Heart failure
How a heart that contracts weakly or fills poorly lowers output, why the body’s own responses add to the load, and how left- and right-sided congestion explain breathlessness and swelling.
By the end, you can
- Explain how preload, afterload and contractility set stroke volume, and why filling needs active relaxation.
- Distinguish impaired contraction (HFrEF) from impaired filling (HFpEF).
- Explain how sympathetic, renin–angiotensin–aldosterone and ADH activation first support and then worsen heart failure.
- Relate left-sided failure to lung congestion and right-sided failure to systemic venous congestion.
- Explain why natriuretic peptides rise in heart failure.
- Recognise the classic appearances, classifications and tests of heart failure, and explain how each main drug class acts on its mechanism.
What it is
Heart failure is a syndrome in which the heart cannot pump enough blood for the body’s needs, or can do so only at raised filling pressures. It results from impaired contraction (heart failure with reduced ejection fraction, HFrEF), impaired filling (heart failure with preserved ejection fraction, HFpEF), or both. Its symptoms come largely from congestion and from the body’s compensating responses.
4 types to tell apart
- HFrEF (reduced ejection fraction)
- The ventricle contracts weakly and usually dilates; the fraction of its volume ejected with each beat falls.
- HFpEF (preserved ejection fraction)
- The ventricle empties normally but is stiff and relaxes slowly, so it fills only at a high pressure.
- Left- and right-sided failure
- Describes where congestion dominates: the lungs (left) or the systemic veins (right). Right-sided failure most often follows left-sided failure.
- Chronic and acute
- Chronic failure develops over months with compensation; acute failure is a rapid onset or worsening, often with pulmonary oedema.
US spelling: litres → liters.
Normal function
Filling and emptying the ventricles
With each beat the ventricles fill in diastole and empty in systole. Cardiac output is heart rate × stroke volume, about 5 litres a minute at rest. The fraction of the filled volume ejected with each beat, the ejection fraction, is normally about 55–70%.
Stroke volume depends on how much the ventricle is filled and stretched before it contracts (preload), the pressure it must eject against (afterload), and the strength of contraction (contractility). Within limits, a more stretched ventricle contracts more strongly (the Frank–Starling relationship), which keeps the output of the and matched.
Filling is not passive. The muscle must actively relax, pumping calcium back into its stores, and a compliant wall lets the ventricle fill at low pressure. Late in diastole the contracts and tops it up.
Underlying change · Step 1 of 5
Impaired contraction (HFrEF)
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 5
Impaired filling (HFpEF)
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 5
The body’s responses add to the load
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 4 of 5
Left-sided congestion: the lungs
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 5 of 5
Right-sided congestion: the body
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .