When should a patient undergo an electrocardiogram (ECG)?

Indications for Electrocardiogram (ECG)

An electrocardiogram (ECG) should be performed in patients with suspected cardiac disease, known cardiovascular disease with changes in symptoms, before surgery in patients over 40 years old, and in patients receiving medications known to affect cardiac function. 1

Patients with Known Cardiovascular Disease

Baseline/Initial Evaluation

• All patients with known cardiovascular disease should have a baseline ECG as part of their initial evaluation 1
• ECG provides immediate information about arrhythmias, conduction defects, chamber enlargement, hypertrophy, ischemia, necrosis, and electrolyte disturbances 1

Response to Therapy

• ECG is indicated when prescribed therapy is known to produce ECG changes that correlate with therapeutic responses or disease progression 1
• ECG should be performed when medications may produce adverse effects detectable by ECG changes (e.g., psychotropic agents, anti-infective agents, antihypertensive drugs, antineoplastic agents) 1
• Patients undergoing cardioversion should have an ECG before and immediately after the procedure, and before hospital discharge 1
• Patients with pacemakers should have ECGs soon after insertion/revision, whenever malfunction is suspected, and at periodic intervals 1

Follow-up

• ECG is indicated in patients with known cardiovascular disease who experience:
  • Syncope or near-syncope 1
  • Unexplained changes in angina pattern 1
  • New or worsening dyspnea 1
  • Extreme fatigue, weakness, or prostration 1
  • Palpitations 1
• Patients with implanted pacemakers or anti-tachycardia devices should have periodic ECGs 1

Before Surgery

• All patients with known cardiovascular disease should have a preoperative ECG before cardiac or noncardiac surgery 1
• This includes patients with coronary artery disease, peripheral vascular disease, or cerebrovascular disease undergoing intermediate or high-risk surgery 1

Patients Suspected of Having Cardiovascular Disease

Initial Evaluation

• ECG is indicated in patients with suspected cardiac disease or dysfunction 1
• ECG should be performed in patients at increased risk for developing cardiac disease 1
• Patients presenting with chest pain should have an ECG to help determine risk of myocardial infarction 1, 2
• ECG is particularly important in patients with syncope to evaluate for cardiac causes 1

Specific Symptoms Warranting ECG

• Chest pain (to evaluate for possible acute coronary syndrome) 1, 3, 2
• Dyspnea (which may represent cardiac origin) 1
• Palpitations (to identify arrhythmias) 1
• Syncope or near-syncope (to rule out cardiac causes) 1

Patients with No Apparent Heart Disease

Preoperative Evaluation

• ECG is recommended for patients >40 years old before surgery 1
• ECG is not indicated for asymptomatic patients undergoing low-risk surgery 1
• ECG is not indicated for patients <30 years old with no risk factors for coronary artery disease 1

Follow-up

• ECG is not indicated for asymptomatic adults who have had no interval change in symptoms, signs, or risk factors and who have had a normal ECG within the recent past 1

Special Considerations

Medication Monitoring

• ECG should be performed when starting medications known to affect cardiac conduction or repolarization 1
• Common medications requiring ECG monitoring include:
  • Psychotropic agents (phenothiazines, tricyclic antidepressants, lithium)
  • Anti-infective agents (erythromycin, pentamidine)
  • Antihypertensive agents
  • Antineoplastic agents
  • Heart failure medications (digitalis, dopamine, dobutamine) 1

Common Pitfalls to Avoid

• Performing ECGs in asymptomatic patients with no risk factors leads to unnecessary testing 4, 5
• Not obtaining an ECG in patients with chest pain can miss critical diagnoses like myocardial infarction 3, 2
• Failure to compare with previous ECGs may lead to missed diagnoses of evolving cardiac conditions 1
• Over-reliance on computerized ECG interpretation algorithms without physician review can lead to diagnostic errors 4

Clinical Decision Algorithm

1. Known cardiovascular disease?

   • Yes → Perform ECG at baseline, with symptom changes, before surgery, and with cardioactive medications 1
   • No → Proceed to next question

2. Presenting with cardiac symptoms? (chest pain, dyspnea, palpitations, syncope)

   • Yes → Perform ECG 1
   • No → Proceed to next question

3. Age >40 years and preparing for surgery?

   • Yes → Perform ECG 1
   • No → Proceed to next question

4. Taking medications known to affect cardiac function?

   • Yes → Perform ECG 1
   • No → ECG likely not indicated unless other risk factors present 1, 4