Jugular veins in dogs and cats

System venous and right heart filling pressures are reflected at the jugular veins in dogs and cats. These veins should not be distended when the animal is standing with its head in a normal position (jaw parallel to the floor). Persistent jugular vein distention occurs in association with right-sided congestive heart failure (because of high right heart filling pressure), external compression of the cranial vena cava, or jugular vein or cranial vena cava thrombosis.

Also abnormal are jugular pulsations extending higher than one third of the way up the neck from the thoracic inlet. Sometimes the carotid pulse wave is transmitted through adjacent soft tissues, mimicking a jugular pulse from carotid transmission, the jugular vein is occluded lightly below the area of the visible pulse. If the pulse disappears, it is a true jugular pulsation; if the pulse continues, it is being transmitted from the carotid artery.

Jugular pulse waves are related to atrial contraction and filling. Visible pulsations occur in dogs and cats with tricuspid insufficiency (after the first heart sound, during ventricular contraction), conditions causing a stiff and hypertrophied right ventricle (just before the first heart sound, during atrial contraction), or arrhythmias that cause the atria to contract against closed atriaventricular (AV) valves (so-called cannon A waves).

Impaired right ventricular filling, reduced pulmonary blood flow, or tricuspid regurgitation can cause a positive hepatojugular reflux even in the absence of jugular distention or pulsations at rest. To test for this reflux, firm pressure is applied to the cranial abdomen while the animal stands quietly. This transiently increases venous return. Jugular distention that persists while abdominal pressure is applied constitutes a positive (abnormal) test; normal dogs and cats have little to no change in the jugular vein.