Cardiovascular Physiology and Pharmacology Flashcards

Which ion channel is primarily responsible for the plateau phase (phase 2) of the ventricular action potential?

Answer: L-type calcium channels

L-type (long-lasting) calcium channels carry slow inward calcium current responsible for the prolonged plateau phase 2 of the ventricular action potential.

In a patient with right heart failure, which hemodynamic finding is MOST characteristic?

Answer: Elevated CVP with relatively normal PCWP

Right heart failure causes venous congestion (elevated CVP/JVP) but initially without pulmonary congestion, so PCWP may remain relatively normal.

Which of the following describes the effect of increased afterload on the LV pressure-volume loop?

Answer: Decreased stroke volume with increased end-systolic volume

Increased afterload raises the pressure against which the ventricle must eject, resulting in decreased stroke volume and an elevated end-systolic volume.

Nitroglycerin at low doses primarily reduces preload by:

Answer: Venodilation reducing venous return and LVEDP

At low doses, nitroglycerin predominantly dilates veins, pooling blood in the venous capacitance system, reducing venous return and cardiac preload.

The oxygen delivery (DO2) equation is best represented as:

Answer: DO2 = CO × (Hb × 1.34 × SaO2 + 0.003 × PaO2)

DO2 = CO × CaO2, where CaO2 = (Hb × 1.34 × SaO2) + (0.003 × PaO2), reflecting both hemoglobin-bound and dissolved oxygen contributions.

Beta-blockers reduce myocardial oxygen demand primarily by:

Answer: Decreasing heart rate and contractility

Beta-blockers reduce heart rate and myocardial contractility by blocking beta-1 receptors, both of which are major determinants of myocardial oxygen consumption.

Which finding on a pulmonary artery catheter tracing suggests mitral regurgitation?

Answer: Large V waves on the PCWP tracing

Severe mitral regurgitation produces large V waves on the PCWP tracing due to regurgitant systolic volume entering the compliant left atrium.