The most common variations of sinus rhythm include: - Sinus bradycardia: when the SA node fires less than 60 times per minute resulting in a slower heart rate of less than 60 beats per minute.

心率为60-100次/分钟。窦性心律最常见的变体包括：-窦性心动过缓：当SA结放电少于60次/分钟，导致心率低于60次/分钟。