Pulse Pressure

What is Pulse Pressure?

Pulse pressure (PP) is the difference between systolic and diastolic arterial pressures.

PP = SBP – DBP

In healthy young adults this number may vary, but largely averages around ~40-50mmHg. It reflects both left ventricular stroke volume and the compliance of the arterial system, roughly described as PP ≈ SV ÷ C .

What physiologic pressure does it represent?

Pulse Pressure reflects the interaction between stroke volume (flow) and arterial compliance/systemic vascular resistance.

• Systolic BP rises primarily with stroke volume and ejection velocity into the aorta

• Diastolic BP is governed by systemic vascular resistance and arterial compliance/recoil, which maintain pressure during diastole. 

When arteries are compliant, systolic pressure rises less and diastolic pressure is maintained, producing a narrower pulse pressure. When stroke volume is high or arteries are stiff, systolic pressure rises disproportionately and diastolic pressure falls, resulting in a wider pulse pressure. Conversely, when stroke volume falls, systolic BP lowers as well, with organs often relying on high diastolic pressures and subsequently narrow pulse pressures to maintain perfusion. 

What does a narrow pulse pressure imply?

A narrow PP usually indicates low stroke volume and/or obstructed forward flow. Important clinical settings include:

• Hemorrhagic shock: Progressive blood loss reduces preload and stroke volume, narrowing PP, often before hypotension manifest

• Cardiac tamponade: Pericardial fluid restricts diastolic filling, leading to low SV and a classically narrow PP. May coexist with pulsus paradoxus .

• Severe left ventricular failure: In advanced systolic dysfunction, stroke volume is diminished, lowering PP.

• Severe aortic stenosis (AS): Fixed outflow obstruction prevents normal systolic rise, yielding a low, slow-rising pulse with narrow PP. 

• Other causes: tension pneumothorax, massive PE, or severe hypovolemia all can reduce effective preload or outflow.
  

What Does a Widened Pulse Pressure Imply?

A widened PP reflects either increased stroke volume or reduced arterial compliance:

• Aortic regurgitation: Large forward stroke volume and rapid diastolic runoff cause high systolic, low diastolic → very wide PP (hence, a “water hammer pulse”) .

• Chronic hypertension & arterial stiffening: Aging and arteriosclerosis stiffen the aorta, elevating systolic and widening PP 

• Thyrotoxicosis: High-output state with increased contractility and SV widens PP.

• Severe anemia: Reduced viscosity and compensatory high-output state widen PP.

• Physiologic: Endurance athletes may show exercise-induced widened PP due to augmented stroke volume

What is a “narrow” pulse pressure?

General / Low Stroke Volume

• A pulse pressure less than 25% of systolic pressure (e.g., <30 mmHg if SBP is 120 mmHg) is considered low and indicative of reduced stroke volume (e.g., heart failure, aortic stenosis) 

Sepsis / Septic Shock

• Narrow pulse pressure in sepsis is typically defined as < 40 mmHg and is associated with increased 30‑day mortality (adjusted hazard ratio ~1.61) 

• Conversely, a PP > 70 mmHg in septic patients is correlated with lower mortality and better fluid responsiveness  

• Wide or narrow pulse pressures in sepsis may help guide our next steps in management. A narrow pulse pressure may indicate the presence of low stroke volume and prompt volume responsiveness testing or assessment for septic cardiomyopathy. A wide pulse pressure may indicate vasoplegia and suggest, as in ANDROMEDA-SHOCK-2, benefit from diastolic augmentation with vasopressors. 

Trauma / Hemorrhagic Shock

• In penetrating or blunt trauma, a PP < 30 mmHg predicts need for massive transfusion or emergency operation  

• ATLS indicates that in Class IV hemorrhage (> 40% blood volume loss), PP narrows to < 25 mmHg  

The Bottom Line

PP is a dynamic marker of stroke volume warranting serial evaluation.. In sepsis, pulse pressure may initially widen, then narrow with progression or intervention. Additionally, measurement artifacts, vascular compliance, chronic conditions, and medications may skew PP. Ultimately, pulse pressure provides clinicians with another quick, bedside clinical tool that should be integrated into the broader clinical and hemodynamic picture, allowing for deeper understanding of shock patients and how we can best care for them.