Overview
This lecture explains pulse pressure, its calculation, and the clinical significance of wide and narrow pulse pressures, including causes and underlying mechanisms.
Pulse Pressure Basics
- Pulse pressure is the difference between systolic blood pressure (SBP) and diastolic blood pressure (DBP).
- Systolic BP is the pressure in arteries when ventricles contract.
- Diastolic BP is the pressure in arteries when ventricles relax.
- Normal blood pressure is about 120/80 mmHg, giving a normal pulse pressure of 30-40 mmHg.
Causes of Wide Pulse Pressure
- Wide pulse pressure occurs when the gap between systolic and diastolic pressures increases.
- Aging and atherosclerosis cause arterial stiffness, raising systolic pressure.
- Increased stroke volume from heart-stimulating drugs or hyperthyroidism also widens pulse pressure.
- Aortic regurgitation allows blood to flow back into the left ventricle, increasing preload and systolic pressure.
- Anaphylaxis and sepsis cause vasodilation, lowering diastolic pressure and raising pulse pressure.
Causes of Narrow Pulse Pressure
- Narrow pulse pressure means systolic and diastolic pressures are closer together.
- Young, elastic arteries stretch well during systole, causing a smaller pressure difference.
- Decreased stroke volume (e.g., hypovolemia from bleeding or dehydration) lowers systolic pressure.
- Hypothyroidism and heart failure reduce heart contractility, decreasing systolic BP.
- Aortic stenosis restricts blood flow out of the ventricle, lowering systolic BP.
- Cardiogenic shock and cardiac tamponade reduce cardiac output, lowering systolic BP toward diastolic.
Key Terms & Definitions
- Systolic Blood Pressure (SBP) — pressure in arteries during ventricular contraction.
- Diastolic Blood Pressure (DBP) — pressure in arteries during ventricular relaxation.
- Pulse Pressure — the difference between systolic and diastolic blood pressure.
- Atherosclerosis — stiffening and plaque buildup in arteries.
- Aortic Regurgitation — backflow of blood from the aorta to left ventricle.
- Aortic Stenosis — narrowing of the aortic valve, restricting blood flow.
- Cardiac Tamponade — fluid buildup around the heart, restricting function.
Action Items / Next Steps
- Review the causes and mechanisms for both wide and narrow pulse pressure.
- Memorize normal ranges and clinical examples for exam preparation.