Orris

In Heart Failure with reduced ejection fraction why is the ventricle dilated

Reading File
Reading File
Finding Sources
Searching PubMed

heart failure AND ventricular remodeling

Searching the Web

HFrEF ventricular dilation pathophysiology remodeling renin angiotensin sympathetic activation

Finding Sources
Finding Sources
In HFrEF, the ventricle dilates because a weakened myocardium cannot eject its normal proportion of blood. More blood is left behind after systole, so end-systolic and then end-diastolic ventricular volumes rise.
Initially, dilation is compensatory:
  • A larger end-diastolic volume stretches myocardial fibers.
  • This can temporarily increase contraction by the Frank-Starling mechanism, helping preserve stroke volume.
  • With chronic volume loading, myocytes add sarcomeres in series, producing eccentric hypertrophy and chamber enlargement.
But it becomes harmful remodeling. Persistent sympathetic and renin-angiotensin-aldosterone system activation, along with inflammation and fibrosis, alter myocytes and the extracellular matrix. The ventricle becomes more spherical and dilated, rather than the efficient elliptical shape.
The dilated ventricle then worsens failure because, by Laplace's principle, wall stress rises as chamber radius increases:
[ \text{Wall stress} \propto \frac{\text{pressure} \times \text{radius}}{\text{wall thickness}} ]
Higher wall stress means higher oxygen demand and less mechanical efficiency, which further impairs systolic contraction. It may also pull apart the mitral-valve apparatus, causing functional mitral regurgitation and adding further volume overload.
So the key sequence is:
Myocardial injury / impaired contraction → residual blood and increased filling volume → initially compensatory dilation → pathological remodeling, high wall stress, fibrosis, and progressively lower EF.
This is why therapies such as ACE inhibitors/ARBs/ARNI, beta-blockers, mineralocorticoid antagonists, and SGLT2 inhibitors aim not only to improve symptoms but also to limit or reverse adverse ventricular remodeling. Textbook support: Braunwald’s Heart Disease describes volume overload causing increased diastolic wall stress, serial sarcomere addition, and eccentric LV dilation; Miller’s Anesthesia notes that dilation raises wall stress and myocardial oxygen consumption.

Catecholamines, angiotensin 2, aldosterone cause eccentric hypertrophy

Reading File
Finding Sources
Searching PubMed

heart failure neurohormonal activation ventricular remodeling

Searching the Web

heart failure catecholamines angiotensin II aldosterone eccentric hypertrophy ventricular remodeling pathophysiology

Yes, but with an important distinction.
Catecholamines, angiotensin II, and aldosterone promote pathological ventricular remodeling, including myocyte hypertrophy, fibrosis, cell death, and fluid retention. In HFrEF, this remodeling often occurs in a ventricle already exposed to increased end-diastolic volume and wall stress, so the overall geometry is commonly eccentric hypertrophy with dilation.
However, they do not by themselves determine “eccentric” hypertrophy:
  • Volume overload / increased preload is the main mechanical driver of eccentric hypertrophy.
    • Sarcomeres are added in series
    • Myocytes become longer
    • LV cavity enlarges
  • Pressure overload / increased afterload tends to cause concentric hypertrophy.
    • Sarcomeres are added in parallel
    • Wall thickness increases relatively more than cavity size
In HFrEF, neurohormonal activation worsens the volume-load pathway:
  1. Reduced cardiac output activates sympathetic nerves and RAAS.
  2. Catecholamines increase heart rate, oxygen demand, toxicity, apoptosis, and maladaptive signaling.
  3. Angiotensin II promotes myocyte hypertrophy, fibrosis, apoptosis, vasoconstriction, and aldosterone release.
  4. Aldosterone causes sodium and water retention, increasing preload, and also promotes myocardial fibrosis.
  5. Higher preload and diastolic wall stress lead to chamber dilation and serial sarcomere addition, giving eccentric hypertrophy.
So the concise statement is:
Neurohormones drive adverse remodeling; chronic volume overload and increased diastolic wall stress determine the eccentric, dilated pattern.
Goodman & Gilman notes that norepinephrine and angiotensin II accelerate pathological remodeling through hypertrophy, fibrosis, and cell death, while aldosterone contributes importantly to the maladaptive process. Braunwald’s Heart Disease describes volume overload as causing serial sarcomere addition and eccentric LV dilation.
This is a shared conversation. Sign in to Orris to start your own chat.