Illusion of reperfusion. Does anyone achieve optimal reperfusion during acute myocardial infarction?

Augmentation of reperfusion by noninvasive, transcutaneous delivery of low-frequency, high-intensity ultrasound

There is a need for developing alternative safe, inexpensive and noninvasive methods for rapid and effective recanalization of thrombosed arteries and veins that can be commenced immediately upon admission to hospital, or even prior to admission. Transcutaneous delivery of low-frequency, high-intensity ultrasound has the potential to be used clinically in various types of thrombotically occluded blood vessels including acute myocardial infarction, strokes, ischemic limbs, obliteration of A-V fistulas of patients undergoing hemodialysis, retinal vein thrombosis, deep vein thrombosis, and even thrombotically stuck prosthetic heart valves. Thus far, various noninvasive ultrasound systems have been used in several animal models. These systems vary in the mode of ultrasound delivery (continuous versus pulse, diffuse versus concentrated or pulsed beam), frequency (between 20 kHz and 1 mHz), and intensity. In general, lower frequencies have better penetration through overlying tissue (skin, fat, bone) and, probably, better efficacy.

Treatment strategies for microvascular dysfunction following acute myocardial infarction

Successful reperfusion following acute myocardial infarction is considered to be restoration of epicardial infarct vessel patency, but recent studies suggest that disrupted microvascular function and inadequate myocardial tissue perfusion are often present despite epicardial patency. New angiographic techniques, including the corrected Thrombolysis in Myocardial Infarction (TIMI) frame count and myocardial blush grade, have been used to demonstrate that restoration of downstream coronary flow and tissue perfusion may be the key links to improved clinical outcomes. Additionally, other diagnostic techniques, including infarct size measurement with cardiac marker release patterns, or (99m) Tc-sestamibi single photon emission computed tomography imaging, and analysis of ST-segment resolution have also been used to assess microvascular function and tissue perfusion. Promising adjunctive therapies that target microvascular dysfunction, including platelet glycoprotein IIb/IIIa inhibitors, anti-inflammatory agents, vasodilators, glucose-insulin-potassium, and embolization protection devices, may ameliorate microvascular dysfunction following epicardial reperfusion. However, these therapies have not yet been shown to improve clinical outcomes and are thus currently being studied together with fibrinolytics and primary angioplasty in clinical trials. Therefore, shifting the focus of reperfusion therapy to the microcirculation offers the potential to further improve myocardial salvage and clinical outcomes following acute myocardial infarction.

Microparticle-containing oncotic solutions augment in-vitro clot disruption by ultrasound

Echocardiographic contrast agents enhance blood clot disruption by ultrasound. It has been suggested that the microbubbles add nuclei for the enhancement of cavitation by ultrasound. However, microbubbles are rapidly destroyed by the ultrasound energy. We assessed whether non-gas filled colloidal solutions (hyperoncotic medium molecular hydroxyethyl starch and degraded gelatin polypeptides) will facilitate clot disruption by ultrasound. In two separate experiments human blood clots, 200-400 mg in weight, were weighed and then immersed for 15 seconds in 10 ml normal saline solution containing 0%, 0.1%, 1%, 2%, and 5% of hyperoncotic medium molecular hydroxyethyl starch or 0%, 0.035%, 0.175%, 0.35%, and 0.7% degraded gelatin polypeptides. Clots were randomized to 10 seconds 20 kHz ultrasound or immersion without ultrasound. After treatment, the clots were reweighed, and the percent difference in weight was calculated. Non-gas filled microparticle-containing solutions such as hyperoncotic medium molecular hydroxyethyl starch and degraded gelatin polypeptides significantly augmented blood clot disruption by ultrasound. The effect is dependent on the colloidal solution concentration with maximal effect achieved with 1% hyperoncotic medium molecular hydroxyethyl starch and 0.35% degraded gelatin polypeptides.

Reperfusion syndrome: relationship of coronary blood flow reserve to left ventricular function and infarct size

OBJECTIVES

We tested the hypothesis that the reperfusion syndrome (RS), defined as an additional elevation of the ST segment upon reperfusion, may be a marker of microcirculatory reperfusion injury during acute myocardial infarction (AMI).

BACKGROUND

The pathophysiology of the RS is unknown, and its prognostic implications are controversial.

METHODS

Twenty-one patients with an anterior AMI treated < or =12 h after onset by primary coronary angioplasty (PTCA) were studied. Coronary velocity reserve (CVR), an index of microcirculatory function, was measured using a Doppler guidewire. Left ventricular (LV) ejection fraction, infarct size (percent defect) and LV end-systolic volume index (LVESVi) were evaluated by radionuclide ventriculography, 201T1 single-photon emission computed tomography and contrast ventriculography, respectively.

RESULTS

Baseline ST elevation and pain-to-TIMI 3 time were similar in patients with and without RS. Patients with RS (10/21) had a lower post-PTCA CVR than patients without RS (median [95% confidence interval]: 1.2 [1-1.3] vs. 1.6 [1.5-1.7], p < 0.005). Even though predischarge CVR was similar in the two groups, infarct size at six weeks (26 [21 to 37] vs. 14 [10-17]% 201T1 defect, p = 0.001) and predischarge LVESVi (45% [40 to 52] vs. 30% [29 to 38] mL/m2, p = 0.001) were larger, and LV ejection fraction at six weeks (40% [37 to 46] vs. 55% [50 to 60], p = 0.004) was lower in patients with RS than in patients without RS.

CONCLUSIONS

Patients with RS during primary PTCA for an anterior AMI have a transiently lower CVR than patients without RS, but sustained LV dysfunction and larger infarct size, suggesting that RS is a marker of microcirculatory reperfusion injury.

Pressure-derived fractional collateral blood flow: a primary determinant of left ventricular recovery after reperfused acute myocardial infarction

OBJECTIVES

We evaluated the relation between pressure-derived fractional collateral flow (PDCF) and left ventricular (LV) recovery after reperfused acute myocardial infarction (AMI).

BACKGROUND

The functional significance of collateral flow remains uncertain in AMI.

METHODS

The PDCF was measured in 70 patients with first AMI (pain onset <12 h) treated with primary angioplasty (PA), being determined by simultaneous measurement of mean aorta pressure (Pa), distal coronary pressure during the balloon occlusion (Poc), and central venous pressure (CVP): (Poc - CVP)/(Pa - CVP)*100. Sufficient collateral (group I) was defined as PDCF index >24% and insufficient collateral (group II) as PDCF index <24%. Echocardiography was performed before, and on day 3, day 7, and day 30 after PA. Wall-motion recovery index (RI) was obtained by dividing the number of improved wall-motion segments (>grade 1) at follow-up by the number of abnormal wall-motion segments within the infarct zone at baseline.

RESULTS

Baseline characteristics were similar between both groups. Peak levels of creatine kinase were lower in group I than in group II (2,600+/-1,900 U/liter vs. 4,100+/-3,000, p < 0.05). At one month, infarct zone wall-motion score index (1.65+/-0.54 vs. 2.31+/-0.46, p < 0.01) and LV volume indexes were smaller in group I than in group II, whereas, LV ejection fraction was higher in group I than in group II (52.8+/-8.3 vs. 45.9+/-9.0, p < 0.01). The PDCF index was the strongest predictor of RI at one month (r = 0.61, p < 0.01). Time to reperfusion was not related to RI at one month. However, it was significantly related to RI in group II (r = -0.34, p < 0.05).

CONCLUSIONS

The LV recovery after reperfused AMI is primarily determined by PDCF and is less dependent on time to reperfusion in patients with sufficient collaterals.

Prognostic implications of TIMI flow grade in the infarct related artery compared with continuous 12-lead ST-segment resolution analysis. Reexamining the "gold standard" for myocardial reperfusion assessment

OBJECTIVE

To compare the prognostic significance of reperfusion assessment by Thrombolysis in Myocardial Infarction (TIMI) flow grade in the infarct related artery and ST-segment resolution analysis, by correlating with clinical outcomes in patients with acute myocardial infarction (AMI).

BACKGROUND

Angiographic assessment, based on epicardial coronary anatomy, has been considered the "gold standard" for reperfusion. The electrocardiogram (ECG) monitoring provides a noninvasive, real-time physiologic marker of cellular reperfusion and may better predict clinical outcomes.

METHODS

Two hundred fifty-eight AMI patients from the Thrombolytics and Myocardia Infarction phase 7 and Global Utilization of Streptokinase tPA for Occluded coronary arteries phase 1 trials were stratified based on blinded, simultaneous reperfusion assessment on the acute angiogram (divided into TIMI grades 0 & 1, TIMI grade 2 and TIMI grade 3) and ST-segment resolution analysis (divided into: <50% ST-segment elevation resolution or reelevation and > or =50% ST-segment elevation resolution). In-hospital mortality, congestive heart failure (CHF) and combined mortality or CHF were compared to determine the prognostic significance of reperfusion assessment by each modality using chi-square and Fisher's Exact tests for univariable correlation and logistic regression analysis for univariable and multivariable prediction models.

RESULTS

By logistic regression analysis, ST-segment resolution patterns were an independent predictor of the combined outcome of mortality or CHF (p = 0.024), whereas TIMI flow grade was not (p = 0.693). Among the patients determined to have failed reperfusion by TIMI flow grade assessment (TIMI flow grade 0 & 1), the ST-segment resolution of > or =50% identified a subgroup with relatively benign outcomes with the incidence of the combined end point of mortality or CHF 17.2% versus 37.2% in those without ST-segment resolution (p = 0.06).

CONCLUSION

Continuous 12-lead ECG monitoring can be an inexpensive and reliable modality for monitoring nutritive reperfusion status and to obtain prognostic information in patients with AMI.

Rescue PTCA Following Failed Thrombolysis and Primary PTCA: A Retrospective Study of Angiographic and Clinical Outcome

Evidence is increasing that a patent culprit artery improves the prognosis of patients with acute myocardial infarction (AMI). Primary percutaneous transluminal coronary angioplasty (PTCA) has shown to be more effective than thrombolytic therapy alone. How effective is rescue PTCA after failed thrombolytic treatment? In a retrospective analysis, 176 consecutive patients with AMI and TIMI 0 or 1 perfusion grade were included. Patients had either rescue PTCA after failed thrombolysis (100 patients) or primary PTCA (76 patients). Angiographic data and in-hospital and 1-year outcome were analyzed. Comparison of baseline data of the two groups showed a higher proportion of long-standing angina and use of nitrates and aspirin in the primary PTCA group. Also, the delay between the onset of pain and PTCA was not significantly different, with a mean of 222 minutes for rescue PTCA and 245 minutes for primary PTCA (p = 0.52). The angiographic outcomes in the rescue PTCA group and the primary PTCA group were identical: The intervention was successful (TIMI 3 flow and residual stenosis <50%) in 86.0% and 85.5%, respectively. Complication rates of the procedure were also similar, except for bleeding complications. Blood transfusion was only needed after rescue PTCA in 3.0% versus 0.0% in primary PTCA patients. Clinical outcomes during hospital stay in terms of death rate (4.0% and 6.6%), reinfarction (6.0% and 3.9%), recurrent angina (16.0% and 11.8%), and repeat interventions were comparable, as was the first-year outcome. Failed PTCA was the most important predictor of a poor 1-year outcome; 28.0% died after failed PTCA versus 4.6% after successful PTCA (p < 0.001). In this retrospective analysis of 176 AMI patients, angiographic and clinical outcome, including a 1-year follow-up in patients who had rescue PTCA after failed thrombolysis, were of the same magnitude of patients in whom primary PTCA was performed. These findings suggest that in this subset the outcome of patients with rescue PTCA because of failed thrombolysis is good and is comparable with patients who underwent primary PTCA.

Early, Complete Infarct Vessel Patency: Arriving at a Gold Standard for Future Clinical Investigation in Myocardial Reperfusion

Early clinical trials of thrombolytic therapy in the setting of acute myocardial infarction (AMI) demonstrated that early angiographic reperfusion correlated with improved survival. This supported the open-artery hypothesis that early reperfusion decreases infarct size, improves left ventricular function, and improves survival. Two subsequent comparative thrombolytic trials showed no difference in left ventricular function or survival between agents with different rates of reperfusion. Additionally, reduction in mortality was demonstrated without improvement in left ventricular function and with the late administration of thrombolytic therapy. Therefore, there was a real question as to the importance of infarct vessel patency, and its relation to clinical outcome. This article discusses the various markers of coronary artery patency, their relation to clinical outcome, and how they reflect perfusion at the tissue level. The coronary angiogram gives a snapshot view of the infarct-related artery (IRA) that does not reflect the dynamic process of vessel reocclusion and recanalization. The patent artery is therefore "open" at only a given time frame, and may undergo cyclic or complete reocclusion. Angiographically characterized flow has been demonstrated to be more clinically meaningful. The GUSTO-I trial was designed to test the open-artery hypothesis. This trial confirmed that improved early IRA patency and optimal (TIMI-3) flow correlated with improved survival. The presence of TIMI-3 flow in the IRA has consistently demonstrated significant improvement in patient morbidity and mortality, and conversely, less than optimal, but still "patent" (TIMI-2) flow in the IRA correlates with clinical outcomes observed in patients with occluded infarct vessels. Even TIMI-3 flow in the IRA does not always confirm perfusion of the myocardium at risk. Therefore, the "patent" IRA can be subsequently compromised by intermittent patency, reocclusion, less than TIMI-3 flow, and a "no-reflow" effect at the tissue level. The development of accurate, reliable non-invasive markers of IRA patency is crucial. This would allow a more selective application of invasive and interventional techniques to restore patency to the IRA. The merits and faults of these noninvasive markers are discussed. The ideal gold standard for establishing the adequacy of therapy in AMI is one that could detect rapid, complete, and sustained coronary reperfusion with adequate myocardial perfusion. Current technologic achievements allow an approach to this ideal; however, as of 1997, the coronary angiogram demonstrating TIMI-3 flow represents the clinically proven standard of optimal therapeutic efficacy.

Efficacy and Safety of Low-Dose Streptokinase plus Desmopressin in Acute Myocardial Infarction: A Pilot Study

In this pilot study the combined use of desmopressin, which releases tissue plasminogen activator from vascular endothelium, and a low dose of streptokinase as a new thrombolytic regimen for acute myocardial infarction is proposed. Eighteen patients with acute myocardial infarction were treated intravenously with 150,000 U (4 patients) or 250,000 U (14 patients) of streptokinase infused over 10 minutes, followed by 24 µg of desmopressin infused over 5-10 minutes. Aspirin and beta-blockers were administered at admission, and heparin and oral anticoagulants were started at the end of the thrombolytic regimen. Hemostatic parameters were studied before and 30, 60, 120, and 240 minutes after starting thrombolytic therapy. Fifteen patients (83.3%) had evidence of clinical reperfusion. Angiography was performed with a mean delay of 8.8 hours (range 1.5-22 hours) from the start of thrombolytic therapy. Fourteen patients (77.8%) had patency of the infarct-related artery: 10 patients (55.6%) achieved TIMI grade 3, and 4 patients (22%) achieved TIMI grade 2. Two patients (one TIMI grade 1 and one TIMI grade 2) underwent coronary angioplasty. No patient died during the in-hospital period. At 18 months follow-up, all patients are alive. No major or minor bleeding was detected. The significant decline in plasma fibrinogen and in the euglobulin lysis time, and the increase in fibrinogen/fibrin degradation products, indicate a plasma lytic state. Crosslinked fibrin degradation products increased from 310 +/- 120 ng/ml to 670 +/- 310 ng/ml (p = 0.009), suggesting that fibrin digestion occurred in vivo. This pilot study provides data supporting the feasibility and efficacy of a new and more economic thrombolytic treatment of acute myocardial infarction without hemorrhagic complications.

Randomized, Placebo-Controlled Study of Lamifiban with Thrombolytic Therapy for the Treatment of Acute Myocardial Infarction: Rationale and Design for the Platelet Aggregation Receptor Antagonist Dose Investigation and Reperfusion Gain in Myocardial Infarction (PARADIGM) Study

The benefits of thrombolytic therapy in the treatment of acute myocardial infarction are incontrovertible. Large-scale studies combining angiographic and clinical end-points have demonstrated a perfusion-mortality relationship, with the highest survival rate among patients with early restoration of TIMI grade 3 coronary arterial flow. Despite advances in thrombolytic strategies, a substantial number of patients fail to rapidly achieve and maintain adequate coronary perfusion with thrombolysis. Conjunctive therapy with aspirin has proven useful in thrombolytic regimens, likely countering the heightened platelet activity central to acute coronary syndromes. The antiplatelet effect of aspirin is relatively weak compared with that of glycoprotein IIb/IIIa platelet receptor antagonists, which block the final common pathway of platelet aggregation. Lamifiban is a nonpeptide glycoprotein IIb/IIIa receptor antagonist. In early experimental studies, Lamifiban in combination with thrombolytic therapy has been shown to effectively restore coronary arterial patency, and phase I and phase II data have shown its use to be safe. To determine the optimal dose with regard to safety and efficacy of Lamifiban to be used with thrombolytic therapy in a large-scale trial, a phase II study is underway. The Platelet Aggregation Receptor Antagonist Dose Investigation and Reperfusion Gain in Myocardial Infarction (PARADIGM) study is a randomized, placebo-controlled study of Lamifiban in 400 patients receiving thrombolysis as treatment for acute myocardial infarction. By studying 90-minute angiography, platelet aggregation, continuous electrocardiography, and clinical outcome in PARADIGM, important insights will be obtained to determine the optimal dose of Lamifiban for phase III study. We provide the background and rationale for the study of Lamifiban in PARADIGM and other ongoing studies in acute coronary syndromes.

Myocardial perfusion and oxygen consumption in reperfused noninfarcted dysfunctional myocardium after unstable angina: direct evidence for myocardial stunning in humans

OBJECTIVES

To positively establish the diagnosis of myocardial stunning in patients with unstable angina and persistent wall motion abnormalities after reperfusion by coronary angioplasty.

BACKGROUND

Although myocardial stunning is thought to occur in several clinical conditions, definite proof of its existence in humans is still lacking, owing to the difficulty of measuring myocardial blood flow (MBF) in absolute terms.

METHODS

We studied 14 patients with unstable angina due to proximal left anterior descending coronary artery disease who presented persistent anterior wall motion abnormalities despite revascularization of the culprit lesion by percutaneous coronary angioplasty (PTCA) and who did not have clinical evidence of necrosis. Dynamic positron emission tomography (PET) with [13N]-ammonia and [11C]-acetate was performed 48 h after PTCA to determine absolute MBF and oxygen consumption (MVO2). Regional wall thickening and regional cardiac work were determined using two-dimensional echocardiography. Improvement of segmental wall motion abnormalities was followed for a median of 4 months (1.5 to 14 months).

RESULTS

As judged from the changes in segmental wall motion score, regional dysfunction was spontaneously reversible in 12/14 patients and improved from 2.2 +/- 0.3 to 1.2 +/- 0.3 at late follow-up (p < 0.001). With PET, [13N]-ammonia MBF was similar among dysfunctional and remote normally contracting segments (85 +/- 29 vs. 99 +/- 20 ml x min (-1) x 100g(-1), p = not significant [n.s.]), thus demonstrating a perfusion-contraction mismatch. Despite the reduced contractile function, dysfunctional myocardium presented near normal levels of MVO2 (6.5 +/- 4.2 vs. 8.0 +/- 1.9 ml x min (-1)x 100g(-1), p = n.s.). Consequently, the regional myocardial efficiency (regional work divided by MVO2) of the dysfunctional myocardium was found to be markedly decreased as compared with normally contracting myocardium (6 +/- 6% vs. 26 +/- 6%, p < 0.001).

CONCLUSIONS

This study demonstrates that human dysfunctional myocardium capable of spontaneously recovering contractile function after unstable angina endures a state of perfusion-contraction mismatch. These data for the first time provide unequivocal direct evidence for the existence of acute myocardial stunning in humans.

Coronary microembolization--its role in acute coronary syndromes and interventions

The diagnosis coronary artery disease is classically based on patient's symptoms and morphology, as analyzed by angiography. The importance of risk factors for the development of coronary atherosclerosis and disturbance of coronary vasomotion is clearly established. However, microembolization of the coronary circulation has also to be taken into account. Microembolization may occur as a single or as multiple, repetitive events, and it may induce inflammatory responses. Spontaneous microembolization may occur, when the fibrous cap of an atheroma or fibroatheroma (Stary i.v. and Va) ruptures and the lipid pool with or without additional thrombus formation is washed out of the atheroma into the microcirculation. Such events with progressive thrombus formation are known as cyclic flow variations. Plaque rupture occurs more frequently than previously assumed, i.e. in 9% of patients without known heart disease suffering a traffic accident and in 22% of patients with hypertension and diabetes. Also, in patients dying from sudden death microembolization is frequently found. Patients with stable and unstable angina show not only signs of coronary plaque rupture and thrombus formation, but also microemboli and microinfarcts, the only difference between those with stable and unstable angina being the number of events. Appreciation of microembolization may help to better understand the pathogenesis of ischemic cardiomyopathy, diabetic cardiomyopathy and acute coronary syndromes, in particular in patients with normal coronary angiograms, but plaque rupture detected by intravascular ultrasound. Also, the benefit from glycoprotein IIb/IIIa receptor antagonist is better understood, when not only the prevention of thrombus formation in the epicardial atherosclerotic plaque, but also that of microemboli is taken into account. Microembolization also occurs during PTCA, inducing elevations of troponin T and I and elevations of the ST segment in the EKG. Elevated baseline coronary blood flow velocity, as a potential consequence of reactive hyperemia in myocardium surrounding areas of microembolization, is more frequent in patients with high frequency rotablation than in patients with stenting and in patients with PTCA. The hypothesis of iafrogenic microembolization during coronary interventions is now supported by the use of aspiration and filtration devices, where particles with a size of up to 700 microns have been retrieved. In the experiment, microembolization is characterized by perfusion-contraction mismatch, as the proportionate reduction of flow and function seen with an epicardial stenosis is lost and replaced by contractile dysfunction in the absence of reduced flow. The analysis of the coronary microcirculation, in addition to that of the morphology and function of epicardial coronary arteries, and in particular appreciation of the concept of microembolization will further improve the understanding of the pathophysiology and clinical symptoms of coronary artery disease.

Microvascular integrity after reperfusion therapy

Several perfusion techniques have definitively shown that microvascular dysfunction plays a crucial role in patients with acute myocardial infarction. In those patients, despite a rapid and sustained restoration of flow throughout a previously occluded epicardial coronary artery, microvascular damage still may be observed. Duration of ischemia and/or time to recanalization are the most powerful determinants of microvascular dysfunction. However, the amount of tissue perfusion in infarcted patients is dependent on many other complex interrelated factors including extent of collateral circulation before recanalization, residual stenosis severity of the culprit artery, vasodilator reserve in the infarct territory, extent of reperfusion injury, and loading conditions. Because microvascular dysfunction is associated with progressive left ventricular dilation and a high frequency of postinfarction complications, all of the efforts to improve the relation between coronary reflow and microvascular perfusion are justified.

Saruplase is a safe and effective thrombolytic agent; observations in 1,698 patients: results of the PASS study. Practical Applications of Saruplase Study

Saruplase (unglycosylated human-type high molecular weight single-chain urokinase-type plasminogen activator) was given to 1698 patients in the open-label Practical Applicability of Saruplase Study (PASS), which assessed the safety and efficacy of saruplase in the treatment of acute myocardial infarction. Thirty-seven hospitals in Europe participated in the study. All patients received 20 mg saruplase as a bolus followed by an infusion of 60 mg saruplase over 1 hour. Prior to the infusion of saruplase, 62% of the patients received a bolus of 5000 U of heparin, and after saruplase a 24-hour intravenous infusion of heparin was given to 95% of patients. The mean age of the patients was 59 years and 80.1% were male. The median delay from the onset of chest pain to the start of saruplase infusion was 145 minutes. Acute angiography was performed in 8 of the participating 37 centers in 350 patients (20.6%), on average 85 minutes (median) after the start of the saruplase infusion. TIMI 3 flow was obtained in 186 patients (53.1%) and TIMI 2 flow in 61 patients (17.4%). Patency rates were similar for patients with anterior and inferior infarction. ECG signs suggestive of reperfusion were seen in 63% of the patients. In-hospital mortality was low (92 patients; 5.4%), and nonfatal recurrent myocardial infarction was seen in 60 patients (3.5%). Severe bleeding complications occurred in 92 patients (5.4%), 21 of whom (1.2%) needed a blood transfusion. An intracerebral hemorrhage was observed in eight patients (0.5%), and seven patients (0.4%) suffered from a thromboembolic stroke. At discharge 85.9% of the patients were in NYHA functional class I. One-year mortality was low (142 patients; 8. 4%). Mortality was high in patients with TIMI 0 or 1 flow at the acute angiography who did not undergo rescue PTCA (9/39; 23.1%), lower in patients with TIMI 0 or 1 flow followed by successful rescue PTCA (7/64; 10.9%), and low in patients with TIMI 2 flow (1/61; 1.6%) or with TIMI 3 flow (2/186; 1.1%). Patency rates and (bleeding) complications did not differ between patients with a body weight greater than or less than 70 kilograms. No antibodies against saruplase were detected in samples from 455 patients. In conclusion, it can be stated that saruplase, given in combination with aspirin and intravenous heparin, can be given safely and effectively to patients with acute myocardial infarction.

Optimal management of acute myocardial infarction at the dawn of the next millennium

At the dawn of the next millennium, the optimal management of acute myocardial infarction will have been defined by multiple clinical trials of acute reperfusion strategies, in conjunction with adjunctive pharmacotherapy. Reperfusion therapy with thrombolytic agents or primary angioplasty is the standard of care for many patients examined with ST-segment elevation or left bundle branch block within approximately 12 hours of symptoms. The superiority of fibrin-specific agents over streptokinase has been established, as have the advantages of primary angioplasty in selected institutions with the requisite expertise and logistical capabilities. The key to successful reperfusion lies more in the efficiency of delivery than in the choice of modality. Reocclusion remains the "Achilles' heel" of reperfusion therapy, as does the presence of reperfusion injury microvascular dysfunction and the "no-reflow" phenomenon. These entities are major targets for further investigation in the next 5 years. The wealth of adjunctive pharmacologic agents currently available presents a challenge to the optimal treatment of myocardial infarction. A major objective is to define the magnitude of the incremental benefits and risks of using the available and new drugs, both alone and in combination. Moreover, community-wide studies indicate a marked underutilization of therapies that are available and are of proven effectiveness. The key to optimal management, as we enter the new millennium, lies in the search for new therapies in concert with the most effective use of those agents already at our disposal.

Clinical applications of transpulmonary contrast echocardiography

BACKGROUND

The recent development of new fluorocarbon-based echocardiographic contrast agents that are capable of opacification of the left-sided cardiac chambers after intravenous injection is a major new advance in diagnostic cardiac imaging.

METHODS AND RESULTS

This is a review article focusing on these novel contrast agents, new echocardiographic imaging techniques to optimize their efficacy, and their clinical applications. Specific clinical applications of these agents are (1) enhancement of endocardial border definition to improve assessment of regional and global left ventricular function, (2) myocardial perfusion imaging by intravenous contrast echocardiography, (3) augmentation of spectral and color flow Doppler images, and (4) tissue-specific targeting of microbubbles for delivery of therapeutic agents.

CONCLUSIONS

New intravenous contrast agents offer the possibility to assess myocardial perfusion echocardiographically. It is also possible to use these agents for delivery of therapeutic agents, including gene therapy.

Combining thrombolysis with the platelet glycoprotein IIb/IIIa inhibitor lamifiban: results of the Platelet Aggregation Receptor Antagonist Dose Investigation and Reperfusion Gain in Myocardial Infarction (PARADIGM) trial

OBJECTIVES

The trial was designed to assess the safety, pharmacodynamics and effects on reperfusion of the platelet glycoprotein (GP) IIb/IIIa inhibitor lamifiban when given with thrombolysis to patients with ST segment elevation acute myocardial infarction.

BACKGROUND

Studies of fibrinolytic agents in acute myocardial infarction have demonstrated a direct relationship between early complete reperfusion and survival. Blockade of the platelet GP IIb/IIIa receptor complex inhibits platelet aggregation and may speed reperfusion when given in conjunction with thrombolysis to patients with acute myocardial infarction.

METHODS

Patients with ST segment elevation presenting within 12 h of symptom onset who were treated with either tissue-plasminogen activator or streptokinase were enrolled in this three-part Phase II dose exploration study. In Part A, all patients received the GP IIb/IIIa inhibitor lamifiban in an open-label, dose escalation scheme. Parts B and C were a randomized, double-blind comparison of a bolus plus 24-h infusion of lamifiban versus placebo with patients randomized in a 2:1 ratio. The goal was to identify a dose(s) of lamifiban that provided >85% adenosine diphosphate (ADP)-induced platelet aggregation inhibition. A composite of angiographic, continuous electrocardiographic and clinical markers of reperfusion was the primary efficacy end point, and bleeding was the primary safety end point.

RESULTS

Platelet aggregation was inhibited by lamifiban in a dose-dependent manner with the highest doses exceeding 85% ADP-induced platelet aggregation inhibition. There was more bleeding associated with lamifiban (transfusions in 16.1% lamifiban-treated vs. 10.3% placebo-treated patients). Lamifiban induced more rapid reperfusion as measured by all continuous electrocardiographic (ECG) parameters.

CONCLUSIONS

Lamifiban given with thrombolytic therapy appears to be associated with more rapid and complete reperfusion than placebo. As expected in this small sample, there were no obvious clinical benefits to lamifiban over placebo. Reconciliation of ECG monitoring with clinical outcomes will require a larger, adequately powered clinical trial.

Early changes in myocardial perfusion patterns after myocardial infarction: relation with contractile reserve and functional recovery

OBJECTIVES

The purpose of this study was to assess early temporal changes in myocardial perfusion pattern by myocardial contrast echocardiography (MCE) and their relation to myocardial viability in patients with reperfused acute myocardial infarction (AMI).

BACKGROUND

Myocardial contrast echocardiography no-reflow is associated with poor contractile recovery after AMI. However, little is known regarding early reversibility of microvascular dysfunction and its relation to myocardial viability.

METHODS

Intracoronary MCE was performed immediately after reflow and 9 days later in 28 patients with a first AMI and successful coronary recanalization (Thrombolysis in Myocardial Infarction trial grade 3 flow). Semiquantitative contrast score and wall motion score (WMS) were assessed in each initially asynergic segment at initial and repeat MCE study. Low dose dobutamine echocardiography (DE) was performed at day 10, and follow-up (FU) rest echocardiography was performed 6 weeks later.

RESULTS

Among 200 initially asynergic segments, 49% exhibited no or heterogeneous contrast enhancement at initial MCE versus 24% at restudy (p < 0.001). Three groups of segments were defined according to early changes in contrast pattern: group A, "sustained no-reflow" (n = 17); group B, improved contrast score (n = 68), and group C, "sustained reflow" (n = 112). Group A segments showed no improvement in WMS at FU. In contrast, group B segments showed significant improvement in WMS at FU (p < 0.0001), and exhibited more frequently contractile reserve at DE (36% vs. 6%, p = 0.02) and contractile recovery at FU (34% vs. 7%, p = 0.03) than group A segments. Group C segments exhibited contractile reserve and contractile recovery in 47% and 51% of segments respectively.

CONCLUSIONS

Improvement in MCE perfusion pattern may occur after initial no-reflow in the days following reperfused AMI and is associated with preservation of contractile reserve and gradual regional functional recovery.

Current issues in reperfusion therapy

With the establishment of thrombosis as the cause of myocardial infarction, the pivotal role of thrombolytics and primary angioplasty has evolved. Large randomized trials with innovative methodologies have examined the role of these reperfusion therapies in the management of acute coronary syndromes. Intravenous thrombolytic therapy decreases mortality in a broad group of patients with acute myocardial infarction. The GUSTO trial established intravenous tissue plasminogen activator (tPA) used in combination with intravenous heparin as the most effective thrombolytic therapy. Importantly, the time to achieve reperfusion is crucial to the mortality benefit observed, and rapid attainment of Thrombolysis in Myocardial Infarction (TIMI) trial grade 3 flow is achieved in only approximately 55% of patients who receive thrombolytics. Reocclusion, cellular damage, and microvascular dysfunction may contribute to less than optimal results. Percutaneous transluminal coronary angioplasty (PTCA) may be the preferred method of acute reperfusion therapy based on higher rates of TIMI grade 3 flow and lower rates of reocclusion and recurrent myocardial infarction. However, marked variation exists in outcomes and utilization rates among individual institutions, and the benefits of PTCA have not been consistently maintained at 6 months. The use of stents and anticoagulants may improve results, and pre-PTCA strategies also are under investigation. Limitations remain in the efficacy of current reperfusion therapies, supporting the search for improved thrombolytic agents, primary angioplasty, stents, and antithrombotics with the goal of improving TIMI 3 flow rates and achieving reperfusion more rapidly.

Bolus Administration of Saruplase in Europe (BASE), a Pilot Study in Patients with Acute Myocardial Infarction

To study the safety and efficacy of the thrombolytic agent saruplase as a bolus, the angiographic and clinical outcomes of three bolus regimens were investigated in a pilot study conducted in 192 patients with an acute myocardial infarction and were compared with the standard regimen. Fifty-two patients received a double bolus of 40 mg and 40 mg after 30 minutes, 51 patients a bolus of 80 mg, and 36 patients a bolus of 60 mg. Fifty-three patients received the standard regimen (a bolus of 20 mg and 60 mg IV infusion over 1 hour). At 60 minutes TIMI 2 and 3 flow were, respectively, 9.6% and 61.5% with the 40/40-mg bolus, 15.7% and 51.0% with the 80-mg bolus, 16.7% and 30.6% with the 60-mg bolus, and 7.5% and 54.7% with the standard 20/60-mg infusion. At 90 minutes TIMI 2 and 3 flow improved to 9.6% and 73.1%, 15.7% and 56.9%, 13.9% and 36.1%, and 5.7% and 71.7%, respectively. The primary endpoint, persistent patency (TIMI 2 + 3) at 24-45 hours, was seen in 69.2%, 64.7%, 44.4%, and 67.9% of patients who had no rescue PTCA, respectively. Inclusion in the 60-mg bolus group was prematurely stopped because of their low patency rates. The 40/40-mg bolus group had the highest mortality rate (13.5%), whereas the 60-mg bolus group had no deaths. Other adverse event rates were similar in the four groups. This clinical outcome is highly influenced by rescue PTCA of patients with insufficient TIMI flow. This pilot study indicates that in patients with an acute myocardial infarction, a double bolus of 40/40 mg resulted in the highest patency but also had the highest complication rate. The 80-mg single bolus is an attractive alternative for further evaluation because of its acceptable patency and event profile, and its easy form of administration.

Influence of insurance coverage on delays in seeking emergency care in patients with acute chest pain

The time required to decide to seek medical care for acute chest pain is the major modifiable component in the process of care delivery. This study demonstrates that prehospital delay in the setting of acute chest pain was related to the type of health insurance.

Thrombolysis in acute myocardial infarction improves prognosis and prolongs life but will increase the prevalence of heart failure in the geriatric population

This paper will review the hypothesis that early complete thrombolytic therapy in acute myocardial infarction reduces mortality and improves prognosis. ACE inhibitors improve remodelling and anti-platelet drugs or interventional procedures prevent reocclusion of the infarct related coronary artery. Most patients are left with significant myocardial damage and this effect is cumulative with subsequent infarction. The average age of death has increased by 10 years in the last three decades, so that many older patients survive. They have survived acute myocardial infarction and we now have a significant population with important heart failure despite good thrombolytic therapy.

Enhancement of thrombolysis in vivo without skin and soft tissue damage by transcutaneous ultrasound

Previous studies have shown that transcutaneous ultrasound enhances thrombolysis by streptokinase in animals in vivo; however, skin and soft tissue damage induced by ultrasound energy has been a major limitation. The objective of this study was to examine the efficacy of thrombolysis and damage to skin and soft tissues using a newly designed concentrated ultrasound system with a cooling manifold. Using a rabbit model with iliofemoral arterial thrombotic occlusions, 15 pairs of arteries were randomized to receive ultrasound treatment or no ultrasound treatment. Streptokinase (25,000 unit/kg) was given intravenously. Skin temperature was maintained at 25-33 degrees C when ultrasound energy was applied. The serum level of creatine kinase, lactate dehydrogenase, red blood cell counts, and platelet counts were checked at baseline, after thrombus induction, and after ultrasound treatment. Fifteen of fifteen (100%) iliofemoral arteries were angiographically recanalized after ultrasound treatment. In contrast, only 1/15 (6.7%) contralateral arteries were patent after 1 hour. After the subsequent hour with heparin the patency was 14/15 in the ultrasound treated group and 3/15 in the control group. Histologically, the patent arteries had only minimal focal mural thrombus, whereas the angiographically occluded arteries had occlusive thrombi. There was no histologic evidence of ultrasound induced damage to overlying skin, soft tissues, or arteries. In addition, there was no significant rise of creatine kinase, lactate dehydrogenase, or decrease in red blood cell counts and platelet counts induced by ultrasound. In conclusion, transcutaneous concentrated ultrasound which significantly enhances streptokinase induced thrombolysis in vivo can be delivered without concomitant tissue damage. This simple combination therapy has clinical potential for safely treating patients with arterial or venous thromboses.

Tissue-type plasminogen activator therapy versus primary coronary angioplasty: impact on myocardial tissue perfusion and regional function 1 month after uncomplicated myocardial infarction

OBJECTIVES

This study sought to compare the impact of primary coronary angioplasty and thrombolytic therapy for acute myocardial infarction (AMI) on 1-month infarct size and microvascular perfusion.

BACKGROUND

The effect of the reperfusion strategies of primary coronary angioplasty and thrombolytic therapy on microvascular integrity still remains to be determined.

METHODS

Sixty-two consecutive patients with a first AMI, undergoing intravenous tissue-type plasminogen activator (t-PA) therapy (32 patients, Group I) or primary angioplasty (30 patients, Group II), were studied. Only patients with 1-month Thrombolysis in Myocardial Infarction (TIMI) flow grade 2 or 3 were selected for the study. Patients in whom primary angioplasty was unsuccessful or those with clinical evidence of failed reperfusion were excluded. Microvascular perfusion was assessed at 1 month by intracoronary injection of sonicated microbubbles. Contrast score index (CSI) and wall motion score index (WMSI) were derived using qualitative methods.

RESULTS

At baseline there were no significant differences between groups for age, risk factors, time to hospital presentation, Killip class on admission, prevalence of multivessel disease or anterior infarct site, infarct area extension before reperfusion, peak creatine kinase levels and postinfarction treatment. Conversely, significant differences between groups were found at follow-up for percent residual infarct related-artery (IRA) stenosis (70 +/- 12 vs 36 +/- 14 [mean +/- SD], p = 0.0001), CSI (1.02 +/- 0.4 vs. 1.49 +/- 0.5, p = 0.0003) and WMSI (1.67 +/- 0.3 vs. 1.45 +/- 0.3, p = 0.015). In particular, in the subset of patients with TIMI grade 3 flow, a perfusion defect occurred in one or more segments subtended by the IRA in 72% of Group I versus 31% of Group II patients (p < 0.00001) and in 27% of Group I versus 8% of Group II segments (p < 0.00001).

CONCLUSIONS

The present study shows, in a highly selected cohort with successful IRA recanalization, that primary angioplasty is more effective than thrombolysis in preserving microvascular flow and preventing extension of myocardial damage at 1-month after AMI.

A comparison of reteplase with alteplase for acute myocardial infarction

BACKGROUND

Reteplase (recombinant plasminogen activator), a mutant of alteplase tissue plasminogen activator, has a longer half-life than its parent molecule and produced superior angiographic results in pilot studies of acute myocardial infarction. In this large clinical trial, we compared the efficacy and safety of these two thrombolytic agents.

METHODS

A total of 15,059 patients from 807 hospitals in 20 countries who presented within 6 hours after the onset of symptoms with ST-segment elevation or bundle-branch block were randomly assigned in a 2:1 ratio to receive reteplase, in two bolus doses or 10 MU each given 30 minutes apart, or an accelerated infusion of alteplase, up to 100 mg infused over a period of 90 minutes. The primary hypothesis was that mortality at 30 days would be significantly lower with reteplase.

RESULTS

The mortality rate at 30 days was 7.47 percent for reteplase and 7.24 percent for alteplase (adjusted P=0.54; odds ratio, 1.03; 95 percent confidence interval, 0.91 to 1.18). The 95 percent confidence interval for the absolute difference in mortality rates was -1.1 to 0.66 percent. Stroke occurred in 1.64 percent of patients treated with reteplase and in 1.79 percent of those treated with alteplase (P= 0.50). The respective rates of the combined end point of death or nonfatal, disabling stroke were 7.89 percent and 7.91 percent (P=0.97; odds ratio, 1.0; 95 percent confidence interval, 0.88 to 1.13).

CONCLUSIONS

As compared with an accelerated infusion of alteplase, reteplase, although easier to administer, did not provide any additional survival benefit in the treatment of acute myocardial infarction. Other results, particularly for the combined end point of death or nonfatal, disabling stroke, were remarkably similar for the two plasminogen activators.

Rapid reduction of ST-segment elevation after successful direct angioplasty in acute myocardial infarction

The aim of this study was to evaluate whether assessment of ST-segment changes in the 12-lead electrocardiogram from admission to 30 minutes after successful direct coronary angioplasty can predict myocardial damage and functional outcome in patients with acute myocardial infarction (AMI). Of 158 consecutive patients, 117 (92 men, aged 61 +/- 11 years) were prospectively classified into 2 groups: group 1, <50% reduction in ST-segment elevation in a single selected lead (42 patients); group 2, > or =50% reduction in ST-segment elevation (75 patients). Baseline characteristics were similar except for anterior wall AMI and Killip class >2, which were more prevalent in group 1. Peak creatine kinase was significantly higher in group 1 (3,690 +/- 2,809 vs 2,592 +/- 1,960 U/L; p = 0.018). One-month echocardiograms were obtained in 102 patients (87%). Infarct zone wall motion score index decreased in both groups, but this reduction was higher in group 2 (p <0.001). Functional recovery (>0.22 decrease in infarct zone wall motion score index) was observed in 34% of group 1 and in 78% of group 2 patients (p <0.001). One-month left ventricular ejection fraction was higher in group 2 (p <0.001). At multivariate analysis, reduction of ST-segment elevation was the only independent predictor of functional recovery (p <0.001). In conclusion, ST-segment analysis provides rapid and inexpensive information allowing identification of patients who are likely to benefit the most from myocardial reperfusion as early as 30 minutes after the last balloon inflation.

Dissolution of thrombotic arterial occlusion by high intensity, low frequency ultrasound and dodecafluoropentane emulsion: an in vitro and in vivo study

OBJECTIVES

We examined the effectiveness of the microbubbles of an echo contrast agent, dodecafluoropentane (DDFP) emulsion, to enhance low frequency ultrasound clot disruption in vitro and in vivo.

BACKGROUND

Ultrasound is reported to facilitate clot dissolution, and microbubbles could theoretically enhance ultrasound clot dissolution by augmenting cavitational effects.

METHODS

IN VITRO STUDIES

The disruption rate of fresh human clots by ultrasound (24 kHz, 2.9 W/cm2) was examined in saline and DDFP emulsion. In vivo studies: Using a rabbit iliofemoral thrombotic occlusion model, recanalization rate and histopathologic findings were compared among groups treated with DDFP emulsion alone, transcutaneous ultrasound (20 kHz, 1.5 W/cm2) alone and with DDFP emulsion and ultrasound combined.

RESULTS

The ultrasound clot disruption rate was significantly (p < 0.01) increased, from 72 +/- 18% (mean +/- SD) in saline to 98 +/- 4% in DDFP emulsion in 3 min in vitro. No vessel was recanalized by DDFP emulsion alone (0%), and only a single artery was patent after ultrasound treatment alone (9%). In contrast, 82% of iliofemoral arteries were angiographically recanalized after ultrasound treatment with DDFP emulsion. Histologically, the patent arteries had only minimal focal mural thrombus, with no evidence of vessel wall damage. However, substantial damage was observed in rabbit dermis and subcutaneous tissue.

CONCLUSIONS

1) DDFP emulsion, an echo contrast agent, significantly enhances the clot-disrupting effect of low frequency ultrasound in vitro and in an in vivo rabbit iliofemoral occlusion model. 2) This simple combination therapy has potential for clinical application in patients with thrombotic arterial occlusions.

Adenosine for myocardial protection in acute myocardial infarction

Although reperfusion therapy for acute myocardial infarction is known to reduce infarct size, improve left ventricular function, and reduce mortality, the full potential benefit may be limited by acceleration of damage resulting from reperfusion, or "reperfusion injury." Evidence of a variety of mechanisms of reperfusion injury has led to a wide range of proposed therapeutic interventions, including agents to prevent oxygen free radical damage, inhibit white blood cell function, reduce calcium influx, improve microvascular blood flow, inhibit sympathetic stimulation, and improve energy stores. A multitude of agents have been shown to limit infarct size in animals when administered before or during reperfusion. Unfortunately, most have been disappointing when tested clinically. Adenosine, a theoretically attractive agent for preventing reperfusion injury, has shown promise in small, clinical studies, and appears to be an endogenous substance involved in the protective effect of ischemic preconditioning. When studied in the setting of angioplasty for acute myocardial infarction, adenosine was associated with small infarct size and improved coronary flow. As myocardial preservation with reperfusion during bypass surgery shares pathophysiologic characteristics with the reperfused myocardium in acute infarction, early results of adenosine during bypass surgery presented at this symposium support the concept that adenosine may be beneficial. Two ongoing Phase II trials of adenosine in acute myocardial infarction-one with thrombolysis and one with direct angioplasty-will provide important information about the potential benefits of adenosine in the context of reperfusion.

Changing paradigms in thrombolysis in acute myocardial infarction

Acute myocardial infarction occurs when a ruptured coronary artery plaque causes sudden thrombotic occlusion of a coronary artery and cessation of coronary artery blood flow. This paper reviews the underlying coronary pathology in progressive coronary atherosclerosis, mechanisms of plaque rupture and arterial occlusion and the time relationship between coronary occlusion and myocardial necrosis. Reperfusion can be achieved by chemical thrombolysis with different thrombolytic agents. Early lysis is achieved best by prehospital administration, a transtelephonic monitor, a mobile intensive care unit, active general practitioner treatment or by warning the emergency room of impending arrival of a patient. Thrombolytic therapy may be unsuccessful and not achieve Grade III TIMI flow in less than 4 h (or even 2 h) due to inadequate or intermittent perfusion or reocclusion. Adjuvant therapy includes aspirin and platelet receptor antagonists. Bleeding is a constant danger. Direct percutaneous transluminal coronary angioplasty (PTCA) may be as effective or better than chemical thrombolysis. Reperfusion protects the myocardium and salvages viable tissue. It also improves mechanical remodelling of the ventricle. Long-term follow-up has shown that quantum leaps of fresh coronary occlusion causes step-wise progression in patient disability and that further early, prompt reperfusion can salvage myocardium and prevent this inexorable progress of the disease.

Trandolapril plus verapamil inhibits the coronary vasospasm induced by hypoxia following ischemia-reperfusion injury in dogs

1. Dogs were exposed to hypoxemia followed by a coronary angiogram at three different times: under control conditions, after ischemia-reperfusion injury, then 30 min later. 2. In the study group, the dogs were treated with trandolapril (0.05 mg/kg) and verapamil (0.1 mg/ kg) just prior to the final hypoxic challenge. 3. Under control conditions, the left anterior descending coronary artery (LAD) dilated in response to hypoxia. Following ischemia-reperfusion injury, however, it constricted significantly in response. 4. In the control group, repeat hypoxia 30 min later resulted in vasoconstriction of the LAD which was comparable to the preceding response. 5. However, in the study group, treatment with trandolapril plus verapamil inhibited the vasoconstriction in response to repeat hypoxia.

Time from symptom onset to treatment and outcomes after thrombolytic therapy. GUSTO-1 Investigators

OBJECTIVES

This study sought to examine the relations among patient characteristics, time to thrombolysis and outcomes in the international GUSTO-I trial.

BACKGROUND

Studies have shown better left ventricular function and decreased infarct size as well as increased survival with earlier thrombolysis, but the relative benefits of various thrombolytic agents with earlier administration are uncertain.

METHODS

We evaluated the relations of baseline characteristics to three prospectively defined time variables: symptom onset to treatment, symptom onset to hospital arrival (presentation delay) and hospital arrival to treatment (treatment delay). We also examined the relations of delays to clinical outcomes and to the relative 30-day mortality benefit with accelerated tissue-type plasminogen activator (t-PA) versus streptokinase.

RESULTS

Female, elderly, diabetic and hypertensive patients had longer delays at all stages. Previous infarction or bypass surgery was an additional risk factor for treatment delay. Early thrombolysis was associated with lower overall mortality rate (< 2 h, 5.5%; > 4 h, 9.0%), but no additional relative benefit resulted from earlier treatment with accelerated t-PA versus streptokinase (p = 0.38). Longer presentation and treatment delays were both associated with increased mortality rate (presentation delay < 1 h, 5.6% and > 4 h, 8.6%; treatment delay < 1 h, 5.4%, and > 90 min, 8.1%). As time to treatment increased, the incidence of recurrent ischemia or reinfarction decreased, but the rates of shock, heart failure and stroke increased.

CONCLUSIONS

Earlier treatment resulted in better outcomes, regardless of thrombolytic strategy. Elderly, female and diabetic patients were treated later, adding to their already substantial risk.

Decreased prevalence of late potentials with mechanical versus thrombolysis-induced reperfusion in acute myocardial infarction

OBJECTIVES

We sought to evaluate the influence of the method used to achieve early coronary reperfusion (i.e., intravenous thrombolysis or percutaneous transluminal coronary angioplasty) on the prevalence of late potentials after acute myocardial infarction.

BACKGROUND

After myocardial infarction, late potentials are associated with an increased risk of ventricular tachyarrhythmia and sudden death. Although their prevalence is lower in patients with coronary reperfusion, the influence of the method used to achieve reperfusion remains debated.

METHODS

We retrospectively analyzed 109 patients with acute myocardial infarction who were treated within 6 h of symptom onset and had angiographically proved early reperfusion. A signal-averaged electrocardiogram was recorded > or = 5 days after infarction.

RESULTS

Reperfusion was successfully achieved by intravenous thrombolysis alone in 37 patients (34%), by "rescue" coronary angioplasty in 26 (24%) and by primary angioplasty in 46 (42%). There was no significant difference between groups in terms of gender ratio, infarct location, time to admission or to reperfusion, peak creatine kinase value or left ventricular ejection fraction. The prevalence of late potentials was similar in the two groups in which patency was achieved by primary and rescue coronary angioplasty (17.4% and 7.7%, respectively [p=NS]) but higher in patients who had successful thrombolysis (35.1%, p < 0.05). Multivariate analysis showed that the use of thrombolysis instead of angioplasty as the reperfusion method was the only variable significantly associated with the presence of late potentials.

CONCLUSION

This study suggests that after acute myocardial infarction the prevalence of late potentials is lower when reperfusion is achieved by angioplasty (either primary or as a rescue procedure after failed thrombolysis) than by thrombolysis.

Peripheral intravenous myocardial contrast echocardiography using a 2% dodecafluoropentane emulsion: identification of myocardial risk area and infarct size in the canine model of ischemia

OBJECTIVES

This study assessed the accuracy of 2% dodecafluoropentane (EchoGen), an intravenous echocardiographic contrast agent, in identifying myocardial area at risk and infarct size in the canine model of myocardial ischemia.

BACKGROUND

Myocardial contrast echocardiography allows determination of myocardial area at risk and infarct size but requires intracoronary injection in humans. The development of agents that can be delivered by peripheral intravenous injection could enable bedside myocardial contrast echocardiographic assessment of risk area, infarct size and reperfusion.

METHODS

Two protocols were used. Protocol 1 assessed the accuracy of myocardial contrast echocardiography using intravenous dodecafluoropentane in defining myocardial area at risk and infarct size in the canine model of regional myocardial ischemia versus gross pathologic specimens stained with monastral blue to determine area at risk and triphenyltetrazolium chloride to determine the area of necrosis. Protocol 2 assessed the effects of repeated injections of dodecafluoropentane (0.5 ml/kg body weight, four doses 30 min apart or eight doses 10 min apart) on myocardial blood flow and hemodynamic variables.

RESULTS

Myocardial contrast echocardiography accurately defined area at risk and infarct size (r = 0.96 vs. triphenyltetrazolium chloride). Myocardial blood flow remained stable after multiple serial injections of dodecafluoropentane. However, a significant increase in pulmonary artery pressure and pulmonary vascular resistance, along with a decrease in arterial oxygen saturation and cardiac output, was seen in dogs that received eight injections at 10-min intervals.

CONCLUSIONS

Myocardial contrast echocardiography using intravenous dodecafluoropentane accurately defined myocardial area at risk and infarct size. Hemodynamic variables and regional myocardial blood flows remained stable when dodecafluoropentane was injected at 30-min intervals for up to four doses; more frequent administration led to cardiopulmonary deterioration. Dodecafluoropentane offers the potential for reliable, noninvasive assessment of reperfusion after therapeutic interventions.

Factors influencing myocardial salvage with primary angioplasty

BACKGROUND

The purpose of this study was to evaluate the factors influencing the salvage of jeopardized myocardium in patients treated with primary angioplasty for acute myocardial infarction.

METHODS AND RESULTS

This multicenter study involved 59 patients with acute myocardial infarction who underwent primary angioplasty without antecedent thrombolytic therapy and paired baseline (before angioplasty) and predischarge tomographic perfusion imaging by quantitative 99mTc-labeled sestamibi techniques for assessing the initial area at risk and eventual infarct size. Of the 59 patients who underwent primary angioplasty, Thrombolysis In Myocardial Infarction (TIMI) level 3 perfusion was restored in the infarct vessel in 54 patients (92%). On average, approximately one third of the left ventricular myocardial mass was initially jeopardized by the infarction in progress; eventual infarct size was 18% +/- 15% of the left ventricle; myocardial salvage was 16% +/- 17% of the left ventricle. Primary angioplasty salvaged 46% +/- 50% of initially jeopardized myocardium. Factors correlated with myocardial salvage included elapsed time from onset of pain to reperfusion, infarct location (anterior infarcts had more myocardial salvage than inferior infarcts), and residual flow to the infarct zone at preangioplasty baseline levels. In the five patients reperfused less than 2 hours from onset of pain, 80% of the jeopardized myocardium was salvaged. Myocardial salvage beyond 2 hours was much more variable.

CONCLUSIONS

Primary angioplasty was highly effective at restoring normal perfusion in the infarct vessel and salvaging jeopardized myocardium. The myocardial salvage was highly variable and correlated with elapsed time to reperfusion, baseline residual flow to the infarct zone, and infarct location.