Heart Failure

1. 1

   System

   the whole body at work

   • A healthy heart functions as a demand-responsive pump where the Frank-Starling law reigns supreme.
   • Venous return fills the chambers (preload), stretching the myocytes to an optimal point where they snap back with enough force to overcome systemic resistance (afterload).
   • This cycle ensures that forward flow perfectly matches the oxygen needs of the tissues, regulated by a delicate balance of pressure sensors and hormonal signals.
2. 2

   Organ

   the healthy sequence, step by step

   • Venous return fills the ventricles to create preload stretch
   • Myocytes contract via calcium-induced calcium release
   • Left ventricle ejects blood against systemic afterload
   • Forward flow perfuses the kidneys and brain
   • Baroreceptors signal the brain that pressures are stable
3. 3

   Tissue & mechanism

   where and why it breaks

   • The mechanism of Heart Failure is Neurohormonal Overdrive.
   • When the pump fails, the body thinks you're bleeding out, so it activates the Sympathetic Nervous System (SNS) and the Renin-Angiotensin-Aldosterone System (RAAS).
   • This increases heart rate, clamps down on vessels, and sucks up salt and water—all of which increase the workload on an already exhausted heart, leading to a vicious cycle of remodeling and further failure.
4. 4

   Cell & molecule

   the break at its smallest scale

   • Baroreceptors sense low stretch and trigger SNS 'Fight or Flight'
   • SNS increases heart rate and systemic vasoconstriction
   • Low renal flow triggers RAAS to retain Sodium and Water
   • High wall stress and Angiotensin II trigger ventricular remodeling/fibrosis
   • Fluid backup leads to pulmonary and systemic congestion
5. 5

   The result

   what the break produces

   • Reduced Stroke Volume (Contractility failure or excessive Afterload)
   • End-diastolic pressures rise as blood 'backs up'
   • Hydrostatic pressure forces fluid into the lungs or periphery
   • Renal perfusion drops, triggering the 'panic' hormones

• A healthy heart functions as a demand-responsive pump where the Frank-Starling law reigns supreme.
• Venous return fills the chambers (preload), stretching the myocytes to an optimal point where they snap back with enough force to overcome systemic resistance (afterload).
• This cycle ensures that forward flow perfectly matches the oxygen needs of the tissues, regulated by a delicate balance of pressure sensors and hormonal signals.

• The mechanism of Heart Failure is Neurohormonal Overdrive.
• When the pump fails, the body thinks you're bleeding out, so it activates the Sympathetic Nervous System (SNS) and the Renin-Angiotensin-Aldosterone System (RAAS).
• This increases heart rate, clamps down on vessels, and sucks up salt and water—all of which increase the workload on an already exhausted heart, leading to a vicious cycle of remodeling and further failure.

• The shift into failure begins when an insult—like a massive MI, chronic hypertension, or a leaky valve—blunts the pump's efficiency.
• Because the heart can no longer eject an adequate stroke volume, blood begins to pool behind the failing chamber, and the kidneys sense a drop in perfusion.
• This isn't just a pump problem anymore; it's a systemic alarm state.

The chain that produces them

1. 1End-diastolic pressures rise as blood 'backs up'
2. 2Hydrostatic pressure forces fluid into the lungs or periphery
3. 3Renal perfusion drops, triggering the 'panic' hormones
4. 4Cardiac output fails to meet metabolic demand

• Labs in HF confirm the syndrome, identify the trigger, and stage end-organ damage.

Uncertainty: The mechanism of HFpEF (preserved ejection fraction) is still heavily debated and likely involves systemic inflammation beyond just neurohormonal activation.