abstract
presented
at the 1998 International Congress on Holter and Noninvasive Electrocardiography
Ulm, Germany
May 22-23, 1998
Onset Heart Rate of T Wave Alternans in Different Risk Groups for Ventricular Tachycardia.
Annals of Noninvasive Electrocardiography May. 1998; Volume 3, Number3, Part 2: July 98
P. Kluge, A.Posselt, A. Neugebauer, T. Walter, D. Pfeiffer.
Department of Cardiology, University Leipzig, Germany
The occurrence of T Wave Alternans (TWA) is related to electrical vulnerability of miocardium. Due to rate dependence of TWA , Heart Rate needs to be accelerated during investigation. By analyzing TWA in different risk groups ( post MI patients with documented ventricular arrhythmias - VTA, and without documented arrhythmias - CAD, and with idiopathic ventricular tachicardia - iVT) a relatively high number of patients were noted to be positive.
In order to find parameters that are different between the three groups, 96 patients (15 VTA, 66 CAD, 16 iVT) were examined regarding their TWA values. TWA was analyzed during bicycle stress test using spectral method. Maximum alternans voltage ( Valt, ratio, maximum heart rate during exercise) and threshold heart rate ( i.e. the onset heart rate of sustained alternans) were compared.
Results:
|
VTA |
CAD |
iVT |
|
|
Valt |
3.3± 1.2 |
3.4± 2 |
6.1± 2 # + |
|
ratio |
10± 6 |
7± 3 |
17± 9 # + |
|
Max heart rate |
116± 9 bpm |
119± 17 |
134± 18 # + |
|
Theshold heart rate |
94 ± 18 bpm * |
118± 14 bpm |
123± 20 # |
Comments: *:<0.05 VTA versus CAD; # p<0.05 iVT versus VTA; values of CAD
Conclusions
: Rate dependence of TWA is reflected in higher values of Valt and ratio in iVT patients. Patients at low ( or none) risk and high risk for life threatening VTA differ clearly in their heart rate threshold for sustained TWA. Therefore, heart rate threshold is fundamental addition factor of TWA analysis for differentiation of groups with high and low risk regarding electrical instability.
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