, repeated measurements of all physiology metrics (Pd/Pa, iFR, contrast-based FFR, and FFR) were made. A central core laboratory analyzed blinded pressure tracings in a standardized fashion.ResultsOf 763 subjects enrolled at 12 international centers, 219 (29%) had diabetes. The two groups were well-balanced for age, clinical presentation (stable or unstable), coronary vessel studied, volume and type of intracoronary contrast, and volume of intracoronary adenosine. A binary threshold of cFFR ≤ 0.83 produced an accuracy superior to both Pd/Pa and iFR when compared with FFR ≤ 0.80 in the absence of significant interaction with diabetes status; indeed, accuracy in subgroups of patients with or without diabetes was similar for cFFR (86.7 vs 85.4% respectively; p = 0.76), iFR (84.2 vs 80.0%, p = 0.29) and Pd/Pa (81.3 vs 78.9%, p = 0.55). There was no significant heterogeneity between patients with or without diabetes in terms of sensitivity and specificity of all metrics. The area under the receiver operating characteristic (ROC) curve was largest for cFFR compared with Pd/Pa and iFR which were equivalent (cFFR 0.961 and 0.928; Pd/Pa 0.916 and 0.870; iFR 0.911 and 0.861 in diabetic and non-diabetic patients respectively).ConclusionscFFR provides superior diagnostic performance compared with Pd/Pa or iFR for predicting FFR irrespective of diabetes (clinicaltrials.gov identifier NCT02184117).

Use of a pressure wire to evaluate right heart pressures in a pre-liver transplant recipient through a peripheral IV.

Use of a pressure wire to evaluate right heart pressures in a pre-liver transplant recipient through a peripheral IV.

INFLUENCE OF LESION LOCATION ON THE DIAGNOSTIC ACCURACY OF ADENOSINE-FREE CORONARY PRESSURE WIRE MEASUREMENTS: THE CONTRAST (CAN CONTRAST INJECTION BETTER APPROXIMATE FFR COMPARED TO PURE RESTING PHYSIOLOGY?) SUBSTUDY

Several adenosine-free coronary pressure wire indices have been proposed to assess the functional significance of coronary artery lesions; however, there is a theoretical concern that lesion location and the amount of myocardium interrogated may affect diagnostic performance. In a total of 763

Optical coherence tomography of re-pressurised porcine coronary arteries: A systematic study

Abstract Cardiovascular death is the most frequently reported cause of adult natural death in autopsy reports in the UK. However, the approach used for diagnosing coronary artery disease at autopsy is largely based on visual assessment of coronary artery cross sections to determine the severity of stenosis. This is subject to criticism and heterogeneity. Objective We investigated the potential role of a novel intravascular imaging technique, optical coherence tomography (OCT), in post-mortem diagnosis of coronary artery disease and what effect re-pressurisation has on vessel dimensions, as measured by OCT. Our long term aim is to investigate the role of OCT as a minimally invasive autopsy tool. Materials and methods We used several ex-vivo porcine hearts to develop the techniques. Subsequently, 6 coronary arteries were used for detailed experiments. Vessels were gradually re-pressurised using normal saline and clinical coronary pressure wire and OCT systems were used for recording the pressure and intracoronary imaging. Results Our data showed re-pressurisation significantly alters the vessel dimensions. The mean cross sectional area increased from 3.3 to 8.4 mm 2 proximally and from 2.5 to 7.4 mm 2 distally. Conclusion We conclude that OCT in the ex-vivo setting is feasible and re-pressurisation significantly alters vascular dimensions. This implies, there might be significant discrepancies between the true severities of stenosis in life and that which is determined by visual estimation during autopsy in the collapsed vessels. OCT of re-pressurised vessel can overcome this issue and has the potential to improve the accuracy of post-mortem assessment of coronary artery disease.

Increase in ultrasonic intensity of blood speckle across moderate coronary artery stenosis is an independent predictor of functional coronary artery stenosis measured by fractional flow reserve: pilot study.

Background and AimsThe degree of coronary artery stenosis should be assessed both anatomically and functionally. We observed that the intensity of blood speckle (IBS) on intravascular ultrasound (IVUS) is low proximal to a coronary artery stenosis, and high distal to the stenosis. We defined step-up IBS as the distal minus the proximal IBS, and speculated that this new parameter could be used for the functional evaluation of stenosis on IVUS. The aims of this study were to assess the relationships between step-up IBS and factors that affect coronary blood flow, and between step-up IBS and fractional flow reserve (FFR).Methods and ResultsThis study enrolled 36 consecutive patients with angina who had a single moderate stenosis in the left anterior descending artery. All patients were evaluated by integrated backscatter IVUS and intracoronary pressure measurements. FFR was calculated from measurements using a coronary pressure wire during hyperemia. Conventional gray-scale IVUS images were recorded, and integrated backscatter was measured in three cross-sectional slices proximal and distal to the stenosis. Step-up IBS was calculated as (mean distal integrated backscatter value) − (mean proximal integrated backscatter value). Stepwise multiple linear regression analysis showed that the heart rate (r = 0.45, P = 0.005), ejection fraction (r = −0.39, P = 0.01), and hemoglobin level (r = −0.32, P = 0.04) were independently correlated with step-up IBS, whereas proximal and distal IBS were not associated with these factors. There was a strong inverse correlation between step-up IBS and FFR (r = −0.84, P < 0.001), which remained significant on stepwise multiple linear regression analysis.ConclusionsThe newly defined parameter of step-up IBS is potentially useful for the functional assessment of coronary artery stenosis.

Nicorandil prevents microvascular dysfunction resulting from PCI in patients with stable angina pectoris: a randomised study

Nicorandil, an ATP sensitive potassium channel opener, may reduce the incidence of microvascular dysfunction after percutaneous coronary intervention (PCI) by dilating coronary resistance vessels. The aim of the study was evaluation of the impact of the administration of intravenous nicorandil on measuring the index of microcirculatory resistance (IMR) in PCI to patients with stable angina pectoris (SAP). Intravascular ultrasound (IVUS), fractional flow reserve (FFR), IMR and blood examination (CK-MB), cardiac troponin I (cTnI) immediately post-PCI (and 24 hours later) were performed in 62 consecutive patients with SAP undergoing PCI. FFR and IMR were measured simultaneously with a single coronary pressure wire. IMR was defined as Pd/coronary flow (or Pd* mean transit time) at peak hyperaemia. Patients were randomised to the control (n=29), or nicorandil group (n=33). In the nicorandil group, nicorandil was intravenously administered as a 6 mg bolus injection just before PCI and as a constant infusion at 6 mg/hour for 24 hours thereafter. All volumetric IVUS parameters and FFR were similar between the two groups both pre- and post-PCI. However, IMR immediately post-PCI and cTnI 24 hours post-PCI were significantly higher in the control group compared to the nicorandil group (IMR: 25.4±12.1 vs. 17.9±9.1 units, and cTnI: 0.21±0.13 vs. 0.12±0.08 ng/mL, for control vs. nicorandil). The incidence for cTnI elevation more than fivefold the normal range (>0.20 ng/mL) was significantly larger in the control group than in the nicorandil group (41% vs. 12%, p<0.01). Additionally, the control group showed a closer correlation between plaque volume reduction during stenting as assessed by volumetric IVUS, and cTnI elevation than the nicorandil group (r=0.55 vs. 0.42, p<0.001 for control vs. nicorandil). In patients undergoing successful coronary stenting for stable angina, administration of nicorandil is associated with reduced microvascular dysfunction induced by PCI.

Physiologic approach for coronary intervention

When invasively assessing coronary artery disease, the primary goal should be to determine whether the disease is causing a patient's symptoms and whether it is likely to cause future cardiac events. The presence of myocardial ischemia is our best gauge of whether a lesion is responsible for symptoms and likely to result in a future cardiac event. In the catheterization laboratory, fractional flow reserve (FFR) measured with a coronary pressure wire is the reference standard for identifying ischemia-producing lesions. Its spatial resolution is unsurpassed with it not only being vessel-specific, but also lesion-specific. There is now a wealth of data supporting the accuracy of measuring FFR to identify ischemia-producing lesions. FFR-guided percutaneous coronary intervention of these lesions results in improved outcomes and saves resources. Non-hemodynamically significant lesions can be safely managed medically with a low rate of subsequent cardiac events.

Comparison of Hyperemic Efficacy Between Central and Peripheral Venous Adenosine Infusion for Fractional Flow Reserve Measurement

Maximal hyperemia is a prerequisite for the accurate measurement of fractional flow reserve (FFR). Although continuous infusion of adenosine via the femoral vein is considered to be the gold standard, this requires an additional invasive procedure for femoral vein access and is difficult to use during transradial coronary catheterization. We performed this prospective study to evaluate the feasibility and efficacy of peripheral intravenous infusion of adenosine for FFR measurement. Seventy-one patients were prospectively enrolled, and FFR was measured using a 0.014-inch coronary pressure wire. Hyperemic efficacy of adenosine was compared among intracoronary bolus injection and continuous IV infusion (140 μg/min/kg) via the femoral and via the forearm vein. In 20 patients, hyperemic mean transit time and index of microcirculatory resistance were also measured. Mean FFR after bolus administration of adenosine was 0.81±0.10. As compared with femoral vein infusion (FFR: 0.80±0.10), hyperemic efficacy of forearm vein infusion of adenosine (FFR: 0.80±0.11) was not inferior (P for noninferiority=0.01). The number of functionally significant stenoses (FFR <0.75) was also not different between the 2 methods (femoral vein versus forearm vein; 17 (25.0%) versus 17 (25.0%), P=1.0). Both hyperemic mean transit time and index of microcirculatory resistance were not different between the 2 routes of adenosine infusion. Additional bolus injection of adenosine during IV infusion did not improve the hyperemic efficacy but increased the risk of atrioventricular block. This study suggests that continuous intravenous infusion of adenosine via the forearm vein is a convenient and effective way to induce steady-state hyperemia for invasive physiological measurements. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01070420.

FEASIBILITY, SAFETY, AND OUTCOMES WITH A CORONARY PRESSURE WIRE SYSTEM USED FOR THE ASSESSMENT OF SEVERE AORTIC STENOSIS

Retrograde passage through a stenotic aortic valve (AV), with the purpose of measuring invasively the gradient across the AV, is not without risk. The utility of a 0.014” coronary pressure wire (CPW) for crossing severely stenotic AV has not been investigated. We examined the feasibility,

Myocardial fractional flow reserve

Revascularization of coronary artery lesions should be based on objective evidence of ischemia, as recommended by the guidelines of the European Society of Cardiology. However, even in the case of stable coronary artery disease and elective percutaneous coronary intervention (PCI), pre-procedural noninvasive stress test results are available in a minority of patients only. It is common practice for physicians to make decisions on revascularization in the catheterization laboratory after a cursory review of the angiogram, despite the well-recognized inaccuracy of such an approach. Myocardial fractional flow reserve (FFR) measured by a coronary pressure wire is a specific index of the functional significance of a coronary lesion, with superior diagnostic accuracy for the detection of ischemia than any noninvasive stress test. FFR trials on patients with single and multivessel disease, such as the DEFER and FAME studies, have demonstrated that the clinical benefit of PCI with respect to patient outcome is greatest when revascularization is limited to lesions inducing ischemia, whereas lesions not inducing ischemia should be treated medically.

21 Influence of fractional flow reserve measurement on treatment-decisions in patients with recent acute non-ST elevation myocardial infarction

<h3>Introduction</h3> Non-ST elevation acute myocardial infarction (NSTEMI) is the most common form of acute coronary syndrome and has a relatively poor prognosis. Visual interpretation of the coronary angiogram is the standard approach to guide treatment decisions in patients with recent acute NSTEMI. The aim of our study was to determine whether measurement of coronary pressure derived fractional flow reserve (FFR), compared to coronary angiography alone, might influence treatment decisions. <h3>Setting</h3> The cardiac catheterisation laboratory in a regional heart centre in the UK. <h3>Definitions</h3> The clinical indication for FFR measurement was the presence of an intermediate coronary stenosis (50%–75% of the reference vessel diameter) which resulted in diagnostic and treatment uncertainty. FFR measurement was used to provide functional information on lesion severity and an FFR &lt;0.80 was taken to represent a flow-limiting stenosis. <h3>Methods</h3> The study involved three accredited interventional cardiologists and a study coordinator. The cardiologists separately reviewed the coronary angiograms and together with the clinical history, made a decision for medical therapy, PCI, CABG/MDT, or deferred management. The FFR results were then disclosed and the initial management decision was reviewed in light of the FFR result and changed as appropriate. <h3>Results</h3> Of 1621 acute NSTEMI patients (January 2009–March 2010) in our hospital, 100 (6.2%) had FFR recorded. The treatment decisions for each cardiologist were: medical therapy 7%, 10%, 1%; PCI 64%, 70%, 60%; CABG/MDT 13%, 12%, 15%; deferred management 16%, 8%, 24%). The proportion of patients allocated to each treatment group differed between the 2nd and 3rd Cardiologist (p=0.02). Following FFR disclosure, each cardiologist changed his/her treatment decision in 58%, 50% and 62% of patients (p&lt;0.05). Of the new decisions made following FFR disclosure, the proportion of patients allocated to medical therapy increased by 26%, 19% and 29%, whereas the proportion of patients allocated to deferred management or multi-vessel PCI decreased by 16%, 8%, 24% and by 5%, 7% and 5%, respectively (all p&lt;0.05). The number of patients in whom the treatment decisions made by each cardiologist independently conformed (and so represented a consensus in at least 2 of the 3 decisions) increased from 74% to 92% as a result of FFR disclosure (p&lt;0.001). <h3>Conclusion</h3> In our hospital about 1 in 20 NSTEMI had a coronary pressure wire study because of diagnostic uncertainty based on coronary angiography alone. In NSTEMI patients selected for FFR measurement, the FFR resulted in a change in management in at least half of the patients. FFR use increased the proportion of patients in whom treatment decisions conformed suggesting FFR use may also help to reduce the variation in treatment decisions using angiography alone. These results support further studies of the clinical utility and prognostic implications of FFR measurement in patients with NSTEMI.

Importance of Diffuse Atherosclerosis in the Functional Evaluation of Coronary Stenosis in the Proximal-Mid Segment of a Coronary Artery by Myocardial Fractional Flow Reserve Measurements

The objective of this study was to evaluate the impact of diffuse coronary atherosclerosis on the functional evaluation of moderate coronary lesions in the proximal-mid segment of a coronary artery and its clinical implications. This was a prospective study including 100 consecutive patients with a moderate lesion (45 ± 9% diameter stenosis) in the proximal-mid coronary segment who were evaluated with fractional flow reserve (FFR) measurement. No patient had any other angiographic stenosis distal to the evaluated coronary stenosis. FFR measurements were obtained just distal (~2 to 3 cm) to the lesion (FFR proximal measurement [FFR-PM]) and as distally as possible in the artery (FFR distal measurement [FFR-DM]) after administration of the same dose of intracoronary adenosine. Thirty-nine patients underwent dipyridamole or exercise myocardial single-photon emission computed tomography within 3 months of the FFR study. Mean FFR-PM was significantly higher compared to FFR-DM (0.84 ± 0.08 vs 0.78 ± 0.09, median gradient 0.06, 25th to 75th interquartile range 0.02 to 0.10, p <0.0001). FFR-DM was <0.75 in 33% of patients with FFR-PM ≥0.75, leading to the decision of revascularization in these patients. Performing FFR measurement in the left main/left anterior descending artery predicted a higher gradient between FFR-DM and FFR-PM (odds ratio 4.58, 95% confidence interval 1.4 to 15.03, p = 0.007). FFR-DM exhibited a better correlation with results of myocardial single-photon emission computed tomography compared to FFR-PM (kappa 0.33 vs 0.22, p <0.0001). In conclusion, significant differences between FFR-DM and FFR-PM were observed in patients with moderate coronary stenosis in the proximal-mid segment of a coronary artery, with FFR-DM exhibiting a better correlation with results of noninvasive functional tests. These differences influenced the treatment decision in about 1/3 of patients and highlight the potential clinical relevance of coronary pressure wire positioning for functional evaluation of lesions in the proximal-mid segment of the coronary arteries.

Effect of Lipid Exposure on Progression of Native Vessel Disease in Vein-Grafted Vessels in Coronary Bypass Patients

Methods: Microvascular resistance was measured utilising the index of microcirculatory resistance (IMR) in 24 patients undergoing elective PCI for stable angina. A coronary PressureWire was used to measure IMR prior to PCI using the equation PaTmn(Pd−Pw/Pa−Pw), where Pa and Pd refer to hyperaemic aortic and distal coronary pressure respectively, Tmn the mean transit time of 3ml of saline injected into the culprit artery and Pw the coronary wedge pressure. Body mass index, age, fasting LDL, HDL and blood sugar, blood pressure and smoking status (pack-years) were recorded in each patient prior to PCI. Associations were assessed using Pearson’s correlation coefficients. Linear regression analysis was used to assess correlates of IMR. Results: Mean IMR was 14.3± 7.9. There were positive correlations between IMR and age (r= 0.55, p= 0.006), fasting blood sugar (r= 0.35, p= 0.08). Therewere also negative correlation between LDL (r=−0.52, p= 0.01) and BMI (r=−0.53, p= 0.007). There was no correlation between IMR and HDL, smoking status or blood pressure. Multivariate regression analysis showed that reduced BMI was the only independent predictor of higher microvascular resistance in our model (B=−0.684, p= 0.033). Conclusions: Microvascular resistance is correlated with risk factors for atherosclerosis. A lower BMI appears to be a primary determinant of microvascular resistance and possibly a further aspect of the obesity paradox. Furt

Assessment of myocardial viability using coronary zero flow pressure and fractional flow reserve in swine model of acute myocardial infarction

Objective This study is to make into the swine model of acute myocardial infarction(AMI) and detect viable myocardium. Methods Thirteen swines， their pressure of aotic artery were measured through guiding wire and the distal pressure of left anterior descending(LAD)measured through coronary pressure wire， then calculated fractional flow reserve (FFR). Coronary blood flow velocity was recorded through coronary doppler wire and calculated zero flow pressure (Pzf). Blocked up distal of LAD by angioplasty balloon to establish the model of AMI. Calculated the FFR and Pzf repeadly. Analysis the difference of FFR and Pzf between before and after the model of AMI established. Taken out of those swines\'heart after executed them， sliced the cardiac muscle and dyed with TTc to detect the viable myocardium. Calculated the percent ratio of viable myocardium to the whole left ventrcular myocardium using image tool 3.0.Drawed the percent ratio of viable myocardium？Pzf coordinate graph and observed the relationship between them. Results Eleven swines were successfully established models of AMI by occlusion of the coronaries. 2 swines died of ventricular fibrillation after the coronaries were occluded 45 and 65 minutes respectively. The viable myocardium could be detected by TTc dyeing. After the model of AMI established， all FFR＜0.75 and the FFR of the models of AMI were less than before (P＜0.001) while the Pzf of the models of AMI were more than before (P＜0.001). The percent radio of viable myocardium were negative correlation with Pzf after the model of AMI established. Conclusions The swine model of AMI can be established by coronary occlusion with angioplasty balloon. FFR＜0.75 is a criterion to detect the viable myocardium and Pzf is an index that can predict the extent of viable myocardium after AMI.

Acute Cardiovascular Effects of Apelin in Humans

Apelin, the endogenous ligand for the novel G protein-coupled receptor APJ, has major cardiovascular effects in preclinical models. The study objectives were to establish the effects of acute apelin administration on peripheral, cardiac, and systemic hemodynamic variables in healthy volunteers and patients with heart failure. Eighteen patients with New York Heart Association class II to III chronic heart failure, 6 patients undergoing diagnostic coronary angiography, and 26 healthy volunteers participated in a series of randomized, double-blind, placebo-controlled studies. Measurements of forearm blood flow, coronary blood flow, left ventricular pressure, and cardiac output were made by venous occlusion plethysmography, Doppler flow wire and quantitative coronary angiography, pressure wire, and thoracic bioimpedance, respectively. Intrabrachial infusions of (Pyr(1))apelin-13, acetylcholine, and sodium nitroprusside caused forearm vasodilatation in patients and control subjects (all P<0.0001). Vasodilatation to acetylcholine (P=0.01) but not apelin (P=0.3) or sodium nitroprusside (P=0.9) was attenuated in patients with heart failure. Intracoronary bolus of apelin-36 increased coronary blood flow and the maximum rate of rise in left ventricular pressure and reduced peak and end-diastolic left ventricular pressures (all P<0.05). Systemic infusions of (Pyr(1))apelin-13 (30 to 300 nmol/min) increased cardiac index and lowered mean arterial pressure and peripheral vascular resistance in patients and healthy control subjects (all P<0.01) but increased heart rate only in control subjects (P<0.01). Acute apelin administration in humans causes peripheral and coronary vasodilatation and increases cardiac output. APJ agonism represents a novel potential therapeutic target for patients with heart failure.

Reduction in Myocardial Perfusion Territory and its Effect on the Physiological Severity of a Coronary Stenosis

Received August 22, 2009; accepted December 3, 2009. A man aged 56 years presented with worsening exertional angina. Coronary angiography showed a moderate-to-severe stenosis in the midleft anterior descending artery (LAD) [Figure 1a]. The right coronary artery (RCA) was chronically occluded (Figure 1b). A coronary pressure wire assessment of the mid-LAD lesion yielded a fractional flow reserve (FFR) of 0.72, indicating this to be functionally significant (Figure 2a). The patient did not wish to have cardiac surgery, and thus, a percutaneous revascularization strategy was proposed. The RCA was successfully revascularized with 2 drug-eluting stents (Figure 1e). Repeat coronary pressure assessment of the mid-LAD lesion yielded an FFR of 0.84, indicating this to be no longer functionally significant (Figure 2b). Given this result, we decided not to proceed with …

Assessment of a Coronary Artery Fistula Using Coronary Pressure Wire

Assessment of a Coronary Artery Fistula Using Coronary Pressure Wire

Assessment of renal artery fibromuscular dysplasia: Angiography, intravascular ultrasound (with virtual histology), and pressure wire measurements

Fibromuscular dysplasia (FMD) of the renal arteries is classically associated with secondary hypertension in younger individuals, which may be treatable and even curable by percutaneous transluminal renal angioplasty. Angiography of these renal arteries often displays "beaded" luminal abnormalities. The angiographic findings, however, may not accurately reflect the severity or precise location of the intraluminal obstruction. We present a case of an older individual with longstanding hypertension and FMD, in whom the use of a coronary pressure wire and intravascular ultrasound enabled precise localization and treatment of the hemodynamically significant stenosis. Virtual histology of FMD in the renal vasculature is also reported.

Comparison of medical treatment and coronary revascularization in patients with moderate coronary lesions and borderline fractional flow reserve measurements

(1) To evaluate the clinical outcomes of patients with moderate coronary lesions and borderline fractional flow reserve (FFR) measurements (between 0.75 and 0.80), comparing those who underwent coronary revascularization (CR) to those who had medical treatment (MT), and (2) to determine the predictive factors of major adverse cardiac events (MACE) at follow-up. A total of 107 consecutive patients (mean age 62 +/- 10 years) with at least one moderate coronary lesion (mean percent diameter stenosis 47 +/- 12%) evaluated by coronary pressure wire with FFR measurement between 0.75 and 0.80 (mean 0.77 +/- 0.02) were included in the study. MACE [CR, myocardial infarction (MI), cardiac death) and the presence of angina were evaluated at follow-up. Sixty-three patients (59%) underwent CR and 44 patients (41%) had MT, with no clinical differences between groups. At a mean follow-up of 13 +/- 7 months, MACE related to the coronary lesion evaluated by FFR were higher in the MT group compared with CR group (23% vs. 5%, P = 0.005). Most MACE consisted of CRs, with no differences between groups in MI and cardiac death rate at follow-up. Both MT and FFR measurements in an artery supplying a territory with previous MI were independent predictive factors of MACE at follow-up, respectively (hazard ratio 5.2, 95% CI 1.4-18.9, P = 0.01; hazard ratio 4.1, 95% CI 1.1-15.3, P = 0.03). The presence of angina at follow-up was more frequent in the MT group compared with the CR group (41% vs. 9%, P = 0.002). In patients with moderate coronary lesions and borderline FFR measurements deferral of revascularization was associated with a higher rate of MACE (CR) and a higher prevalence of angina at follow-up, especially in those with previous MI in the territory evaluated by FFR. Further prospective randomized studies should confirm whether or not an FFR cut-off point of 0.80 instead of 0.75 would be more appropriate for deferring CR in these cases.

Pharmacological options for inducing maximal hyperaemia during studies of coronary physiology

The coronary pressure wire is used for physiological assessment of the coronary vasculature increasingly frequently in clinical practice. Fractional flow reserve (FFR) can now be used to assess lesion severity in a variety of anatomical situations. Increasingly, the coronary pressure wire is being used to interrogate the coronary microvasculature. Coronary flow reserve (CFR) and Index of microcirculatory resistance (IMR) require hyperaemia to accurately assess thermodilution-derived mean transit times, and pressure derived collateral flow index (CFIp) is calculated from coronary wedge pressure and aortic pressure at hyperaemia. In addition, coronary flow velocity as assessed by a coronary Doppler flow wire needs appropriate induction of hyperaemia. However, the majority of this article will however focus on hyperaemia induction for pressure wire studies particularly FFR. Significant clinical decisions are made as a result of FFR readings, therefore it is imperative that they are carried out correctly. Maximal coronary hyperaemia is essential in producing accurate, reproducible measurements. This article focuses on the pharmacological agents that can be used for this purpose, discusses which agents can be used in specific situations, and briefly addresses the future of pharmacological stress in the catheter laboratory.