What is the management approach for a patient with low voltage on an electrocardiogram (ECG)?

Management Approach for Low Voltage on ECG

Patients with low voltage on ECG require a thorough diagnostic evaluation to identify potentially serious underlying conditions, as low voltage can be a warning sign of several life-threatening disorders that require prompt intervention.

Definition and Clinical Significance

• Low voltage on ECG is defined as QRS amplitude <5 mm in all limb leads and <10 mm in all precordial leads 1
• Low voltage isolated to limb leads (with normal precordial voltages) is still clinically significant and requires evaluation 2
• Low voltage should be considered a red flag that warrants further investigation, as it may indicate several serious underlying conditions 3

Common Causes of Low Voltage on ECG

• Cardiac causes:

  • Cardiac amyloidosis (seen in approximately 25% of ATTR amyloidosis and 50% of AL amyloidosis) 4
  • Pericardial effusion (even small effusions can cause low voltage when PR-segment depression is present) 5
  • Dilated cardiomyopathy (found in >60% of patients with low voltage isolated to limb leads without other causes) 2
  • Myocarditis with associated fluid retention 6

• Non-cardiac causes:

  • Obesity
  • Emphysema
  • Hypothyroidism
  • Anasarca/peripheral edema (fluid retention can account for >64% of QRS attenuation) 6

Diagnostic Approach

1. Initial assessment:

   • Review patient's history for symptoms such as syncope, dyspnea, chest pain, fatigue, or edema 4
   • Assess for risk factors of cardiac disease and family history of sudden cardiac death 4
   • Perform physical examination focusing on signs of heart failure, murmurs, or pericardial rubs 4

2. First-line investigations:

   • Obtain a complete 12-lead ECG to confirm low voltage and identify other abnormalities 4
   • Compare with previous ECGs when available 4
   • Evaluate for other ECG findings that may accompany low voltage:
     • Pseudoinfarct pattern (common in cardiac amyloidosis) 4
     • PR-segment depression (common in pericardial effusion) 5
     • Conduction disturbances 4

3. Second-line investigations:

   • Echocardiography is essential to evaluate:
     • Ventricular wall thickness (may be increased in amyloidosis despite low voltage) 4
     • Presence of pericardial effusion 5
     • Left ventricular function and chamber size 2
     • Specific findings suggestive of infiltrative disease (sparkling appearance, thickened valves) 4

4. Additional testing based on clinical suspicion:

   • Cardiac biomarkers (troponin, NT-proBNP) if cardiac involvement is suspected 4
   • Cardiac MRI for tissue characterization if infiltrative cardiomyopathy is suspected 4
   • Nuclear scintigraphy for suspected cardiac amyloidosis 4
   • Laboratory testing for systemic conditions (thyroid function, serum protein electrophoresis) 4

Management Approach

Management should be directed at the underlying cause:

1. For cardiac amyloidosis:

   • Refer to cardiology for specialized management 4
   • Diagnostic approach should include testing for monoclonal protein followed by scintigraphy or biopsy 4

2. For pericardial effusion:

   • Small effusions with no hemodynamic compromise may be observed 5
   • Moderate to large effusions or those with signs of tamponade require urgent drainage 1
   • Investigate underlying cause (infection, malignancy, autoimmune disease) 5

3. For dilated cardiomyopathy:

   • Standard heart failure management 2
   • Consider referral to heart failure specialist 2

4. For myocarditis with fluid retention:

   • Appropriate fluid management and supportive care 6
   • Serial monitoring of ECG voltage may correlate with clinical improvement 6

Follow-up and Monitoring

• Serial ECGs to monitor for changes in voltage 6
• Follow-up echocardiography to assess response to treatment 4
• Continued surveillance for progression of underlying disease 4

Special Considerations

• Low voltage on ECG combined with increased ventricular wall thickness on echocardiography is highly suggestive of infiltrative cardiomyopathy, particularly amyloidosis 4
• The presence of PR-segment depression significantly increases the likelihood that even a small pericardial effusion may cause low voltage 5
• Patients with unexplained low voltage should be considered for referral to cardiology for comprehensive evaluation 3