JVP waveform interpretation (cannon waves, a/v waves, x/y descents)
Core concept
- The JVP is a manometer for the right atrium - internal jugular, no valves, direct column to the RA
- Three positive waves, two negative descents
| Wave | Event | Lost when |
|---|---|---|
| a | Atrial contraction (pre-systolic) | Absent in AF |
| c | Tricuspid bulging into RA during isovolumic contraction | |
| x descent | Atrial relaxation + downward pull of the tricuspid annulus in systole | |
| v | Passive RA filling against a closed tricuspid valve | |
| y descent | Tricuspid opens - rapid ventricular filling |
- Venous vs arterial pulsation - the discriminators
- Biphasic/undulating, not palpable, varies with respiration and position
- Obliterated by light compression at the root of the neck - the column fills passively from above and collapses promptly on release; an arterial pulse persists
- Rises with hepatojugular reflux
- Normal <3 cm above the sternal angle (~8 cmH2O / ~4 mmHg RA pressure) at 45 degrees
3 more sections, plus exam facts
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