| Abstract: | Background
Heart rate turbulence (HRT) is a new and auspicious
parameter for risk stratification in patients suffering from structural heart
disease. The HRT parameters onset (TO) and slope (TS) are derived from
Holter ECGs. Only a few studies have evaluated physiologic properties like
age or prematurity of the ventricular beat on HRT. Until now, to our knowledge,
little is known about the influence of the point of origin of the premature
beat on HRT. Therefore, we conducted a study consisting of 25 patients
(pts) with premature beats generating from 2 different sites in the atrium and
ventricle.
Methods
During an electrophysiologic study, premature extra
beats were induced. The high right atrium (HRA) and the lateral part of the
coronary sinus (CS) represented the atrial pacing sites, while the right ventricular
apex (RVAP) and right ventricular outflow tract (RVOT) represented
the ventricular pacing sites. Prematurity started at 450 ms and was decreased
to the refractoriness of each site. TO and TS were computed and correlated to
the site of origin and the coupling interval (CI).
Results
Atrial TO was positive
in 9 pts (HRA) and 7 (CS) as well as ventricular TO in 2 pts, respectively.
TO induced in CS correlated with the CI (r = –0.50, p < 0.05). TS was negative,
independent of the site of origin. Atrial TS showed no correlation with
the CI. TO generated from both ventricular sites was positive in 2 pts. TO from
RVAP correlated with the CI (r = –0.81, p < 0.005), but not with RVOT. TS
from both ventricular sites exhibited no correlation with the pacing site, but
correlated with themselves (r = –0.69, p < 0.03).
Conclusion
The site of origin
of the premature beat exhibits no influence on heart rate turbulence slope.
The prematurity of the extra beat correlates with turbulence onset, but not
with slope. Finally, the site of origin revealed no influence on HRT slope.
Therefore, the calculation of heart rate turbulence derived from extra beats
extracted from Holter ECG is reliable. |
