Changes in jugular venous pulse in cardiac arrhythmia

1.  a wave and v wave roughly correspond to P wave and QRS complex in electrocardiogram respectively. 
2. a wave falls on S1 and v falls on S2. Hence, in sinus rhythm a wave is preceded by v wave. 
3. In 1st degree heart block, a wave (P) will occur much before S1 (onset of ventricular systole) and denotes a prolonged PR interval. And, with further prolongation, a wave may merge with previous v wave. 
4.  In 2nd degree type 1 AV block, there will gradual prolongation of a-v interval in JVP ending with a wave which is not followed by v wave. 
5. In 2:1 AV block, there will be two a waves for each v wave. Alternate a wave will coincide with ventricular systole resulting in regular cannon a waves. 
6. In complete heart block, a-v interval is variable with a more than v waves along with irregular cannon a waves. Irregular cannon a waves will be seen whenever a wave coincides with ventricular systole because of AV dissociation in CHB. 
7. Irregular cannon a waves may also be seen during ventricular ectopics or ventricular tachycardia. 
8. Junctional rhythm produces regular cannon a waves. 
9. In atrial fibrillation, a waves are absent and there is diminished x descent. Reduced atrial compliance results in a steeper v wave and a prominent y descent.