- a wave and v wave roughly correspond to P wave and QRS complex in electrocardiogram respectively.
- a wave falls on S1 and v falls on S2. Hence, in sinus rhythm a wave is preceded by v wave.
- 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.
- 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.
- 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.
- 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.
- Irregular cannon a waves may also be seen during ventricular ectopics or ventricular tachycardia.
- Junctional rhythm produces regular cannon a waves.
- 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.
Case History: A 46-year old female presents with history of palpitations. At the time of palpitations, she also had rapid neck pulsations. She presented to emergency and an ECG was done. What are the findings? What is the diagnosis? Click here to reveal the answer The ECG shows a regular narrow complex tachycardia (ventricular rate of approximately 250/min). The P waves are not clearly visible, but there is a small deflection at the end of QRS in various leads. In lead I, this is pseudo r' and in leads this is pseudo s wave. The patient was found to have AVNRT on EPS and slow pathway was ablated successfully.
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