What is the best course of action for a patient with a history of coronary artery bypass grafting (CABG) and pericardectomy, presenting with symptoms suggestive of acute coronary syndrome (ACS) but with a normal troponin level?

Management of Suspected ACS in Post-CABG Patient with Normal Initial Troponin

Admit the patient to a monitored unit, repeat troponin at 3-6 hours after symptom onset (or initial presentation if timing unclear), and do not discharge without objective cardiac testing even if serial troponins remain negative, given the intermediate-risk status conferred by prior CABG. 1

Immediate Actions

• Obtain a 12-lead ECG immediately if not already done within the last 10 minutes, and have it interpreted by an experienced physician 2, 1
• Perform serial ECGs at 15-30 minute intervals while the patient remains symptomatic or if clinical suspicion remains high, even with a normal initial ECG 1
• Admit to a monitored unit with continuous rhythm monitoring until ACS is established or ruled out 2, 1
• Consider additional ECG leads (V3R, V4R, V7-V9) if ongoing ischemia is suspected but standard leads are inconclusive 2, 1

Serial Troponin Protocol

The critical issue here is that a single normal troponin does not exclude ACS, particularly in patients with prior CABG who carry intermediate risk by definition.

• Repeat troponin at 3-6 hours after the initial draw (or 8-12 hours after symptom onset if known) 1, 3
• If using high-sensitivity troponin assays, the ESC 0h/1h algorithm with repeat at 1 hour is an alternative, though the 3-6 hour protocol remains valid 2, 1
• Obtain additional troponin levels beyond 6 hours if the first two measurements are not conclusive and clinical suspicion remains high, particularly if ECG changes are present 1, 3
• Look for a rising and/or falling pattern of troponin values, which is essential to distinguish acute from chronic myocardial injury 4

Risk Stratification Context

Prior CABG is itself an intermediate-risk criterion for ACS, even without elevated troponin 1. This fundamentally changes the management approach compared to patients without prior cardiac surgery.

• Patients with intermediate-risk features should undergo an invasive strategy within 72 hours if ACS is confirmed 1
• Between 2-5% of patients with ACS are inappropriately discharged from the emergency department, highlighting the danger of premature discharge 5

Additional Diagnostic Testing

• Perform echocardiography to evaluate regional wall motion abnormalities, LV function, and rule out differential diagnoses like pericardial complications from prior pericardectomy 2, 1
• Echocardiography is particularly important in this patient given the history of pericardectomy, as pericardial complications could mimic ACS 2

Management During Observation Period

While awaiting repeat troponin results:

• Initiate aspirin 150-300mg loading dose (or 75-250mg IV) if not contraindicated 1
• Continue beta-blockers unless contraindicated 1
• Administer sublingual nitroglycerin for ongoing symptoms 1
• Consider a P2Y12 inhibitor (ticagrelor or clopidogrel) if high clinical suspicion persists, though definitive dual antiplatelet therapy decisions should await confirmation of ACS 1

If Repeat Troponin Remains Normal

This is where the prior CABG history becomes critically important—do not discharge without objective testing.

• With normal serial troponins at 8-12 hours, normal ECG, and resolution of symptoms, the patient can be risk-stratified as low-risk 1
• Non-invasive stress testing (preferably with imaging) or coronary CT angiography must be performed before discharge to assess for inducible ischemia 2, 1
• Patients with prior CABG presenting with chest pain should not be discharged without objective testing, even with negative biomarkers 1

Critical Pitfalls to Avoid

• Coronary CT angiography has not been validated in the acute setting for patients with prior CABG 2, so stress testing with imaging may be the preferred non-invasive approach
• Failing to repeat troponin in patients with high-risk features (including prior CABG) despite initially negative results is a common and dangerous pitfall 3
• Relying solely on troponin without considering the clinical context, ECG findings, and prior cardiac history can result in missed diagnoses 3, 4
• The history of pericardectomy adds complexity, as pericardial complications could present similarly to ACS and should be actively excluded with echocardiography 2