Pulse Pressure

Pulse pressure (PP) is the difference between systolic and diastolic arterial pressures, reflecting the interplay of stroke volume and arterial compliance (PP ≈ SV ÷ C). A normal young adult at rest typically has a pulse pressure of ~40 mmHg. Narrow pulse pressure indicates diminished stroke volume and is clinically valuable in conditions such as hemorrhagic shock, cardiac tamponade, severe heart failure, and aortic stenosis. Importantly, thresholds for defining "narrow" vary: some use <40 mmHg (e.g. sepsis), others <30 mmHg in hemorrhage, or <25% of systolic pressure.

Pulse pressure trends often matter more than absolute cut-offs. Because systemic vascular resistance can maintain MAP despite reduced forward flow, pulse pressure offers additional insight into the adequacy of circulation. This separation of flow and pressure underpins the interest in narrow PP as a marker of stroke volume or 'flow'.

Conversely, widened pulse pressure reflects increased stroke volume or decreased compliance of large arteries. Common causes include aortic regurgitation (high systolic with low diastolic), aging-related vascular stiffening, arteriosclerosis, severe anemia, and hyperthyroidism. Exercise-induced wide PP in athletes represents a physiologic counterpart.

Interpretation requires attention to artifacts: damping of arterial lines can mislead, with under-damping exaggerating PP and over-damping narrowing it. Clinicians should integrate PP into a broader hemodynamic assessment, recognizing it as a dynamic marker of stroke volume and vascular properties rather than a rigid number.