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Multicenter Study
. 2018 Apr 19;7(9):e008528.
doi: 10.1161/JAHA.118.008528.

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

Michael E Field  1 , Paolo Donateo  2 , Nicola Bottoni  3 , Matteo Iori  3 , Michele Brignole  1   2 , Ryan T Kipp  1 , Douglas E Kopp  1 , Miguel A Leal  1 , Lee L Eckhardt  1 , Jennifer M Wright  1 , Kathleen E Walsh  1 , Richard L Page  1 , Mohamed H Hamdan  4
Affiliations
Multicenter Study

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

Michael E Field et al. J Am Heart Assoc. .

Abstract

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.

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Figures

Figure 1
Figure 1
PR intervals during lower and higher heart rate (HR) in patients with inappropriate sinus tachycardia (IST Group, left), healthy controls at baseline and following isoproterenol infusion (Isuprel Group, middle), and sinus rhythm and atrial tachycardia (AT Group, right). The PR interval significantly shortened with the increases in HR in the IST Group, with a similar decrease noted in the Isuprel Group. In contrast, patients in the AT Group experienced PR lengthening during AT when compared with baseline normal sinus rhythm (*P<0.05, lower HR vs higher HR within each group). The larger dots indicate sample means. Bars represent 1 SD.
Figure 2
Figure 2
Sample tracings showing changes in P‐wave amplitude and PR interval in (1) a patient with inappropriate sinus tachycardia (top tracings), (2) a healthy control patient before and after isoproterenol infusion (middle tracings), and (3) a patient during sinus rhythm and high cristae atrial tachycardia (lower tracings). Note the increase in P‐wave amplitude in lead II and PR shortening at faster rates when compared with slower rates in the patient with inappropriate sinus tachycardia (IST) and healthy control following isoproterenol infusion. In the patient with atrial tachycardia (AT), the PR interval increased at faster rates when compared with slower rates.
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