abstract
presented
at the 1996 ACC
Orlando, Florida
March 24-27, 1996
Exercise Induced T-Wave Alternans as a Marker
of High-risk Patients with Hypertrophic Cardiomyopathy
J Am Coll Cardio Feb. 1996; Special Issue: 715-4
Yukihiko Momiyama, Juha Hartikainen, Hirokazu
Nagayoshi, *Paul Albrecht, Josef Kautzner, William J McKenna,
A John Camm, *Cambridge Heart, Inc., Bedford, MA and St. George's
Hospital Medical School, London, UK
Previous studies have shown that the presence of
subtle T-wave alternans (TWA) (alternating T-wave morphology from
beat-to-beat) measured during atrial pacing and during exercise
is predictive of spontaneous and inducible VT/VF in patients (pts)
with ischemic heart disease. We tested the hypothesis that TWA
measured during exercise could identify high-risk pts with hypertrophic
cardiomyopathy (HCM). Of 14 pts with HCM, 7 pts were classified
as high-risk for ventricular arrhythmic events (1 with sustained
VT, 3 with increased fractionation of paced ventricular electrograms
as seen in VF pts, and 3 with nonsustained VT and/or a family
history of sudden death), and 7 patients without risk factors
were classifies as low-risk. All had no medication. There was
no significant differences in age, sex and the degree of LV hypertrophy
between the high-risk and the low-risk pts. All pts were prospectively
evaluated for TWA using the CH 2000 system and 7 multi-segment
electrodes positioned in a Frank orthogonal (XYZ) configuration.
In order to increase the heart rate (HR) up to 110/min, bicycle
ergometer exercise was used. The alternans analysis was performed
blind to clinical data. TWA was considered to be present if the
alternans magnitude exceeded the previously published threshold
of >1.9UV in X, Y, Z, V4 leads or the vector magnitude and
was consistently present with HR in excess of a pt-specific HR
threshold. In 5 of 7 high risk pts (71%), TWA was found at HR
of 95-110/min, whereas none of the 7 low-risk pts (0%) had TWA
(p<0.025). Especially, all 4 pts with sustained VT or abnormal
paced ventricular electrograms showed TWA. Conclusions:
Pts with HCM who are at high risk for arrhythmic events often
show TWA. Subtle TWA during exercise may be an excellent marker
for arrhythmic risks in HCM pts.
1 Oak Park Drive
Bedford, MA 01730
617-271-1200