ECG Review-How Much Benefit from tPA?
November 1, 1999 2 minutes read
ECG Review-How Much Benefit from tPA?
By Ken Grauer, MD
Clinical Scenario: The ECG in the figure was obtained from a middle-aged man who had just received infusion of tPA for acute myocardial infarction. The initial ECG had shown marked ST segment elevation in the inferior leads, but no Q waves. Based on the findings in the tracing shown and the fact that the patient’s chest pain completely resolved during tPA infusion, would you say the infusion was optimally successful?
Interpretation: Three noninvasive indicators have been described for suggesting successful reperfusion with thrombolytic therapy. They are: 1) complete resolution of chest pain; 2) complete resolution of ST segment elevation; and 3) development of reperfusion arrhythmias. When seen together, the first two signs (resolution of both chest pain and ST segment elevation) are surprisingly reliable indicators of reperfusion—provided that resolution of both chest pain and ST segment elevation is complete. Development of reperfusion arrhythmias by itself is not nearly as reliable an indicator of successful reperfusion. However, the finding of such arrhythmias (most commonly accelerated idioventricular rhythm and/or late-cycle or end-diastolic PVCs) may be viewed as supportive evidence in favor of reperfusion if they occur in conjunction with the first two signs.
Administration of thrombolytic therapy would seem to be most beneficial if it results in complete resolution of chest pain and ST segment elevation—and the post-thrombolytic tracing does not show development of Q waves.
At first glance, one might think thrombolytic therapy was less than optimally successful in this case, since beat #2 in leads II and III seems to suggest persistence of ST segment elevation and development of a deep and wide Q wave. However, beat #2 is not a pure sinus conducted beat. A look at lead aVF reveals the true QRS morphology for the inferior leads (i.e., narrow QRS complex and no residual ST elevation). Instead, beat #2 in lead II is a fusion beat that manifests a QRS complex with a morphology that is intermediate between the pure sinus beat in this lead (beat #1) and the late-cycle PVC (beat #3). The ST segment elevation that is seen for beat #2 in lead II is the result of fusion between the ST segment and T wave of the normally conducted beat (beat #1) and the ST segment and T wave of the PVC (beat #3). Thus, assessment of sinus-conducted beats in this ECG obtained after thrombolytic therapy shows that Q waves did not develop and that ST segment elevation has completely resolved. This suggests that the patient did, in fact, benefit optimally from timely administration of tPA.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content