American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the criterion for indicating successful reperfusion after thrombolytic therapy?

1. Decrease in heart rate

2. Improvement in ST-segment elevation greater than 50%

3. Normalization of troponin levels

4. Reduction of chest pain

The correct answer is: Improvement in ST-segment elevation greater than 50%

Successful reperfusion after thrombolytic therapy is primarily indicated by clinical and electrocardiographic criteria, with one of the most significant being improvement in ST-segment elevation. This improvement reflects the resolution of myocardial ischemia and the restoration of blood flow to the affected area of the heart. During a myocardial infarction, the ST-segment elevation observed on an electrocardiogram is caused by myocardial injury due to inadequate blood supply. When thrombolytic therapy is effective, the blood clot is dissolved, facilitating improved blood flow and leading to a notable reduction in ST-segment elevation. The other options, while potentially related to the overall clinical picture, do not serve as definitive criteria for assessing successful reperfusion. Decrease in heart rate can be influenced by a variety of factors unrelated to blood flow restoration, such as medications or autonomic effects. Normalization of troponin levels is a late marker that may not occur immediately after therapy and is less useful in the acute setting for evaluating immediate reperfusion success. Similarly, reduction of chest pain may indicate improvement but is subjective and can vary among patients; it does not provide a direct assessment of myocardial blood flow restoration. Hence, improvement in ST-segment elevation is the most reliable criterion indicating successful reperfusion