From the Guidelines
Low voltage QRS on an EKG suggests a potential underlying condition such as cardiac amyloidosis, which is characterized by decreased electrical activity in the heart. This finding is defined as QRS amplitude less than 5 mm in all limb leads or less than 10 mm in all precordial leads, as seen in approximately 50% of patients with AL amyloidosis and in approximately 25% of patients with ATTR amyloidosis 1. The low voltage occurs because fluid, air, or tissue between the heart and recording electrodes dampens the electrical signal. Some possible causes of low voltage QRS include:
- Pericardial effusion
- Pleural effusion
- Obesity
- Emphysema
- Myxedema
- Infiltrative cardiomyopathies (like amyloidosis or sarcoidosis)
- Severe coronary artery disease
- Hypothyroidism
- Anasarca (severe generalized edema) When encountering low voltage QRS, further evaluation with echocardiography, chest imaging, or laboratory testing is typically warranted to identify the underlying cause, as the clinical significance varies based on the etiology, with some causes requiring urgent intervention (like large pericardial effusions) while others may represent chronic conditions 1. The patient's clinical presentation should guide the diagnostic approach and management strategy. It is essential to note that low voltage QRS has limited usefulness as a screening test due to its low sensitivity, particularly in cardiac amyloidosis, where QRS voltages are often disproportionate to the thickness of the left ventricular wall 1.
From the Research
Low Voltage QRS on EKG
Low voltage QRS on an electrocardiogram (EKG) can suggest several underlying conditions. The causes of low voltage QRS can be divided into cardiac and extracardiac factors 2.
Cardiac Causes
Some cardiac causes of low voltage QRS include:
- Cardiac amyloidosis, as highlighted in a case study where ECG findings led to the diagnosis of this rare condition 3
- Arrhythmogenic cardiomyopathy and Takotsubo syndrome, which are associated with low QRS voltage in a significant proportion of cases 4
- Pericardial effusion, although the relationship between the volume of effusion and low voltage is not always clear 5, 6
Extracardiac Causes
Extracardiac causes of low voltage QRS include:
- Peripheral edema, which can induce reversible low QRS voltage and alter other EKG parameters 2
- Other conditions that affect the body's volume conductor, such as large pericardial effusions or cardiac tamponade 3, 5, 6
Clinical Implications
Low voltage QRS can be a sign of severe cardiac dysfunction and is associated with a higher risk of adverse clinical outcomes, including in-hospital death or discharge against medical advice 4. The presence and severity of cardiac tamponade, as well as inflammatory mechanisms, may contribute to the development of low QRS voltage in patients with large pericardial effusions 6.