Two positive waves are seen (see figure below). The a-wave‚ originates from right atrial contraction. It precedes the carotid pulse; i.e. it occurs in late diastole.
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It increases in amplitude as the vigor of atrial contraction increases.
Increased right ventricular end-diastolic pressure from pulmonary hypertension is the commonest cause. Occasionally, a giant a-wave, termed cannon wave, ‚ will be seen when atrial and ventricular contraction are out of phase and the atrium contracts against a closed tricuspid valve. This occurs in cardiac rhythm disorders such as complete heart block.
The v-wave' ‘ begins during ventricular systole just after the carotid pulse.
When increased, it signifies tricuspid regurgitation. In this circumstance, the right ventricle ejects some of its volume retrogradely into the atrium. The resultant v wave has a slow and undulatory form and is accentuated with deep inspiration.
The x‚ descent follows the a wave.
When prominent, it suggests pericardial constriction. The y‚ descent follows the v wave. Abnormalities include a rapid descent as seen in constrictive pericarditis and a slow decline with tricuspid stenosis.