Low QRS voltage on ECG indicates –
**Core Concept**
Low QRS voltage on an electrocardiogram (ECG) refers to the reduced amplitude of the QRS complex, which represents the depolarization of the ventricles. This finding is often associated with conditions that affect the conduction system of the heart or the myocardium itself.
**Why the Correct Answer is Right**
Low QRS voltage is typically seen in conditions that reduce the size or mass of the ventricles, such as in cardiac amyloidosis, where amyloid deposits infiltrate the myocardium, or in conditions that affect the conduction system, such as in bundle branch block or ventricular hypertrophy. The reduced amplitude of the QRS complex is due to the decreased electrical activity generated by the smaller or less active ventricles. In cardiac amyloidosis, for example, the amyloid deposits disrupt the normal functioning of the cardiac myocytes, leading to a decrease in the electrical activity and thus a decrease in the amplitude of the QRS complex.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because low QRS voltage is not typically seen in conditions that increase the mass of the ventricles, such as in hypertrophic cardiomyopathy.
* **Option B:** This option is incorrect because low QRS voltage is not typically seen in conditions that affect the atria, such as atrial fibrillation.
* **Option C:** This option is incorrect because low QRS voltage is not typically seen in conditions that affect the conduction system of the heart, such as in Wolff-Parkinson-White syndrome.
**Clinical Pearl / High-Yield Fact**
Low QRS voltage is often seen in cardiac amyloidosis, a condition where amyloid deposits infiltrate the myocardium, leading to a decrease in the electrical activity and thus a decrease in the amplitude of the QRS complex.
**Correct Answer: D. Cardiac amyloidosis.