Comparison of intravenous adenosine to intracoronary papaverine for calculation of pressure-derived fractional flow reserve

Feasibility of intracoronary nicorandil for inducing hyperemia on fractional flow reserve measurement: Comparison with intracoronary papaverine

BACKGROUND

Adenosine and adenosine triphosphate (ATP) are widely used to induce hyperemia for fractional flow reserve (FFR) measurements. Caffeine attenuates their hyperemic effects, but not those of nicorandil and papaverine. No studies have systematically compared the hyperemic efficacies of nicorandil, papaverine, and ATP with and without caffeine abstention.

METHODS

FFRs were measured using nicorandil 2 mg (FFR_NC2), nicorandil 4 mg (FFR_NC4), and papaverine (FFR_PAP) in 40 patients (group 1), and using nicorandil 2 mg, ATP (FFR_ATP), ATP plus nicorandil (FFR_ATP+NC2), and papaverine in 20 patients with (group 2) and in 20 patients without caffeine abstention (group 3).

RESULTS

In group 1, FFR_NC2 and FFR_NC4 did not differ (p = 0.321) and were higher than FFR_PAP (p < 0.001 and p = 0.0026). Likewise, FFR_NC2 was higher than FFR_PAP in groups 2 (p = 0.049) and 3 (p < 0.010). In the whole group, Bland-Altman analysis showed a modest mean difference (0.015, p < 0.001) and narrow 95% limits of agreement (-0.025 and 0.056). FFR_NC2 and FFR_PAP strongly correlated (r = 0.975, p < 0.001). Compared with FFR_PAP, FFR_ATP and FFR_ATP+NC2 did not differ in group 2 (p = 1.0 and p = 0.780), but they were higher (p = 0.002 and p = 0.02) in group 3. Adjunctive nicorandil did not decline FFR further in groups 2 (p = 0.942) and 3 (p = 0.294).

CONCLUSIONS

Nicorandil 2 mg is a safe and practical alternative for patients who consume caffeine-containing products before the test or have contraindications for adenosine/ATP. Increasing the nicorandil dose to 4 mg or administering adjunctive nicorandil during ATP infusions does not offer any clinical advantages compared with administering nicorandil 2 mg alone.

Instantaneous wave-free ratio-guided paclitaxel-coated balloon treatment for de novo coronary lesions

Paclitaxel-coated balloon (PCB) treatment guided by fractional flow reserve (FFR) is safe and effective for de novo coronary lesions. It is unknown whether the instantaneous wave-free ratio (iFR), an alternative measure that does not require the administration of adenosine, will offer benefits similar to those of FFR in de novo lesion treatment with PCB. Baseline, post-balloon and 9-month angiographical parameters were obtained from 116 lesions of 104 patients. The cutoff value of iFR after balloon angioplasty used to define functionally nonsignificant residual stenotic lesions was 0.86 and they were subdivided into PCB or Stent group according to the treated device. The primary endpoint was late lumen loss at 9 months and the secondary endpoint was target vessel failure (TVF) at 3 years. Fifty-eight lesions were treated with PCB only and 58 lesions were treated with metal stent implantation. There were no differences in iFR between PCB and Stent groups at baseline (0.76 ± 0.19 vs. 0.73 ± 0.23, p = 0.630) and after procedure (0.93 ± 0.04 vs. 0.94 ± 0.05, p = 0.574). At 9 months, late lumen loss was significantly lower in PCB group compared with Stent group (0.04 ± 0.32 mm vs. 0.59 ± 0.77 mm, p = 0.001). At 3-year follow-up, TVF were not different between the treatment groups (5.2% vs. 8.6%, p = 0.453). PCB treatment guided by iFR measured right after balloon angioplasty is safe and effective for de novo coronary lesions with good angiographic results at 9 months and similar clinical outcomes at 3 years compared to stent group.

Fractional flow reserve (FFR) as a guide to treat coronary artery disease

INTRODUCTION

The presence and extent of myocardial ischemia are the major determinants of prognosis in patients with coronary artery disease (CAD). Unlike coronary angiography alone, fractional flow reserve (FFR) has enabled interventional cardiologists to accurately determine whether coronary atherosclerotic plaques are responsible for myocardial ischemia, and therefore deserve to be revascularized. Areas covered: An overview on the role of FFR in the diagnosis and treatment of coronary artery disease, as well as the potential related controversies is provided. Authors describe the coronary physiology underneath this technique and all the procedural aspects in the catheterization laboratory. The landmark trials and the current applications in different coronary lesions and syndromes are also described and potential future research involving FFR and comparisons with other methodologies for the evaluation of coronary physiology are introduced. Expert commentary: FFR is still unsurpassed in diagnostic performance when compared to non-hyperemic indices and noninvasive techniques, and remains the gold standard for the detection of ischemia-inducing coronary stenoses. FFR-guided PCI has been demonstrated superior to an angiography-guided PCI and over medical therapy alone, and ongoing investigation will clarify whether it could perform better, or at least equalize the results of cardiac surgery in patients with severe multivessel disease.

Resting Pd/Pa and haemodynamic relevance of coronary stenosis as evaluated by fractional flow reserve

BACKGROUND

Fractional flow reserve (FFR) currently represents the gold standard in the evaluation of the haemodynamic relevance of coronary stenoses. However, both intracoronary and intravenous adenosine may be tolerated poorly by some patients. Therefore, considerable interest had been focused in the last few years on new adenosine-free indexes to define the haemodynamic relevance of coronary stenoses. So far, few data have been reported on resting Pd/Pa and its correlation with FFR as evaluated with high-dose intracoronary adenosine administration, which is the aim of the current study.

MATERIALS AND METHODS

FFR was assessed in 120 patients with 137 intermediate lesions during cardiac catheterization by a pressure-recording guidewire (PrimeWire). FFR was calculated as the ratio of the distal coronary pressure to the aortic pressure at hyperaemia. Intracoronary doses of adenosine were administered up to 720 μg as intracoronary boli. Exclusion criteria were as follows: (a) allergy to adenosine; (b) baseline bradycardia (heart rate <50 bpm); (c) hypotension (blood pressure <90 mmHg); and (d) refusal to provide signed informed consent.

RESULTS

High doses of intracoronary adenosine were well tolerated, with no major side effects. Increasing doses up to 720 μg progressively decreased FFR values and increased the percentage of patients showing an FFR less than 0.80. Resting Pd/Pa showed good accuracy in the identification of patients with significant FFR values (<0.80) [area under the curve=0.9 (0.84-0.96), P<0.0001]. Using receiver-operating characteristic curves, we identified a threshold less than 0.93 as the best accurate cut-off value in the prediction of a positive FFR value. A value up to 0.88 was associated with a 100% positive predictive value, whereas a value of at least 0.95 was associated with a 95% negative predictive value.

CONCLUSION

This study showed that in intermediate lesions, resting Pd/Pa was related linearly to FFR. We identified 0.93 as the best cut-off value in the prediction of haemodynamically significant coronary stenosis as evaluated by FFR. However, cut-off values of 0.88 and 0.95 could provide the maximal predictive positive and negative values, suggesting the additional use of FFR only in patients with resting values within this range.

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.

[The diagnostic value of measuring the momentary blood flow reserve versus non-invasive methods to detect myocardial ischemia in assessing the functional significance of borderline coronary artery stenoses]

AIM

To estimate the diagnostic value of measuring the momentary blood flow reserve (MBFR) versus the surrogate non-invasive standard (SNS) for myocardial ischemia verification (MIV) (a combination of stress echocardiography and single-photon emission computed tomography).

SUBJECTS AND METHODS

The investigation enrolled 50 patients with stable angina in the presence of chronic coronary heart disease (CHD) or suspected CHD, in whom coronary angiography (CA) revealed borderline coronary stenoses (50-70% lumen diameters). The examination algorithm had two options. In one option, when included in the study, patients had already CA results not older than 1 month, and MBFR was measured 4-7 days after non-invasive stress tests. In the other option, MBFR in the area of borderline coronary artery stenosis was measured simultaneously with CA; and the noninvasive stress tests were carried out in the following week. A total of 74 coronary stenoses were examined.

RESULTS

SNS for MIV was positive in 14 (28%) patients. When comparing with the non-invasive methods of myocardial ischemia verification, the area under the ROC curve for MBFR was 0.961±0.019 (95% confidence interval, 0.888-0.992). The optimal cut-point was 0.92, which is corresponded by a sensitivity of 100% and a specificity of 84%.

CONCLUSION

When compared with SNS for MIV, the method for measuring MBFR has a high diagnostic accuracy.

Intracoronary adenosine-induced ventricular arrhythmias during fractional flow reserve (FFR) measurement: case series and literature review

Fractional flow reserve (FFR) is a standardized and well-established method frequently used in clinical practice to evaluate the hemodynamic significance of epicardial coronary stenosis identified by coronary angiography. It is based on the change in the pressure gradient across the stenosis after the achievement of maximal hyperemia of the coronary circulation which is commonly induced by intravenous (IV) or intracoronary (IC) administration of adenosine. Here, we have described three cases of IC adenosine-induced ventricular arrhythmias during FFR measurement from our institution, and after literature review we found that all the cases of ventricular arrhythmias induced by adenosine during FFR measurement were observed where it was administered via IC route. Although a causal relationship between the use of IC adenosine during FFR measurement and the induction of ventricular arrhythmias is not yet established, we suggest using IV adenosine as the preferred route of administration until we better understand the incidence and mechanism underlying this phenomenon.

Comparison of fractional flow reserve measurements using intracoronary adenosine versus intracoronary sodium nitroprusside infusions in moderately stenotic coronary artery lesions

INTRODUCTION

The aim of this study was to investigate the efficacy and safety of intracoronary (IC) sodium nitroprusside infusion in comparison to IC adenosine for fractional flow reserve (FFR) measurement in moderately diseased coronary artery lesions for functional assessment.

METHODS

During a nine month period, a consecutive of 98 patients with suspected or known coronary artery disease with moderate stenosis found during angiography (40% to 70% stenosis), were enrolled in this study. Hyperemia was induced by bolus doses of IC adenosine followed by sodium nitroprusside for FFR measurement.

RESULTS

Both IC adenosine and IC sodium nitroprusside induced similar and significant reduction in FFR. There was no statistically difference in FFR values between adenosine vs sodium nitroprusside infusions (mean FFR 84.3±6.3 vs 85.7±6.2, p=0.1) respectively. Furthermore, comparing different FFR cut-off points between the groups (FFR<0.75, 0.75-0.8 and >0.8) showed no significant differences (p value=0.7).

CONCLUSION

An IC bolus of sodium nitroprusside (0.6μg/kg) infusion induces a similar degree of hyperemia to IC bolus of 100-300μg of adenosine. Therefore, IC sodium nitroprusside could be considered as an alternative drug to adenosine for FFR measurement with lower side effect profile.

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.

Ventricular Fibrillation Precipitated by Intracoronary Adenosine During Fractional Flow Reserve Assessment - A Cautionary Tale

Fractional flow reserve (FFR) measurement is the current benchmark for assessing the physiologic significance of a coronary stenosis. Intravenous / intra-coronary adenosine is a commonly used agent to induce hyperaemia, required for FFR measurement. In our institute, we have observed three cases of ventricular fibrillation (VF) after intra-coronary adenosine injection. Volume of the injections appeared to be the responsible mechanism, supported by evidence from optical coherence tomography (OCT) experience. Since doubling the concentration of adenosine to reduce the volume of injection by half, no further incidence of VF has been noted.

Assessment of lower limb flow and adequate intra-arterial papaverine doses to achieve maximal hyperemia in elder subjects

Previous studies reported that invasive physiological assessment for significance of the lesions in the patients with claudication under the condition of pharmacological hyperemia was important to identify the patients who will benefit from revascularization. However, the maximal hyperemic response in lower limb and the method to induce maximum dilatation of vascular bed in lower limb were not well established. The aim of this study was to investigate the range of maximal hyperemic response in lower limb of the normal subjects and to identify the ideal lower limb vasodilatory stimulation. Twelve limbs without stenotic lesions from 12 subjects (average age: 72 ± 6 years) were analyzed. Thermodilution-derived mean transit time (Tmn) was obtained at baseline and during pharmacological hyperemia with incremental dose of intra-arterial papaverine (10, 20, 30, and 40 mg) using a 0.014-inch pressure/temperature sensor-tipped wire in the superficial femoral artery (SFA). Percent increase in blood flow (%IBF) of lower limb was defined as the ratio between baseline Tmn and hyperemic Tmn. Mean ankle brachial index score of the subjects was 1.14 ± 0.09. The %IBF values were enhanced by papaverine in a dose-dependent manner. A dose of 30 mg of intra-arterial papaverine was sufficient to achieve maximum hyperemia (%IBF: range 219-769 %). In conclusion, the increase in blood flow of lower limb during maximal hyperemia varied between individuals and maximal hyperemia can be achieved with 30 mg of papaverine for the SFA lesion.

ST elevation after intracoronary administration of Papaverine for fractional flow reserve estimation

INTRODUCTION

Intracoronary (IC) papaverine which is one of the commonly used agents for Fractional Flow Reserve (FFR) estimation has been reported to cause transient ST elevation in some patients. This phenomenon has not been systematically studied.

MATERIAL AND METHODS

This is a prospective, observational study. Consecutive patients, who underwent FFR at our institute using IC papaverine from May 2012 to April 2013, were included. FFR was done when clinically indicated. The procedure involved administration of 20 mg papaverine (Paparin)--Troikaa, Ahmedabad) as a fast bolus by intracoronary route followed by a 10 cc contrast flush, following which pressure measurements were made. Continuous ECG recording by Philips Hemodynamic Laboratory was obtained for all patients throughout the procedure. Post procedure, they were observed for any delayed effects and eventual outcome was documented. Fischer's mid-p test was used for statistical analysis.

RESULT

Twenty-five patients (18 males, 7 females, mean age 57.9 ± 20 years) underwent FFR using Papaverine. The mean LVEF was (51 ± 15%). Fourteen patients (56%) developed transient ST elevation ≥0.5 mm in one or more leads which resolved spontaneously in all cases without any sequelae. The presence of a significant lesion either in the coronary artery being evaluated or in a remote coronary artery did not predict the ST elevation. 70.5% of diabetics (p = 0.02), 75% of hypertensives (p = 0.008) and 75% of patients with LVH (p = 0.008) had ST elevation. None of the 5 patients without any one of these comorbidities showed ST elevation.

CONCLUSION

Transient ST elevation occurs in a significant proportion of cases receiving IC papaverine which is not associated with any adverse clinical outcomes. Micro vascular dysfunction is the most likely mechanism of this phenomenon.

Hemodynamic response to intravenous adenosine and its effect on fractional flow reserve assessment: results of the Adenosine for the Functional Evaluation of Coronary Stenosis Severity (AFFECTS) study

BACKGROUND

We studied the hemodynamic response to intravenous adenosine on calculation of fractional flow reserve (FFR). Intravenous adenosine is widely used to achieve conditions of stable hyperemia for measurement of FFR. However, intravenous adenosine affects both systemic and coronary vascular beds differentially.

METHODS AND RESULTS

A total of 283 patients (310 coronary stenoses) underwent coronary angiography with FFR using intravenous adenosine 140 mcg/kg per minute via a central femoral vein. Offline analysis was performed to calculate aortic (Pa), distal intracoronary (Pd), and reservoir (Pr) pressure at baseline, peak, and stable hyperemia. Seven different hemodynamic patterns were observed according to Pa and Pd change at peak and stable hyperemia. The average time from baseline to stable hyperemia was 68.2±38.5 seconds, when both ΔPa and ΔPd were decreased (ΔPa, -10.2±10.5 mm Hg; ΔPd, -18.2±10.8 mm Hg; P<0.001 for both). The fall in Pa closely correlated with the reduction in peripheral Pr (ΔPr, -12.9±15.7 mm Hg; P<0.001; r=0.9; P<0.001). ΔPa and ΔPd were closely related under conditions of peak (r=0.75; P<0.001) and stable hyperemia (r=0.83; P<0.001). On average, 56% (10.2 mm Hg) of the reduction in Pd was because of fall in Pa. FFR lesion classification changed in 9% using an FFR threshold of ≤0.80 and 5.2% with FFR threshold <0.75 when comparing Pd/Pa at peak and stable hyperemia.

CONCLUSIONS

Intravenous adenosine results in variable changes in systemic blood pressure, which can lead to alterations in FFR lesion classification. Attention is required to ensure FFR is measured under conditions of stable hyperemia, although the FFR value at this point may be numerically higher.

Comparison of hyperemic efficacy between central and peripheral venous adenosine infusion for fractional flow reserve measurement

BACKGROUND

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.

METHODS AND RESULTS

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.

CONCLUSIONS

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.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01070420.

Clinical utility of regadenoson for assessing fractional flow reserve

OBJECTIVES

The aim of this study was to evaluate the efficacy of regadenoson, in comparison with adenosine, for assessing fractional flow reserve (FFR) of intermediate coronary artery stenoses (CAS).

BACKGROUND

Fractional flow reserve is an established invasive method for assessing the physiological significance of CAS. Regadenoson, a selective A(2A) receptor agonist, is an approved hyperemic agent for pharmacological stress imaging, but its role for measuring FFR is unknown.

METHODS

This prospective, single-center study enrolled 25 consecutive patients with intermediate CAS discovered during elective angiography (25 lesions). In each patient, FFR of the CAS was measured first by IV adenosine (140 μg/kg/min), followed by IV regadenoson (400 μg bolus). The intrapatient FFR correlation between adenosine and regadenoson was evaluated.

RESULTS

The mean age was 63 ± 11 years, and mean left ventricular ejection fraction was 58 ± 11%. Most patients were male (52%) and had hypertension (84%) and dyslipidemia (84%), with 24% having diabetes mellitus and 20% chronic obstructive pulmonary disease. The CAS was visually estimated during angiography (mean 58 ± 9%) and most often found in the left anterior descending coronary artery (48%). A strong, linear correlation of FFR was noted with adenosine and regadenoson (r = 0.985, p < 0.001). A hemodynamically significant lesion (FFR ≤ 0.80) was present in 52% with no reclassification of significance between adenosine and regadenoson. No serious events occurred with administration of either drug.

CONCLUSIONS

Our results suggest that a single IV bolus of regadenoson is as effective as an intravenous infusion of adenosine for measuring FFR and, given its ease of use, should be considered for FFR measurement in the catheterization laboratory.

Effects of increasing doses of intracoronary adenosine on the assessment of fractional flow reserve

OBJECTIVES

The purpose of this study was to investigate the effects of increasing dose of intracoronary adenosine on fractional flow reserve (FFR) measurement.

BACKGROUNDS

FFR is a validated method for the assessment of the severity of coronary artery stenosis. It is based on the change in the pressure gradient across the stenosis after the achievement of maximal hyperemia of the coronary microcirculation that may be obtained by either intracoronary bolus or intravenous infusion of adenosine. No study has explored so far the effects of very high doses of intracoronary adenosine on FFR.

METHODS

FFR was assessed in 46 patients with 50 intermediate lesions during cardiac catheterization by pressure-recording guidewire (PrimeWire, Volcano, San Diego, California). FFR was calculated as the ratio of the distal coronary pressure to the aortic pressure at hyperemia. Increasing doses of adenosine were administrated (60, 120, 180, 360, and 720 μg) as intracoronary boluses. Exclusion criteria were: 1) allergy to adenosine; 2) baseline bradycardia (heart rate <50 beats/min); 3) hypotension (blood pressure <90 mm Hg); and 4) refusal to provide signed informed consent.

RESULTS

High doses of intracoronary adenosine were well tolerated, with no major side effects. Increasing doses up to 720 μg progressively decreased FFR values and increased the percentage of patients showing an FFR <0.75. Among angiographic parameters, both percent stenosis and lesion length were independently associated with lower FFR values.

CONCLUSIONS

This study shows that high doses of intracoronary adenosine (up to 720 μg) increased the sensitivity of FFR in the detection of hemodynamically relevant coronary stenoses. Furthermore, lesion length and stenosis severity were independent angiographic determinants of FFR.

Comparison of the intracoronary continuous infusion method using a microcatheter and the intravenous continuous adenosine infusion method for inducing maximal hyperemia for fractional flow reserve measurement

BACKGROUND

Inducing stable maximal coronary hyperemia is essential for measurement of fractional flow reserve (FFR). We evaluated the efficacy of the intracoronary (IC) continuous adenosine infusion method via a microcatheter for inducing maximal coronary hyperemia.

METHODS

In 43 patients with 44 intermediate coronary lesions, FFR was measured consecutively by IC bolus adenosine injection (48-80 microg in left coronary artery, 36-60 microg in the right coronary artery) and a standard intravenous (IV) adenosine infusion (140 microg x min(-1) x kg(-1)). After completion of the IV infusion method, the tip of an IC microcatheter (Progreat Microcatheter System, Terumo, Japan) was positioned at the coronary ostium, and FFR was measured with increasing IC continuous adenosine infusion rates from 60 to 360 microg/min via the microcatheter.

RESULTS

Fractional flow reserve decreased with increasing IC adenosine infusion rates, and no further decrease was observed after 300 microg/min. All patients were well tolerated during the procedures. Fractional flow reserves measured by IC adenosine infusion with 180, 240, 300, and 360 microg/min were significantly lower than those by IV infusion (P < .05). Intracoronary infusion at 180, 240, 300, and 360 microg/min was able to shorten the times to induction of optimal and steady-stable hyperemia compared to IV infusion (P < .05). Functional significances were changed in 5 lesions by IC infusion at 240 to 360 microg/min but not by IV infusion.

CONCLUSIONS

The results of this study suggest that an IC adenosine continuous infusion method via a microcatheter is safe and effective in inducing steady-state hyperemia and more potent and quicker in inducing optimal hyperemia than the standard IV infusion method.

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.

Intracoronary Continuous Adenosine Infusion A Novel and Effective Way of Inducing Maximal Hyperemia for Fractional Flow Reserve Measurement

BACKGROUND

Various methods are used to induce maximal hyperemia for physiologic studies, but the feasibility and efficacy of continuous intracoronary (IC) infusion of adenosine for measurement of fractional flow reserve (FFR) has not been well-defined.

METHODS AND RESULTS

Patients with intermediate coronary artery stenosis were consecutively enrolled. In the phase I study, FFR was measured after 3 dosages of IC adenosine infusion (180, 240 and 300 microg/min) in 30 patients. The phase II study was performed to compare the hyperemic efficacy of IC infusion (240 microg/min) with IC bolus injection (40, 80 microg) and intravenous (IV) infusion (140 microg x kg (-1) x min(-1)) of adenosine in 20 patients. In the phase I study, no significant differences in FFR were observed with the 3 different doses of IC infusion (p = 0.06). In the phase II study, FFR after an IC bolus injection (0.83+/-0.06) was significantly higher than with IV (0.79+/-0.07) or IC (0.78+/-0.09) infusion (p < 0.01). However, no difference in FFR was observed for IC and IV infusions.

CONCLUSION

IC infusion of adenosine seems to be a safe and effective method of inducing maximal hyperemia for FFR measurement.

Are high doses of intracoronary adenosine an alternative to standard intravenous adenosine for the assessment of fractional flow reserve?

BACKGROUND

Achievement of maximal hyperemia of the coronary microcirculation is a prerequisite for the measurement of fractional flow reserve (FFR). Intravenous adenosine is considered the standard method, but its use in the catheterization laboratory is time consuming and expensive compared with intracoronary adenosine. Therefore, this study compared different high, intracoronary doses of adenosine for the potential to achieve a maximal hyperemia equivalent to the standard intravenous route.

METHODS

FFR was assessed in 50 patients with 50 intermediate lesions during cardiac catheterization. FFR was calculated as the ratio of the distal coronary pressure to the aortic pressure at hyperemia. Different incremental doses of intracoronary adenosine (60, 90, 120, and 150 microg as boli) and a standard intravenous infusion of 140 microg/kg/min were administered in a randomized fashion.

RESULTS

Different incremental doses of intracoronary adenosine were well tolerated, with fewer systemic adverse effects than intravenous adenosine. At baseline, there were no significant differences for mean aortic and distal coronary pressure or heart rate in the different adenosine doses and routes. FFR decreased with increasing adenosine doses, with the lowest values observed with the 150-microg intracoronary bolus and 140-microg/kg/min dose of intravenous adenosine. All intracoronary doses, except the 150-microg bolus, resulted in mean FFR values that were significantly (P <.05) higher than FFR after the administration intravenous adenosine. Furthermore, 5 patients (10%) with a FFR value >0.75 and 3 subjects (6%) with a FFR value >0.80 who received a 60-microg intracoronary bolus reached a value below the cutoff point of 0.75 with the intravenous administration.

CONCLUSIONS

This study suggests a dose-response relationship on hyperemia for intracoronary adenosine doses >60 microg. The administration of very high intracoronary adenosine boli is safe and associated with fewer systemic adverse effects than standard intravenous adenosine. However, intravenous adenosine administration with 140 microg/kg/min produced a more pronounced hyperemia than intracoronary adenosine in most patients and should be the preferred mode of application for the assessment of FFR.

Role of incremental doses of intracoronary adenosine for fractional flow reserve assessment

BACKGROUND

The achievement of maximal vasodilatation of the coronary microvessels is mandatory for the accurate determination of fractional flow reserve (FFR); the optimal dosing to achieve maximal vasodilation is unclear. This study was designed to address the hypothesis that incremental doses of intracoronary adenosine are necessary to ensure complete vasodilatation of the coronary microcirculation and accurate assessment of FFR. We also examined the relationship between FFR and coronary artery disease risk factors.

METHODS

A total of 191 patients (215 vessels) with intermediate coronary lesions were examined. FFR was measured during cardiac catheterization with a pressure monitoring wire. Incremental doses of intracoronary adenosine (12-42 microg, left coronary artery; 12-48 microg, right coronary artery) were administered.

RESULTS

Diabetes mellitus was present in 23% of patients, hypertension was present in 65% of patients, and prior myocardial infarction had occurred in 25% of patients. The average percent stenosis in vessels was 57% +/- 15%. Vessels were subdivided on the basis of initial FFR (group 1, <0.75; group II, 0.75-0.79; group III, 0.80-0.89; group IV, >or=0.9). Five of the 24 (21%) vessels with an initial FFR in the 0.75 to 0.80 range had a subsequent FFR of <0.75. There was no difference in FFR or doses of adenosine in the patients with coronary artery disease risk factors. The average adenosine dose given at the achievement of minimal FFR was 26 microg in the right coronary artery (RCA) and 34 microg in the left coronary artery (LCA). The average maximum dose of intracoronary adenosine administered was 29 microg for the RCA and 37 microg for the LCA. The maximum dose of adenosine ever required to achieve minimum FFR was 42 microg in both the LCA and RCA.

CONCLUSION

This study suggests that a single high dose of 42 microg of intracoronary adenosine for both the RCA and LCA is sufficient to achieve maximum hyperemia and accurate FFR in most patients, independent of risk factors. Alternatively, when a lower initial dose is administered and FFR is in the 0.75 to 0.90 range, incremental doses of adenosine should be administered to ensure maximal hyperemia.

Intracoronary and intravenous adenosine 5'-triphosphate, adenosine, papaverine, and contrast medium to assess fractional flow reserve in humans

BACKGROUND

Inducing both maximal and steady-state coronary hyperemia is of clinical importance to take full advantage of fractional flow reserve measurements. The present study compares different dosages and routes of administration of adenosine 5'-triphosphate (ATP), adenosine, contrast medium, and papaverine regarding their potential to achieve both maximal and steady-state hyperemia.

METHODS AND RESULTS

In 21 patients with an isolated coronary stenosis, coronary vasodilation was induced successively by papaverine (20 mg intracoronary), adenosine (20 and 40 microg intracoronary), ATP (20 and 40 microg intracoronary), iohexol (6 mL intracoronary), adenosine or ATP through an antecubital vein (140 and 180 microg x kg(-1) x min(-1)), or adenosine or ATP through a femoral vein (140 and 180 microg x kg(-1) x min(-1)). Because vessel dimensions did not change, the ratio of distal coronary pressure (Pd) to aortic pressure (Pa) was used as an index of myocardial resistance. Pd/Pa was 0.77+/-0.21 at rest and decreased to 0.61+/-0.21 after papaverine. Pd/Pa decreased to a similar level with all other vasodilators, except with contrast medium (0.68+/-0.21; P<0.01 versus papaverine). Steady-state hyperemia could only be obtained by intracoronary papaverine and by intravenous ATP or adenosine. In another 23 patients, an intravenous infusion of ATP was varied from 0 to 280 microg x kg(-1) x min(-1). At doses >140 microg x kg(-1) x min(-1), there was neither a further decrease in Pd/Pa ratio nor a further increase in coronary flow velocities.

CONCLUSIONS

Provided sufficient dosages are used, ATP, adenosine, and papaverine (but not contrast medium) induce maximal hyperemia and are therefore suitable to assess fractional flow reserve. Only intracoronary papaverine and intravenous ATP or adenosine induce steady-state hyperemia enabling a pressure pullback maneuver that is useful in assessing diffuse coronary atherosclerosis.

Value of fractional flow reserve in making decisions about bypass surgery for equivocal left main coronary artery disease

OBJECTIVE

To investigate the value of coronary pressure derived fractional flow reserve (FFR) measurements in supporting decisions about medical or surgical treatment in patients with angiographically equivocal left main coronary artery stenosis.

DESIGN

A two centre prospective single cohort follow up study.

INTERVENTIONS

FFR of the left main coronary artery was determined in 54 consecutive patients with angiographically equivocal left main coronary artery disease. If FFR was >/= 0.75, medical treatment was chosen; if FFR was < 0.75, surgical treatment was chosen.

MAIN OUTCOME MEASURES

Freedom from death, myocardial infarction, or any coronary revascularisation procedure.

RESULTS

In 24 patients (44%), FFR was >/= 0.75 and medical treatment was chosen (medical group). In the remaining 30 patients (56%), FFR was < 0.75 and bypass surgery was performed (surgical group). Mean (SD) follow up was 29 (15) months (range 12-65 months). Survival among patients at three years of follow up was 100% in the medical group and 97% in the surgical group. Event-free survival was 76% in the medical group and 83% in the surgical group.

CONCLUSIONS

FFR supports decision making in equivocal left main coronary artery disease. If FFR is below 0.75, the decision for bypass surgery is supported. If FFR is above 0.75, a conservative approach is justified.

Noninvasive assessment of coronary flow reserve in the right gastroepiploic artery graft

BACKGROUND

To investigate the functional capacity of the right gastroepiploic artery graft (GEA) and its ability to adapt to provide adequate flow at peak myocardial demand, we investigated the feasibility of determining coronary flow reserve (CFR) provided by this vessel using transabdominal color Doppler echocardiography and the correlation between this noninvasive determination of flow reserve and nuclear stress scintigraphy.

METHODS

In 40 selected patients, who underwent complete arterial myocardial revascularization using the GEA and the internal thoracic arteries (ITAs), CFR of the GEA was measured at maximum coronary hyperemia induced by intravenous adenosine infusion, 7 months (range 3 to 20) after surgery. In the same period, in 31 of this group of patients, exercise thallium scintigraphy was performed.

RESULTS

We succeeded in measuring CFR in 37 of 40 patients with values ranging from 1.1 to 3.6 with an average of 2.1 +/- 0.7. During adenosine infusion, mean velocity in the GEA significantly increased from 48 +/- 20 to 89 +/- 41 cm/sec (p < 0.001), mean arterial blood pressure significantly decreased from 96 +/- 11 to 87 +/- 11 mm Hg (p < 0.001), and heart rate significantly increased from 74 +/- 11 to 87 +/- 15 beats/min (p < 0.001). In 8 of these 37 patients, the nuclear exercise test was positive (compatible with reversible ischemia in the distribution area of the GEA). Average CFR in these 8 patients with positive nuclear stress test was 1.46 +/- 0.28 versus 2.27 +/- 0.70 in those patients with a negative test (p < 0.001).

CONCLUSIONS

Noninvasive determination of CFR of GEAs is feasible, using transabdominal Doppler echocardiography. The present study shows that coronary vasodilator reserve and autoregulation is maintained in myocardium supplied by the GEA and that the CFR has a significant correlation with the results of noninvasive nuclear exercise testing. Therefore, noninvasive determination of CFR by transabdominal Doppler echocardiography might be a valuable contribution to functional assessment of GEAs.

Intermediate coronary artery stenosis: evidence-based decisions in interventions to avoid the oculostenotic reflex

The prevalence of intermediate coronary artery stenosis (defined as a diameter stenosis of 40% to 70%) is quite large in patients undergoing PTCA. The coronary angiogram is considered the 'gold standard' for the definition of coronary anatomy, in spite of various limitations associated with its use. In recent years, sensor tipped guidewire based methods of physiologic assessment of stenosis severity, like myocardial fractional flow reserve, and poststenotic coronary flow reserve had established their role in the decision making in catheterization laboratory. The decision making should combine morphologic and physiologic assessment as better evidence based approach in guiding therapy to avoid the 'oculostenotic reflex'.

Effects of intravenous and intracoronary adenosine 5'-triphosphate as compared with adenosine on coronary flow and pressure dynamics

BACKGROUND

Measurements of Doppler derived coronary flow reserve (CFR) and pressure derived fractional flow reserve (FFR) for coronary stenosis assessment depend on the induction of maximal hyperemia. Adenosine is the most widely used pharmacological agent but is expensive and poorly tolerated by some patients.

METHODS AND RESULTS

The objective of this study was to test the equivalency of adenosine 5'-triphosphate (ATP) to adenosine in their ability to cause maximal hyperemia as compared with the hyperemic response of complete coronary occlusion in 6 canines. Intracoronary administration of either ATP or adenosine resulted in a significant increase in CFR (2.79+/-0.64 and 2.22+/-0.7 for 10 microgram versus 4. 65+/-1.22 and 4.25+/-0.78 for 100 microgram for ATP and adenosine, respectively, P for trend <0.001) but not reaching the level of coronary occlusion (6.35+/-2.26). Additionally, FFR and CFR were measured in 35 different stenoses using ATP, adenosine, and coronary occlusion. There was an excellent linear correlation between ATP and adenosine for both CFR (R=0.934, P<0.001) and FFR (R=0.985, P<0.001). However, hyperemia with either ATP or adenosine was less than postocclusion hyperemia, resulting in significantly different reserve measurements (CFR: 1.93+/-0.66 and 2.08+/-0.81 versus 2.35+/-0.97, P<0.001; FFR: 0.62+/-0.24 and 0.63+/-0.23 versus 0.58+/-0.2, P<0.001).

CONCLUSIONS

1) Step up in dosage of ATP and adenosine beyond currently recommended clinical doses resulted in a significant increase in coronary hyperemia; 2) ATP was equivalent to adenosine for both CFR and FFR; and 3) complete coronary occlusion yielded a better hyperemic response than either drug, indicating that maximal hyperemia was not achieved by either pharmacological stimulus.

Practice and potential pitfalls of coronary pressure measurement

Guidewire-based coronary pressure measurement has emerged over the last years as a promising approach in the invasive assessment of coronary artery disease. It enables calculation of fractional flow reserve (FFR) which closely relates distal coronary pressure to myocardial blood flow during maximal arteriolar vasodilation. Coronary pressure measurement and FFR provide important information, both for decision making in diagnostic angiography and for monitoring and evaluating coronary interventions. In this review, the practical set-up of coronary pressure measurement in the catheterization laboratory is discussed step-by-step, special attention is given to potential pitfalls and how to avoid them, and the interpretation of coronary pressure measurement in a variety of pathologic conditions is clarified. Cathet. Cardiovasc. Intervent. 49:1-16, 2000.

Clinical potential of intravascular ultrasound for physiological assessment of coronary stenosis: relationship between quantitative ultrasound tomography and pressure-derived fractional flow reserve

BACKGROUND

Little is known regarding intravascular ultrasound (IVUS) criteria to determine the functional severity of coronary stenosis. Recently, fractional flow reserve (FFR) has emerged as a lesion-specific index of the functional severity of a coronary stenosis that is independent of systemic hemodynamic variability. The present study was undertaken to determine the IVUS parameters for the physiological severity of coronary stenosis.

METHODS AND RESULTS

Fifty-one lesions in 42 patients were evaluated by means of quantitative coronary angiogram, IVUS, and intracoronary pressure measurements. The FFR was calculated as the ratio of the distal coronary pressure divided by the proximal coronary pressure under hyperemia. We considered a value of the FFR <0.75 as significant in determining inducible ischemia, according to the previous studies. The minimal luminal area (MLA) and the area stenosis were measured by IVUS. By regression analysis, the MLA showed a positive correlation with the FFR value (r(2)=0.62, P<0.0001). The area stenosis had a significant inverse correlation with the value of FFR (r(2)=0.60, P<0.0001). The IVUS thresholds that maximized the sensitivity and specificity were MLA <3.0 mm(2) (sensitivity, 83.0%; specificity, 92.3%) and area stenosis >0.6 (sensitivity, 92.0%; specificity, 88.5%). The combination of both criteria (MLA <3.0 mm(2) and area stenosis <0.6) without exception met a value of the FFR <0.75.

CONCLUSIONS

Anatomic parameters obtained by IVUS showed a significant correlation to the FFR values. The present study demonstrated that the combination of the MLA and area stenosis measured by IVUS can be an anatomic predictor for the physiological impact of coronary epicardial stenosis.

Effects of dobutamine on coronary stenosis physiology and morphology: comparison with intracoronary adenosine

BACKGROUND

The mechanisms leading to dobutamine-induced ischemia are not fully understood. In the present study, we investigated the effects of high-dose intravenous dobutamine on morphological and physiological indexes of coronary stenoses.

METHODS AND RESULTS

Twenty-two patients with normal left ventricular function and isolated coronary stenoses were studied. At catheterization, mean aortic pressure (P(a)), mean distal coronary pressure (P(d)), and P(d)/P(a) as an index of myocardial resistance were recorded at rest, after intracoronary adenosine, and during intravenous infusion of dobutamine (10 to 40 micrograms . kg(-1). min(-1)). Reference vessel diameter and minimal luminal diameter, as assessed by coronary angiography, did not change during dobutamine infusion compared with baseline (2.84+/-0.49 versus 2.77+/-0.41 mm and 1.35+/-0.38 versus 1. 27+/-0.31 mm, respectively; both P=NS). During peak dobutamine infusion, P(d) and P(d)/P(a) reached similar levels as during adenosine infusion (60+/-18 versus 59+/-18 mm Hg and 0.68+/-0.18 versus 0.68+/-0.17, respectively; all P=NS). In 9 patients, an additional bolus of intracoronary adenosine given at the peak dose of dobutamine failed to further decrease P(d)/P(a). Furthermore, in patients with dobutamine-induced wall motion abnormalities, the maximal decrease in P(d)/P(a) was similar during dobutamine and adenosine infusions.

CONCLUSIONS

High-dose intravenous infusion of dobutamine does not modify the dimensions of the epicardial coronary stenosis. However, much like the direct coronary vasodilator adenosine, dobutamine fully exhausts myocardial resistance regardless of the presence of mechanical dysfunction.

Long-term follow-up after deferral of percutaneous transluminal coronary angioplasty of intermediate stenosis on the basis of coronary pressure measurement

OBJECTIVES

This study sought to determine the safety of deferral of percutaneous transluminal coronary angioplasty (PTCA) of angiographically intermediate but functionally nonsignificant stenosis, as assessed by coronary pressure measurement and myocardial fractional flow reserve (FFRmyo).

BACKGROUND

Decision making in patients with chest pain and intermediate coronary stenosis remains difficult. In these cases it is unclear whether the risk of an intervention and the potentially subsequent restenosis outweigh the future risk of an event if the lesion remains untreated. FFRmyo is a lesion-specific functional index of epicardial stenosis severity that accurately distinguishes stenoses associated with inducible ischemia.

METHODS

Retrospective analysis and follow-up was performed in 100 consecutive patients referred to our centers for PTCA of an intermediate stenosis but in whom the planned intervention was deferred on the basis of an FFRmyo > or = 0.75.

RESULTS

During a follow-up period of 18+/-13 months (mean +/- SD, range 3 to 42), two patients died of noncardiac causes. Ninety patients remained free of any coronary events, and their average Canadian Cardiovascular Society class decreased from 2.0+/-1.2 at baseline to 0.7+/-0.9 at follow-up (p < 0.0001). A coronary event occurred in eight patients and was target-vessel related in four.

CONCLUSIONS

In patients with chest pain referred for PTCA of an intermediate stenosis, deferral of the intervention on the basis of an FFRmyo > or = 0.75 is safe and is associated with a much lower clinical event rate than if the procedure had been performed as initially planned in these patients.

[Methods for coronary functional assessment]

Functional evaluation of coronary vasomotion encompasses the assessment of dynamic changes in coronary lumen, vessel wall, blood flow, intracoronary pressure and myocardial perfusion in response to specific pharmacologic stimuli. These parameters are obtained to characterize mechanisms of physiologic regulation and to evaluate pathophysiologic processes and potential therapeutic strategies, especially with regard to the development of coronary atherosclerosis. To this end, a variety of direct (invasive) and indirect (non-invasive) diagnostic tools are employed. Among the invasive methods are registration of intracoronary Doppler flow, coronary pressure measurements, quantitative coronary angiography and intravascular ultrasound. The non-invasive modalities consist of coronary Doppler echocardiography, positron emission tomography, myocardial scintigraphy and magnetic resonance imaging. Because of the different technical and physiological principles involved, these methods are complementary by providing independent access to different aspects. The combined invasive functional testing as employed in the cardiac catheterization laboratory allows for a simultaneous synopsis of high-resolution coronary imaging and direct measurement of physiologic parameters during local application of defined pharmacologically active substances. However, the demands in terms of equipment, time and operator skills are high and limit this combined invasive approach to specialized centers. Besides these research purposes, a number of functional methods has entered the clinical arena. They are employed to evaluate the hemodynamic significance of coronary lesions and to assess functional outcome of therapeutic interventions in the catheterization laboratory. The underlying principles and applications of the different methods are described and an overview of selected results is presented.

Clinical assessment of functional stenosis severity: use of coronary pressure measurements for the decision to bypass a lesion

BACKGROUND

In the selection of patients eligible for minimally invasive coronary artery bypass grafting (MICABG), knowledge about the pathophysiologic significance of individual coronary stenoses is important. Only if the lesion amenable to MICABG can be identified as the culprit lesion, and other lesions can be demonstrated not to be responsible for reversible ischemia, will MICABG be an appropriate procedure.

METHODS

By simultaneous measurement of mean aortic pressure and transstenotic coronary pressure, a pathophysiologic index can be obtained that specifically indicates the influence of an epicardial coronary stenosis on maximum achievable blood flow of the supplied myocardial territory. This index is called myocardial fractional flow reserve (FFR(myo)).

RESULTS

Myocardial fractional flow reserve is a reliable, lesion-specific index for determining whether a particular stenosis is responsible for reversible myocardial ischemia. If FFR(myo) is less than 0.75, revascularization is indicated, whereas if FFR(myo) is greater than 0.75, revascularization usually is not warranted. Moreover, in contrast to classic coronary flow or flow velocity reserve, FFR(myo) is independent of changes in heart rate, blood pressure, and contractility, and also accounts for the contribution of collaterals.

CONCLUSIONS

Pressure-derived FFR(myo) is an accurate pathophysiologic index for reliable identification of functionally significant epicardial lesions and can be obtained easily and quickly during routine cardiac catheterization. Therefore, FFR(myo) facilitates clinical decision-making with respect to the appropriateness of MICABG.