Ventriculophasic sinus arrhythmia is a non-respiratory sinus arrhythmia seen in complete AV block.
The PP interval enclosing a QRS complex is shorter than a PP interval not enclosing a QRS.
The Mechanism
The proposed mechanism is the increased blood flow into the SA node artery during ventricular systole stimulating it to produce an early pacemaker activity and thus shortening the sinus cycle length.
Clinical significance : None for the patient Academic purpose for the students
Dr.S.Venkatesan MD 
Hello Dr. I have just reviewed your ECG you have diagnosed as a sinus arrhythmia in complete heart block.
Thank you for your interest in teaching and sharing your cases, however, I must disagree with your diagnosis of this ECG. It represents a simple sinus rhythm with second degree type I (Wenckebach) AV block, not complete AV block. If you note the group beating, and follow the P-R prolongation in the shortest cycles, you will see the Wenckebach. There are three junctional escape beats (the 3, 5, & 8th beats in the strip. You may not be seeing the sinus P waves hidden in QRS complexes and on T waves, but they are there. To diagnose complete AV block you need a sinus rate of 130 or less and a ventricular rate of 45 or less which certainly is not the case here. Hope this helps and if you need a great reference, see Henry Marriott, MD, FACC’s written works.
All the best. Jonni Cooper
Hi
I agree with your observation it may not be CHB at all .
But the rule that atrial rate must be higher than ventricular rate to diagnose CHB may not be always correct. We know complete AV block and siuns node dysfunction often co exists. So a slow sinus rate can very well occur in association with CHB.
Further in a patient with dynamic ischemia of RCA/LCX territory or high vagal tone .The degree of AV block can fluctuate any where between 1 degree to 3rd degree AV block.
Finally sinus arrhythmia can be associated all grades of lesser grades of AV block .
May be my diagnosis of CHB is in dispute or wrong.
But it is certain the PP interval enclosing a qrs complex is shorter whatever be the AV conduction ?
This , infact suggest (Also with some with published evidence ) ventriculo phasic arrhythmia is not an exclusive phenomenon in CHB , it can occur in lesser degrees of AV block also
Dear Dr. Venkatesen,
If you’ll please respond back to me by e-mail, I would be more than happy to provide you with evidence as to the true nature of your 12-lead ECG titled “ventriculophasic sinus arrhythmia in complete heart block”.
Thank you,
Jason Roediger
Hi
This post is attracting interesting comments.I am learning a lot from them. Please share your observations.