Hypertension, Systemic

DEFINITION
Sustained elevation in systolic or diastolic (or both) arterial blood pressure

PATHOPHYSIOLOGY
Blood pressure is determined by cardiac output and systemic vascular resistance; cardiac output determined by heart rate and stroke volume; systemic arterial blood pressure regulation depends on integration of complex mechanisms within the central and peripheral nervous systems, renal and cardiac tissues, and humoral factors, which synergistically affect cardiac output and peripheral vascular resistance.
Baroreceptors in the carotid sinus and aortic arch respond to changes in blood pressure; a fall in blood pressure increases sympathetic discharge, causing vasoconstriction and increased cardiac contractility and heart rate to return blood pressure to normal, humoral substances that modulate blood pressure include catecholamines, vasopressin, kinins, renin, angiotensin, aldosterone, prostaglandins, and atrial natriuretic peptide; the renin-angiotensin-aldosterone system is probably the most important component.
Hypertension—primary (e.g., essential or idiopathic) or secondary to an underlying disease process; secondary hypertension is more common in veterinary medicine; cause of primary hypertension is not fully understood but some have a hereditary component.