What are the next steps for a patient with an abnormal electrocardiogram (ECG)?

Management of Abnormal ECG Findings

Patients with ECG abnormalities including left axis deviation, left atrial enlargement, and possible anteroseptal infarct require immediate cardiac biomarker testing and echocardiography to exclude acute coronary syndrome and structural heart disease. 1

Immediate Actions in the Emergency Setting

Acute Evaluation Protocol

• Obtain serial cardiac troponins immediately and repeat at 3-6 hours to detect myocardial injury, as a single normal ECG never excludes acute coronary syndrome 2, 1, 3

• Initiate continuous cardiac monitoring to detect dynamic ECG changes or arrhythmias that may evolve during observation 1

• Perform repeat ECG if symptoms persist or recur, as up to 6% of patients with evolving ACS are discharged with an initially normal ECG 2, 3

• Consider posterior leads (V7-V9) if clinical suspicion remains high, as left circumflex occlusions causing posterior wall ischemia are often "electrically silent" on standard 12-lead ECG 2, 4

Risk Stratification

• Categorize patients into definite ACS, possible ACS, chronic stable angina, or noncardiac diagnosis by integrating history, physical examination, ECG findings, and initial cardiac biomarkers 2

• Patients with definite ACS (ongoing pain, positive biomarkers, new ST-segment deviations, new deep T-wave inversions, or hemodynamic abnormalities) should be admitted to the hospital for further management 2

• Patients with possible ACS and normal initial biomarkers should be observed in a facility with cardiac monitoring, with repeat ECG and biomarkers obtained 6-12 hours after symptom onset 2

Specific Management Based on Your ECG Findings

Left Axis Deviation

• Evaluate for left ventricular hypertrophy, conduction system disease, or prior inferior myocardial infarction, as left axis deviation is considered a "borderline" finding in athletes but may indicate underlying cardiac disease in non-athletes 2, 1

• Obtain echocardiography to assess left ventricular structure and function 1

Left Atrial Enlargement

• Investigate underlying causes including hypertension, valvular heart disease, heart failure with preserved ejection fraction, or atrial fibrillation 1

• Echocardiography is essential to evaluate left atrial size, valvular function, and diastolic function 1

Possible Anteroseptal Infarct

• This finding requires urgent evaluation as it may represent acute or prior myocardial infarction 1

• If cardiac biomarkers are elevated, manage as NSTEMI with appropriate antiplatelet therapy, anticoagulation, and consideration for early invasive strategy 1

• If biomarkers are negative, echocardiography should assess for regional wall motion abnormalities suggesting prior infarction 1

Low Voltage in Extremity Leads

• Consider pericardial effusion, infiltrative cardiomyopathy, obesity, emphysema, or prior myocardial infarction as potential causes 1

• Echocardiography is mandatory to exclude pericardial effusion and assess myocardial thickness 1

Diagnostic Testing Algorithm

If Initial Biomarkers and Repeat ECG Are Normal

• Perform stress testing (exercise or pharmacological) within 72 hours to provoke ischemia, either in the ED, chest pain unit, or outpatient basis 2

• Low-risk patients with negative stress test can be managed as outpatients with appropriate follow-up 2

• Patients unable to exercise or with abnormal resting ECG should undergo pharmacological stress testing 2

Echocardiography Indications (Class I)

• Measure left ventricular ejection fraction, volumes, and wall motion abnormalities 2

• Assess left atrial size and valvular function 1

• Evaluate for structural heart disease including cardiomyopathy 1

Advanced Imaging Considerations

• Cardiac MRI should be considered if echocardiogram is normal but high clinical suspicion persists, particularly for detecting subtle myocardial disease or prior small infarctions 2

• Coronary angiography is indicated for patients with elevated troponin, ongoing symptoms, or high-risk features on non-invasive testing 1

Critical Pitfalls to Avoid

• Never rely on a single normal ECG to exclude ACS in patients with ongoing chest pain or high clinical suspicion—this is the most dangerous error in chest pain evaluation 2, 3

• Left ventricular hypertrophy, bundle branch blocks, and ventricular pacing can mask signs of ischemia on the initial ECG, requiring heightened vigilance 2, 3

• Do not delay repeat ECGs waiting for scheduled intervals if symptoms change—symptom-driven timing takes priority over predetermined schedules 2, 3

• Always compare current ECG with previous ECGs when available, as a normal but changed ECG may reveal subtle new abnormalities 2, 3

Disposition and Follow-Up

For Patients with Negative Initial Evaluation

• Arrange cardiology follow-up within 1-2 weeks for persistent ECG abnormalities despite negative acute workup 1

• Consider ambulatory ECG monitoring (24-48 hour Holter or event recorder) if arrhythmia is suspected 1

For Patients with Confirmed Cardiac Pathology

• Initiate appropriate disease-specific therapy based on final diagnosis 1

• Establish regular cardiac follow-up with consideration of implantable cardiac monitor for high-risk patients 1

Discharge Instructions

• Provide specific instructions for activity, medications, additional testing, and follow-up with a personal physician 2

• Precautionary pharmacotherapy (aspirin, sublingual nitroglycerin, beta blockers) should be given to low-risk patients awaiting outpatient stress testing 2