Eduardo Benchimol Saad
Sixth year medical student - The Federal University of Rio de Janeiro
Unstable angina is characterized by rupture of unstable coronary plaques, with predominantely platelet-rich thrombi partially ocluding the lumen of main coronary arteries. Aspirin is considered a must in treating this patients, as they irreversibly inhibit platelets.
Inhibitors of the GP IIb - IIIa platelet receptors are much more potent platelet inhibitors than aspirin, inhibiting the final common pathway of platelet activation, and was shown in recent trials to improve the outcomes of high risk and elective PTCA.
Results of two large clinical trials indicate that Tirofiban, a GP IIb - IIIa inhibitor, significantly reduces the risk of death, refractory ischemia, and AMI when given to patients with unstable angina and Non Q wave AMI. More than 3200 patients were enrolled in the PRISM trial, which were randomized to receive either Heparin or a 48 h infusion of Tirofiban. After 48 h of treatment, patients on Tirofiban had a 36 % reduction in the combined risk of death, refractory ischemia and AMI. At 30 days, Tirofiban patients had a 39 % reduction in mortality.
In PRISM - PLUS, Tirofiban was used in combination with Heparin to treat patients with unstable angina and Non Q wave AMI. Nearly 1600 patients were randomized to receive either Heparin or Heparin plus Tirofiban. At 7 days, the study’s primary end point, there was a 34 % reduction in the combined risk of death, refractory ischemia and AMI in the combination group, and the overall risk of AMI was reduced by 47 %.
Patients with Non Q wave AMI are generally considered to be at high risk of recurrent ischemic events, so as to be an accepted indication for routine coronary angiography after MI. TheVANQWISH trial was conducted to assess wether patients with Non Q wave AMI would benefit from routine coronary angiography ( done 3-7 days after AMI ), as compared with a noninvasive strategy of risk stratification and catheterization only when ischemia could be induced, in a manner similar to Q wave AMI patients.
This trial showed a 71 % increase in mortality at hospital discharge, a 60 % increase at 30 days and 30 % in the long term ( 44 months of follow up ) in the invasive group as compared to the stratified group. Hospitalization was significantly reduced in the conservative group (9.5 x 8.2 days). This trial concluded that there is no benefit of implementing an early invasive strategy in Non Q wave AMI patients; instead, this strategy could be harmfull. So they recommended that patients with Non Q wave AMI should be revascularized selectively and electively.
LMWH are being increasingly used as an alternative to unfractionated Heparin, by virtue of its increased bioavailability, more stable and predictive effect, easiness of administration, less risk of induced thrombocytopenia and osteoporosis, avoidance of need for laboratory monitorization of effect, less rebound effect and similarity in efficacy and safety.
The ESSENCE trial was reviewed in this meeting.
2 ) Unstable Angina / Non Q wave AMI
5 ) Atrial Fibrilation and Atrial Flutter
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