While an ECG cannot directly measure ejection fraction, it can provide indirect clues suggestive of a decline in ejection fraction, particularly when interpreted in the context of a patient's clinical presentation.

Here are some ECG findings that may raise suspicion for reduced ejection fraction:

• Left Ventricular Hypertrophy (LVH): This indicates thickening of the heart muscle, often a compensatory response to decreased pump function. While not always associated with reduced ejection fraction, it warrants further investigation.

• Q waves: Pathological Q waves can signify prior myocardial infarction, which can lead to decreased ejection fraction.  

• ST-segment and T-wave changes: Non-specific ST-segment and T-wave abnormalities can sometimes be seen in patients with heart failure and reduced ejection fraction.

• Low voltage QRS complexes: This may indicate diffuse myocardial disease or poor left ventricular function.

• Arrhythmias: Atrial fibrillation or other arrhythmias can worsen heart failure symptoms and potentially contribute to a decline in ejection fraction.

Important Considerations:

• Non-Specific Findings: The ECG findings listed above are not specific for reduced ejection fraction and can also be seen in other conditions.

• Clinical Correlation: It's crucial to interpret the ECG in conjunction with the patient's clinical presentation (symptoms, physical exam, medical history) and other diagnostic tests (e.g., echocardiogram) to assess ejection fraction accurately.

• Dynamic Changes: Serial ECGs can be helpful in monitoring for changes that might indicate a decline in heart function, but again, imaging is needed for definitive assessment.

In summary, while an ECG cannot directly measure ejection fraction, certain findings can suggest a potential decline. These findings warrant further investigation with imaging studies, particularly if a patient is experiencing symptoms suggestive of heart failure.

 What are Low voltage QRS complexes?

Low voltage QRS complexes, also referred to as low QRS voltage, is an electrocardiogram (ECG) finding where the amplitude (height) of the QRS complexes is smaller than normal.  

Diagnostic Criteria

• Limb leads: The amplitude of all QRS complexes is less than 5 mm.  

• Precordial leads: The amplitude of all QRS complexes is less than 10 mm.  

Causes

Low QRS voltage can be caused by several factors that either reduce the electrical signal generated by the heart or impede its conduction to the surface electrodes. These factors can be broadly categorized as:  

1. Increased Impedance/Damping:

• Extracardiac:

  • Obesity: Excess subcutaneous fat  

  • Pericardial effusion: Fluid accumulation around the heart  

  • Pleural effusion: Fluid buildup in the pleural space  

  • COPD or Emphysema: Air trapping in the lungs  

  • Subcutaneous emphysema: Air trapped under the skin  

2. Myocardial Factors:

• Loss of viable myocardium:

  • Prior extensive myocardial infarction

  • Dilated cardiomyopathy  

• Diffuse myocardial disease/infiltration:

  • Amyloidosis  

  • Sarcoidosis

  • Hemochromatosis

  • Myocarditis

3. Other:

• Hypothyroidism

• Constrictive pericarditis

• Scleroderma

• Technical errors (e.g., incorrect ECG settings)

Clinical Significance

Low QRS voltage, while sometimes a normal variant, often indicates an underlying cardiac or systemic condition. It can be associated with:  

• Poor left ventricular function

• Increased risk of heart failure

• Higher mortality in certain conditions  

Key takeaway:

• Low QRS voltage on an ECG is not a diagnosis in itself but a sign that warrants further investigation to identify the underlying cause.

• If you notice low QRS voltage on an ECG, it's important to correlate it with the patient's clinical presentation and consider additional tests (like echocardiogram or cardiac MRI) to assess cardiac structure and function.

  

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