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Heart Rate Variability
18
Heart rate variability and its relation to ventricular
tachycardia in patients with coronary artery disease.
PETER MAIER, MARCELL TOEPFER, MARTIN
DAMBACHEW, KARL THEISEN, HELMUT ROSKAMM"
and AXEL W. FREY'.
Medizinische Klinik, Klinikum Innenstadt, Ludwig
Maximilans-Universitgt, Miinchen and 'Herz-Zentrum, Bad
Krozingen, Germany.
OBJECTIVES Disorders of the autonomic nervous
function have been shown to contribute to the genesis of
ventricular arrhythmias. Particularly low heart rate
variability (HRV) and the loss of protective vagal reflexes
are associated with an increased incidence of arrhythmic
deaths following myocardial infarction (Valkama 1993).
Power spectral analysis and time domain analysis of heart
rate variability have the potential to quantify the cardiac
autonomic tone during ambulatory electrocardiographic
recording. It is not known whether transient changes of
autonomic balance can be measured immediately before
the onset of episodes of spontaneous ventricular
tachycardia using HRV analysis. The aim of this study was
to deternine the relation between autonomic control of
heart rate and the spontaneous occurrence of ventricular
arrhythmias in patients with coronary artery disease and
post-myocardialinfarction.
METHODS: We analysed from 24-h ambulatory
electrocardiographic recordings time domain and power
spectral components of HRV in 28 patients (64.8
11.4
years, 20 male, 8 female) with coronary artery disease,
assessed by coronary angiography, and post-myocardial
infarction. 19 patients have had anterior wall infarction, 9
posterior wall infarction. 35 episodes of ventricular
tachycardia (VT) were documented. Eight patients had
episodes of sustained VT (>30 sec.). We excluded patients
with more than 15% ventricular or supraventricular
extrasystoles during the recorded periods, with diabetes
mellitus or blood pressure more than 160/95 mmHg. For
time domain measurements standard deviation of sinus
rhythm RR intervals (SD), standard deviation of 5-minute
normal sinus RR intervals (SDANN) and the percentage of
differences greater than 50 ms for successive sinus rhythm
R-R intervals (pNN50) were used. In the frequency domain
total power (TP), low frequency power (0.04-0.15 Hz, LF)
and high frequency power (0.15-0.40 Hz, HF) was
calculated. The spectral areas and time domain
components were measured in 5 min and 15 min periods
preceding the onset of ventricular tachycardias. This
parameters were also computed for the entire 24-h
recordings, for daytime, nighttime, for 5- and 10-min
periods directly after VT and for one hour with less than 30
ventricular extrasystoles (VES) during daytime.
*
RESULTS A significant increase in mean heart rate (HR)
was noted before the onset of ventricular tachycardia
compared to HR during night (72+/-15 to 82+/-21 bpm,
pc0,05) and HR during an hour with less than 30 VES
during daytime (73+/-11 to 82+/-21 bpm, p<0,05). HR
before VT was also increased compared to mean HR of
24-hour recording, but without significance. SD and
SDANN measured over a 15- and 5-min period before VT
was significantly decreased compared with 24-hour
67
analysis (81,8+/-35 to 132+/-63 ms, p<0,05). SD and
SDANN of a 5-min period before VT was decreased
significantly compared with the one-hour period with less
than 30 VES (80+/-44 to 43+/-35 ms, p<O,Ol). The total
power and LF power of HRV was increased before the
onset of VT episodes, but without significance. The high
frequency power was not significantly decreased. But the
LF/HF-ratio was significantly higher during the 15-min and
5min interval immediately before the onset of VT
compared with the one-hour period with <30 VES (2,46+12,2 to 2,10+/- 1,4, p<0,05). Calculatingwith a 3-min interval
before VT did not change this results. Heart rate variability
data did not differ between sustained and nonsustained
episodes.
CONCLUSIONS: It is still disputed whether there is a
change in autonomic balance and heart rate Variability
immediately before the onset of episodes of idiopathic
ventricular tachycardia in post-infarction patients. In this
study an increased LF/HF ratio before the onset of
ventricular tachycardia was observed as well as a
decreased HRV in the time domain and a trend towards an
increased average heart rate. This is suggesting alterations
in autonomic tone at the onset of ventricular tachycardia
and may reflect susceptibility to the spontaneous
occurrence of lifethreatening arrhythmias in patients with
coronary artery disease.
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