During V-tach, does the SA node continue to pace the atria?

During V-tach, does the SA node continue to pace the atria?

• A. No, the SA node is inactive during V-tach.
• B. Yes, but it has no effect on ventricular contraction.
• C. Yes, this condition is known as AV dissociation.
• D. No, the atria stop contracting completely.

Answer: (C)

During ventricular tachycardia (V-tach), there can be a phenomenon known as AV dissociation, which allows the atria to continue beating independently of the ventricles. In this condition, while the ventricles are contracting rapidly and out of synch with the normal rhythm regulated by the SA node, the SA node may still be capable of sending electrical impulses to the atria. This results in the atria contracting at their own intrinsic rate, separate and often slower than the rapid ventricular rate.

AV dissociation demonstrates that the normal conduction pathway can be disrupted, leading to a scenario where the atrial and ventricular activities are not coordinated. This can sometimes be observed in cases of V-tach, allowing for the atria to still have a degree of pacing activity. Furthermore, while the atrial contractions may remain functional, they do not significantly contribute to effective ventricular filling during the high rates of V-tach, which may lead to decreased cardiac output.

Thus, the correct answer emphasizes the ability of the SA node to continue pacing the atria in the context of V-tach while highlighting the concept of AV dissociation.