Challenges, Controversies, and Advances in Aortic Catastrophes

Emergency physicians (EPs) are commonly faced with life-threatening entities. Particularly challenging are the aortic catastrophes, such as penetrating aortic ulcers (PAUs), intramural hematomas (IMHs), and atypical presentations of acute aortic dissections and ruptured abdominal aortic aneurysms. Several factors account for this: (1) the rapidly evolving knowledge (particularly in the pathogenesis and precursors of aortic dissection [AD]), (2) the lack of comfort caused by infrequent exposure, (3) the misconceptions about the work up and treatment, (4) the lack of emergent vascular surgery back up in the community, and finally (5) the high short-term mortality and missed rates. Finally, the media has publicized cases of celebrities and other patients who experienced fatal outcomes when their aortic catastrophes went undiagnosed. Practitioners of emergency care should, therefore, understand the challenges, be aware of the recent advances, and help limit the controversies in the evaluation and management of these patients.

A randomized, double-blinded, placebo-controlled, dose-ranging study measuring the effect of an adenosine agonist on infarct size reduction in patients undergoing primary percutaneous transluminal coronary angioplasty: the ADMIRE (AmP579 Delivery for Myocardial Infarction REduction) study

BACKGROUND

Evidence suggests that myocardial ischemic preconditioning and reperfusion injury may be mediated by adenosine A1 and A2 receptors. AMP579 is a mixed adenosine agonist with both A1 and A2 effects. In animal models of acute myocardial infarction (MI), AMP579 reduced infarct size at serum levels of 15 to 24 ng/mL.

METHODS

The AMP579 Delivery for Myocardial Infarction REduction study evaluated AMP579 in a double-blind, multicenter, placebo-controlled trial of 311 patients undergoing primary percutaneous transluminal coronary angioplasty (PTCA) after acute ST-segment elevation MI. Patients were randomly assigned to placebo or to 3 different doses of AMP579 continuously infused over 6 hours. The primary end point was final MI size measured by technetium Tc-99m sestamibi scanning at 120 to 216 hours after PTCA. Secondary end points included myocardial salvage and salvage index at the same time interval (in a subset of patients who underwent baseline technetium Tc-99m sestamibi scan), left ventricular ejection fraction and heart failure at 4 to 6 weeks, duration of hospitalization, and cardiac events at 4 weeks and 6 months.

RESULTS

Final infarct size did not differ among the placebo group and the active treatment groups for either anterior MI or nonanterior MI. In patients with anterior MI, median myocardial salvage was increasingly higher in the groups receiving ascending dosages of AMP579 plus PTCA. Serum levels approaching levels shown to reduce infarct size in animal models were achieved only in the 60-mcg/kg treatment group.

CONCLUSION

AMP579 was safe at the doses tested, but it did not reduce infarct size. There was a trend toward greater myocardial salvage in treated patients with anterior MI.

Intravenous adenosine and lidocaine in patients with acute myocardial infarction

OBJECTIVES

A pilot study was designed to assess the safety of combined intravenous adenosine and lidocaine in patients with acute myocardial infarction and to estimate the likelihood of a beneficial effect on final infarct size.

BACKGROUND

Adenosine plus lidocaine reduces infarct size in animals, but the safety and efficacy in human beings is unknown.

METHODS AND RESULTS

Adenosine (70 microg/kg per minute intravenous infusion) plus lidocaine (1 mg/kg intravenous bolus injection and 2 mg/kg per minute infusion) was given to 45 patients with acute myocardial infarction. Patients underwent immediate balloon angioplasty without preceding thrombolytic therapy. Myocardial perfusion defects were measured with serial technetium 99m sestamibi studies. One patient developed persisting hypotension in conjunction with a large inferolateral myocardial infarction. Transient hypotension in three other patients resolved with a reduction in adenosine. Advanced atrioventricular block was never observed. Other adverse events (including atrial fibrillation, ventricular tachyarrhythmia, bradycardia, and respiratory distress) occurred at low frequencies, as expected for patients with acute myocardial infarction. An initial median perfusion defect of 45% of the left ventricle (60% for anterior infarction, 17% for nonanterior infarction) was observed. At hospital discharge (mean +/- SD = 4.3 +/- 2.1 days) the median value was 12%, and at 8 +/- 4 weeks it was 3% (7% for anterior infarction, 0% for nonanterior infarction); 14 patients had no measurable follow-up. Compared with historical control patients, prehospital discharge measurements were not different but late perfusion defects were improved.

CONCLUSIONS

Treatment with intravenous adenosine and lidocaine during acute myocardial infarction has sufficient safety and potential for improved myocardial salvage. Randomized studies are justified.

Emergency management of cocaine intoxication. Counteracting the effects of today's 'favorite drug'

The toxic effects of cocaine are becoming more widely recognized as the popularity of the drug increases. Although overdose is usually fatal, treatment is available for users who experience agitation, seizure, arrhythmias, severe hypertension, or other side effects. Hospital admission is often necessary to allow monitoring of the acute situation. Initial management involves standard life-support measures. Therapeutic agents are given, as appropriate, both to control acute reactions and to counteract continuing toxicity.