Why is phenylephrine considered a safer choice during arrhythmias?

Phenylephrine is considered a safer choice during arrhythmias primarily because it has no beta-1 activity. This characteristic is crucial in patients experiencing arrhythmias since beta-1 adrenergic stimulation can lead to increased heart rate and enhanced myocardial contractility, which may exacerbate an already unstable cardiac rhythm. By not engaging with beta-1 receptors, phenylephrine allows for vasoconstriction and increased systemic vascular resistance without influencing heart rate or causing further cardiac stress. This mechanism makes it more suitable for managing conditions where heart rhythm is compromised, as it helps maintain hemodynamic stability without triggering the potentially detrimental effects associated with increased heart rate.