Angiographic monitoring of reperfusion therapy for acute myocardial infarction. TIMI grade 3 perfusion is the goal

Development of myocardial microcirculation and metabolism in acute ST-elevation myocardial infarction evaluated with positron emission tomography

BACKGROUND

Early reperfusion is an established therapeutic objective in acute myocardial infarction (MI). The relationship of regional myocardial microcirculation and metabolism toward outcome in acute human MI is not well known.

METHODS AND RESULTS

In 8 patients, positron emission tomography (PET) was performed with oxygen 15-labeled water at 3 hours, 24 hours, and 3 weeks after the start of fibrinolytic treatment, with carbon 11 acetate at 3 hours and with fluorine 18 fluorodeoxyglucose at 24 hours and 3 weeks. Absolute quantification of perfusion and water-perfusable tissue fraction (PTF), metabolic activity, and substrate extraction in 4 regions of interest was performed. Coronary angiography was performed at 24 hours. Short-term outcome at 3 weeks was evaluated by contractile reserve with dobutamine stress echocardiography and lung water measurements with PET. Early regional perfusion, PTF, and extraction and utilization of oxygen and glucose decreased closer to the infarct region ( P < .001 for all). Infarct-related oxygen utilization and extraction of oxygen and glucose were closely related to outcome ( P < .01 for all). PTF improved significantly in the infarct-related regions over time in proportion to early oxygen extraction and utilization.

CONCLUSIONS

This pilot study indicates that PET might be useful in the evaluation of treatment efficacy and that restoration of oxidative metabolism is more closely related to myocardial damage recovery than perfusion in the early phase after MI.

Initial Therapy for Acute Myocardial Infarction

BACKGROUND

The optimal therapeutic approach for acute myocardial infarction (AMI) is still evolving; however, many would consider one of two basic options: "medical"-only thrombolysis or reperfusion, or an early (invasive), percutaneous coronary intervention (PCI). The decision about which is most appropriate depends (perhaps unfortunately) on more than just medical factors. That is, the choice for some patients is also limited by payor source and the technical capabilities at the site of the initial treatment. Practically speaking, a significant portion of the US population simply does not have the option of (at least, initial) PCI.

METHODS AND RESULTS

Kino Community Hospital in Tucson, AZ, serves primarily an indigent population in southern Arizona, near the border with Mexico. This facility does not have in-house capability for PCI. Therefore, shortly after the publication of the original Thrombolysis in Myocardial Infarction (TIMI) 14 study (June 1999), we implemented their combination reperfusion protocol for the initial therapy of eligible patients admitted to the hospital with AMI. This report documents our experience with this medical reperfusion regimen in 42 patients over a span of almost 3 years. A retrospective chart review was conducted to evaluate outcome in 42 patients with ST-segment elevation myocardial infarction given the TIMI-14 reperfusion regimen. Resolution of ST-segment changes occurred in 30 patients (71.4%) [complete resolution in 25 patients (59.5%) and incomplete resolution in 5 patients (1.9%)], with major bleeding complicating the therapy of only 1 patient (2.38%) [corrected]. After stabilization in our facility, 28 patients (66.6%) needed PCI.

CONCLUSION

This report summarizes the experience of a small county hospital where medical thrombolysis is the only immediate therapy available.

Facilitated thrombolysis: dethrombosis?

Intracoronary thrombus formation results from the combined effects of platelet aggregation and fibrin formation. Fibrinogen plays a significant role in each of these components. Dethrombosis is a therapeutic approach that allows dissolution of a recent thrombus while avoiding the potent fibrinolytic therapies. The less aggressive strategies suggested to achieve dethrombosis are antifibrin, antiplatelet, and defibrinogenation. Glycoprotein receptor antagonists have been beneficial in patients undergoing percutaneous transluminal coronary angioplasty; however, little is known about their potency of inducing reperfusion in acute myocardial infarction. Early use of the strategies suggested to induce dethrombosis (antifibrin, antiplatelet, and defibrinogenation) may facilitate fibrinolysis and primary angioplasty and further induce reperfusion. Nevertheless, the theoretical arguments of facilitated thrombolysis (dethrombosis) have not yet been fruitful as a major clinical benefit except in patients undergoing primary percutaneous coronary intervention.

Low molecular weight heparin (dalteparin) as adjuvant treatment of thrombolysis in acute myocardial infarction--a pilot study: biochemical markers in acute coronary syndromes (BIOMACS II)

OBJECTIVES

This randomized, double blind, placebo-controlled pilot trial evaluated the effect of dalteparin as an adjuvant to thrombolysis in patients with acute myocardial infarction regarding early reperfusion, recurrent ischemia and patency at 24 h.

BACKGROUND

Low-molecular-weight heparin, given subcutaneously twice daily without monitoring, might be an attractive alternative to conventional intravenous heparin in the treatment of acute myocardial infarction.

METHODS

In 101 patients dalteparin/placebo 100 IU/kg was given just before streptokinase and a second injection 120 IU/kg after 12 h. Monitoring with continuous vector-ECG was done to obtain signs of early reperfusion and later ischemic episodes. Blood samples for myoglobin were obtained at start and after 90 min to evaluate signs of reperfusion. Coronary angiography was performed after 20-28 h to evaluate TIMI-flow in the infarct-related artery.

RESULTS

Dalteparin added to streptokinase tended to provide a higher rate of TIMI grade 3 flow in infarct-related artery compared to placebo, 68% versus 51% (p = 0.10). Dalteparin had no effects on noninvasive signs of early reperfusion. In patients with signs of early reperfusion, there seemed to be a higher rate of TIMI grade 3 flow, 74% versus 46% (myoglobin) (p = 0.04) and 73% versus 52% (vector-ECG) (p = 0.11). Ischemic episodes 6-24 h. after start of treatment were fewer in the dalteparin group, 16% versus 38% (p = 0.04).

CONCLUSIONS

When dalteparin was added as an adjuvant to streptokinase and aspirin, there were tendencies for less ECG monitoring evidence of recurrent ischemia and better patency at 24 h, warranting further study.

Efficacy of streptokinase, but not tissue-type plasminogen activator, in achieving 90-minute patency after thrombolysis for acute myocardial infarction decreases with time to treatment. PERM Study Group. Prospective Evaluation of Reperfusion Markers

OBJECTIVES

We sought to examine the relation between time to treatment and 90-min patency rates in patients receiving intravenous streptokinase (SK) or accelerated tissue-type plasminogen activator (t-PA).

BACKGROUND

Early patency of the infarct-related artery is a major determinant of survival after thrombolysis for acute myocardial infarction. Some data suggest that time to treatment may influence the efficacy of nonfibrin-specific thrombolytic agents in restoring early patency of the infarct-related vessel.

METHODS

We performed a retrospective analysis of a cohort of 481 patients receiving thrombolytic therapy for acute myocardial infarction <6 h after pain onset, all of whom underwent 90-min coronary angiography. Patency of the infarct-related artery was graded by two observers who had no knowledge of the treatment received or the time between pain and therapy.

RESULTS

There was no difference in baseline clinical or angiographic characteristics according to the timing or nature of treatment. Thrombolysis in Myocardial Infarction (TIMI) flow grade 2 or 3 patency rate after SK correlated negatively with the time between onset of pain and thrombolysis (r = 0.8, p = 0.05), whereas the 90-min patency rate after t-PA appeared stable as a function of time to treatment. When patients were categorized as having received treatment <3 or > or = 3 h after pain onset, the patency rate was similar with t-PA, but significantly higher when SK was administered early rather than late, regardless of whether TIMI flow grades 2 and 3 were pooled (86.9% vs. 59.4%, p = 0.0001) or TIMI flow grade 3 alone was considered to indicate patency (81.7% vs. 53.6%, p = 0.0001). Multivariate logistic regression analysis showed a negative effect of time to treatment on the patency probability for SK (p = 0.0001) but not for t-PA.

CONCLUSIONS

The efficacy of streptokinase but not t-PA in restoring early coronary patency after intravenous thrombolysis is markedly lower when patients are treated later after onset of pain.

Early behavior of biochemical markers in patients with thrombolysis in myocardial infarction grade 2 flow in the infarct artery as opposed to other flow grades after intravenous thrombolysis for acute myocardial infarction. PERM Study Group. Prospective Evaluation of Reperfusion Markers

BACKGROUND

Biochemical markers have been suggested for the noninvasive diagnosis of reperfusion early after thrombolysis. Their ability to discriminate between Thrombolysis in Myocardial Infarction (TIMI) 2 and 3 flow grades remains unknown.

METHODS

In 97 patients with myocardial infarction < or =6 hours, myoglobin, troponin T, MBCK, and MMCK isoforms were measured before thrombolysis and after 90 minutes. A 90-minute coronary angiography ascertained the potency status of the infarct-related artery in all patients according to the TIMI grade flow (group A: TIMI 0-1 (n = 35), group B: TIMI 2 (n = 17), and group C: TIMI 3 (n = 45). For each marker the absolute rate of increase and the relative increase 90 minutes after thrombolysis were studied.

RESULTS

Both absolute values and absolute rates of increase at 90 minutes of myoglobin were higher in group B than in groups A and C (p < 0.05, not significant for other markers). Relative increases were consistently higher in group C than in other groups with statistical significance for myoglobin in the subset of patients treated for >3 hours.

CONCLUSION

Diagnostic indexes based on relative increases tend to discriminate between patients with TIMI 2 and 3 flow, and the best performance is obtained when the relative increase of myoglobin at 90 minutes is used in patients treated later than 3 hours after onset of symptoms.

Conservative management of patients with acute myocardial infarction and spontaneous acute patency of the infarct-related artery

The role of systematic emergency percutaneous transluminal coronary angioplasty (PTCA) in patients with spontaneous reperfusion during myocardial infarction is debated. We retrospectively examined the inhospital outcome of 47 consecutive patients with myocardial infarction < 6 hours and angiographically proven spontaneous patency of the infarct artery managed without initial PTCA. There was one death (2.1%) and no incidence of reinfarction. Predischarge angiography showed regression of the culprit coronary lesion to < 50% stenosis in 23% of the patients, therefore obviating the need for PTCA. However, 17% of the patients had acute recurrent ischemia, requiring emergency intervention in 10.6%. Comparison with matched patients in whom Thrombolysis in Myocardial infarction grade 3 patency was achieved by thrombolysis or by primary PTCA showed that patients with spontaneous patency tended to have smaller infarctions, as judged from a lower peak creatine kinase level (1132 +/- 1002, 2051 +/- 1536, and 2715 +/- 2146 i.u., respectively; p = 0.001) and a higher left ventricular ejection fraction (56.4%, 47.9%, and 48.7% respectively; p = 0.02). In conclusion, these patients have an excellent inhospital outcome, with evidence of less myocardial damage than in patients in whom reperfusion therapy was required to achieve TIMI 3 patency. Initial conservative treatment appears safe.

Can we provide reperfusion therapy to all unselected patients admitted with acute myocardial infarction?

OBJECTIVES

This study sought to assess the maximal rate of acute Thrombolysis in Myocardial Infarction (TIMI) grade 3 patency that can be achieved in unselected patients.

BACKGROUND

Early and complete (TIMI grade 3 flow) reperfusion is an important therapeutic goal during acute myocardial infarction. However, thrombolysis, although widely used, is often contraindicated or ineffective. The selective use of primary and rescue percutaneous transluminal coronary angioplasty (PTCA) may increase the number of patients receiving reperfusion therapy.

METHODS

A cohort of 500 consecutive unselected patients with acute myocardial infarction were prospectively treated using a patency-oriented scheme: Thrombolysis-eligible patients received thrombolysis (n = 257) and underwent 90-min angiography to detect persistent occlusion for treatment with rescue PTCA. Emergency PTCA (n = 193) was attempted in patients with contraindications to thrombolysis, cardiogenic shock or uncertain diagnosis and in a subset of patients admitted under "ideal conditions." A small group of patients (n = 38) underwent acute angiography without PTCA. Conventional medical therapy was used in 12 patients with contraindications to both thrombolysis and PTCA.

RESULTS

Ninety-eight percent of patients received reperfusion therapy (thrombolysis, PTCA or acute angiography), and angiographically proven early TIMI grade 3 patency was achieved in 78%. Among patients with TIMI grade 3 patency, thrombolysis alone was the strategy used in 37%, emergency PTCA in 40% and rescue PTCA after failed thrombolysis in 15%; spontaneous patency occurred in 8%.

CONCLUSIONS

Reperfusion therapy can be provided to nearly every patient (98%) with acute myocardial infarction. Rescue and direct PTCA provided effective early reperfusion to patients in whom thrombolysis failed or was excluded.