Ragavendra R. Baliga, M.D
Assistant Professor
Division of Cardiology
University Of Michigan

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Question 15 of 39:

This patient's history, examination and EKG suggest that thrombolysis will be ineffective in this patient.

You clicked 'True'

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Thrombolytic therapy is highly effective in patients with ST-elevation MI (>0.1mV) or presumably new left bundle branch block (LBBB) (which obscures the electrocardiographic diagnosis of MI)[1].

Treatment benefit is present regardless of gender, presence of diabetes, blood pressure (if<180 mm Hg systolic), heart rate, or history of previous MI. Benefit is greater in the setting of anterior MI, diabetes, low blood pressure (<100 mm Hg systolic), or tachycardia (>100 bpm).

The earlier the therapy the better the outcome, with the greatest benefit within the first three hours; proven benefit occurs, however, up to at least within 12 hours of the onset of symptoms. Generally there is a small trend for benefit of therapy after a delay >12 to 24 hours, but thrombolysis may be considered for selected patients with ongoing ischemic pain and extensive ST elevation. Risk of cardiac rupture appeared to increase with prolonged time to therapy in an earlier meta-analysis[2] but not associated with increased risk of rupture in a later, larger study[3]. Generally patients presenting >12 hours after symptom onset were excluded from some but not all trials.

Risk of intracranial hemorrhage is greater when the presenting blood pressure >180/110 mm Hg and in this situation the potential benefit of therapy must be carefully weighed against the risk of hemorrhagic stroke. An attempt to lower blood pressure first (with nitrates or beta-blockers) is recommended but is not of proven benefit in lowering the risk of intracranial hemorrhage. Primary PTCA or CABG may be considered if available.

Reference:

1. Fibrinolytic Therapy Trialists (FTT) Collaborative Group. Indications for fibrinolytic therapy in suspected acute myocardial infarction: collaborative overview of early mortality and major morbidity results from all randomized trials of more than 1000 patients. Lancet 1994;343:311-322.

2. Honan MB, Harrel FE, Reimer KA et al. Cardiac rupture, mortality and timing of thrombolytic therapy: a meta-analysis. J Am Coll Cardiol 1990;16:359-367.

3. Becker RC, Charlesworth A, Wilcox RG et al. Cardiac rupture associated with thrombolytic therapy: impact of time to treatment in the Late Assessment of Thrombolytic Efficacy (LATE) Study. J Am Coll Cardiol 1995;25:1063-1068.