Further insights into the no-reflow phenomenon after primary angioplasty in acute myocardial infarction: the role of microthromboemboli

Current and Future Roles of Glycoprotein IIb-IIIa Inhibitors in Primary Angioplasty for ST-Segment Elevation Myocardial Infarction

Acute myocardial infarction still represents the major cause of mortality in high-income countries. Therefore, considerable efforts have been focused on the treatment of myocardial infarctions in the acute and long-term phase, with special attention being paid to reperfusion strategies and adjunctive antithrombotic therapies. In fact, despite the successful mechanical recanalization of the epicardial conduit, a substantial percentage of patients still experience poor myocardial reperfusion or acute/subacute in-stent thrombosis. Due the delayed onset of action of currently available oral antiplatelet therapies, glycoprotein (GP) IIb-IIIa inhibitors could be expected to improve clinical outcomes, especially when administrated in the early phase of the infarction, due to the larger platelet composition of fresh thrombi, the dynamic nature of early thrombi, and the larger amount of viable myocardium existing in the early, as compared to a delayed, phase. Considerable evidence has accumulated regarding the benefits from GP IIb-IIIa inhibitors on mortality, especially among high-risk patients and when administered as an upstream strategy. Therefore, based on currently available data, GP IIb-IIIa inhibitors can be considered when the drug can be administered within the first 3 h of symptom onset and among high-risk patients (e.g., those with advanced Killip class or an anterior myocardial infarction). Even though it is not universally accepted, in our opinion, this strategy should be implemented in a pre-hospital setting (in an ambulance) or as soon as possible when arriving at the hospital (at the Emergency Room or Coronary Care Unit, irrespective of whether they are in spoke or hub hospitals). A new, second-generation GP IIb-IIIa inhibitor (zalunfiban) appears to be highly suitable as a pre-hospital pharmacological facilitation strategy at the time of first medical contact due to its favourable features, including its simple subcutaneous administration, rapid onset of action (15 min), and limited time of action (with a half-life of ~1 h), which is likely to minimize the risk of bleeding. The ongoing CELEBRATE trial, including 2499 STEMI patients, may potentially provide compelling data to support the upstream treatment of STEMI patients undergoing mechanical reperfusion. In fact, although the current therapeutic target of increased rates of timely reperfusion has been achieved, the future goal in myocardial infarction treatment should be to achieve the most rapid reperfusion prior to primary percutaneous coronary intervention, thus further minimizing myocardial damage, or, in some cases, even preventing it completely, and improving survival.

Quantification of microbubble-induced sonothrombolysis in an ex vivo non-human primate model

BACKGROUND

In vitro studies with ultrasound (US) and microbubbles (MB) have reported that sono-thrombolysis can be achieved at high peak rarefactional acoustic pressure amplitudes (PRAPAs) using 0.25 and 1.05 MHz US frequencies.

OBJECTIVE

The aim of the current study was to determine if these parameters work on an ex vivo physiological model of thrombosis.

METHODS

A thrombogenic device was placed in an ex vivo chronic arteriovenous shunt in juvenile baboons. Platelet accumulation was measured by dynamic imaging of the device and the 10 cm thrombus tail with 111 In-labeled platelets. After 15 minutes of thrombus formation, treatment with either low-dose recombinant tissue plasminogen activator (rtPA) or low-dose rtPA + MB+US was performed for 20 minutes. Four US settings at 0.25% duty cycle were used: 0.25 MHz at PRAPAs of 1.20 and 2.20 MPa, and 1.05 MHz at 1.75 and 4.75 MPa.

RESULTS

Platelet accumulation was not inhibited by low-dose rtPA or MB with US alone. Platelet accumulation was significantly reduced with 0.25 MHz US at 2.20 PRAPA (P < .001) and with 1.05 MHz at 1.75 MPa and 4.75 MPa (P < .05) when used with MB and low-dose rtPA. Although this approach prevented platelet accumulation it did not cause thrombolysis on the device.

CONCLUSIONS

rtPA + MB + US (0.25 and 1.05 MHz) resulted in inhibition of platelet accumulation on the thrombogenic device when moderately high PRAPAs (≥1.75 MPa) were used. These results taken in context with lytic effects of US on myocardial microthrombi and direct effect on myocardial blood flow and function provide direction for the use of therapeutic US in acute coronary syndromes.

Therapeutic Ultrasound Improves Myocardial Blood Flow and Reduces Infarct Size in a Canine Model of Coronary Microthromboembolism

BACKGROUND

Therapeutic ultrasound (TUS) has been used to lyse infarct-related coronary artery thrombus. There has been no study examining the effect of TUS specifically on myocardial microthromboemboli seen in acute myocardial infarction and acute coronary syndromes. The aim of this study was to test the hypothesis that TUS improves myocardial blood flow (MBF) and reduces infarct size (IS) in this situation by dissolving myocardial microthrombi.

METHODS

An open-chest canine model of myocardial microthromboembolism was created by disrupting a thrombus in the left anterior descending coronary artery, and 1.05- and 0.25-MHz TUS (n = 7 each) delivered epicardially for 30 min was compared with control (n = 6). MBF and IS (as a percentage of left anterior descending coronary artery perfusion bed size) were measured 60 min after treatment. In addition, immunohistochemistry was performed to assess microthrombi, and histopathology was performed to define inflammation.

RESULTS

Transmural, epicardial, and endocardial myocardial blood volume and MBF (measured using myocardial contrast echocardiography) and percentage wall thickening were significantly higher 60 min after receiving TUS compared with control. The ratio of IS to left anterior descending coronary artery perfusion bed size was significantly smaller (P = .03) in the 1.05-MHz TUS group (0.14 ± 0.04) compared with the control (0.31 ± 0.06, P = .04) and 0.25-MHz (0.36 ± 0.08) groups. MBF versus percentage wall thickening exhibited a linear relation (r = 0.65) in the control and 1.05-MHz TUS groups but not in the 0.25-MHz TUS group (r = 0.29). The presence of myocardial microemboli in vessels >10 μm in diameter was significantly reduced in the 1.05-MHz TUS group compared with the other two groups. The distribution and intensity of inflammation was higher in the 0.25-MHz TUS group compared with the other groups.

CONCLUSIONS

TUS at 1.05 MHz is effective in restoring myocardial blood volume and MBF, thus reducing IS by clearing the microcirculation of microthrombi. IS reduction is not seen at 0.25 MHz, despite improvement in MBF, which may be related to the increased inflammation noted at this frequency. Because both acute myocardial infarction and acute coronary syndromes are associated with microthromboembolism, these results suggest that TUS could have a potential adjunctive role in the treatment of both conditions.

Efficacy of Sonothrombolysis Using Microbubbles Produced by a Catheter-Based Microfluidic Device in a Rat Model of Ischemic Stroke

Limitations of existing thrombolytic therapies for acute ischemic stroke have motivated the development of catheter-based approaches that utilize no or low doses of thrombolytic drugs combined with a mechanical action to either dissolve or extract the thrombus. Sonothrombolysis accelerates thrombus dissolution via the application of ultrasound combined with microbubble contrast agents and low doses of thrombolytics to mechanically disrupt the fibrin mesh. In this work, we studied the efficacy of catheter-directed sonothrombolysis in a rat model of ischemic stroke. Microbubbles of 10-20 µm diameter with a nitrogen gas core and a non-crosslinked albumin shell were produced by a flow-focusing microfluidic device in real time. The microbubbles were dispensed from a catheter located in the internal carotid artery for direct delivery to the thrombus-occluded middle cerebral artery, while ultrasound was administered through the skull and recombinant tissue plasminogen activator (rtPA) was infused via a tail vein catheter. The results of this study demonstrate that flow focusing microfluidic devices can be miniaturized to dimensions compatible with human catheterization and that large-diameter microbubbles comprised of high solubility gases can be safely administered intraarterially to deliver a sonothrombolytic therapy. Further, sonothrombolysis using intraarterial delivery of large microbubbles reduced cerebral infarct volumes by approximately 50% vs. no therapy, significantly improved functional neurological outcomes at 24 h, and permitted rtPA dose reduction of 3.3 (95% CI 1.8-3.8) fold when compared to therapy with intravenous rtPA alone.

Optimal strategy of primary percutaneous coronary intervention for acute myocardial infarction due to unprotected left main coronary artery occlusion (OPTIMAL): study protocol for a randomised controlled trial

BACKGROUND

Primary percutaneous coronary intervention (PCI) for patients presenting with acute myocardial infarction (AMI) caused by left main coronary artery occlusion is associated with significantly higher mortality and risks of major adverse cardiovascular events. Deferred stent implantation may improve prognosis of primary PCI by reducing distal embolization and no-reflow phenomenon. There is no randomized clinical trial focusing on the effect and outcome of deferred stent implantation on primary PCI for left main coronary artery occlusion in contrast with conventional strategy.

METHODS

The Optimal Strategy of Primary Percutaneous Coronary Intervention for Acute Myocardial Infarction due to Unprotected Left Main Coronary Artery Occlusion (OPTIMAL) study (ClinicalTrials.gov Identifier: NCT03282773) is an open-label, randomized, multicenter clinical trial in which 480 patients presenting with AMI caused by left main coronary artery occlusion recruited from 30 hospitals in mainland China will be randomly assigned 1:1 to immediate stenting or deferred stenting (scheduled 4-10 days after primary angioplasty) groups. The primary endpoint is a composite of all-cause mortality or recurrent myocardial infarction at 30 days after randomization. The secondary outcomes include all-cause mortality, cardiac death, recurrent myocardial infarction, and unplanned target vessel revascularization at 30 days, 6 months, and 12 months.

DISCUSSION

The OPTIMAL study is designed to compare the clinical performance of deferred stenting with that of immediate stenting for AMI caused by left main coronary artery occlusion.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03282773 . Registered on 10 September 2017.

Contrast agent dose and slow/no-reflow in percutaneous coronary interventions : A case-control study of patients with non-ST-segment elevation acute coronary syndromes

BACKGROUND

The angiographic slow/no-reflow phenomenon after primary percutaneous coronary intervention carries a poor prognosis for patients with non-ST-segment elevation acute coronary syndrome (NSTEACS). There is evidence that contrast agents cause endothelial dysfunction, myocardial cell damage, and coronary spasms. We hypothesized that the contrast agent dose may be related to slow/no-reflow in patients with NSTEACS undergoing percutaneous transluminal coronary angioplasty and stent (PTCA + stent).

PATIENTS AND METHODS

We enrolled 3369 patients with NSTEACS who underwent PTCA + stent only in the culprit vessel for the first time from September 2007 to May 2017 in this study. Coronary blood flow of ≤TIMI grade 2 after PTCA + stent was defined as slow/no-reflow. The relationship between the contrast agent dose and slow/no-reflow phenomenon was analyzed by multivariate conditional logistic regression and smooth curve fitting.

RESULTS

In multivariable conditional logistic regression analysis, the contrast agent dose was found to be an independent risk factor for slow/no-reflow after adjusting for the number of stents and the thrombus burden (OR: 1.0112; 95% CI: 1.0049-1.0176; p < 0.0001), and after adjusting for type 2 diabetes mellitus, NSTEACS risk stratification, application of platelet glycoprotein (GP) IIB/IIIA receptor antagonists, type of contrast agent, number of balloon dilatations, number of stents, and thrombus burden (OR: 1.0113; 95% CI: 1.0036-1.0191; p = 0.004). Further, the risk of slow/no-reflow increased significantly with the contrast agent level up to the inflection point of 160 ml.

CONCLUSION

The contrast agent dose may be a risk factor for slow/no-reflow phenomenon after PTCA + stent in patients with NSTEACS. When the dose was greater than 160 ml, the risk of slow/no-reflow increased significantly.

Severely impaired microvascular reactivity in diabetic patients with an acute coronary syndrome

Background

Microvascular function is impaired in patients with stable coronary artery disease. The aim was to study microvascular function in patients with diabetes and acute coronary syndrome (ACS).

Methods

Microvascular function was evaluated in 83 patients by laser Doppler fluxmetry (LDF) [PU; perfusion unit, median (interquartile range)] measuring resting LDF and peak LDF following a six min heating of the skin to 44 °C at the foot, respectively. All patients with ACS and without previously known diabetes underwent oral glucose tolerance test. Thirty-nine patients with type 2 diabetes mellitus free from coronary artery disease served as controls.

Results

Peak LDF was significantly (P = 0.03) lower in patients with ACS and diabetes (n = 22; 72 (52)) and diabetes without coronary artery disease (n = 39; 69 (51)) as compared to patients with ACS without diabetes (n = 46; 97 (60)), and patients without ACS (n = 15; 140 (121)), respectively. Patients with ACS (n = 68) had significantly (P = 0.04) lower peak LDF (92 (49)) as compared to patients without ACS (n = 15) (140 (121)).

Conclusion

Microvascular reactivity is severely impaired in patients with diabetes and ACS. Diabetes has a major influence on microvascular function in patients with coronary artery disease.

Development and Validation of a Distal Embolization Risk Score During Primary Angioplasty in ST-Elevation Myocardial Infarction

This study aims to develop and validate a new angiographic risk score to predict the risk of distal embolization (DE) during primary percutaneous coronary intervention (p-PCI) for ST-elevation myocardial infarction. Study included data from 1,200 patients who underwent p-PCI. The cohort was randomly split into a derivation cohort (n = 814) and a validation cohort (n = 386). Logistic regression was used to examine the relation between risk factors and the occurrence of DE. To each covariate in the model was assigned an integer score based on the regression coefficients. Variables included in the risk score, according to multivariable analysis, were occlusion pattern of infarct-related artery, Thrombolysis In Myocardial Infarction Thrombus Score 2 to 4, reference vessel diameter ≥3.5 mm, and lesion length >20 mm. To each variable was assigned a 0- to +2-point score according to the strength of the statistical association. Rates of DE in low-, intermediate-, and high-risk groups were 5.6%, 15.8%, and 40% in the derivation cohort (p for trend <0.0001; C-statistic 0.70) and 7.5%, 12.1%, and 37.9% in the validation cohort (p for trend <0.0001; C-statistic 0.62), respectively. In conclusion, the individual risk of DE in patients who underwent p-PCI can be predicted using a simple 4-variables model based on angiographic features.

Effect of diabetes on scintigraphic infarct size in STEMI patients undergoing primary angioplasty

BACKGROUND

It has been shown that among patients with ST-segment elevation myocardial infarction (STEMI), diabetes is associated with a significantly higher mortality, mainly because of impaired reperfusion. However, few data have been reported so far on infarct size as evaluated by well-refined techniques, such as nuclear imaging techniques. Therefore, the aim of the current study was to investigate the effect of diabetes in infarct size as evaluated by myocardial scintigraphy in a large cohort of STEMI patients undergoing primary PCI.

METHODS

We included 830 STEMI patients undergoing primary PCI. Infarct size was evaluated at 30 days by technetium-99 m-sestamibi. A logistic regression analysis was performed to determine the relation between diabetes and infarct size (as above the median) after correction for baseline confounding factors.

RESULTS

A total of 115 (13.8%) out of 830 patients suffered from diabetes. Diabetic patients were older (p < 0.001), with larger prevalence of female gender (p = 0.006) and hypertension (p = 0.001) but were less often smokers (p = 0.003). Diabetic patients had more often preprocedural thrombolysis in myocardial infarction grade 3 flow (p = 0.034) and less complete ST-segment resolution (p = 0.009). No difference was observed in scintigraphic infarct size between diabetes and control patients (p = 0.6)), which was confirmed at multivariate analysis after correction for baseline confounding factors (Adjusted OR [95% CI] = 0.87 [0.57-1.31, p = 0.51).

CONCLUSION

Our study showed that among STEMI patients undergoing primary angioplasty, diabetes did not affect infarct size as compared with non-diabetic patients.

Preprocedural TIMI flow and infarct size in STEMI undergoing primary angioplasty

Despite optimal epicardial recanalization, primary angioplasty for STEMI is still associated with suboptimal reperfusion in a relatively large proportion of patients. The aim the current study was to evaluate the impact of preprocedural TIMI flow on myocardial scintigraphic infarct size among STEMI undergoing primary angioplasty. Our population is represented by 793 STEMI patients undergoing primary PCI. Infarct size was evaluated at 30 days by technetium-99m-sestamibi. Poor preprocedural TIMI flow (TIMI 0-1) was observed in 645 patients (81.3%). Poor preprocedural TIMI flow was associated with more hypercholesterolemia (p = 0.012), and a trend in lower prevalence of diabetes (p = 0.081). Preprocedural TIMI flow significantly affected scintigraphic and enzymatic infarct size. Similar findings were observed in the analysis restricted to patients with postprocedural TIMI 3 flow. The impact of preprocedural TIMI flow on scintigraphic infarct size was confirmed when the analysis was performed according to the percentage of patients above the median (p < 0.001) and after adjustment for baseline confounding factors (Hypercholesterolemia and diabetes) [adjusted OR (95% CI) for pre preprocedural TIMI 3 flow = 0.59 (0.46-0.75), p < 0.001]. This study shows that among patients with STEMI undergoing primary angioplasty, poor preprocedural TIMI flow is independently associated with larger infarct size.

Rosuvastatin reduces ischemia-reperfusion injury in patients with acute coronary syndrome treated with percutaneous coronary intervention

BACKGROUND

Statins reduce the incidence of cardiovascular events after percutaneous coronary intervention (PCI), but no clinical studies have investigated the role of statins in ischemia-reperfusion injury after PCI.

HYPOTHESIS

Rosuvastatin could reduce ischemia-reperfusion injury in patients with acute coronary syndrome treated with PCI.

OBJECTIVES

We investigated the effects of rosuvastatin on ischemia-reperfusion injury in patients with acute coronary syndrome after PCI and evaluated short-term prognosis.

METHODS

Patients scheduled for emergent PCI were given either rosuvastatin for ≥6 months (10 mg/d, every night; n = 55) or no statins (control group; n = 65). Serum superoxide dismutase activity, malondialdehyde, brain natriuretic peptide (BNP), and high-sensitivity C-reactive protein (hs-CRP) were determined before and after PCI, as well as left ventricular ejection fraction and left ventricular end-diastolic volume. Major adverse cardiac events were observed at follow-ups for 6 months.

RESULTS

Superoxide dismutase activity in the rosuvastatin-treated group was higher than that of the control group; serum levels of malondialdehyde were lower. BNP and hs-CRP levels in the rosuvastatin-treated group were lower than that of the control group. Four weeks after PCI, the left ventricular ejection fraction in the treatment group was higher than that of the control group, and the left ventricular end-diastolic volume was lower. At the 6-month follow-up, there was no difference in major adverse cardiac events between the 2 groups.

CONCLUSIONS

Rosuvastatin before PCI reduced ischemia-reperfusion injury in patients with acute coronary syndrome, which suggests the importance of application of rosuvastatin before PCI for early intervention.

The "no reflow" phenomenon following acute myocardial infarction: mechanisms and treatment options

If 'no reflow' is observed within 45min of reperfusion using balloon angioplasty or stent, it is probably related to microthromboemboli, which may also contribute to the extension of the 'no reflow' zone by converting 'low reflow' areas into necrotic ones even when reperfusion is achieved more than 45min after the onset of coronary occlusion. Since 'no reflow' is noted when 45min of coronary occlusion has elapsed even in the absence of a thrombus, 'no reflow' late after reperfusion is predominantly due to tissue necrosis and unlikely to be resolved unless methods to reduce infarct size are used. Attempts at reducing the intracoronary thrombus burden during a coronary procedure for acute myocardial infarction (AMI) have been shown to reduce 'no reflow' and improve clinical outcome, as has the use of potent antithrombotic agents. Drugs that can reduce infarct size, when given intracoronary or intravenous in conjunction with a coronary intervention during AMI can also reduce 'no reflow' and improve outcomes in patients with AMI. The prognostic importance of 'no reflow' post-AMI is related to its close correspondence with infarct size. Although several imaging and non-imaging methods have been used to assess 'no reflow' or 'low reflow' myocardial contrast echocardiography remains the ideal method for its assessment both in and outside the cardiac catheterization laboratory.

Thrombus burden and myocardial damage during primary percutaneous coronary intervention

Large thrombus burden (LTB) lesions in the context of primary percutaneous coronary intervention (p-PCI) have been related to unsuccessful angiographic reperfusion and unfavorable clinical outcomes. However, the hazard of LTB treatment on myocardial damage has not been evaluated. We investigated the impact of LTB on myocardial damage using contrast-enhanced cardiac magnetic resonance (CE-CMR) in the setting of p-PCI. In 327 patients, who underwent p-PCI without thrombus aspiration within 12 hours from symptom onset, we prospectively assessed the impact of LTB on infarct size and microvascular damage using CE-CMR. LTB was defined by the presence of Thrombolysis In Myocardial Infarction thrombus score ≥3 in patent infarct-related artery (IRA); or by "cut-off" occlusion pattern and/or large reference vessel diameter (≥3.5 mm) in occluded IRA. One hundred ninety-seven patients (60.2%) showed LTB and 130 (39.8%) did not. Distal embolization occurred in 18.8% patients with versus 6.9% without LTB (p = 0.003). At CE-CMR, patients with LTB had larger infarct size index (27.5 ± 11.1 vs 22.1 ± 17.5, p = 0.009) and more often transmural necrosis (70.5% vs 55.4%, p = 0.008) compared with patients without LTB. Excluding patients with distal embolization, patients with LTB still had larger necrosis. At multivariate analysis, occluded (IRA) at baseline, anterior infarction, and presence of LTB predicted transmural necrosis. In conclusion, LTB in the setting of p-PCI is related to larger myocardial damage as detected by CE-CMR, regardless of angiographic detectable distal embolization.

Diagnostic ultrasound induced inertial cavitation to non-invasively restore coronary and microvascular flow in acute myocardial infarction

Ultrasound induced cavitation has been explored as a method of dissolving intravascular and microvascular thrombi in acute myocardial infarction. The purpose of this study was to determine the type of cavitation required for success, and whether longer pulse duration therapeutic impulses (sustaining the duration of cavitation) could restore both microvascular and epicardial flow with this technique. Accordingly, in 36 hyperlipidemic atherosclerotic pigs, thrombotic occlusions were induced in the mid-left anterior descending artery. Pigs were then randomized to either a) ½ dose tissue plasminogen activator (0.5 mg/kg) alone; or same dose plasminogen activator and an intravenous microbubble infusion with either b) guided high mechanical index short pulse (2.0 MI; 5 usec) therapeutic ultrasound impulses; or c) guided 1.0 mechanical index long pulse (20 usec) impulses. Passive cavitation detectors indicated the high mechanical index impulses (both long and short pulse duration) induced inertial cavitation within the microvasculature. Epicardial recanalization rates following randomized treatments were highest in pigs treated with the long pulse duration therapeutic impulses (83% versus 59% for short pulse, and 49% for tissue plasminogen activator alone; p<0.05). Even without epicardial recanalization, however, early microvascular recovery occurred with both short and long pulse therapeutic impulses (p<0.005 compared to tissue plasminogen activator alone), and wall thickening improved within the risk area only in pigs treated with ultrasound and microbubbles. We conclude that although short pulse duration guided therapeutic impulses from a diagnostic transducer transiently improve microvascular flow, long pulse duration therapeutic impulses produce sustained epicardial and microvascular re-flow in acute myocardial infarction.

Impact of diabetes on long-term outcome after primary angioplasty: insights from the DESERT cooperation

OBJECTIVE

Diabetes has been shown to be associated with worse survival and repeat target vessel revascularization (TVR) after primary angioplasty. The aim of the current study was to evaluate the impact of diabetes on long-term outcome in patients undergoing primary angioplasty treated with bare metal stents (BMS) and drug-eluting stents (DES).

RESEARCH DESIGN AND METHODS

Our population is represented by 6,298 ST-segment elevation myocardial infarction (STEMI) patients undergoing primary angioplasty included in the DESERT database from 11 randomized trials comparing DES with BMS.

RESULTS

Diabetes was observed in 972 patients (15.4%) who were older (P < 0.001), more likely to be female (P < 0.001), with higher prevalence of hypertension (P < 0.001), hypercholesterolemia (P < 0.001), and longer ischemia time (P < 0.001), and without any difference in angiographic and procedural characteristics. At long-term follow-up (1,201 ± 441 days), diabetes was associated with higher rates of death (19.1% vs. 7.4%; P < 0.0001), reinfarction (10.4% vs. 7.5%; P < 0.001), stent thrombosis (7.6% vs. 4.8%; P = 0.002) with similar temporal distribution--acute, subacute, late, and very late--between diabetic and control patients, and TVR (18.6% vs. 15.1%; P = 0.006). These results were confirmed in patients receiving BMS or DES, except for TVR, there being no difference observed between diabetic and nondiabetic patients treated with DES. The impact of diabetes on outcome was confirmed after correction for baseline confounding factors (mortality, P < 0.001; repeat myocardial infarction, P = 0.006; stent thrombosis, P = 0.007; TVR, P = 0.027).

CONCLUSIONS

This study shows that among STEMI patients undergoing primary angioplasty, diabetes is associated with worse long-term mortality, reinfarction, and stent thrombosis in patients receiving DES and BMS. DES implantation, however, does mitigate the known deleterious effect of diabetes on TVR after BMS.

A meta-analytic overview of thrombectomy during primary angioplasty

INTRODUCTION

Even though primary angioplasty restores TIMI 3 flow in more than 90% of STEMI patients, the results in terms of myocardial perfusion are still unsatisfactory in a relatively large proportion of patients. Great interest has been focused in the last years on distal embolization as major determinant of poor reperfusion and clinical outcome after primary angioplasty. The aim of this article is to perform an updated meta-analysis of thrombectomy devices in STEMI patients undergoing primary angioplasty.

METHODS

The literature was scanned by formal searches of electronic databases (MEDLINE, Pubmed) from January 1990 to December 2010, the scientific session abstracts (from January 1990 to December 2010) and oral presentation and/or expert slide presentations (from January 2002 to December 2010) (on TCT, AHA, ESC, ACC and EuroPCR websites). No language restrictions were enforced.

RESULTS

A total of 21 randomized trials were finally included in the meta-analysis, involving 4514 patients (2270 or 50.3% randomized to thrombectomy and 2244 or 49.7% to standard angioplasty). Overall thrombectomy did not reduce 30-day mortality, with more benefits observed only with manual thrombectomy. No difference was observed in the 30-day reinfarction rate, whereas a trend in higher risk of stroke was observed with thrombectomy (p=0.06). Manual but not mechanical thrombectomy significantly improved postprocedural TIMI 3 flow, however, both devices significantly improved myocardial reperfusion as evaluated by ST-segment resolution. By meta-regression analysis a linear relationship was observed between benefits from thrombectomy in ST-segment resolution and in the presence of thrombus at baseline angiography (p=0.0016).

CONCLUSIONS

The present meta-analysis has demonstrated that, among patients with STEMI, manual thrombectomy significantly improved myocardial perfusion, with a trend in short-term mortality benefits, whereas mechanical thrombectomy, despite the benefits in myocardial perfusion, did not impact on short-term survival. However, the benefits in myocardial perfusion were significantly related to prevalence of coronary thrombus. In light of the observed higher risk of stroke, thrombectomy cannot be routinely recommended, but should be used in case of evident intracoronary thrombus. Mechanical thrombectomy devices may be considered as well to further improve reperfusion and facilitate optimal stent implantation, especially in the presence of large thrombus burden.

Efficacy of dual antiplatelet therapy combined with Naoxintong capsules [see text] following coronary microembolization induced by homologous microthrombi in rats

OBJECTIVE

To evaluate the effificacy of dual antiplatelet therapy combined with Naoxintong Capsule ([see text], NXTC) in a rat model of coronary microembolization (CME).

METHODS

A total of 95 rats were randomly divided into 6 groups: control, sham-operation, CME model, NXTC, dual antiplatelet (clopidogrel and aspirin) intervention (DA), and NXTC combined with DA (NDA) groups. The complete data in 69 rats were obtained. The number of CME, myocardial apoptosis rate, bleeding time, clotting time, and adensosine diphosphate (ADP)-induced platelet aggregation were assessed.

RESULTS

Compared with the CME group, the number of CME and myocardial apoptosis rates were signifificantly decreased in the NXTC, DA, and NDA groups (P <0.01). Compared with other intervention groups, the number of CME and myocardial apoptosis rates were the least in the NDA group (P <0.01), and the incidence of surgical bleeding was the highest in the DA group (P <0.01). Compared with the CME group, ADP-induced maximum platelet aggregation rate was significantly inhibited in the NXTC, DA, and NDA groups (P <0.01), both bleeding time and clotting time were signifificantly increased in the NXTC, DA, and NDA groups (P <0.01), while the above parameters were the highest in the DA group (P <0.05).

CONCLUSION

The combination therapy of NXTC and DA enhanced the anti-CME effect of either therapy alone and reduced the risk of the DA therapy-associated bleeding, demonstrating an improved benefifit/ risk ratio in the rat model of CME.

Coronary and microvascular thrombolysis with guided diagnostic ultrasound and microbubbles in acute ST segment elevation myocardial infarction

BACKGROUND

During a microbubble infusion, guided high-mechanical index impulses from a diagnostic two-dimensional transducer improve microvascular recanalization in acute ST-segment elevation myocardial infarction. The purpose of this study was to further elucidate the mechanism of improved microvascular flow in normal and hyperlipidemic atherosclerotic pigs.

METHODS

In 14 otherwise normal pigs, acute left anterior descending thrombotic coronary occlusions were created. Pigs subsequently received aspirin, heparin, and half-dose fibrinolytic agent (tenecteplase or tissue plasminogen activator), followed by randomization to either no additional treatment (group I) or a continuous infusion of nontargeted microbubbles and guided high-mechanical index impulses from a three-dimensional transducer (group II). Epicardial recanalization rates, ST-segment resolution, microsphere-derived myocardial blood flow, and ultimate infarct size using myocardial contrast echocardiography were compared. The same coronary thrombosis was created in a set of 12 hypercholesterolemic pigs, which were then treated with the same pharmacologic and ultrasound regimen (group III, n = 6) or the pharmacologic regimen alone (group IV, n = 6).

RESULTS

Epicardial recanalization rates in groups I and II were the same (29%), but peri-infarct myocardial blood flow and ultimate infarct size improved after treatment in group II (P < .01 vs group I). In group III, epicardial recanalization was 100% (vs. 50% in group IV), and there were significant reductions in ultimate infarct size (P = .02 compared with group IV).

CONCLUSIONS

Guided high-mechanical index impulses from a diagnostic transducer and nontargeted microbubbles improve peri-infarct microvascular flow in acute ST-segment elevation myocardial infarction, even when epicardial recanalization does not occur.

Glycoprotein IIb-IIIa inhibitors

Platelets play a pivotal role in the pathogenesis of coronary artery disease and myocardial infarction. Therefore, great interests have been focused in the last decades on improvement in antiplatelet therapies, that currently are regarded as main pillars in the prevention and treatment of coronary artery disease, with special attention to glycoprotein IIb-IIIa (GP IIb-IIIa) receptors, that mediates the final stage of platelet activation. GP IIb-IIIa inhibitors, especially abciximab, have been shown to improve clinical outcome in patients undergoing primary angioplasty for STEMI. Upstream administration cannot routinely recommended, but may potentially be considered among high-risk patients within the first 4 h from symptoms onset. In case of periprocedural administration of antithrombotic therapy, Bivalirudin should be considered, especially in patients at high risk for bleeding complications. Among high-risk patients with acute coronary syndromes, an early invasive strategy with selective downstream administration of GP IIb-IIIa inhibitors is the strategy of choice, whereas bivalirudin should be considered in patients at high risk for bleeding complications. Among patients with unstable angina GP IIb-IIIa inhibitors should be considered only in case of evidence of intracoronary thrombus or in case of thrombotic complications (as provisional use). Further, randomized trials are certainly needed in the era of new oral antiplatelet therapies, and with strategies to prevent bleeding complications such as larger use of radial approach, mechanical closure devices, bivalirudin, or postprocedural protamine administration to promote early sheat removal.

Association between advanced Killip class at presentation and impaired myocardial perfusion among patients with ST-segment elevation myocardial infarction treated with primary angioplasty and adjunctive glycoprotein IIb-IIIa inhibitors

BACKGROUND

Although primary angioplasty has been shown to improve survival as compared with thrombolysis, the outcome is still unsatisfactory in subsets of patients such as those with signs of heart failure at presentation. In fact, although primary angioplasty is able to restore TIMI 3 flow in most patients, suboptimal myocardial reperfusion is observed in a relatively large proportion of patients. The aim of this study was to investigate among patients with ST-segment elevation myocardial infarction undergoing primary angioplasty the association between heart failure at presentation and myocardial perfusion and its implications in terms of survival.

METHODS

Our population is represented by patients undergoing primary angioplasty who are included in the EGYPT database. Congestive heart failure was defined as Killip class >1 at admission. Myocardial perfusion was evaluated by myocardial blush grade and ST-segment resolution. Follow-up data were collected between 30 days and 1 year after primary angioplasty.

RESULTS

Detailed data on Killip class at presentation were available in 1,427 of 1,662 patients (86% of the initial population) who represent the final population of this study. Killip class was associated with myocardial perfusion, distal embolization, enzymatic infarct size, predischarge ejection fraction, and 1-year mortality rate. Myocardial blush was an independent predictor of 1-year mortality (hazard ratio 7.44, 95% CI 1.82-30.4, P = .005) in patients with advanced Killip class at presentation.

CONCLUSIONS

Our study shows that patients with heart failure complicating ST-segment elevation myocardial infarction have impaired myocardial perfusion, which accounts for the poor outcome observed in these patients. Further efforts should be aimed at improving myocardial perfusion, beyond epicardial recanalization, to further improve the outcome of these high-risk patients.

Diagnostic ultrasound combined with glycoprotein IIb/IIIa-targeted microbubbles improves microvascular recovery after acute coronary thrombotic occlusions

BACKGROUND

The high mechanical index (MI) impulses from a diagnostic ultrasound transducer may be a method of recanalizing acutely thrombosed vessels if the impulses are applied only when microbubbles are channeling through the thrombus.

METHODS AND RESULTS

In 45 pigs with acute left anterior descending thrombotic occlusions, a low-MI pulse sequence scheme (contrast pulse sequencing) was used to image the myocardium and guide the delivery of high-MI (1.9 MI) impulses during infusion of either intravenous platelet-targeted microbubbles or nontargeted microbubbles. A third group received no diagnostic ultrasound and microbubbles. All groups received half-dose recombinant prourokinase, heparin, and aspirin. Contrast pulse sequencing examined replenishment of contrast within the central portion of the risk area and guided the application of high-MI impulses. Angiographic recanalization rates, resolution of ST-segment elevation on ECG, and wall thickening were analyzed. Pigs receiving platelet-targeted microbubbles had more rapid replenishment of the central portion of the risk area (80% versus 40% for nontargeted microbubbles; P=0.03) and higher epicardial recanalization rates (53% versus 7% for prourokinase alone; P=0.01). Replenishment of contrast within the risk area (whether with platelet-targeted microbubbles or nontargeted microbubbles) was associated with both higher recanalization rates and even higher rates of ST-segment resolution (82% versus 21% for prourokinase alone; P=0.006). ST-segment resolution occurred in 6 pigs (40%) treated with microbubbles who did not have epicardial recanalization, of which 5 had recovery of wall thickening.

CONCLUSIONS

Intravenous platelet-targeted microbubbles combined with brief high-MI diagnostic ultrasound impulses guided by contrast pulse sequencing improve both epicardial recanalization rates and microvascular recovery.

Predictors and time-related impact of distal embolization during primary angioplasty

AIMS

We sought to identify predictors of distal embolization (DE) occurring during primary percutaneous coronary intervention (p-PCI) as well as to assess its impact on both myocardial reperfusion and necrosis, according to time-to-treatment.

METHODS AND RESULTS

Clinical and angiographic characteristics were prospectively assessed in 400 consecutive patients who underwent p-PCI, in order to identify predictors of DE. The impact of DE on Thrombolysis in Myocardial Infarction (TIMI) flow, myocardial blush, and troponin I (TnI) was assessed according to symptom onset-to-balloon time. DE occurred in 64 (16%) patients and did not change with time-to-treatment (P = 0.87). The occlusion pattern of infarct-related artery (IRA), treatment of right coronary artery, higher TIMI thrombus score, longer lesion, and large IRA diameter were predictors of DE. The rate of TIMI 0/1 and myocardial blush 0/1 was higher in patients exhibiting DE when time-to-treatment was < or =6 h (P < 0.0001), while TnI was higher in patients with DE when time-to-treatment was <3 h.

CONCLUSION

DE during p-PCI occurs more often in the presence of high thrombus burden lesion. It reduces the effectiveness of myocardial reperfusion within 6 h and enhances myocardial damage within 3 h after symptom onset. Afterwards, it does not affect myocardial reperfusion or the extent of myocardial damage.

Push-pull theory: using mechanotransduction to achieve tissue perfusion and wound healing in complex cases

Wound healing has evolved from gauze therapy to the use of proteomics, gene therapy, and cellular-based therapies in the short time span of 45 years. Education for health care providers has not kept pace with the logarithmic acceleration in technology development and treatment options. A patient with a non-healing wound requires a comprehensive work-up, including a focus on six primary points of interest. These points include the status of tissue perfusion, role of bacterial contamination, pressure applied to the tissue, the immune status of the host, co-morbid medical conditions including the patient's psychosocial status, and lastly, the status of the wound itself. Even after re-establishing macrovascular flow, many wounds either fail to improve or paradoxically worsen. Potential mechanisms for these unexpected findings include reperfusion injury, no-reflow, and the presence of stunned/hibernating tissue. Using the concept of mechanotransduction, the clinician can simulate normal pulsatile blood flow and re-establish adequate microvascular perfusion. Treatment regimens may include negative pressure therapy, electrical stimulation, ultrasound therapy, and other energy-based modalities.

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.

Intracoronary streptokinase after primary percutaneous coronary intervention

BACKGROUND

Microvascular perfusion is often impaired after primary percutaneous coronary intervention (PCI). We proposed that in situ thrombosis might contribute to poor myocardial perfusion in this setting. To test this hypothesis, we evaluated the effect of low-dose intracoronary streptokinase administered immediately after primary PCI.

METHODS

Forty-one patients undergoing primary PCI were randomly assigned to receive intracoronary streptokinase (250 kU) or no additional therapy. Two days later, cardiac catheterization was repeated, and coronary hemodynamic end points were measured with the use of a guidewire tipped with pressure and temperature sensors. In patients with anterior myocardial infarction, the deceleration time of coronary diastolic flow was measured with transthoracic echocardiography. At 6 months, angiography, echocardiography, and technetium-99m single-photon-emission computed tomography were performed.

RESULTS

Two days after PCI, all measures of microvascular function (means +/-SD) were significantly better in the streptokinase group than in the control group, including coronary flow reserve (2.01+/-0.57 vs. 1.39+/-0.31), the index of microvascular resistance (16.29+/-5.06 U vs. 32.49+/-11.04 U), the collateral-flow index (0.08+/-0.05 vs. 0.17+/-0.07), mean coronary wedge pressure (10.81+/-5.46 mm Hg vs. 17.20+/-7.93 mm Hg), systolic coronary wedge pressure (18.24+/-6.07 mm Hg vs. 33.80+/-11.00 mm Hg), and diastolic deceleration time (828+/-258 msec vs. 360+/-292 msec). The administration of intracoronary streptokinase was also associated with a significantly lower corrected Thrombolysis in Myocardial Infarction frame count (the number of cine frames required for dye to travel from the ostium of a coronary artery to a standardized distal coronary landmark) at 2 days. At 6 months, however, there was no evidence of a difference between the two study groups in left ventricular size or function.

CONCLUSIONS

In our pilot trial, the administration of low-dose intracoronary streptokinase immediately after primary PCI improved myocardial reperfusion but not long-term left ventricular size or function. These findings require clarification in a larger trial. (ClinicalTrials.gov number, NCT00302419.)

Significance of additional ST segment elevation in patients with no reflow after angioplasty for acute myocardial infarction

OBJECTIVES

We sought to evaluate the incidence, timing, and clinical significance of additional increase in ST segment elevation (ST-SE) in patients showing no reflow after angioplasty for acute myocardial infarction.

METHODS

We studied 26 patients with acute myocardial infarction showing myocardial contrast echocardiography no reflow after successful angioplasty. Baseline and 6-month 2-dimensional echocardiograms were obtained in 21 surviving patients.

RESULTS

After angioplasty, 13 patients showed greater than 30% additional increase in ST-SE (group 1), whereas 13 did not (group 2). Baseline clinical, echographic, and angiographic characteristics, and 6-month patency and restenosis rate, were similar between the two groups. From baseline to 6 months, a similar global and regional systolic function was found between the two groups, whereas a higher increase in left ventricular end-diastolic volume occurred in group 1 (135 +/- 45 vs 168 +/- 42 mL, P = .033). The additional increase in ST-SE was not associated with more severe microvascular damage (myocardial contrast echocardiography score index: 0.14 +/- 0.26 vs 0.22 +/- 0.27), higher peak creatine kinase value (4888 +/- 2533 vs 3109 +/- 2055 U/L, P = .061), higher incidence of left ventricular remodeling (73% vs 60%, P = .537), or worse outcome (26 +/- 24 months) such as death (15% vs 23%, P = .619), hospitalization for heart failure (8% vs 23%, P = .277), or reinfarction (8% vs 0%, P = .308).

CONCLUSIONS

Our data show that in patients showing no reflow after angioplasty a transient additional increase in ST-SE occurs in half of patients. The prognostic value of additional increase in ST-SE remains uncertain in the era of primary angioplasty.

A pilot study with a new, rapid-exchange, thrombus-aspirating device in patients with thrombus-containing lesions: the Diver C.E. study

BACKGROUND

In patients with acute coronary syndromes (ACS), distal embolization of thrombotic material is more likely to play a key role in the pathogenesis of myocardial no-reflow during percutaneous coronary intervention (PCI). Thus, interventional techniques able to reduce thrombus burden at the culprit vessel might improve final myocardial reperfusion.

OBJECTIVE

To evaluate a new rapid-exchange thrombus-aspirating catheter, the Diver C.E., in patients with thrombotic coronary lesions undergoing PCI.

METHODS

Fifty patients with acute myocardial infarction (n = 44) or with non-ST-elevation ACS and angiographic evidence of coronary thrombus (n = 6) undergoing urgent PCI were prospectively enrolled. The Diver C.E. was used to aspirate coronary thrombus from the culprit lesion after placement of the guidewire. Adjunctive balloon inflations and stent implantation were used to achieve good angiographic result. Angiographic coronary flow (by means of TIMI score and corrected TIMI frame count, cTFC), thrombus score (TS), and myocardial perfusion (by means of postintervention myocardial blush grade, MBG) were assessed in all patients.

RESULTS

The device could be successfully employed in 96% of the cases (48/50) and yielded significant (P < 0.0001) acute reduction in thrombus burden (TS: predevice 3.5 +/- 0.8, postdevice 2.5 +/- 0.9) and improvement in coronary flow (TIMI grade: predevice 1.0 +/- 0.9, postdevice 2.0 +/- 0.9; CTFC predevice 71 +/- 31, postdevice 39 +/- 26). Final TIMI grade 0-1 was observed in one patient only (2%). A significant (P = 0.02) correlation was found between preintervention TS and efficacy of thrombus aspiration. A more pronounced acute reduction of thrombus burden after thrombus aspiration (TS reduction > or = 2) was associated with a better postintervention angiographic myocardial perfusion (MBG 2.3 +/- 0.9 vs 1.7 +/- 0.8; P = 0.05).

CONCLUSIONS

This new, easy-to-use, device is able to reduce thrombus burden and to improve coronary flow in patients with thrombus-containing lesions. The improvement in myocardial perfusion associated to greater thrombus removal highlights the importance of thrombus aspiration in the management of thrombus-burdened coronary lesions.

Evaluating the ‘no reflow’ phenomenon with myocardial contrast echocardiography

Based on its ability to measure myocardial blood volume and capillary flow, myocardial contrast echocardiography (MCE) has provided invaluable pathophysiological information regarding the no reflow phenomenon both in humans and in the experimental laboratory. The new area of molecular imaging with MCE allows the identification of molecular events within the microcirculation that have provided further insights into the mechanisms involved in the no-reflow phenomenon. Molecular imaging with MCE has the potential for monitoring molecular events associated with no reflow phenomenon and also to develop strategies to limit the no reflow phenomenon via pharmacological means. This paper will cover these areas briefly.

Impact of routine stenting on myocardial perfusion and the extent of myocardial necrosis in patients undergoing primary angioplasty for ST-segment elevation myocardial infarction

BACKGROUND

Primary stenting for ST-segment elevation myocardial infarction (STEMI) has been shown to improve the outcome because of the benefits in terms of restenosis. However, still controversial are the benefits in terms of reperfusion. In the Zwolle-6 randomized trial, a consecutive cohort of patients with STEMI was randomized to balloon angioplasty or stenting, without exclusion criteria. In this study, we analyzed data on myocardial perfusion and the extent of myocardial necrosis.

METHODS

From April 1997 to October 2001, a total of 1683 consecutive patients with STEMI were randomized to stenting or balloon angioplasty. No exclusion criteria were applied. Myocardial perfusion was evaluated by myocardial blush grade and ST-segment resolution. The extent of myocardial necrosis was evaluated by enzymatic infarct size and predischarge ejection fraction. All data were prospectively collected.

RESULTS

A total of 785 patients (92.5%) in the stent group and 763 patients (91.5%) in balloon group underwent primary angioplasty. The 2 groups showed similar baseline characteristics. No difference was observed between stent and balloon in myocardial blush grade, complete ST-segment resolution, distal embolization, enzymatic infarct size, and predischarge ejection fraction at both intention-to-treat and actual treatment analysis, even when restricted to patients with anterior infarction. Time delay to treatment (earlier or later than 6 hours) did not affect the results. No difference was observed in 1-year mortality (6.0% vs 5.9%, P = NS).

CONCLUSIONS

As compared with balloon angioplasty, routine stenting does not improve myocardial perfusion, the rate of distal embolization, and the extent of myocardial necrosis in a large cohort of unselected patients with STEMI.

Microvascular obstruction after successful fibrinolytic therapy in acute myocardial infarction. Comparison of reteplase vs reteplase+abciximab: A cardiovascular magnetic resonance study

BACKGROUND.: About one third of patients with TIMI 3 after reperfusion have evidence of microvascular obstruction (MO) which represents an independent predictor of myocardial wall rupture. This explains all efforts made to prevent MO. Magnetic resonance imaging (MRI) has proved to be particularly useful in detecting MO. The aim of this study was to evaluate with MRI if different fibrinolytic regimens in acute myocardial infarction display different effects on left ventricle (LV) volumes and ejection fraction (EF), as well as on myocardial infarct size (MIsz) and MO. METHODS.: Twenty male patients, mean age 58 years, affected by acute myocardial infarction, ten anterior and ten inferior, were treated with: full dose reteplase in ten, and half dose reteplase plus full dose abciximab (R+Abcx) in the other ten patients. In the fourth day after hospital admission, MRI STIR T2 images were used to quantify MIsz, while 2dflash cineloops were used after the injection of gadolinium, to quantify LV volumes, EF and to detect MO. RESULTS.: LV EF was higher in R+Abcx 51±10 than in reteplase 41±8. MIsz was similar in both treatment groups: however a close relationship was present between MIsz and EF in the reteplase group indicating that the greater the MIsz the lower the EF. In R+Abcx this relationship was no longer present, suggesting a protective effect of the drug on microcirculation. In fact extensive MO was present in 25% of all cases, 80% of which in the reteplase group while only 20% in R+Abcx. CONCLUSION.: R+Abcx prevents MO: compared to traditional fibrinolytic therapy it allows better LV function and most likely improved long term survival.

Effects of nitroglycerin on erythrocyte rheology and oxygen unloading: novel role of S-nitrosohemoglobin in relieving myocardial ischemia

BACKGROUND

We hypothesized that nitroglycerin improves O2 delivery to ischemic tissue by altering erythrocyte rheology and O2 unloading through an increase in bioactive nitric oxide (NO) content.

METHODS AND RESULTS

Twelve dogs with resting flow-reducing single-vessel stenosis were studied at rest and during intracoronary infusion of nitroglycerin (0.3 to 0.6 microg.kg(-1).min(-1)). Half the dogs also had occlusion of the remote coronary artery to remove any collateral effects. Systemic and coronary hemodynamics, myocardial blood flow (MBF), whole blood viscosity (WBeta), erythrocyte charge (EC) and mobility (EM), regional myocardial O2 delivery and consumption, and tissue O2 pressure (Po2) were measured. No changes in systemic hemodynamics were seen with nitroglycerin. Despite flow-limiting stenosis, MBF increased significantly in the central 25% of the ischemic bed, which was associated with an approximately 19% decrease in WBeta. There was a good correlation (r=0.87) between the two. The decrease in WBeta was associated with a decrease in EC and an increase in EM (r=0.83). The nitroglycerin-induced increase in tissue Po2 was disproportionate to the increase in MBF, indicating enhanced O2 unloading. Erythrocyte S-nitrosothiol content (reflecting mainly S-nitrosohemoglobin) was significantly higher for blood exposed in vitro to 0.1 micromol/L nitroglycerin or the NO donor SNAP, as compared with control (18.9+/-8.8 and 10.5+/-6.5 versus 2.6+/-0.5x10(-5), P<0.05).

CONCLUSIONS

The augmented MBF in the ischemic microcirculation during nitroglycerin administration occurs in tandem with increased erythrocyte S-nitrosothiol content, EM, and O2 unloading. These additional microvascular mechanisms may contribute to the powerful antiischemic effects of nitroglycerin, especially during low-flow states.

Effective intracoronary thrombectomy with the X-sizer catheter of the right coronary artery and left anterior descending artery in a patient with acute inferior and right ventricular infarction complicated by hypotension and diffuse intracoronary thrombosis

Intracoronary thrombosis of non infarct-related arteries during an episode of acute myocardial infarction can be correlated with a general thrombogenic state and precipitated by prolonged hypotension. We report the case of a patient with acute inferior and right ventricular infarction with acute thrombotic obstruction of the proximal right coronary artery and associated sessile thrombus in the proximal left anterior descending artery, both successfully treated by thromboaspiration with the X-Sizer catheter (ev3, Inc., Plymouth, Minnesota, USA).

Assessing myocardial perfusion after myocardial infarction

Ashrafian and colleagues describe the use of myocardial contrast echocardiography to assess a 63-year-old man with ischemic heart disease.

EMERALD, AIMI, and PROMISE: is there still a potential for embolic protection in primary PCI?

The recent trials of routine use of embolic protection devices for primary percutaneous coronary interventions (PCI) (the EMERALD, PROMISE, and AIMI trials) have demonstrated neutral or even negative effects of these devices on myocardial reperfusion and final infarct size. Despite these results, there is still ground to believe that PCI-induced embolization may be clinically relevant in specific subsets of patients with acute myocardial infarction (AMI). Significant clinical consequences may be expected when embolization is quantitatively relevant and/or is qualitatively characterized by lipid-rich athero-embolism (as is the case of lipid core embolization through the ruptured cap of a fibro-atheroma). Future trials on embolic protection devices in primary PCI should adopt a selective, rather than a routine strategy, through the identification, by angiographic or intravascular imaging parameters, of patients at highest risk of clinically relevant embolization. Such trials should also adopt specific endpoints able to evaluate the effect of micro-embolization, which is currently far from optimally assessed by the standard markers of myocardial reperfusion.

Circadian variation in myocardial perfusion and mortality in patients with ST-segment elevation myocardial infarction treated by primary angioplasty

BACKGROUND

Little is known about whether the physiological factors that determine the circadian variation in ST-segment elevation myocardial infarction (STEMI) onset and thrombolysis efficacy may affect myocardial perfusion and long-term outcome of patients with STEMI treated with primary angioplasty.

METHODS

Our study population consisted of 1548 consecutive patients with STEMI treated by primary angioplasty between April 1997 and October 2001. All clinical, angiographic, and follow-up data were collected.

RESULTS

Most of the patients (65.2%) were treated at daytime (between 8 AM and 8 PM). Patients treated between 1 PM and midnight had a lower prevalence of anterior infarction and longer door-to-balloon time, whereas the shortest ischemic time and the largest use of stent were observed in patients treated between midnight and 4 AM Patients treated between 4 and 8 AM showed the worst outcome in terms of myocardial perfusion, enzymatic infarct size, and 1-year outcome, whereas patients treated between 8 AM and 4 PM had the best myocardial perfusion and lowest 1-year mortality rate. After correction for baseline confounding factors, the time of treatment (between 4 and 8 AM) was still significantly associated with 1-year mortality (relative risk 1.92, 95% CI 1.13-3.26, P = .016).

CONCLUSIONS

This is the first study showing a significant relationship between the time of treatment, myocardial perfusion, and long-term mortality in patients with STEMI undergoing mechanical reperfusion.

Intravenous Versus Intracoronary Myocardial Contrast Echocardiography for Evaluation of No-Reflow After Primary Percutaneous Coronary Intervention

OBJECTIVE

We sought to compare intravenous myocardial contrast echocardiography (IV-MCE) with intracoronary myocardial contrast echocardiography (IC-MCE) in detecting no-reflow and predicting the short-term outcome of left ventricular function after primary percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI).

METHODS

IC-MCE and IV-MCE were performed immediately after PCI (D1) of 28 patients with anterior wall AMI. IV-MCE was repeated at the next day of PCI (D2), and left ventricular systolic function was evaluated at D2 and 30 days later (D30).

RESULTS

There was good agreement between IC-MCE and IV-MCE at D1 in determining no-reflow (kappa= 0.78, P < 0.001) as well as between IV-MCE at D1 and D2 (kappa= 0.93, P < 0.001). The patients with no-reflow on IC-MCE (n = 13) and those on IV-MCE at D2 (n = 11) showed no improvement in left ventricular ejection fraction (LVEF) after 1 month (49 +/- 9% to 48 +/- 7%, P = 0.55, and 51 +/- 6% to 49 +/- 7%, P = 0.20). However, the patients with reflow on IC-MCE (n = 15) and those on IV-MCE at D2 (n = 17) demonstrated significant improvement in LVEF (55 +/- 6% to 62 +/- 5%, P < 0.005, and 53 +/- 7% to 60 +/- 8%, P < 0.005). In predicting segmental functional recovery after 1 month, sensitivity and specificity of IC-MCE were 85% and 67%, respectively, and those of IV-MCE at D2 were 95% and 40%, respectively.

CONCLUSION

IV-MCE at D2 might be substituted for IC-MCE performed immediately after PCI for the evaluation of no-reflow and prediction of left ventricular systolic function after 1 month in patients with anterior wall AMI.