Key result
ICD patients demonstrated significantly higher peak T-wave alternans amplitudes compared to healthy subjects during treadmill stress testing (37±20 µV vs 26±13 µV; p=0.009).
Why the study?
Do healthy subjects and ICD patients have distinct quantitative T-wave alternans profiles during treadmill stress testing?
Cross-Sectional (n=63)
Do healthy subjects and ICD patients have distinct quantitative T-wave alternans profiles during treadmill stress testing?
Absolute Event Rate: 37% vs 26%
p-value: p=0.009
Quantitative T-wave alternans profiles, represented as amplitude-heart rate pairs, can effectively discriminate between healthy subjects and ICD patients.
TWA amplitude differences may aid discrimination in ICD evaluation; leaves open prospective validation for risk stratification.
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.
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Samesima et al. (2009) conducted a cross-sectional in ICD patients and healthy subjects (n=63). ICD patient status vs. Healthy subjects was evaluated on Peak T-wave alternans (TWA) amplitude (p=0.009). ICD patients demonstrated significantly higher peak T-wave alternans amplitudes compared to healthy subjects during treadmill stress testing (37±20 µV vs 26±13 µV; p=0.009).
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