ST Elevation on the Monitor During a Diagnostic Case
A 63-year-old man with hypertension and a 40-pack-year smoking history is undergoing elective diagnostic catheterization for stable angina. During engagement of the left main with a 6F catheter, the patient reports chest pressure. The monitor shows 2–3 mm of ST elevation in leads II, III, and aVF, with reciprocal ST depression in I and aVL. Blood pressure is 102/64 and heart rate 88. The pressure tracing from the catheter shows a damped waveform with a ventricularized appearance. The physician is looking at the fluoroscopy screen and has not yet reacted to the monitor.
1. What is happening, and what does the catheter pressure waveform tell you?
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This is an acute catheter-induced coronary occlusion/air or thrombus in the left main or a dominant vessel, producing an inferior ST-elevation pattern (II, III, aVF with reciprocal I/aVL) - consistent with occlusion of a dominant right or circumflex artery, or left main compromise with inferior predominance.
The damped, ventricularized pressure waveform is the critical clue: it indicates the catheter tip is wedged/occluding the coronary ostium (or there is air/thrombus), reducing coronary flow. A ventricularized tracing means the catheter is damping aortic pressure and the tip is compromising the vessel - this is a mechanical emergency, not just an electrical one.
This is a time-critical event: prolonged occlusion causes myocardial injury. The judgment tested is recognizing the waveform + ECG + symptoms together and acting immediately.
2. What are your immediate actions, in priority order?
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- Disengage/pull back the catheter immediately - relieve the ostial occlusion. This is the single most important step and must happen now.
- Alert the physician loudly and clearly - announce the ST elevation and the damped/ventricularized pressure so they stop and look.
- Ensure the patient is on oxygen/monitored, confirm IV access, and get 12-lead ECG confirmation.
- Give intracoronary nitroglycerin (per physician order) for spasm; consider intracoronary air aspiration if air embolism is suspected, and anticoagulation is already in play.
- Prepare for PCI: ensure a guidewire, balloons, and stents are ready in case of thrombus/occlusion requiring intervention.
- Treat pain and hemodynamics; watch for arrhythmia or hypotension. Call for additional help and prepare for possible CPR/defibrillation if the patient deteriorates.
The sequence matters: disengage first, then diagnose and treat. Waiting for the physician to notice the monitor is the error the scenario is testing.
3. After the catheter is pulled back, the ST elevation resolves and the waveform normalizes. What follow-up is required before continuing?
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- Reassess the patient: symptoms, vital signs, and repeat 12-lead ECG to confirm resolution and detect any residual ischemia.
- Inspect the system: check for air, clot, or damping; flush carefully; verify the catheter tip is intact.
- Re-engage cautiously with a technique that avoids ostial wedging (e.g., careful seating, avoid deep intubation, consider a different catheter curve), watching the pressure waveform continuously.
- Consider intracoronary vasodilators if spasm contributed.
- Document the event, the ST changes, the intervention, and the resolution; inform the patient and the care team.
- Monitor for recurrence and for any rise in troponin if there was prolonged ischemia; consider whether the diagnostic study should be completed or staged.
The key point: resolution does not mean the event is over - you must confirm the patient is stable, the equipment is intact, and the risk of recurrence is addressed before resuming.