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Microvolt T-wave alternans is related to ventricular
tachycardia in adults with repaired tetralogy of fallot |
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Purpose: Microvolt T-wave alternans (MTWA) is a novel non-invasive method to
identify patients at increased risk of cardiac arrest and sudden cardiac
death from ventricular arrhythmias in ischemic heart disease and cardiomyopathies.
Ventricular arrhythmia and sudden death are leading causes of morbidity and
mortality late after repair of tetralogy of Fallot. We hypothesised that MTWA
may related to the ventricular tachycardia (VT). Method: Fifty-five patients with repaired ToF and freepulmonary regurgitation
and 11 patients with ToF and documented VT were included study. Microvolt TWA
was measured during submaximal treadmill exercise in all patients. Eight
patients were excluded from the study because of poor electrocardiogram
recordings with noise or frequent ectopic beats (n=4) and indeterminate
result (n=4). As a result 58 patients (36 male, mean age, 35.3±12.2)including
9 patients with history of VT were evaluated for further analysis. Results: MTWA was positive in 18 patients (31%) and negative in 40 patients
(69%). Patients with VT were older than those without VT (45.14±13.4 versus
33.9±11.5 years, p=0.02). Age at first intervention (7.7±4.2 versus 4.4±5.3
years, p=0.2), age of repair (7±3.7 versus 5.7±5.6 years, p=0.1) or follow-up
duration (34.5±2.7 years 28.2±8.2 versus p=0.09) were not significantly
different between patients with and without VT. The sensitivity, specificity
and negative predictive value of MTWA for VT were 66.6%, 75.5% and 92.5%,
respectively. Patients with VT had more positive MTWA results than the ones
without VT (6/9 (66%) versus 12/49 (24%) p=0.01). Patients with positive MTWA
test had 6.1 times risk for having ventricular tachycardia (odds ratio 6.1,
95% CI 1.3 to 28.2). No significant relationship was found between presence
of VT, maximal V alt and onset heart rate in patients with
positive TWA (7.4±2.8 versus 6.7±2.1 mV, p=0.6 and 104.4±6.1 versus 102.5±5.7
bpm, p=0.5, respectively)Conclusion: MTWA was relatively common and relate to
a history of documented VT in adult patients with repaired tetralogy of
Fallot. Therefore MTWA may emerge as a useful non-invasive tool to identify
Fallot patients at risk for malignant arrhythmia. Further prospective studies
are needed to evaluate the prognostic value of this test. |