A physical therapist observes an electrocardiogram of a patient on beta-blockers. Which of the following electrocardiogram changes could be facilitated by beta blockers?

Beta-blockers are a class of medications that primarily work by blocking the effects of adrenaline on β-adrenergic receptors, which play a crucial role in regulating heart rate and contractility. When a patient is on beta-blockers, a common electrocardiogram change that can occur is sinus bradycardia.

Sinus bradycardia is characterized by a slower than normal heart rate, typically below 60 beats per minute, resulting from increased vagal tone or decreased sympathetic stimulation. Beta-blockers reduce the heart rate by inhibiting the action of catecholamines like epinephrine and norepinephrine at the cardiac beta-adrenergic receptors, leading to this slower heart rate. Consequently, in patients on beta-blockers, the electrocardiogram may show a consistent pattern of sinus bradycardia, as the medication effectively lowers the heart rate.

In contrast, sinus tachycardia is an increased heart rate that would be less likely with beta-blocker therapy, as these medications are designed to decrease the heart rate. Premature ventricular contractions (PVCs) and ST segment sagging are not directly facilitated by beta-blockers; rather, they may indicate underlying cardiac issues or responses to other stimuli that are not directly managed