What effect does caffeine have on cardiac function?

Caffeine primarily acts as a stimulant on the central nervous system and has notable effects on the heart and cardiovascular system. One significant effect of caffeine is that it can increase the likelihood of premature atrial contractions (PACs), which are early heartbeats originating from the atria. This occurs because caffeine enhances the excitability of cardiac tissues and can lead to increased heart rate and more frequent depolarizations in the atria. These factors can contribute to arrhythmias, of which PACs are a common type.

While caffeine might stabilize some heart rhythms in certain contexts, it primarily promotes increased electrical activity, which is why premature atrial contractions are a known consequence of caffeine intake. This connection underscores the stimulatory nature of caffeine on the heart, distinguishing it from effects like decreasing heart rate or increasing blood viscosity, which are not associated with caffeine's impact on cardiac function.