Registered Cardiovascular Invasive Specialist (RCIS) Practice Test

In the formula BP = HR x SV x Systematic Vascular Resistance, how does Dobutamine act?

1. As a vasodilator, to decrease blood pressure

2. As an inotrope, to increase stroke volume by increasing contractility

3. As a chronotrope, to increase heart rate

4. As a diuretic, to reduce fluid volume

The correct answer is: As an inotrope, to increase stroke volume by increasing contractility

Dobutamine primarily acts as an inotropic agent, which means its main function is to enhance myocardial contractility. By increasing the strength of the heart's contractions, Dobutamine effectively boosts stroke volume. Stroke volume is the amount of blood ejected by the ventricle during each contraction, and it is a critical component of cardiac output, which, when multiplied by heart rate, helps determine blood pressure along with systemic vascular resistance. In the context of the formula BP = HR x SV x Systemic Vascular Resistance, an increase in stroke volume leads to improved cardiac output, which can subsequently affect blood pressure positively. This is why selecting the action of Dobutamine as an inotrope is the correct choice. It plays a vital role in managing patients with heart failure or cardiogenic shock by improving cardiac performance without directly altering heart rate or significantly affecting vascular resistance.