U01.07.013 Pressure-volume loops and valvular disease

Pressure-volume (PV) loops provide valuable insights into the pathophysiology of valvular heart diseases. Different valvular conditions alter the normal PV loop due to changes in preload, afterload, stroke volume (SV), and ventricular compliance.

Below is a breakdown of key valvular diseases and their effects on PV loops.

Aortic Stenosis (AS)

Aortic stenosis is characterized by increased resistance to left ventricular (LV) outflow due to a narrowed aortic valve.

Key Features:

Increased LV pressure: Due to increased afterload.
Increased End-Systolic Volume (ESV): The ventricle cannot efficiently eject blood.
No change in End-Diastolic Volume (EDV): Filling remains unaffected.
Decreased Stroke Volume (SV): Less blood is ejected per beat.
Ventricular hypertrophy: This leads to decreased ventricular compliance and increased end-diastolic pressure (EDP).

Mitral Regurgitation (MR)

Mitral regurgitation results in backflow of blood from the LV into the left atrium (LA) during systole.

Key Features:

No true isovolumetric phase: Due to continuous regurgitation.
Decreased ESV: Due to lower resistance against ejection.
Increased EDV: LA volume/pressure increases due to regurgitation, leading to increased ventricular filling.
Increased SV: More blood is ejected, but some is regurgitated into the LA.
Tall V-wave in LA pressure tracing: Due to regurgitant flow into the LA.

Aortic Regurgitation (AR)

Aortic regurgitation occurs when the aortic valve fails to close properly, allowing blood to flow back into the LV during diastole.

Key Features:

No true isovolumetric phase: Blood leaks back into the LV continuously.
Increased EDV: Due to regurgitant blood returning from the aorta.
Increased SV: Due to higher preload and compensatory mechanisms.
Large pulse pressure: Due to high systolic pressure (increased SV) and low diastolic pressure (rapid runoff of blood).

Mitral Stenosis (MS)

Mitral stenosis is characterized by obstruction of blood flow from the LA to the LV due to a narrowed mitral valve.

Key Features:

Increased LA pressure: Due to obstruction of blood flow.
Decreased EDV: Impaired ventricular filling due to stenosis.
Decreased ESV: Less blood enters the ventricle to be ejected.
Decreased SV: Reduced blood output per beat.
LA > LV pressure gradient: A hallmark of mitral stenosis.

Summary of Valvular Disease Effects on PV Loops

Valvular Disease	Key Changes	PV Loop Features
Aortic Stenosis	↑ LV pressure, ↑ ESV, ↓ SV, No change in EDV, Ventricular hypertrophy	Shifted right with increased peak pressure
Mitral Regurgitation	↓ ESV, ↑ EDV, ↑ SV, No true isovolumetric phase, Tall V-wave	Wide loop with increased volume and no isovolumetric contraction
Aortic Regurgitation	↑ EDV, ↑ SV, No true isovolumetric phase, Large pulse pressure	Loop shifts right with increased volume
Mitral Stenosis	↑ LA pressure, ↓ EDV, ↓ ESV, ↓ SV	Narrow loop due to reduced ventricular filling

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USMLE Step 1 Review Series

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U01.07.013 Pressure-volume loops and valvular disease

Aortic Stenosis (AS)

Key Features:

Mitral Regurgitation (MR)

Key Features:

Aortic Regurgitation (AR)

Key Features:

Mitral Stenosis (MS)

Key Features:

Summary of Valvular Disease Effects on PV Loops

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