Rapid Review·Cardiovascular
Select any text to highlight it or add a note.
PHYSIOLOGY
T2High yieldCardiac Pressures & Autoregulation
P298 - 299
Focus on
Normal chamber pressures, wedge pressure as a stand-in for the left atrium, and organ-by-organ autoregulation.
Key takeaways
Wedge pressure
PCWP
estimates left atrial pressure and LV end-diastolic pressure, measured with a Swan-Ganz catheter; normal is 4 to 12 mm Hg. The one exception is mitral stenosis, where PCWP exceeds LVEDP.Normal resting pressures
the chamber values are listed once, on Resistance, Pressure, Flow & Cardiac/Vascular Function Curves.| Finding | Interpretation |
|---|---|
| Normal PCWP | The left heart is fine |
| High PCWP | Left heart pathology |
| High PCWP with low blood pressure | Cardiogenic shock |
| PCWP above LVEDP | Mitral stenosis, the one exception to PCWP approximating LVEDP |
| Normal PCWP with right heart failure | Cor pulmonale |
Autoregulation, organ by organ
Heart
local vasodilatory metabolites, i.e. NO, CO2, and falling O2.Brain
CO2, acting through pH.Kidneys
myogenic (stretch response of the afferent arteriole) plus tubuloglomerular feedback.Skeletal muscle
local metabolites during exercise, by "CHALK": CO2, H+, Adenosine, Lactate, K+. At rest, sympathetic tone dominates instead.Skin
sympathetic vasoconstriction is the main mechanism, and it serves temperature control rather than metabolic demand.| Organ | Determining factors |
|---|---|
| Lungs | Hypoxia causes VASOCONSTRICTION, the unique one |
| Heart | Local vasodilatory metabolites: NO, CO2, falling O2 |
| Brain | Local vasodilatory metabolite: CO2, via pH |
| Kidneys | Myogenic plus tubuloglomerular feedback |
| Skeletal muscle | Exercise: CHALK (CO2, H+, adenosine, lactate, K+). Rest: sympathetic tone |
| Skin | Sympathetic vasoconstriction, for temperature control |
A patient has a high wedge pressure and a low blood pressure. What is it?
Cardiogenic shock. The high PCWP says the left heart is the problem; a normal PCWP would have exonerated it (cor pulmonale).
How it's tested
Hypoxic pulmonary vasoconstriction is the exception that gets asked: in the lung, low oxygen constricts vessels to shunt blood toward ventilated alveoli, whereas everywhere else low oxygen dilates. Mehlman's framing of wedge pressure is worth internalising, because it turns a number into a diagnosis: high PCWP with low blood pressure is cardiogenic shock, and a normal PCWP exonerates the left heart entirely, which is what separates cor pulmonale from congestive heart failure.
Go deeper
First Aid 2026 — CV/Physiology (p.298-299) · B&B — Autoregulation by organ · Mehlman — HY Cardio (PCWP rules, cor pulmonale vs CHF)
High-yield images1
Flashcards for this page
Card 1 of 5 · try-out only, nothing is saved
(...)
You just read one page of 944
The rest of Step 1, written exactly like this.
Rapid Review is the reading layer of a full Step 1 platform: a schedule fitted to your exam date, flashcards for every page, and a mentor a message away.
Every Step 1 system
Written the same way: what to know, how it’s tested, where to go deeper.
A plan built to your exam date
Tell us when you sit, and the schedule fits the whole library and your question bank to it.
Flashcards for every page
Ready-made spaced-repetition decks linked to each topic, so nothing you read gets forgotten.
