Rapid Review·Cardiovascular
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Syncope
T2High yieldExercise-Induced Postural Hypotension
Focus on
The runner who feels faint only after crossing the finish line and standing still: the muscle pump stops while the vessels are still wide open, blood pools in the legs and preload collapses. Legs up, fluids, walk it off. Collapse during the race is a different, dangerous question — the heart.
Key takeaways
Mechanism
The muscle pump
during exertion the skeletal-muscle pump drives venous return while the arterioles of working muscle and skin dilate for perfusion and heat loss.Stopping abruptly while standing
removes the pump before the vasodilation resolves, so blood pools in the legs, stroke volume and cerebral perfusion fall, and the athlete feels faint or briefly collapses.Worse with
dehydration, heat and the post-exercise fall in sympathetic tone.Benign and common
the most common cause of collapse at endurance events.Clinical features and diagnosis
Timing
symptoms begin immediately after finishing strenuous exercise, typically while standing still: dizziness, blurred vision, nausea, weakness, a brief faint.Reassuring signs
oriented within a minute or two, no chest pain or focal deficit, a normal or mildly raised temperature, and prompt improvement supine with the legs elevated.Clinical diagnosis
by the timing (after, not during, exertion) and the response to leg elevation.- Check supine and standing pulse and pressure, rectal temperature, glucose and sodium when available.
Electrocardiogram
if there is any collapse during exertion, chest pain, palpitations, a murmur or a family history of sudden death.| Condition | Timing and clues | Response |
|---|---|---|
| Post-exercise postural hypotension | Immediately after stopping, while standing; rapid improvement supine; normal mentation | Legs up, fluids, gradual cool-down |
| Cardiac syncope | During exertion; abrupt loss of consciousness, chest pain or palpitations, murmur, family history | Urgent electrocardiogram, echocardiography (Hypertrophic Cardiomyopathy, Aortic Stenosis, Anomalous Aortic Origin of a Coronary Artery, Long QT Syndrome) |
| Heat exhaustion | Heavy sweating, weakness, headache, nausea; temperature under 40 C; mentation intact | Cooling, oral or intravenous fluids |
| Exertional heat stroke | Core temperature of 40 C or more with central nervous system dysfunction (confusion, ataxia, seizure) | Immediate whole-body cold-water immersion |
| Exercise-associated hyponatremia | Slow endurance athlete who over-drank water; headache, confusion, vomiting, seizure | Check sodium; hypertonic saline for symptoms; no more hypotonic fluid |
| Hypoglycemia | Prolonged exertion, poor intake, insulin-treated diabetes; sweating, tremor, confusion | Glucose |
Management
Immediate
stop, supine with legs and pelvis elevated for 10 to 20 minutes, loosen clothing, cool if warm, oral fluids and electrolytes once able to drink.- Intravenous fluid only for persistent hypotension.
Prevention
a gradual cool-down (keep walking after finishing), never stand motionless after hard exertion, drink to thirst with electrolyte fluids in long events, acclimatize to heat, avoid alcohol and vasodilators before events.A marathon runner collapses just after crossing the finish line while standing; he is oriented, his temperature is 38.2 C, and he feels better within minutes lying with his legs raised. What is the diagnosis, and which feature would instead suggest a cardiac cause?
Exercise-induced (post-exercise) postural hypotension: blood pools in the legs once the muscle pump stops. Treat with legs up, fluids and a gradual cool-down. Collapse during exertion (with chest pain, palpitations, a murmur or a family history of sudden death) points to cardiac syncope and needs an urgent electrocardiogram and echo.
How it's tested
A marathoner crosses the line, stops, and becomes lightheaded and pale; he is oriented, temperature 38.2 °C, and feels well after five minutes lying with his legs raised: post-exercise postural hypotension — venous pooling; walk-down cooling and oral fluids.
A runner collapses at mile 20 while still running: cardiac until proven otherwise — ECG, echocardiogram, no return to sport until cleared.
Collapsed athlete, confused, rectal temperature 41 °C: exertional heat stroke — cold-water immersion now.
A slow finisher who drank at every station is confused with a sodium of 122: exercise-associated hyponatremia — hypertonic saline, not more water.
Go deeper
Exercise safety resource: American College of Sports Medicine Position Stands
Related Step 2 pages: Approach to Syncope, Orthostatic Hypotension, Reflex Syncope, Anomalous Aortic Origin of a Coronary Artery, Hypertrophic Cardiomyopathy
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