General Medicine
Heart Failure: Pathophysiology
Heart failure pathophysiology for MBBS: staging, left versus right and systolic versus diastolic failure, compensatory mechanisms and key investigations, mapped to NMC codes IM1.4 to IM1.17.
MedNext Academy | 3 min read
Heart Failure: Pathophysiology
Heart failure pathophysiology for MBBS: staging, left versus right and systolic versus diastolic failure, compensatory mechanisms and key investigations, mapped to NMC codes IM1.4 to IM1.17.
This chapter builds the mechanistic foundation of heart failure, covering its epidemiology, causes, staging and the compensatory pathways that later become maladaptive. It links bedside signs such as the jugular venous pressure and gallop rhythm to the underlying haemodynamics, and introduces the valvular lesions that commonly precipitate failure.
High-yield: Heart Failure: Pathophysiology
- Heart failure is a clinical syndrome, not a single diagnosis, and every case needs a cause and a precipitant to be named.
- The New York Heart Association classes I to IV grade symptoms, while the ACC/AHA stages A to D grade disease progression and are complementary.
- Reduced ejection fraction failure means an ejection fraction at or below 40%, while preserved ejection fraction failure keeps it at 50% or more with diastolic dysfunction.
- Left heart failure causes pulmonary congestion and breathlessness, while right heart failure causes raised jugular venous pressure, hepatomegaly and pedal oedema.
- The commonest cause of right heart failure worldwide is left heart failure.
- Compensatory activation of the sympathetic and renin-angiotensin-aldosterone systems supports output early but drives adverse remodelling later.
- A raised jugular venous pressure with a positive hepatojugular reflux is a specific bedside sign of right heart failure.
- An S3 gallop reflects rapid ventricular filling and correlates with raised filling pressures and reduced ejection fraction.
- Orthopnoea and paroxysmal nocturnal dyspnoea are due to redistribution of fluid to the chest on lying flat.
- B-type natriuretic peptide rises with ventricular wall stress and a normal value makes untreated heart failure unlikely.
- Echocardiography is the single most useful investigation because it gives ejection fraction, chamber size, wall motion and valve status.
- Rheumatic heart disease remains a leading cause of valvular heart failure in young Indian patients.
- Common precipitants of decompensation include infection, arrhythmia especially atrial fibrillation, anaemia, non-compliance and excess salt.
- Infective endocarditis should be suspected in any patient with a new murmur, fever and embolic phenomena.
- A displaced, sustained apex beat suggests left ventricular enlargement, a useful bedside clue before imaging.
Framework for a heart failure case
- **Side:** Left failure gives pulmonary congestion; right failure gives raised jugular venous pressure and peripheral oedema.
- **Function:** Reduced ejection fraction (40% or below) versus preserved ejection fraction (50% or above) with diastolic dysfunction.
- **Compensation:** Sympathetic and renin-angiotensin-aldosterone activation, initially helpful, later drives remodelling.
- **Key test:** Echocardiography for ejection fraction and structure; B-type natriuretic peptide to support or exclude the diagnosis.
NMC competencies in this chapter
- **IM1.4:** Staging of heart failure by symptom class and disease progression
- **IM1.5:** Left versus right and systolic versus diastolic failure
- **IM1.6:** Compensatory mechanisms in heart failure
- **IM1.7:** Factors that precipitate and exacerbate heart failure
- **IM1.9:** Common valvular heart disease
- **IM1.14:** Assessment of the jugular venous pressure
- **IM1.15:** Murmurs in heart failure and valve disease
- **IM1.17:** Investigations: ECG, chest X-ray, natriuretic peptide and echocardiography
Frequently Asked Questions
What is the difference between reduced and preserved ejection fraction heart failure?
Reduced ejection fraction failure means the ejection fraction is 40% or below with impaired contraction, while preserved ejection fraction failure keeps the ejection fraction at 50% or more but the ventricle is stiff and fills poorly.
Why does left heart failure cause right heart failure?
Chronic left heart failure raises pulmonary venous and then pulmonary arterial pressure, which increases the load on the right ventricle until it fails; this is the commonest cause of right heart failure.
How useful is B-type natriuretic peptide?
It rises with ventricular wall stress, so a normal value in an untreated breathless patient makes heart failure unlikely, and it is a helpful rule-out test at the bedside.
How does this chapter help for NEET-PG?
Staging, the distinction between systolic and diastolic failure, gallop rhythms and echocardiographic findings are repeatedly tested, so a firm grasp of the pathophysiology transfers directly to exam questions.
Continue reading
MBBSAll General Medicine chapters
Continue through the General Medicine chapter map.
Continue studying General Medicine
Explore clinician-written learning resources, structured revision and practice across the MedNext platform.
Open in the MedNext appSee plans