Coronary Hyperemic Dose Responses of Intracoronary Sodium Nitroprusside

An unusual no-reflow phenomenon due to neointimal tissue embolization during drug eluting balloon intervention in stent restenosis: A case report

Acute coronary syndrome is one of the leading causes of death worldwide. Percutaneous coronary intervention (PCI), along with various devices, have been technically developed to dramatically improve mortality risk in patients with acute myocardial infarction. However, no-reflow phenomenon still remains a problematic complication during a PCI, even in the era of drug eluting stents. There are various hypotheses and mechanisms for no-reflow phenomenon, but none have been confirmed. Treatment for no-reflow phenomenon also depends on various underlying conditions, but have not yet shown effective improvement. We presented a case of no-reflow phenomenon caused by an unusual cause.

“No-Reflow” Phenomenon: A Contemporary Review

Primary percutaneous angioplasty (pPCI), represents the reperfusion strategy of choice for patients with STEMI according to current international guidelines of the European Society of Cardiology. Coronary no-reflow is characterized by angiographic evidence of slow or no anterograde epicardial flow, resulting in inadequate myocardial perfusion in the absence of evidence of mechanical vessel obstruction. No reflow (NR) is related to a functional and structural alteration of the coronary microcirculation and we can list four main pathophysiological mechanisms: distal atherothrombotic embolization, ischemic damage, reperfusion injury, and individual susceptibility to microvascular damage. This review will provide a contemporary overview of the pathogenesis, diagnosis, and treatment of NR.

Comparison of efficacy and safety of intracoronary nicardipine and adenosine for fractional flow reserve assessment of coronary stenosis

BACKGROUND

Administration of intracoronary (IC) adenosine allows an easily feasible, inexpensive, and more rapid alternative method for fractional flow reserve (FFR). It is common practice in many centers worldwide. Nicardipine is a strong coronary vasodilator but its efficacy and safety for assessing FFR is not established. The purpose of present study was to compare the efficacy and safety of IC nicardipine and adenosine for assessing FFR.

METHODS

One hundred and fifty-nine patients with a total of 193 vessels undergoing clinically indicated FFR assessment of intermediate coronary stenoses were included. For the initial assessment of FFR, hyperemia was induced by an IC adenosine. After a washout period of 3 min, FFR was reassessed using 200 μg of IC nicardipine.

RESULTS

Hyperemic efficacy among two different stimuli was compared. The mean FFR with IC adenosine was 0.83 ± 0.09 and that with an IC nicardipine was 0.84 ± 0.09. The median FFR with an IC adenosine was 0.83 (0.78-0.91) and that with an IC nicardipine was 0.85 (0.79-0.91) (p-value 0.246). Both FFR values showed an excellent correlation (R² = 0.982, p < 0.001). Nicardipine produced fewer changes in heart rate, less chest pain and less flushing than adenosine. Transient atrioventricular block occurred in 29 patients with IC adenosine and none with IC nicardipine.

CONCLUSIONS

IC bolus injection of nicardipine could be introduced as a safe and practical alternative method of inducing hyperemia during FFR measurements. Compared to IC adenosine, IC nicardipine has a similar hyperemic efficacy and excellent side-effect profile.

Pathophysiology, Diagnosis, and Management of Coronary No-Reflow Phenomenon

Coronary no-reflow phenomenon is a lethal mechanism of ongoing myocardial injury following successful revascularization of an infarct-related coronary artery. Incidence of this phenomenon is high following percutaneous intervention and is associated with adverse in-hospital and long-term outcomes. Several mechanisms such as ischemia-reperfusion injury and distal microthromboembolism in genetically susceptible patients and those with preexisting endothelial dysfunction have been implicated. However, the exact mechanism in humans is still poorly understood. Several investigative and treatment strategies within and outside the cardiac catheterization laboratory have been proposed, but they have not uniformly shown success in reducing mortality or in preventing adverse left ventricular remodeling resulting from this condition. The aim of this article is to provide a brief and concise review of the current understanding of the pathophysiology, clinical predictors, and investigations and management of coronary no-reflow phenomenon.

Research progress on the molecular mechanism of coronary microvascular endothelial cell dysfunction

Coronary microvascular disease is a high-risk factor for many cardiovascular events. However, due to its high concealment and many etiologies, the current understanding of its pathophysiological mechanism is very limited, which greatly limits its clinical diagnosis and treatment. In the process of the occurrence and development of coronary microvascular disease, the damage of coronary microvascular endothelial cell (CMEC) is the core link. CMEC's stress, metabolism, inflammation and other dysfunctions have a causal relationship with coronary microvascular disease, and are also the main features of coronary microvascular disease in the early stage. This article mainly reviews the molecular mechanisms of CMEC damage.

Pathophysiology, Diagnosis, and Management of Coronary No-Reflow Phenomenon

Coronary no-reflow phenomenon is a lethal mechanism of ongoing myocardial injury, following successful revascularization of an infarct-related coronary artery. Incidence of this phenomenon is high following percutaneous intervention, and is associated with adverse in-hospital and long-term outcomes. Several mechanisms such as ischemia-reperfusion injury and distal microthromboembolism in genetically susceptible patients and those with preexisting endothelial dysfunction have been implicated. However, the exact mechanism in humans is still poorly understood. Several investigative and treatment strategies within and outside the cardiac catheterization laboratory have been proposed, but have not uniformly shown success in reducing mortality or in preventing adverse left ventricular remodeling resulting from this condition. The aim of this article is to provide a brief and concise review of the current understanding of the pathophysiology, clinical predictors, and investigations and management of coronary no-reflow phenomenon.

Safety and efficacy of intracoronary sodium nitroprusside for the assessment of coronary fractional flow reserve

Background

Coronary fractional flow reserve (FFR) determination is a valuable tool for the assessment of stenosis significance in intermediate coronary obstructions. Maximal hyperemia is mandatory for this determination. Although intravenous (IV) Adenosine is the standard agent used, its use carries an elevated incidence of side effects. Intracoronary sodium nitroprusside (IC NTP) is a very well-known coronary vasodilator, but it is not routinely used for FFR determinations.

Objectives

The purpose of the present study was to compare FFR determinations and side effect profile of IC NTP with IV Adenosine.

Methods

We prospectively assessed FFR determinations in a total of 20 intermediate coronary artery stenotic lesions in 18 consecutive patients with the administration of IV Adenosine (140 μg/kg/min) and IC NTP (100 μg). The appearance of side effects was registered.

Results

The mean age was 55.5 ± 7.5 years. Fifteen (83%) of the patients were male. Mean FFR values with IC NTP were similar to those obtained with IV Adenosine (0.82 ± 0.07 vs 0.82 ± 0.06, respectively, r = 0.775, p < 0.0001). Intravenous Adenosine induced side effects in 45% of patients (shortness of breath 30%, flushing 5%, headache 5%, angina pectoris 5%, and transient conduction disturbances 10%). No side effects were reported with IC NTP.

Conclusions

IC NTP at a dose of 100 μg is as effective as IV Adenosine for FFR assessment. Besides, it is better tolerated and should be consider as a vasodilator agent in the assessment of FFR.

Comparison of sodium nitroprusside and adenosine for fractional flow reserve assessment: a systematic review and meta-analysis

BACKGROUND

Fractional flow reserve (FFR) has become a useful tool in the assessment of physiological significance of coronary artery stenosis (CAS), and Adenosine (ADE) is associated with a high incidence of transient side effects. Sodium nitroprusside (NPS) has been proposed as an alternative vasodilator agent. A meta-analysis of studies comparing ADE and NPS for FFR assessment in the same coronary lesions was performed.

METHODS

Authors searched for articles comparing NPS and ADE for FFR assessment in intermediate coronary lesions published through January 2018. The following keywords were used: 'fractional flow reserve' AND 'nitroprusside'. Data were summarized using weighted mean differences for paired data.

RESULTS

Seven studies were identified comprising 342 patients and 401 lesions. Four studies evaluated intravenous ADE and 3 studies intracoronary ADE administration. Weighted means FFR values obtained with ADE and NPS were 0.8411 and 0.8445, respectively (weighted mean difference: 0.00, 95% confidence interval (CI) -0.01 to 0.01, p = 0,548). Adverse events were significantly reduced with IC NPS (RR = 0.08, 95%CI 0.02-0.30, P < 0.0001).

CONCLUSIONS

NPS produces similar FFR measurements compared to ADE with a significant reduction in adverse effects. These results may support its use as a suitable alternative to ADE for FFR assessment.

Advances in Coronary No-Reflow Phenomenon-a Contemporary Review

PURPOSE OF REVIEW

Coronary artery no-reflow phenomenon is an incidental outcome of percutaneous coronary intervention in patients presenting with acute myocardial infarction. Despite advances in pharmacologic and non-pharmacologic therapies, coronary no-reflow phenomenon occurs more commonly than desired. It often results in poor clinical outcomes and remains as a relevant consideration in the cardiac catheterization laboratory. In this systematic review, we have sought to discuss the topic in detail, and to relay the most recent discoveries and data on management of this condition.

RECENT FINDINGS

We discuss several pharmacologic and non-pharmacologic treatments used in the prevention and management of coronary no-reflow and microvascular obstruction. Covered topics include the understanding of pharmacologic mechanisms of current and future agents, and recent discoveries that may result in the development of future treatment options. We conclude that the pathophysiology of coronary no-reflow phenomenon and microvascular obstruction still remains incompletely understood, although several plausible theories have led to the current standard of care for its management. We also conclude that coronary no-reflow phenomenon and microvascular obstruction must be recognized as a multifactorial condition that has certain predispositions and characteristics, therefore its prevention and treatment must begin pre-procedurally and be multi-faceted including certain medications and operator techniques in the cardiac catheterization laboratory.

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.

Management of No-Reflow Phenomenon in the Catheterization Laboratory

At the conclusion of a primary percutaneous coronary intervention for ST-segment elevation myocardial infarction, and after the cardiologist makes certain that there is no residual stenosis following stenting, assessment of coronary flow becomes the top priority. The presence of no-reflow is a serious prognostic sign. No-reflow can result in poor healing of the infarct and adverse left ventricular remodeling, increasing the risk for major adverse cardiac events, including congestive heart failure and death. To achieve normal flow, features associated with a high incidence of no-reflow must be anticipated, and measures must be undertaken to prevent its occurrence. In this review, the authors discuss various preventive strategies for no-reflow as well as pharmacological and nonpharmacological interventions that improve coronary blood flow, such as intracoronary adenosine and nitroprusside. Nonpharmacological therapies, such as induced hypothermia, were successful in animal studies, but their effectiveness in reducing no-reflow in humans remains to be determined.

Comparison of regadenoson and nitroprusside to adenosine for measurement of fractional flow reserve: A systematic review and meta-analysis

BACKGROUND

FFR is useful in defining the physiological significance of intermediate coronary stenosis and requires induction of maximal hyperemia and measurement of pressure proximal and distal to the stenosis. Hyperemia normally is induced by either IV or IC adenosine, a medication associated with short-term side effects. IV regadenoson and IC nitroprusside have been suggested as viable alternatives. This meta-analysis aims to identify all studies comparing use of intravenous (IV) regadenoson or intracoronary (IC) nitroprusside with IV adenosine to determine differences related to the agent utilized for assessment of fractional flow reserve (FFR).

METHODS

We searched PubMed, EMBASE, Web of Science, SCOPUS, ClinicalTrials.gov and the Cochrane Library databases for studies comparing IV regadenoson or IC nitroprusside to IV adenosine for FFR assessment. The main outcome was difference in mean FFR measurement. The main secondary outcomes were composite side-effect profile and reclassification of lesions.

RESULTS

Seven studies were included in the analysis, with a total of 375 patients. Compared to IV adenosine, there was no difference in the mean FFR derived from IV regadenoson (p=1.0) or IC nitroprusside (p=0.48). IV regadenoson was associated with 53% lower risk of pooled side effects compared to IV adenosine (p=0.05). IC nitroprusside was associated with 97% lower risk of pooled side effects compared to IV adenosine (p<0.001).

CONCLUSIONS

IV regadenoson and IC nitroprusside produce similar pressure-derived FFR measurements compared to IV adenosine and have a favorable side effect profile. Both can be considered as alternative agents to IV adenosine for FFR measurement. Further clinical validation is warranted.

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.

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.

History and Development of Coronary Flow Reserve and Fractional Flow Reserve for Clinical Applications

We discuss the historical development of clinical coronary physiology, emphasizing coronary flow reserve (CFR) and fractional flow reserve (FFR). Our analysis focuses on the clinical motivations and technologic advances that prompted and enabled the application of physiology for patient diagnosis. CFR grew from the general concepts of physiologic and coronary reserve, linking the anatomic severity of a lesion to its impact on hyperemic flow. FFR developed from existing models relating pressure measurements to the potential for flow to increase after removing a stenosis. Because pressure measurements have proved easier and more robust than flow measurements, FFR has become the dominant metric.

Fractional flow reserve in acute coronary syndromes: A review

Fractional flow reserve (FFR) assessment provides anatomical and physiological information that is often used to tailor treatment strategies in coronary artery disease. Whilst robust data validates FFR use in stable ischaemic heart disease, its use in acute coronary syndromes (ACS) is less well investigated. We critically review the current data surrounding FFR use across the spectrum of ACS including culprit and non-culprit artery analysis. With adenosine being conventionally used to induce maximal hyperaemia during FFR assessment, co-existent clinical conditions may preclude its use during acute myocardial infarction. Therefore, we include a current review of instantaneous wave free ratio as a novel vasodilator independent method of assessing lesion severity as an alternative strategy to guide revascularisation in ACS.

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Small studies support the use of FFR in non-culprit vessels during ACS.

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FFR demonstrates diagnostic accuracy and reproducibility in AMI, particularly in intermediate lesions.

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Microvascular dysfunction observed from earlier work does not appear to hinder FFR calculation, but further studies are required for validation.

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Vasodilator independent assessment of coronary stenoses has some preliminary data supporting its use in non culprit arteries during ACS, but ongoing trial results are awaited regarding clinical outcomes.

Feasibility and safety of intracoronary nicorandil infusion as a novel hyperemic agent for fractional flow reserve measurements

Fractional flow reserve (FFR) is a useful modality to assess the functional significance of coronary stenoses. Although adenosine triphosphate (ATP) is generally used as the hyperemic stimulus, we sometimes encounter adverse events like hypotension during FFR measurement. Nicorandil, an ATP-sensitive potassium channel opener, recognized as an epicardial and resistance vessel dilator, has not been fully evaluated as a possible alternative hyperemic agent. The aim of this study was to evaluate the feasibility and safety of intracoronary nicorandil infusion compared to intravenous ATP for FFR measurement in patients with coronary artery disease. A total of 102 patients with 124 intermediate lesions (diameter stenosis >40 and <70% by visual assessment) were enrolled. All vessels underwent FFR measurements with both ATP (150 μg/kg/min) and nicorandil (2.0 mg) stimulus. FFR, hemodynamic values, and periprocedural adverse events between the two groups were evaluated. A strong correlation was observed between FFR with ATP and FFR with nicorandil (r = 0.954, p < 0.001). The agreement between the two sets of measurements was also high, with a mean difference of 0.01 ± 0.03. The mean aortic pressure drop during pharmacological stimulus was significantly larger with ATP compared to nicorandil (9.6 ± 9.6 vs. 5.5 ± 5.8 mmHg, p < 0.001). During FFR measurement, transient atrioventricular block was frequently observed with ATP compared to nicorandil (4.0 vs. 0%, p = 0.024). This study suggests that intracoronary nicorandil infusion is associated with clinical utility and safety compared to ATP as an alternative hyperemic agent for FFR measurement.

Spontaneous and procedural plaque embolisation in native coronary arteries: pathophysiology, diagnosis, and prevention

The detachment of atherothrombotic material from the atherosclerotic coronary plaque and downstream embolisation is an underrecognized phenomenon and it causes different degrees of impairment of the coronary microcirculation. During treatment of obstructive atherosclerotic plaque by percutaneous coronary intervention (PCI) distal embolisation (DE) is considered to be inevitable and it is associated with potential clinical and prognostic implications. This review aims to assess the main aspects of both spontaneous and procedural DE, analyze their different pathophysiology, provide specific insights on the main diagnostic tools for their identification, and finally focus on the main strategies for their treatment and prevention.

Use of regadenoson for measurement of fractional flow reserve

OBJECTIVE

To compare the use of regadenoson to adenosine for measurement of fractional flow reserve (FFR).

BACKGROUND

FFR is an accepted method to assess the functional significance of intermediate coronary artery stenoses and uses adenosine to induce maximal hyperemia. The use of the selective A2a receptor agonist regadenoson for FFR is not established.

METHODS

Fifty-seven patients undergoing clinically indicated FFR assessment of intermediate coronary stenoses were included. For the initial assessment of FFR, hyperemia was achieved by a standard intravenous adenosine infusion (140 mcg/kg/min). After a washout period of 10 min, FFR was reassessed using regadenoson as a single 0.4 mg intravenous bolus. FFR measurements were recorded at baseline and following maximal hyperemia with both agents.

RESULTS

Mean age was 57 ± 8 years and 47 were male. Sixty coronary lesions were evaluated and were located in the left anterior descending in 34, the left circumflex in 9, right coronary in 15, and left main coronary artery in 2. Mean ( ± SD) FFR following adenosine and regadenoson was 0.79 ( ± 0.09) and 0.79 (±0.09), respectively, P = NS. Time to FFR nadir was shorter with regadenoson compared to adenosine, 36.6 ± 24 versus 66 ± 0.19 sec, P < 0.0001, respectively. No patients experienced any significant side effects related to regadenoson.

CONCLUSIONS

Regadenoson is a viable alternative to intravenous adenosine for achieving maximal hyperemia during FFR assessment. Compared to adenosine, regadenoson has a similar hemodynamic response, achieves more rapid hyperemia, is easier to use, and has an excellent side-effect profile.

Intracoronary fixed dose of nitroprusside via thrombus aspiration catheter for the prevention of the no-reflow phenomenon following primary percutaneous coronary intervention in acute myocardial infarction

Previous studies have shown that intracoronary (IC) nitroprusside (NTP) injection is a safe and effective strategy for the treatment of no-reflow (NR) during percutaneous coronary intervention (PCI). The present study tested the hypothesis that, on the basis of thrombus aspiration for the treatment of ST-segment elevation myocardial infarction (STEMI), the selective IC administration of a fixed dose of NTP (100 μg) plus tirofiban is a safe and superior treatment method compared with the IC administration of tirofiban alone for the prevention of NR during primary PCI. A total of 162 consecutive patients with STEMI, who underwent primary PCI within 12 h of onset, were randomly assigned to two groups: Group A, IC administration of a fixed dose of NTP (100 μg) plus tirofiban (10 μg/kg) and group B, IC administration of tirofiban (10 μg/kg) alone (n=80 and n=82, respectively). The drugs were selectively injected into the infarct-related artery (IRA) via a thrombus aspiration catheter advanced into the IRA. The primary end-point was post-procedural corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC). The proportion of complete (>70%) ST-segment resolution (STR); the TIMI myocardial perfusion grade (TMPG) 2–3 ratio following PCI; the peak value of creatine kinase (CK)-MB; the TIMI flow grade; the incidence of major adverse cardiac events (MACEs) and the left ventricular ejection fraction (LVEF) after 6 months of follow-up were observed as the secondary end-points. There were no significant differences in the baseline clinical and angiographic characteristics between the two groups. Compared with group B, group A had i) a lower CTFC (23±7 versus 29±11, P=0.000); ii) a higher proportion of complete STR (72.5 versus 55.9%, P=0.040); iii) an enhanced TMPG 2–3 ratio (71.3 versus 53.7%, P=0.030) and iv) a lower peak CK-MB value (170±56 versus 210±48 U/l, P=0.010). There were no statistically significant differences in the final TIMI grade-3 flow between the two groups (92.5 versus 91.5% for groups A and B, respectively; P=0.956). The LVEF at 6 months was higher in group A than group B (63±9 versus 53±11%, respectively; P=0.001); however, the incidence of MACEs was not statistically different between the two groups, although there was a trend indicating improvement in group A (log rank χ²=0.953, P=0.489). The selective IC administration of a fixed dose of NTP (100 μg) plus tirofiban via a thrombus aspiration catheter advanced into the IRA is a safe and superior treatment method compared with tirofiban alone in patients with STEMI undergoing primary PCI. This novel therapeutic strategy improves the myocardial level perfusion, in addition to reducing the infarct size. Furthermore, it may improve the postoperative clinical prognosis following PCI.

Coronary pressure-derived fractional flow reserve in the assessment of coronary artery stenoses

OBJECTIVES

Catheter-based angiography is the reference-standard to establish coronary anatomy. While routinely employed clinically, lumen assessment correlates poorly with physiological measures of ischaemia. Moreover, functional studies to identify and localise ischaemia before elective angiography are often not available. This article reviews fractional flow reserve (FFR) and its role in guiding patient management for patients with a potentially haemodynamic significant coronary lesion.

METHODS

This review discusses the theory, evidence, indications, and limitations of FFR. Also included are emerging non-invasive imaging FFR surrogates currently under evaluation for accuracy with respect to standard FFR.

RESULTS

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

CONCLUSIONS

FFR is an invaluable modality in guiding coronary disease treatment decisions. It is safe, cost-effective and leads to improved patient outcomes. Non-invasive imaging modalities to assess the physiologic significance of CAD are currently being  developed and evaluated.

Comparison of efficacy and safety of intracoronary sodium nitroprusside and intravenous adenosine for assessing fractional flow reserve

OBJECTIVES

The purpose of this study was to compare the efficacy and safety of intracoronary (IC) nitroprusside and intravenous adenosine (IVA) for assessing fractional flow reserve (FFR).

BACKGROUND

IV infusion of adenosine is a standard method to achieve a coronary hyperemia for FFR measurement. However, adenosine is expensive, causes multiple side effects, and is contraindicated in patients with reactive airway disease. Sodium nitroprusside (NTP) is a strong coronary vasodilator but its efficacy and safety for assessing FFR is not well established.

METHODS

We compared FFR response and side effects profile of IC NTP and IVA. Bolus of NTP at a dose of 100 μg and IVA (140 μg/kg/min) were used to achieve coronary hyperemia.

RESULTS

We evaluated 75 lesions in 53 patients (60% male) mean age 61.6 ± 13.9 years. Mean FFR after NTP was similar to FFR after adenosine (0.836 ± 0.107 vs. 0.856 ± 0.106; P = 0.26; r = 0.91, P < 0.001). NTP induced maximal stable hyperemia within 10 sec (mean: 6.4 ± 1) which lasted consistently between 38 and 60 sec (mean 51 ± 7.5). NTP caused significant (14%), but asymptomatic decrease in mean blood pressure which returned to baseline within 60 sec. Adenosine caused shortness of breath in 26%, headache and flushing in 19%, and transient second degree heart block in 6% of patients. No adverse symptoms were reported after NTP.

CONCLUSIONS

IC NTP is as effective as IVA for measuring FFR. NTP is better tolerated by patients. Since NTP is inexpensive, readily available, well tolerated, and safe, it may be a better choice for FFR assessment.

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.

Peri-interventional coronary vasomotion

A percutaneous coronary intervention (PCI) is a unique condition to study the effects of ischemia and reperfusion in patients with severe coronary atherosclerosis when coronary vasomotor function is compromised by loss of endothelial and autoregulatory vasodilation. We studied the effects of intracoronary non-selective α-, as well as selective α(1)- and α(2)-blockade in counteracting the observed vasoconstriction in patients with stable and unstable angina and in patients with acute myocardial infarction. Coronary vasoconstriction in our studies was a diffuse phenomenon and involved not only the culprit lesion but also vessels with angiographically not visible plaques. Post-PCI vasoconstriction was reflected by increased coronary vascular resistance and associated with decreased LV-function. α (1)-Blockade with urapidil dilated epicardial coronary arteries, improved coronary flow reserve and counteracted LV dysfunction. Non-selective α-blockade with phentolamine induced epicardial and microvascular dilation, while selective α(2)-blockade with yohimbine had only minor vasodilator and functional effects. Intracoronary α-blockade also attenuated the no-reflow phenomenon following primary PCI. This article is part of a Special Issue entitled "Coronary Blood Flow".

Management of the no-reflow phenomenon

The lack of reperfusion of myocardium after prolonged ischaemia that may occur despite opening of the infarct-related artery is termed "no reflow". No reflow or slow flow occurs in 3-4% of all percutaneous coronary interventions, and is most common after emergency revascularization for acute myocardial infarction. In this setting no reflow is reported to occur in 30% to 40% of interventions when defined by myocardial perfusion techniques such as myocardial contrast echocardiography. No reflow is clinically important as it is independently associated with increased occurrence of malignant arrhythmias, cardiac failure, as well as in-hospital and long-term mortality. Previously the no-reflow phenomenon has been difficult to treat effectively, but recent advances in the understanding of the pathophysiology of no reflow have led to several novel treatment strategies. These include prophylactic use of vasodilator therapies, mechanical devices, ischaemic postconditioning and potent platelet inhibitors. As no reflow is a multifactorial process, a combination of these treatments is more likely to be effective than any of these alone. In this review we discuss the pathophysiology of no reflow and present the numerous recent advances in therapy for this important clinical problem.

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.

Efficacy of intracoronary nicardipine in the treatment of no-reflow during percutaneous coronary intervention

OBJECTIVES

The goal of this study was to evaluate the safety and efficacy of nicardipine in reversing no-reflow during percutaneous coronary intervention (PCI).

BACKGROUND

No-reflow is a common complication of PCI in patients with acute coronary syndromes or venous bypass graft disease. Although nicardipine has an attractive pharmacological profile and has been used clinically to treat no-reflow, there is a paucity of published data regarding its effectiveness in this setting.

METHODS

We conducted a retrospective analysis of 72 consecutive patients who received intracoronary nicardipine to reverse no-reflow during coronary intervention. Qualitative TIMI flow grade and quantitative TIMI frame count methods were used to assess the efficacy of nicardipine.

RESULTS

A mean of 460 +/- 360 mcg of intracoronary nicardipine was used. No-reflow was successfully reversed with complete restoration of TIMI 3 flow in 71 of 72 patients (98.6%). TIMI flow grade improved from 1.65 +/- 0.53 prior to nicardipine to 2.97 +/- 0.24 after treatment (P < 0.001). TIMI frame count decreased from 57 +/- 40 at the time of no-reflow to 15 +/- 12 after nicardipine administration (P < 0.001). Nicardipine therapy was well tolerated without adverse hemodynamic or chronotropic effects.

CONCLUSIONS

In this largest series to date, intracoronary nicardipine was demonstrated to be a safe and highly effective pharmacological agent to reverse no-reflow during PCI.

Frequency of slow coronary flow following successful stent implantation and effect of Nitroprusside

Nitroprusside (NTP) is used for the treatment of slow coronary flow (SCF) after coronary interventions. The wide variation in dosage, route, and timing of its administration in the reported studies prevents an objective assessment of its efficacy. We report the incidence and response to a standardized NTP protocol of SCF after successful stent implantation. Selective intracoronary administration of incremental doses (initial bolus of 80 microg incremented by 40 microg) of NPT was assessed in 21 patients who developed SCF in a series of 2,212 consecutive patients who underwent successful stent placement from January to October 2005. SCF was observed only in patients treated for acute myocardial infarction (AMI; 11.5%, 12 of 105) or saphenous vein graft (SVG) stenosis (8.2%, 9 of 109). An intracoronary bolus of nitroglycerin did not restore normal Thrombolysis In Myocardial Infarction (TIMI) flow in any patient. The first 80-microg dose of NTP restored normal TIMI flow in 58% of patients (7 of 12) with AMI and in 44% of patients (4 of 9)with SVG stenosis. The maximal dose (120/160 microg) restored normal TIMI flow in all remaining patients with AMI but in only 1 additional patient with SVG stenosis. At the end of the procedure, the percent decrease in corrected TIMI frame count was significantly larger in patients with AMI (-44+/-10%) than in those with SVG stenosis (-24+/-16%, p=0.02). In a large consecutive series of successful stent procedures, SCF was found only in patients with ST-elevation AMI (11.5%) or with a stenosed SVG (8.2%). In conclusion, the standardized protocol of intracoronary NTP administration succeeded in normalizing SCF in all patients with AMI but in only 5 of 9 patients with SVG stenosis. This latter subgroup requires other therapeutic strategies.

Selective Intracoronary Administration of Nitroprusside Before Balloon Dilatation Prevents Slow Reflow During Percutaneous Coronary Intervention in Patients With Acute Myocardial Infarction

BACKGROUND

Previous studies have shown that intracoronary nitroprusside injection is safe and effective after slow reflow complicates percutaneous coronary intervention (PCI).

OBJECTIVES

We sought to determine the safety and efficacy of selective intracoronary administration of nitroprusside through the drug delivery catheter before balloon dilatation to prevent no or slow reflow during PCI for acute myocardial infarction (AMI).

METHODS

We studied 120 consecutive patients with AMI treated by PCI. In 60 patients (nitroprusside group), nitroprusside (120 mug) was selectively administered through the drug delivery catheter into the distal coronary artery to reach the target lesion before balloon dilatation. Clinical and angiographic data, as well as in-hospital outcomes, of the nitroprusside group were retrospectively compared with 60 patients who had conventional PCI without nitroprusside (control group).

RESULTS

There were no significant differences in the baseline clinical and angiographic characteristics between the 2 groups. Compared to the control group, the nitroprusside group had 1) less slow reflow during the procedure (12% versus 35%, P = 0.0025), 2) a shorter fluoroscopic time (14.4 +/- 7.9 versus 18.7 +/- 9.1 minutes, P = 0.0093), 3) a shorter procedure time (57.6 +/- 20.6 versus 78.1 +/- 26.4, P < minutes, P < 0.0001), 4) a better final TIMI flow grade (III:II:I:0 = 59:1:0:0 versus 53:6:1:0, P = 0.0284), 5) a better blush grade (III:II:I:0 = 49:10:1:0 versus 33:15:8:4, P = 0.0006), and 6) a better corrected TIMI coronary flame count (30.8 +/- 13.7 versus 46.5 +/- 44.7, P = 0.0102). There were no particular complications with nitroprusside use.

CONCLUSIONS

The selective intracoronary administration of nitroprusside prior to PCI is safe and well tolerated, prevents no or slow reflows, and improves reperfusion of the infarcted myocardium.

Intracoronary nitroprusside for the prevention of the no-reflow phenomenon after primary percutaneous coronary intervention in acute myocardial infarction. A randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

The aim of this study was to test whether nitroprusside (NTP) injected intracoronary immediately before primary angioplasty for acute ST-elevation acute myocardial infarction (STEMI) prevents no-reflow and improves vessel flow and myocardial perfusion.

METHODS

Ninety-eight patients presenting with STEMI were evenly randomized to receive either NTP (60 microg) or placebo. The drug was selectively injected into the infarct-related artery, distal to the occlusion, in a double-blind manner. The primary end points were postintervention angiographic corrected thrombolysis in myocardial infarction frame count and the proportion of patients with complete (>70%) ST-segment elevation resolution. Secondary end points included myocardial blush score and clinical outcome at 6 months follow-up.

RESULTS

Mean (+/-SD) age was 62 (+/-12) years, and 87% were men. Baseline characteristics (excluding sex) did not differ between groups. The corrected thrombolysis in myocardial infarction frame count after angioplasty was 20.8 (+/-18.6) and 20.3 (+/-21.3) in patients given NTP and placebo, respectively (P = .78). Complete ST-segment resolution was achieved in 61.7% and 61.2% of NTP and placebo subjects, respectively (P = .96). The distribution of myocardial blush score did not differ between groups. At 6 months, the rate of target lesion revascularization, myocardial infarction, or death occurred in 6.3% of the NTP group and 20.0% of the placebo group (P = .05).

CONCLUSIONS

In patients with STEMI, selective intracoronary administration of a fixed dose of NTP failed to improve coronary flow and myocardial tissue reperfusion but improved clinical outcomes at 6 months.

Impact of PercuSurge Device Conjugative With Intracoronary Administration of Nitroprusside on No-Reflow Phenomenon Following Primary Percutaneous Coronary Intervention

BACKGROUND

The present study tested the hypothesis that when administered in conjunction with a PercuSurge device for treatment of acute myocardial infarction (AMI), intracoronary (IC) administration of nitroprusside (NTP) is safe and superior to IC administration of NTP alone or nitroglycerin (NTG) for reversing slow-flow or no-reflow, both of which occur frequently during primary percutaneous coronary intervention (PCI).

METHODS AND RESULTS

Sixty-two patients with ST-segment elevation AMI of <12 h duration undergoing primary PCI were enrolled. When the final Thrombolysis In Myocardial Infarction (TIMI) flow was normal (TIMI-3), NTG 200 microg was administered first, followed by (5 min later) NTP 100 microg via an intra-guiding catheter. When final TIMI flow was <or=2, NTG 200 mug was given, followed by NTP 100 microg via an export suction catheter advanced into the infract-related artery (IRA). Primary endpoint was epicardial blood flow (TIMI-flow), corrected TIMI frame counts, or microvascular circulation [myocardial blush (MB) grade]. Analytical results indicated that the final TIMI-3 flow was significantly higher in patients receiving NTP than in those receiving NTG therapy (100% vs 88.7%, p=0.023). As compared with NTG, NTP therapy significantly improved final MB grade (p<0.0001) and corrected TIMI flame count time (p<0.0001). Subgroup analysis demonstrated that final MB grade (p<0.001) and corrected TIMI flame count time (p<0.01) were significantly higher in patients (n=33) with than in patients (n=29) without the PercuSurge. No significant NTP related adverse events occurred, apart from insignificant transient hypotension.

CONCLUSION

IC administration of NTP is safe and superior to NTG for improving final epicardial blood flow and microvascular circulation in patients with AMI undergoing primary PCI. Combination therapy of PercuSurge device and NTP provided an additional benefit to NTP alone for improving microvascular circulation.

Effects of the nitric oxide donor nitroprusside on no-reflow phenomenon during coronary interventions for acute myocardial infarction

We tested the effects of the nitric oxide donor nitroprusside as treatment for no reflow in 23 consecutive patients who underwent coronary angioplasty for acute myocardial infarction. No reflow was defined as a decrease of >/=1 Thrombolysis In Myocardial Infarction (TIMI) trial flow grade occurring after successful initial coronary recanalization. Nitroprusside induced a significant improvement in coronary flow, with an increase in TIMI flow grade from 1.5 +/- 0.8 to 2.9 +/- 0.3 (p <0.0001) and in TIMI frame count from 46 +/- 25 to 16 +/- 5 (p <0.0001). There were no significant adverse effects apart from transient hypotension. Intracoronary nitroprusside should be considered as a treatment of no reflow occurring in acute myocardial infarction.