After administering streptokinase for acute ST‑segment elevation myocardial infarction (STEMI), how frequently should electrocardiograms be performed?

ECG Monitoring Frequency After Streptokinase Administration

Obtain a 12-lead ECG at 60-90 minutes post-streptokinase to assess ST-segment resolution, which is the most critical timepoint for determining reperfusion success and guiding further management. 1, 2

Initial ECG Timing (First 90 Minutes)

• Perform baseline 12-lead ECG immediately before streptokinase administration to document the extent of ST-elevation and establish a reference for measuring resolution 1

• Obtain a repeat 12-lead ECG at 60-90 minutes after initiating thrombolytic therapy to assess ST-segment resolution, which is the single most important bedside predictor of successful reperfusion 2

• ST-segment resolution at 60-90 minutes should be categorized as:

  • Complete (≥70% resolution): associated with 2.4% mortality 2
  • Partial (30-70% resolution): associated with 4.9% mortality 2
  • None (<30% resolution): associated with 8.1% mortality and indicates failed reperfusion requiring rescue PCI 2

• Less than 50% ST-segment resolution at 90 minutes indicates failed reperfusion and warrants immediate consideration for rescue PCI, particularly in patients with a moderately large area of myocardium at risk 1, 3

Continuous Monitoring Period (First 24-48 Hours)

• Initiate continuous cardiac rhythm monitoring immediately upon streptokinase administration to detect life-threatening arrhythmias, which occur in approximately 5% of STEMI patients, with 60-64% occurring within the first 24 hours 1

• Continue telemetry monitoring for at least 24-48 hours post-thrombolysis in all patients, as 90-92% of malignant ventricular arrhythmias occur within 48 hours 1

• Perform serial 12-lead ECGs if the patient develops recurrent chest pain or hemodynamic instability, as recurrent ST-elevation occurs in up to 58% of patients who initially achieve reperfusion, with 32% of these episodes being silent 4

Extended Monitoring (Days 1-2)

• Obtain 12-lead ECGs on Days 1 and 2 post-streptokinase to assess for evolutionary changes and detect delayed ST-segment resolution patterns, which differ between anterior (61% resolution) and inferior MI (77% resolution) by Day 2 5

• Serial ECGs at 5-10 minute intervals are indicated if the patient remains symptomatic with non-diagnostic initial post-thrombolysis ECG, particularly when there is high clinical suspicion for reocclusion 1

Special Circumstances Requiring Additional ECGs

• Right-sided ECG leads (V3R, V4R) should be obtained in all inferior STEMI patients to screen for right ventricular infarction, which alters management (avoid nitrates and diuretics) 1, 3

• Obtain immediate 12-lead ECG for any new chest pain, hemodynamic deterioration, or arrhythmias to detect acute stent thrombosis or reocclusion, which can occur as sustained recurrent ST-elevation in 19% of patients 4

• Continuous ST-segment monitoring beyond 24 hours may be discontinued in stable, successfully reperfused patients to avoid false alarms from positional changes or evolutionary ST-changes, though monitoring can be reinitiated if symptoms recur 1

Common Pitfalls to Avoid

• Do not delay reperfusion therapy to wait for cardiac biomarker results, as the diagnosis of STEMI is secure with ST-elevation on ECG, and treatment must be initiated immediately 1

• Do not rely solely on the absence of chest pain to determine reperfusion success, as 32-35% of recurrent ST-elevation episodes are clinically silent and only detectable by ECG monitoring 4

• Recognize that persistent ST-elevation on Day 2 in anterior MI may reflect larger infarct size and akinesis rather than failed reperfusion, particularly if the 90-minute ECG showed adequate resolution 5

• Transient recurrent ST-elevation often precedes sustained reocclusion, so any episode of recurrent ST-elevation (median duration 43 minutes) warrants close observation and consideration for urgent angiography 4