Ventriculophasic sinus arrhythmia
Abstract: Ventriculophasic sinus arrhythmia, also known as ventriculophasic response, is the shortening of a PP interval which encloses a QRS complex.
Ventriculophasic sinus arrhythmia is a form of non respiratory sinus arrhythmia seen during complete heart block in which the sinus cycle length is reduced when a QRS complex occurs between two P waves. It is also known as ventriculophasic response. One of the earliest available clinical reports of the phenomenon was by Wilson FN and colleagues in 1918.1
Prevalence of ventriculophasic response
In a study by Dadu RT and colleagues, thirty seven percent ventriculophasic response seen at baseline increased to seventy seven percent with deep inspiration.2 They also documented that PP interval shortening after a spontaneous QRS was more than that after a paced QRS. While the prevalence of ventriculophasic response was twenty five percent in the paced rhythm, it was fifty six percent with intrinsic complexes. The authors suggested the influence autonomic activity on the ventriculophasic response in view of the variation with deep inspiration. Better ventricular synchrony with spontaneous beats may be causative for the higher response with spontaneous beats compared to paced beats.
Mechanism of ventriculophasic sinus arrhythmia
Proposed mechanisms to explain ventriculophasic sinus arrhythmia are:
- Phasic changes in baroreceptor mediated vagal input to the sinus node
- Mechanical effect of ventricular systole on the sinus node
- Effect of pressure changes caused by ventricular systole
- Increased blood flow to the sinus node during ventricular systole
It has been shown that ventriculophasic sinus arrhythmia is absent recipient atria after orthotopic cardiac transplant.3 This is inspite of the intact autonomic innervation of the recipient atria, possibly due to the absence of pulsatile blood flow to the sinus node.
Definition of ventriculophasic response
The ventriculophasic response is likely to be more if the QRS complex occurs in the early part of the PP interval. Ventriculophasic response has been defined as more than three percent shortening of PP interval if the QRS complex occurs within the first sixty percent of the anticipated PP interval.4 It has been documented to be more common in females than males (eighty one percent vs thirty seven percent). It is also more likely when the ejection fraction is forty percent or more.
- Wilson FN, Robinson AC. Two cases of complete heart block showing unusual features Arch Int Med. 1918; 21:166.
- Dadu RT, McPherson CA. The ventriculophasic response: relationship to sinus arrhythmia and the duration of interposed QRS complexes. Ann Noninvasive Electrocardiol. 2013 Jul;18(4):336-43.
- de Marchena E, Colvin-Adams M, Esnard J, Ridha M, Castellanos A, Myerburg RJ. Ventriculophasic sinus arrhythmia in the orthotopic transplanted heart: mechanism of disease revisited. Int J Cardiol. 2003 Sep;91(1):71-4.
- Dadu RT, McPherson CA. The ventriculophasic response revisited: analysis of clinical correlations using a new proposed definition derived in pacemaker patients. Clin Cardiol. 2012 Jan;35(1):21-5.