P-Wave Amplitude and PR Changes in Patients With Inappropriate Sinus Tachycardia: Findings Supportive of a Central Mechanism

J Am Heart Assoc. 2018 Apr 19;7(9):e008528. doi: 10.1161/JAHA.118.008528.


Background: The mechanism of inappropriate sinus tachycardia (IST) remains incompletely understood.

Methods and results: We prospectively compared 3 patient groups: 11 patients with IST (IST Group), 9 control patients administered isoproterenol (Isuprel Group), and 15 patients with cristae terminalis atrial tachycardia (AT Group). P-wave amplitude in lead II and PR interval were measured at a lower and higher heart rate (HR1 and HR2, respectively). P-wave amplitude increased significantly with the increase in HR in the IST Group (0.16±0.07 mV at HR1=97±12 beats per minute versus 0.21±0.08 mV at HR2=135±21 beats per minute, P=0.001). The average increase in P-wave amplitude in the IST Group was similar to the Isuprel Group (P=0.26). PR interval significantly shortened with the increases in HR in the IST Group (146±15 ms at HR1 versus 128±16 ms at HR2, P<0.001). A similar decrease in the PR interval was noted in the Isuprel Group (P=0.6). In contrast, patients in the atrial tachycardia Group experienced PR lengthening during atrial tachycardia when compared with baseline normal sinus rhythm (153±25 ms at HR1=78±17 beats per minute versus 179±29 ms at HR2=140±28 beats per minute, P<0.01).

Conclusions: We have shown that HR increases in patients with IST were associated with an increase in P-wave amplitude in lead II and PR shortening similar to what is seen in healthy controls following isoproterenol infusion. The increase in P-wave amplitude and absence of PR lengthening in IST support an extrinsic mechanism consistent with a state of sympatho-excitation with cephalic shift in sinus node activation and enhanced atrioventricular nodal conduction.

Keywords: atrial tachycardia; atrio‐ventricular conduction; inappropriate sinus tachycardia.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials*
  • Adult
  • Aged
  • Atrioventricular Node / physiopathology*
  • Case-Control Studies
  • Electrocardiography
  • Electrophysiologic Techniques, Cardiac
  • Female
  • Heart Rate*
  • Humans
  • Italy
  • Male
  • Middle Aged
  • Prospective Studies
  • Sinoatrial Node / physiopathology*
  • Tachycardia, Sinus / diagnosis
  • Tachycardia, Sinus / physiopathology*
  • Time Factors
  • Wisconsin
  • Young Adult