Which intervention produces an upward shift of the Frank-Starling curve?

Which intervention produces an upward shift of the Frank-Starling curve?

• A. Increasing afterload
• B. Administration of a positive inotropic drug (e.g., digoxin)
• C. Decreasing afterload
• D. Administration of a negative inotropic agent (beta-blocker)

Answer: (B)

An upward shift of the Frank-Starling curve means the heart can eject more blood for the same filling, i.e., increased contractility. A positive inotropic drug does just that by boosting intracellular calcium during systole, strengthening contraction. Digoxin, for example, increases intracellular Ca2+ (it inhibits Na+/K+ ATPase, which raises Na+ and reduces Ca2+ extrusion via the Na+/Ca2+ exchanger), leading to a stronger beat. As a result, at the same end-diastolic volume, stroke volume is higher, shifting the curve upward. Interventions that alter loading conditions, like decreasing afterload, change stroke volume for a given preload along the same curve rather than shifting the curve itself. A negative inotropic agent would reduce contractility and shift the curve downward.

An upward shift of the Frank-Starling curve means the heart can eject more blood for the same filling, i.e., increased contractility. A positive inotropic drug does just that by boosting intracellular calcium during systole, strengthening contraction. Digoxin, for example, increases intracellular Ca2+ (it inhibits Na+/K+ ATPase, which raises Na+ and reduces Ca2+ extrusion via the Na+/Ca2+ exchanger), leading to a stronger beat. As a result, at the same end-diastolic volume, stroke volume is higher, shifting the curve upward.

Interventions that alter loading conditions, like decreasing afterload, change stroke volume for a given preload along the same curve rather than shifting the curve itself. A negative inotropic agent would reduce contractility and shift the curve downward.