HEART FAILURE (HF) 
 
Definition 
 
Heart failure is a clinical syndrome in which the heart is unable to pump blood at a rate sufficient to meet the metabolic demands of tissues or can do so only with elevated filling pressures (i.e.; in Diastole the heart does not relax fully to maintain the pressure, in the left ventricle, which means that not all the blood is ejected with the heart beat, causing the blood to back up and symptoms such as shortness of breath due to pulmonary congestion).   
 
Heart failure can be acute (e.g.; ischaemia or infarction) or chronic (e.g.; cardiomyopathy, valve disease). 
 
PATHOPHYSIOLOGY 
 
Heart failure results from any structural or functional cardiac disorder that impairs the ventricular filling (diastolic dysfunction) or ejection (systolic dysfunction) of blood. 
 
1. Initiating Event: 
Myocardial injury (e.g., ischemic heart disease, Myocardial infarction (MI), hypertension, cardiomyopathy, valve disease) → decreased cardiac output (CO). 
The fall in CO activates compensatory mechanisms to try to maintain perfusion. 
 
2. Compensatory Mechanisms: 
Initially adaptive but eventually maladaptive — leading to a vicious cycle of worsening HF. 
 
a. Frank-Starling Mechanism 
Acutely: ↓ CO → ↑ end-diastolic volume (EDV) (preload, the amount of stretch left in the heart at the end of diastole (when the heart fills with blood) → ↑ stretch → ↑ contractility (temporary improvement). 
Chronically: Chronic overstretching → myocardial dilation → decreased contractile efficiency. 
 
b. Neurohormonal Activation: 

Sympathetic Nervous System (SNS): 
↑ Heart rate and contractility. 
Vasoconstriction → ↑ afterload → ↑ myocardial oxygen demand. 
Chronic activation → β-receptor downregulation (less B receptors on a cell which makes it less sensitive to Noradrenaline and Adrenaline) and apoptosis (cell death). 
 
Renin-Angiotensin-Aldosterone System (RAAS): 
↓ Renal perfusion → ↑ renin (an enzyme which plays a key role in the regulation of blood pressure) → ↑ angiotensin II (hormone causing vasoconstriction and high BP)→ vasoconstriction + ↑ aldosterone (steroid hormone which helps control blood pressure by maintaining the sodium/potassium regulation in the body) → Na⁺/H₂O retention. 
This leads to volume overload and ventricular remodelling. 
 
Antidiuretic Hormone (ADH) (a hormone which regulates water balance in the body by increasing water reabsorption by the kidneys) 
Too much ADH causes ↑ Water retention → hyponatremia → worsens congestion. 
 
Endothelin & Cytokines: 
Promote vasoconstriction and fibrosis. 
 
c. Ventricular Remodelling: 
 
Changes in size, shape, and function of the ventricle. 
Systolic HF: eccentric hypertrophy (dilated chamber (left ventricle)). 
Diastolic HF: concentric hypertrophy (thickened wall, small chamber (left ventricle)). 
Leads to progressive myocardial dysfunction and fibrosis. 
 
 
 
 
3. Haemodynamic Consequences: 
 


CLASSIFICATIONS OF HEART FAILURE 
 
1. Based on Side of the Heart: 
Left-sided HF: Pulmonary congestion, dyspnoea, orthopnoea, paroxysmal nocturnal dyspnoea. 
Right-sided HF: Peripheral oedema, ascites, hepatomegaly, jugular venous distension. 
Biventricular HF: Failure of both sides. 
 
2. Based on Cardiac Output: 
High-output failure: Heart is normal, but metabolic demands are excessive (e.g., anaemia, thyrotoxicosis, AV fistula, beriberi). 
Low-output failure: Heart cannot maintain adequate output (e.g., IHD, hypertension, cardiomyopathy). 
 
3. Based on Ejection Fraction (EF): 
(EF = % of blood volume ejected from the LV with each heartbeat) 
 

 
4. Based on Time Course: 
 
Acute HF: Sudden onset (e.g., acute MI, hypertensive crisis). 
Chronic HF: Gradual onset with compensatory mechanisms (e.g., long-term hypertension, valve disease). 
Acute-on-Chronic HF: Decompensation of pre-existing chronic HF. 
 
5. Based on Functional Capacity: 
 
New York Heart Association (NYHA) Classification: 

Class 
Description 
I 
No limitation of physical activity 
II 
Slight limitation; comfortable at rest 
III 
Marked limitation; symptoms with less-than-ordinary activity 
IV 
Symptoms at rest 
 
6. Based on Structural and Clinical Stage: 
 
ACC/AHA Staging: 

Stage 
Description 
A 
High risk, no structural disease or symptoms (e.g., hypertension, diabetes) 
B 
Structural heart disease but no symptoms 
C 
Structural heart disease with current/prior symptoms 
D 
Refractory HF requiring specialized interventions (e.g., transplant, LVAD) 
 
 
SUMMARY TABLE: