Vascular resistance

Vascular resistance is a physiological concept referring to the opposition that blood encounters as it flows through vessels[1][7][10]. It is a mathematical function of vessel radius (most important), blood viscosity, and vessel length, with radius having a fourth-power effect—small changes in vessel diameter (via vasodilation or vasoconstriction) markedly affect resistance[8][10]. Clinically, terms such as systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) specify this phenomenon within systemic or pulmonary circulations[7]. Although critical for diagnosis and management of cardiovascular conditions (especially hypertension and heart failure), vascular resistance itself is not a molecular target but is modulated by drugs acting on underlying cellular proteins (such as ion channels, receptors, or enzymes on smooth muscle cells)[1][4][7].

Other names

Systemic vascular resistance (SVR)Peripheral vascular resistance (PVR)Total peripheral resistance (TPR)Pulmonary vascular resistance (also abbreviated as PVR in pulmonary context)

Vasodilation (drugs act on smooth muscle to increase vessel diameter, reducing resistance); Modulation of blood viscosity; Neurohormonal blockade (renin-angiotensin system, endothelin pathway)