Integrated Cardiovascular Cases
Flashcards applying preload, afterload, contractility and reflexes to haemorrhage, exercise and heart failure.
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Questions Covered in This Set
12 cards to master
What four questions form the cardiovascular reasoning framework?
What happened to (1) preload, (2) afterload/TPR, (3) contractility (ESPVR slope), (4) heart rate? Then: what do reflexes do, and at what cost?
Primary haemodynamic insult in acute haemorrhage
Loss of stressed volume → MSFP falls (e.g. 7→4 mmHg) → venous return curve shifts down/left → ↓preload, ↓EDV, ↓SV (Frank–Starling), ↓CO and ↓MAP.
How does the PV loop look in acute haemorrhage?
Narrow loop shifted leftward: lower EDV, smaller width (reduced SV) and lower peak systolic pressure.
Second-to-second baroreflex response to haemorrhage
↓Carotid/aortic stretch → ↓afferent firing to NTS → sympathetic surge, vagal withdrawal: tachycardia, steeper ESPVR (↓ESV), arteriolar constriction (↑TPR), and venoconstriction restoring MSFP.
Why can a young trauma patient have normal BP after losing 30% of blood volume?
Powerful sympathetic compensation defends MAP; clues are cold clammy periphery, narrow pulse pressure and HR ~120 — pulse pressure and skin perfusion fail before MAP does.
What is transcapillary autotransfusion?
Precapillary constriction lowers capillary hydrostatic pressure → Starling forces favour absorption → up to ~500 mL/hour of interstitial fluid enters capillaries, diluting haemoglobin so early haematocrit looks deceptively normal.
Hormonal (minutes–days) response to haemorrhage
Renal hypoperfusion + β1 stimulation of JG apparatus → renin → angiotensin II (vasoconstriction, thirst, aldosterone) → Na⁺/water retention; ADH released from baroreceptor unloading then osmotic drive.
Why does TPR fall during dynamic exercise?
Skeletal muscle metabolic vasodilation (adenosine, K⁺, CO₂, H⁺, low PO₂) collapses local resistance, outweighing sympathetic constriction of gut and kidney beds.
What raises venous return during exercise?
Muscle pump, respiratory pump and venoconstriction — the venous return curve shifts upward and steepens.
Blood pressure pattern in dynamic exercise
Systolic rises to 180–200 mmHg (large SV into stiff aorta), diastolic flat or slightly falls (low TPR), so MAP rises modestly while pulse pressure widens dramatically.
How does CO change during exercise, and what contributes most?
CO rises from ~5 to 20–25 L/min; heart rate does most of the work, SV rises only ~30–50% and plateaus by ~40–50% VO₂max in untrained people.
What is baroreflex resetting in exercise?
Central command and the muscle metaboreflex shift the baroreflex operating point higher, so HR and contractility rise instead of being reflexly suppressed by rising pressure.
