Which mechanism is NOT one of the basic mechanisms responsible for arrhythmias?

The correct answer is based on the fact that ventricular contraction is not a mechanism that directly causes arrhythmias. Arrhythmias are typically caused by disruptions in the normal electrical activity of the heart, which can occur due to changes in how impulses are generated and conducted.

Altered automaticity refers to a change in the rate of impulse generation by pacemaker cells, which can lead to arrhythmic heartbeats. Triggered activity involves abnormal impulses that occur due to afterdepolarizations, which can also result in arrhythmias. Reentry is a mechanism that involves a circuitous pathway for impulse conduction, where an electrical impulse reenters a previously excited area of heart tissue, causing persistent abnormal rhythms.

Ventricular contraction itself is a result of the electrical activity and does not inherently account for the mechanisms that disturb this rhythm or lead to arrhythmias. It’s important to recognize that while proper ventricular contraction is crucial for effective heartbeat and circulation, it is a consequence of the underlying rhythms rather than a cause of the arrhythmias themselves.