Which of the following is NOT classified as a lethal arrhythmia?

Bradycardia is indeed the option that is not classified as a lethal arrhythmia. While bradycardia refers to a slower-than-normal heart rate, it is not considered immediately life-threatening in many cases. The impact of bradycardia on a person's health greatly depends on the context, duration, and whether it is symptomatic. For instance, athletes often have a lower resting heart rate due to physical conditioning, which may not require any medical intervention.

In contrast, a-systole is the lack of electrical activity in the heart, resulting in no heartbeat and is recognized as a lethal arrhythmia that requires immediate resuscitation efforts. Ventricular tachycardia, particularly sustained forms, can also be lethal if it leads to reduced cardiac output or deteriorates into ventricular fibrillation, which is disorganized electrical activity resulting in ineffective heart contractions and is similarly classified as a lethal arrhythmia. Ventricular fibrillation is often the final rhythm seen in cases of sudden cardiac arrest.

Bradycardia, while it can be serious in certain scenarios, does not share the same immediate life-threatening characteristics associated with the other arrhythmias listed.