title: The ventriculophasic response: relationship to sinus arrhythmia and the duration of interposed QRS complexes.
abstract: BACKGROUND
  The ventriculophasic response (VR) refers to shortening of sinus cycle length during heart block when a QRS complex is interposed between 2 P waves. Our purpose was to analyze its relationship to respiratory sinus arrhythmia (SA) and to compare VR in relation to paced versus intrinsic QRS complexes.
  
  
  METHODS
  Patients with advanced heart block had their pacer devices temporarily programmed to ventricular inhibited mode at 30 ppm. In 35 subjects, we analyzed VR and SA before, during and after 3 cycles of deep breathing. In 16 other patients we compared VR in the presence of paced versus narrower intrinsic QRS complexes.
  
  
  RESULTS
  The magnitude of P-P interval shortening surrounding QRS complexes during inspiration correlated with SA (r = 0.36, P = 0.03). The prevalence of VR increased from 37% at baseline to 77% of subjects during deep breathing (P = 0.02). The mean P-P interval shortening was greater surrounding intrinsic QRS complexes than paced QRS complexes (3.6 ± 3.6% vs. 1.4 ± 1.1%, P = 0.02). The prevalence of VR increased from 25% during paced rhythm to 56% when intrinsic complexes were present.
  
  
  CONCLUSIONS
  VR, like SA, increases with deep breathing and likely reflects intact parasympathetic nervous system function. Its increase in the presence of narrower beats suggests it may reflect ventricular synchrony.
authors.affiliation: Bridgeport Hospital/Yale University, Clinical Yale University School of Medicine.
authors.forename: Razvan T
authors.initials: RT
authors.lastname: Dadu
authors.forename: Craig A
authors.initials: CA
authors.lastname: McPherson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001146:Arrhythmia, Sinus / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D015331:Cohort Studies; D015897:Comorbidity; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D005260:Female; D006327:Heart Block / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D006801:Humans; D008297:Male; D010275:Parasympathetic Nervous System / Q000503:physiopathology; D011379:Prognosis; D011446:Prospective Studies; D011930:Reaction Time; D018570:Risk Assessment; D012720:Severity of Illness Index; D016019:Survival Analysis; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology
keywords: autonomic nervous system; heart block; sinus arrhythmia; ventricular synchrony; ventriculophasic response