Incremental doses of intracoronary adenosine for the assessment of coronary velocity reserve for clinical decision making

Innervation of the coronary arteries and its role in controlling microvascular resistance

The coronary circulation plays a crucial role in balancing myocardial perfusion and oxygen demand to prevent myocardial ischemia. Extravascular compressive forces, coronary perfusion pressure, and microvascular resistance are involved to regulate coronary blood flow throughout the cardiac cycle. Autoregulation of the coronary blood flow through dynamic adjustment of microvascular resistance is maintained by complex interactions among mechanical, endothelial, metabolic, neural, and hormonal mechanisms. This review focuses on the neural mechanism. Anatomy and physiology of the coronary arterial innervation have been extensively investigated using animal models. However, findings in the animal heart have limited applicability to the human heart as cardiac innervation is generally highly variable among species. So far, limited data are available on the human coronary artery innervation, rendering multiple questions unresolved. Recently, the clinical entity of ischemia with non-obstructive coronary arteries has been proposed, characterized by microvascular dysfunction involving abnormal vasoconstriction and impaired vasodilation. Thus, measurement of microvascular resistance has become a standard diagnostic for patients without significant stenosis in the epicardial coronary arteries. Neural mechanism is likely to play a pivotal role, supported by the efficacy of cardiac sympathetic denervation to control symptoms in patients with angina. Therefore, understanding the coronary artery innervation and control of microvascular resistance of the human heart is increasingly important for cardiologists for diagnosis and to select appropriate therapeutic options. Advancement in this field can lead to innovations in diagnostic and therapeutic approaches for coronary artery diseases.

IMPROvE-CED Trial: Intracoronary Autologous CD34+ Cell Therapy for Treatment of Coronary Endothelial Dysfunction in Patients With Angina and Non-Obstructive Coronary Arteries

Background: Coronary endothelial dysfunction (CED) causes angina/ischemia in patients with no-obstructive CAD (NOCAD). Patients with CED have decreased number and function of CD34+ cells involved in normal vascular repair with microcirculatory regenerative potential and paracrine anti-inflammatory effects. We evaluated safety and potential efficacy of intracoronary (IC) autologous CD34+ cell therapy for CED.

Methods: Twenty NOCAD patients with invasively-diagnosed CED and persistent angina despite maximally-tolerated medical therapy (MTMT) underwent baseline exercise stress test (EST), GCSF-mediated CD34+ cell-mobilization, leukapheresis, and selective 1x105 CD34+ cells/kg infusion into LAD. Invasive CED evaluation and EST were repeated 6-months after cell infusion. Primary endpoints were safety and effect of IC autologous CD34+ cell therapy on CED at 6-months follow-up. Secondary endpoints were change in CCS angina class, as-needed sublingual nitroglycerin use/day, Seattle Angina Questionnaire (SAQ) scores, and exercise time at 6-months. Change in CED was compared to that of 51 historic-control NOCAD patients treated with MTMT alone.

Results: Mean age was 52{plus minus}13 years, 75% women. No death, myocardial infarction, or stroke occurred. IC CD34+ cell infusion improved microvascular CED [% acetylcholine-mediated coronary blood flow increased from 7.2 (-18.0-32.4) to 57.6 (16.3-98.3) %, p=0.014], decreased CCS angina class (3.7{plus minus}0.5 to 1.7{plus minus}0.9, Wilcoxon signed-rank test p=0.00018) and sublingual nitroglycerin use/day [1 (0.4-3.5) to 0 (0-1), Wilcoxon signed-rank test p=0.00047], and improved all SAQ scores with no significant change in exercise time at 6-months follow-up. Historic-control patients had no significant change in CED.

Conclusion: A single IC autologous CD34+ cell infusion was safe and may potentially be an effective disease-modifying therapy for microvascular CED in humans. Clinical Trial Registration: NCT03471611

Impact of increasing dose of intracoronary adenosine on peak hyperemia duration during fractional flow reserve assessment

BACKGROUND

Fractional Flow Reserve (FFR) is currently indicated as a first line strategy for the functional assessment of intermediate coronary stenoses. However, the protocol for inducing hyperemia still lacks standardization. Intracoronary adenosine boli, with a progressive increase to high-dosage, have been proposed as a sensitive and accurate strategy for the classification of coronary stenoses, although being potentially affected by the achievement of plateau of the effect and by a less prolonged and stable hyperemia as compared to intravenous administration. Therefore, the aim of the present study was to define the conditioning parameters and assess the impact of increasing-dose intracoronary adenosine on peak hyperemia duration in patients undergoing FFR for intermediate coronary stenoses.

METHODS

FFR was assessed in patients with intermediate (40 to 70%) lesions by pressure-recording guidewire (Prime Wire, Volcano), after induction of hyperemia with intracoronary boli of adenosine (from 60 to 1440 μg, with dose doubling at each step). Hyperemic duration was defined as the time for the variation form minimum FFR ± 0.02 and time to recovery till baseline values.

RESULTS

We included 87 patients, undergoing FFR evaluation of 101 lesions. Mean peak hyperemia duration and time to recovery significantly increased with adenosine doses escalation (p = 0.02 and p < 0.001). Peak hyperemia duration and time to recovery with 1440 μg adenosine were 14.5 ± 12.6 s and 45.2 ± 30.7 s, respectively. Hyperemia duration was not related to Quantitative Coronary Angiography (QCA) parameters or FFR values. In fact, a similar increase in the time of hyperemic peak was noted when comparing patients with positive or negative FFR (p_between = 0.87) or patients with lesions < or ≥20 mm (p_between = 0.92) and lesions involving left main coronary or proximal left anterior descending artery (LAD) (p_between = 0.07). A linear relationship was observed between time to recovery and FFR variations, with a greater time to baseline required in patients with FFR ≤ 0.80 (p = 0.003) and in lesions ≥ 20 mm (p = 0.006), but not in LAD/LM lesions (p = 0.55).

CONCLUSIONS

The present study shows a progressive raise in the duration of peak hyperemia and time to recovery, after the administration of increasing doses of intracoronary adenosine for the assessment of FFR. Therefore, considering the potential advantages of a high-dose adenosine protocol, allowing a more prolonged hyperemia and a more precise and reliable measurement of FFR, further larger studies with such FFR strategy should certainly be advocated to confirm its safety and benefits, before its routinely use recommendation.

Past, Present and Future of Coronary Physiology

It is well known that the apparent significant coronary stenosis on angiography sometimes does not cause significant ischemia, and vice versa. For this reason, decision-making based on coronary physiology is becoming more and more important. Fractional flow reserve (FFR), which has emerged as a useful tool to determine which lesions need revascularization in the catheterization laboratory, now has a class IA indication in the European Society of Cardiology guidelines. More recently, the instantaneous wave-free ratio, which is considered easier to use than FFR, has been graded as equivalent to FFR. This review discusses the concepts of FFR and instantaneous wave-free ratio, current evidence supporting their use, and future directions in coronary physiology.

Intracoronary Adenosine: Dose-Response Relationship With Hyperemia

OBJECTIVES

The present study sought to establish the dosage of intracoronary (IC) adenosine associated with minimal side effects and above which no further increase in flow can be expected.

BACKGROUND

Despite the widespread adoption of IC adenosine in clinical practice, no wide-ranging, dose-response study has been conducted. A recurring debate still exists regarding its optimal dose.

METHODS

In 30 patients, Doppler-derived flow velocity measurements were obtained in 10 right coronary arteries (RCAs) and 20 left coronary arteries (LCAs) free of stenoses >20% in diameter. Flow velocity was measured at baseline and after 8 ml bolus administrations of arterial blood, saline, contrast medium, and 9 escalating doses of adenosine (4 to 500 μg). The hyperemic value was expressed in percent of the maximum flow velocity reached in a given artery (Q/Qmax, %).

RESULTS

Q/Qmax did not increase significantly beyond dosages of 60 μg for the RCA and 160 μg for LCA. Heart rate did not change, whereas mean arterial blood pressure decreased by a maximum of 7% (p < 0.05) after bolus injections of IC adenosine. The incidence of transient A-V blocks was 40% after injection of 100 μg in the RCA and was 15% after injection of 200 μg in the LCA. The duration of the plateau reached 12 ± 13 s after injection of 100 μg in the RCA and 21 ± 6 s after the injection of 200 μg in the LCA. A progressive prolongation of the time needed to return to baseline was observed. Hyperemic response after injection of 8 ml of contrast medium reached 65 ± 36% of that achieved after injection of 200 μg of adenosine.

CONCLUSIONS

This wide-ranging, dose-response study indicates that an IC adenosine bolus injection of 100 μg in the RCA and 200 μg in the LCA induces maximum hyperemia while being associated with minimal side effects.

Clinical Relevance of Coronary Fractional Flow Reserve: Art-of-state

Objective:

The objective was to delineate the current knowledge of fractional flow reserve (FFR) in terms of definition, features, clinical applications, and pitfalls of measurement of FFR.

Data Sources:

We searched database for primary studies published in English. The database of National Library of Medicine (NLM), MEDLINE, and PubMed up to July 2014 was used to conduct a search using the keyword term “FFR”.

Study Selection:

The articles about the definition, features, clinical application, and pitfalls of measurement of FFR were identified, retrieved, and reviewed.

Results:

Coronary pressure-derived FFR rapidly assesses the hemodynamic significance of individual coronary artery lesions and can readily be performed in the catheterization laboratory. The use of FFR has been shown to effectively guide coronary revascularization procedures leading to improved patient outcomes.

Conclusions:

FFR is a valuable tool to determine the functional significance of coronary stenosis. It combines physiological and anatomical information, and can be followed immediately by percutaneous coronary intervention (PCI) if necessary. The technique of FFR measurement can be performed easily, rapidly, and safely in the catheterization laboratory. By systematic use of FFR in dubious stenosis and multi-vessel disease, PCI can be made an even more effective and better treatment than it is currently. The current clinical evidence for FFR should encourage cardiologists to use this tool in the catheterization laboratory.

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.

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.

Peri-procedural myocardial injury during percutaneous coronary intervention: an important target for cardioprotection

Percutaneous coronary intervention (PCI) has become the predominant procedure for coronary revascularization in patients with both stable and unstable coronary artery disease (CAD). Over the past two decades, technical advances in PCI have resulted in a better and safer therapeutic procedure with minimal procedural complications. However, about 30% of patients undergoing elective PCI sustain myocardial injury arising from the procedure itself, the extent of which is significant enough to carry prognostic importance. The peri-procedural injury which accompanies PCI might therefore reduce some of the beneficial effects of coronary revascularization. The availability of more sensitive serum biomarkers of myocardial injury such as creatine phosphokinase MB isoenzyme (CK-MB), Troponin T, and Troponin I has enabled the quantification of previously undetectable myocardial injury. Peri-procedural myocardial injury (PMI) can also be visualized by cardiac magnetic resonance imaging, a technique which allows the detection and quantification of myocardial necrosis following PCI. The identification of CAD patients at greatest risk of sustaining PMI during PCI would allow targeted treatment with novel therapies capable of limiting the extent of PMI or reducing the number of patients experiencing PMI.

Usefulness of the fractional flow reserve derived by intracoronary pressure wire for evaluating angiographically intermediate lesions in acute coronary syndrome

INTRODUCTION AND OBJECTIVES

In contrast to findings in stable ischemic heart disease, in acute coronary syndrome (ACS), measurement of the fractional flow reserve (FFR) using an intracoronary pressure wire has not been shown to be useful for evaluating angiographically equivocal coronary lesions. The aim of this study was to analyze outcomes at 1 year in ACS patients with lesions that were classed as intermediate on coronary angiography and which were not nonrevascularized because of the FFR value determined by intracoronary pressure wire.

METHODS

The observational study involved a cohort of patients admitted for ACS who had intermediate lesions on coronary angiography that were not revascularized because the FFR was >0.75. Functional studies were not carried out if there was angiographic evidence of instability. All-cause mortality, non-fatal myocardial infarction, revascularization of the target lesion and readmission for cardiac causes in the first year of the study were recorded.

RESULTS

The study included 106 patients with 127 lesions that were not revascularized because the FFR was >0.75. Their mean age was 69.9+/-10 years, 92 (86.8%) had non-ST-elevation ACS, the mean angiographic stenosis was 40.5+/-7.8%, and the mean FFR was 0.88+/-0.06. There were no complications during the procedure. The follow-up rate at 1 year was 95.1%. Events observed at 1 year were: 2 deaths (total mortality 1.9%), 0 fatal acute myocardial infarctions, 1 (0.9%) target lesion revascularization and 5 (4.7%) readmissions for cardiac causes.

CONCLUSIONS

Once lesions with clear angiographic signs of instability are excluded, intracoronary pressure wire measurement could be useful in ACS patients for avoiding unnecessary revascularization of angiographically intermediate coronary lesions.

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.

Evaluation of intermediate coronary stenosis with intravascular ultrasound and fractional flow reserve: Its use and abuse

Clinical decision making in patients with intermediate coronary stenosis is still debated. Intravascular ultrasound (IVUS) examination and/or functional assessment of coronary stenosis by fractional flow reserve (FFR) are currently used to define the severity of such lesions. There are very few studies with a small sample size that have a head-to-head comparison between IVUS and FFR in the evaluation of angiographically de novo intermediate lesions. There are no randomized, controlled trials to demonstrate the superiority of IVUS versus FFR in providing improved clinical outcomes in comparison with angiography alone. However, the issue of superiority might be irrelevant, because IVUS and FFR could be complementary techniques to be used in the catheterization laboratory to provide critical anatomic and functional data that permit more accurate decisions in the management of the patient.

Coronary circulation responses to binodenoson, a selective adenosine A2A receptor agonist

The purpose of this study was to define binodenoson dosing regimens that produce coronary hyperemia comparable to those of adenosine and that are tolerated well by patients. An open-label, randomized, parallel-group, multicenter study enrolled adult patients who had completed diagnostic cardiac catheterization. Coronary blood flow velocity (CBFV) was measured with a Doppler flow wire, and CBFV reserve was determined before binodenoson administration. Patients (n = 133) received a 3-minute infusion of 0.3, 0.5, or 1 microg/kg/min or a bolus intravenous injection of 1.5 or 3 microg/kg. Coronary hyperemic responses were evident within seconds of administering binodenoson, and the magnitudes and durations of coronary hyperemic responses were dose related. The 1.5- and 3-microg/kg doses, by infusion or bolus, produced maximal coronary hyperemia equivalent to CBFV reserve. All doses transiently decrease blood pressure and increased heart rate and rate-pressure product. In conclusion, the 1.5-microg/kg binodenoson bolus dose produced nearly maximal coronary hyperemia by 4.5 +/- 3.7 minutes that was sustained for 7.4 +/- 6.86 minutes, was accompanied by modest changes in blood pressure, heart rate, and rate-pressure product, and produced no adverse changes on electrocardiogram, including no second- or third-degree atrioventricular block.

Smoking is associated with epicardial coronary endothelial dysfunction and elevated white blood cell count in patients with chest pain and early coronary artery disease

BACKGROUND

Smoking is a major risk factor for cardiovascular events. One of the potential mechanisms may be related to both coronary endothelial dysfunction and increased inflammatory response. The present study was designed to test the hypothesis that smoking is associated with epicardial coronary endothelial dysfunction and inflammation.

METHODS AND RESULTS

Coronary endothelial function in response to acetylcholine was assessed in 881 patients (115 current smokers and 766 nonsmokers, including 314 previous smokers). Smokers were significantly younger than nonsmokers (43+/-1 versus 51+/-1 years, P<0.0001), had more epicardial vasoconstriction in response to intracoronary acetylcholine (-19+/-2% versus -14+/-1% change in coronary artery diameter, P=0.03), and were more likely than nonsmokers to have epicardial endothelial dysfunction (46% versus 35%, P=0.005), but their microvascular endothelial function was intact. Smokers had higher white blood cell counts than nonsmokers (7.7+/-0.2 versus 6.6+/-0.1x10(9)/L, P<0.0001), higher myeloperoxidase (156+/-19 versus 89+/-8 ng/mL), higher lipoprotein-associated phospholipase A2 (242+/-12 versus 215+/-5 ng/mL), and higher levels of intracellular adhesion molecule (283+/-14 versus 252+/-5 ng/mL). There were no differences in the levels of C-reactive protein, fibrinogen, or vascular cell adhesion molecule between the groups.

CONCLUSIONS

Young smokers are characterized by epicardial coronary endothelial dysfunction, preserved microvascular endothelial function, and increased levels of inflammatory biomarkers and oxidative stress. The present study provides further information regarding the potential mechanisms by which smoking contributes to cardiovascular events.

Assessment of intermediate severity coronary lesions in the catheterization laboratory

The management of intermediate coronary lesions, defined by a diameter stenosis of 40% to 70%, continues to be a therapeutic dilemma for cardiologists. The 2-dimensional representation of the arterial lesion provided by angiography is limited in distinguishing intermediate lesions that require stenting from those that simply need appropriate medical therapy. In the era of drug-eluting stents, some might propose that stenting all intermediate coronary lesions is an appropriate solution. However, the possibility of procedural complications such as coronary dissection, no reflow phenomenon, in-stent restenosis, and stent thrombosis requires accurate stratification of patients with intermediate coronary lesions to appropriate therapy. Intravascular ultrasound (IVUS) and fractional flow reserve index (FFR) provide anatomic and functional information that can be used in the catheterization laboratory to designate patients to the most appropriate therapy. The purpose of this review is to discuss the critical information obtained from IVUS and FFR in guiding treatment of patients with intermediate coronary lesions. In addition, the importance of IVUS and FFR in the management of patients with serial stenosis, bifurcation lesions, left main disease, saphenous vein graft disease, and acute coronary syndrome will be discussed.

Physiological assessment of coronary artery disease in the cardiac catheterization laboratory: a scientific statement from the American Heart Association Committee on Diagnostic and Interventional Cardiac Catheterization, Council on Clinical Cardiology

With advances in technology, the physiological assessment of coronary artery disease in patients in the catheterization laboratory has become increasingly important in both clinical and research applications, but this assessment has evolved without standard nomenclature or techniques of data acquisition and measurement. Some questions regarding the interpretation, application, and outcome related to the results also remain unanswered. Accordingly, this consensus statement was designed to provide the background and evidence about physiological measurements and to describe standard methods for data acquisition and interpretation. The most common uses and support data from numerous clinical studies for the physiological assessment of coronary artery disease in the cardiac catheterization laboratory are reviewed. The goal of this statement is to provide a logical approach to the use of coronary physiological measurements in the catheterization lab to assist both clinicians and investigators in improving patient care.

Women and cardiovascular heart disease: clinical implications from the Women's Ischemia Syndrome Evaluation (WISE) Study. Are we smarter?

Review of the trend in cardiovascular disease mortality for males and females clearly demonstrated that whereas the trend shows a decline in males this decline is not observed in females. Multiple important reports emerged from the initial phases of the Women's Ischemic Syndrome Evaluation (WISE) study that may have significant clinical implications for our approach to cardiovascular disease in women. The data derived from the WISE study certainly provided important information to our understanding of the approach to women with cardiovascular disease. The clinical presentation may be different, and a gender-oriented questionnaire may enhance our diagnosis. In a multivariable model, low hemoglobin was associated with significantly higher risk of adverse outcomes. The risk factor assessment and the risk factor profiles in women that are associated with coronary artery disease may be different. Based on the studies from the WISE study, metabolic syndrome is a leading and a major risk factor in women. Moreover, the data further support the concept that the mechanism of ischemia in women may be localized in the microvascular coronary arteries. Therefore, the diagnoses of coronary microvascular dysfunction or endothelial dysfunction should be considered in women with chest pain who do not have obstructive coronary artery disease. It may be advantageous to add such diagnostic tests when the conventional tests are nondiagnostic. A revised clinical approach to cardiovascular disease in women may be designed and tested based on these findings.

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.

Current concepts in coronary physiology for the interventionalist

Coronary angiography remains the 'gold standard' for the diagnosis of epicardial coronary disease. However, precise quantification of stenosis severity is limited because of the complex three-dimensional geometry of epicardial plaques. To assist the angiographer in lesion assessment, several physiologic measurements have been developed to evaluate stenosis severity, including coronary flow reserve, relative coronary flow reserve and fractional flow reserve. Physiologic lesion assessment can also be an invaluable tool in coronary intervention, evaluating efficacy of angioplasty and stent deployment.

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.

Noninvasive assessment of microvascular function in arterial hypertension by transthoracic Doppler harmonic echocardiography

OBJECTIVES

The present study sought to investigate the use of transthoracic Doppler harmonic echocardiography (TTDHE) to evaluate changes in coronary flow dynamics due to microvascular dysfunction.

BACKGROUND

Coronary flow velocity reserve (CFVR) measurements by TTDHE are useful for assessing epicardial coronary artery stenoses. It remains unclear, however, if microvascular disease can be detected.

METHODS

In 54 patients with chest pain, intracoronary Doppler (ICD) and TTDHE were used to measure average peak velocity at baseline and hyperemia. Significant coronary lesions had been ruled out by both angiography and intravascular ultrasound. Comparative measurements were performed in the distal left anterior descending coronary artery after intracoronary and intravenous administration of adenosine, and CFVR was calculated. Hypertensive patients (n = 25) were studied and compared to a control group (26 normotensive individuals).

RESULTS

Three patients (5%) had to be excluded because of insufficient image quality or side effects. In both groups, TTDHE-derived CFVR data correlated closely with ICD measurements (group 1: y = 0.67x + 0.076, standard error of estimate [SEE] = 0.25, r = 0.87, p < 0.001; group 2: y = 0.64x + 1.11, SEE = 0.26, r = 0.87, p < 0.001). CFVR was lower in hypertensives than in normotensive controls (2.44 +/- 0.49 vs. 3.33 +/- 0.40, p < 0.001, cut point = 2.84).

CONCLUSIONS

The newly described echocardiographic method is suitable for assessing microvascular dysfunction noninvasively and corresponds well to invasive measurements.