The physiology that makes the rest of the topic make sense: how blood moves forward, and what pressure builds behind the ventricle.
Each ventricle must fill with an adequate volume and then eject it against vascular resistance. Cardiac output = HR × stroke volume, and stroke volume is shaped by preload, contractility, and afterload. Ejection fraction is the proportion of blood ejected from the LV per beat — it does not directly measure total cardiac output.
Ask just two questions
Heart failure gets easier once you stop memorising isolated symptoms and ask: can the ventricle move blood forward? And what pressure is building behind it? Almost everything later branches from these two questions.
| Concept | What it means | Why the nurse cares |
|---|---|---|
| Cardiac output | Blood pumped per minute: HR × stroke volume | Low CO shows as fatigue, cool skin, confusion, low urine, or hypotension |
| Preload | Filling/stretch before contraction; tied to volume and filling pressure | Excess filling pressure drives pulmonary or systemic congestion |
| Afterload | Resistance the ventricle must overcome to eject | High afterload raises cardiac work and can reduce forward flow |
| Contractility | The myocardium's intrinsic ability to contract | Reduced contractility is central to many systolic problems |
| Ejection fraction | Percentage of LV end-diastolic volume ejected per beat | A useful phenotype marker — but preserved EF does not exclude HF |
Common misconception
“Normal EF means no heart failure.” False. HFpEF is real heart failure with preserved EF; the problem is often impaired relaxation, a stiff ventricle, or abnormal filling pressures.
Check answer
What is cardiac output?
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