CVP is generally measured at the junction of the superior vena cava and the right atrium. This is most commonly this is done via a central venous catheter placed through the right internal jugular vein. A normal CVP waveform contains five components. These components include three peaks (a, c, v) and two descents (x, y). All of these components correspond to various aspects of the cardiac cycle.
The first peak is the a-wave, which immediately follows the p wave of the ECG waveform. The a-wave is a pressure increase that is due to atrial contraction at end-diastole. Shortly after the a-wave there is a second peak , the c-wave. The c-wave immediately follows the r wave of the ECG waveform. This is a pressure increase due to tricuspid bulging into the atrium as a result of isovolumic ventricular contraction (IVC). Note that the a and c-waves are split by the r wave of the ECG waveform. This is because the a-wave always represents end-diastole and the c-wave represents early ventricular systole.
Following the c-wave is the first major descent in the CVP waveform, the x-descent. The x-descent is a drop in atrial pressure during ventricular systole caused by atrial relaxation. At the trough of the x-descent there is an increase in atrial pressure as the atrium begins to fill during late systole. This is called the v-wave. The v-wave corresponds to the end of the t wave in the ECG waveform. The final aspect of the CVP waveform is the y-descent, which is due to an atrial pressure drop as blood enters the ventricle during diastole.
Central Venous Pressure Waveform Components