Chronotropic agents are factors that affect what aspect of cardiac function?

Chronotropic agents are factors that affect what aspect of cardiac function?

• A. Heart rate
• B. Stroke volume
• C. Cardiac output independent of rate
• D. Blood viscosity

Answer: (A)

Chronotropic factors determine how quickly the heart beats. They modify the rate of SA node firing and AV node conduction, so they set the tempo of cardiac cycles. Positive chronotropic effects speed up heart rate (through sympathetic mechanisms that increase nodal firing), while negative chronotropic effects slow it down (through parasympathetic influence that reduces firing). Stroke volume, on the other hand, is mainly governed by contractility (inotropic factors), preload, and afterload, not by chronotropic changes. Blood viscosity is unrelated to the timing of heartbeats. So chronotropic agents influence heart rate.

Chronotropic factors determine how quickly the heart beats. They modify the rate of SA node firing and AV node conduction, so they set the tempo of cardiac cycles. Positive chronotropic effects speed up heart rate (through sympathetic mechanisms that increase nodal firing), while negative chronotropic effects slow it down (through parasympathetic influence that reduces firing). Stroke volume, on the other hand, is mainly governed by contractility (inotropic factors), preload, and afterload, not by chronotropic changes. Blood viscosity is unrelated to the timing of heartbeats. So chronotropic agents influence heart rate.