Both entities refer to contraction of vascular smooth muscle.Vascular smooth muscle tone is under the control of autonomic neuro and humoral system.
Local mechanical , stretch receptors also play a role .( local temperature -Cold vasoconstriction , warmth relieves it ) Abnormal elevated vascular tone occur in pathological situations ( Vascular interventions, surgery , drugs, extreme cold , )
Both terms are closely related often used interchangeably .There are some subtle differences though , mainly in the usage pattern.
Vasospasm
Is generally a regional phenomenon implying central mechanisms are less operative.
A local trigger mechanical or biochemical .( Even a mechanical drag can cause a spasm
It is often transient .
Occurs primarily in small , medium blood vessels .(I wonder whether Aorta can go for spasm !)
Clinical examples
- Catheter induced vasomotor in cath lab (Radial spasm)
- Spasm associated with plaque Prinzmetal angina
- Cerebral vessel spasm after sub arachnoid hemorrhage ( Need not be transient )
Vasoconstriction
This is also result in constriction of blood vessels
But the blood vessels involved are in micro circulation like capillaries and arterioles .
Often sustained (If transient does it become vasospasm ?)
Vasoconstriction often involves wide areas and may result in elevated regional or systemic vascular resistance . Hence it often result in elevated blood pressure.
Clinical example
- Normal Blod pressure regulation y autonomic mediated vasoconstriction
- Arteriolar constriction with Nor adrenaline , dopamine .
- Capillary Vasoconstriction due to cold (Raynaud phenomenon )
* Please note other terms like vascular tone , vasomotion closely competes with above .
Final message
Most of the confusion in medical terminologies are man-made.Both vasospasm and vasoconstriction are often used interchangeably .It is ideal to use the former for a transient , localised response in large caliber vessel , and the latter when it occurs as a general response to altered autonomic tone and involve the micro vasculature.
Dr.S.Venkatesan MD 