What areas of the heart are most sensitive to the effects of digitalis?

What areas of the heart are most sensitive to the effects of digitalis?

• A. Ventricles and AV node
• B. Atria and AV junction
• C. SA node and Purkinje fibers
• D. Right atrium and left ventricle

Answer: (B)

The areas of the heart that are most sensitive to the effects of digitalis are indeed the atria and the AV junction. Digitalis is a cardiac glycoside that primarily affects the conduction system and contractility of the heart muscle. It enhances parasympathetic (vagal) tone, leading to effects such as decreased heart rate and increased force of contraction.

The atria are particularly responsive to digitalis because the drug increases intracellular calcium levels, which enhances myocardial contractility and can help in managing atrial fibrillation by slowing conduction through the AV node. This slowing is significant because it allows for better ventricular filling and can improve symptoms of heart failure.

The AV junction is also highly sensitive to digitalis due to its role in regulating the conduction of impulses from the atria to the ventricles. By enhancing vagal tone and reducing the conduction velocity through this junction, digitalis can effectively control heart rate in patients with atrial fibrillation or flutter.

Other areas, such as the ventricles and the SA node, do not have the same degree of sensitivity to digitalis' effects as the atria and AV junction do. This is critical in understanding the therapeutic use of digitalis, particularly in conditions where atrial activity must be controlled to