Comparison of quantitative T-wave alternans profiles of healthy subjects and ICD patients.
BACKGROUND
Current relevance of T-wave alternans is based on its association with electrical disorder and elevated cardiac risk. Quantitative reports would improve understanding on TWA augmentation mechanisms during mental stress or prior to tachyarrhythmias. However, little information is available about quantitative TWA values in clinical populations. This study aims to create and compare TWA profiles of healthy subjects and ICD patients, evaluated on treadmill stress protocols.


METHODS
Apparently healthy subjects, not in use of any medication were recruited. All eligible ICD patients were capable of performing an attenuated stress test. TWA analysis was performed during a 15-lead treadmill test. The derived comparative profile consisted of TWA amplitude and its associated heart rate, at rest (baseline) and at peak TWA value. Chi-square or Mann-Whitney tests were used with p values < or = 0.05. Discriminatory performance was evaluated by a binary logistic regression model.


RESULTS
31 healthy subjects (8F, 23M) and 32 ICD patients (10F, 22M) were different on baseline TWA (1 +/- 2 microV; 8 +/- 9 muV; p < 0.001) and peak TWA values (26 +/- 13 microV; 37 +/- 20 microV; p = 0,009) as well as on baseline TWA heart rate (79 +/- 10 bpm; 67 +/- 15 bpm; p < 0.001) and peak TWA heart rate (118 +/- 8 bpm; 90 +/- 17 bpm; p < 0.001). The logistic model yielded sensitivity and specificity values of 88.9% and 92.9%, respectively.


CONCLUSIONS
Healthy subjects and ICD patients have distinct TWA profiles. The new TWA profile representation (in amplitude-heart rate pairs) may help comparison among different research protocols.
de Vilhena Garcia
Euler
E
University of Brasília at Gama, DF, Brazil. eulervilhena@yahoo.com.br
Samesima
Nelson
N
Filho
Horácio G Pereira
HG
Quadros
Cristina M
CM
da Silva
Luis Tenório Cavalcante
LT
Filho
Martino Martinelli
MM
Hannouche
Maria Luciana Zacharias
ML
Mathias
Wilson
W
Pastore
Carlos Alberto
CA
D000293:Adolescent; D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000628:therapy; D017147:Defibrillators, Implantable; D004562:Electrocardiography / Q000379:methods* / Q000706:statistics & numerical data*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D055815:Young Adult