Short title: T-wave alternans and arrhythmias in athletes
For corrispondence: Giorgio
Galanti, Centro di Riferimento Regionale di Medicina dello Sport, Clinica
Medica Generale e Cardiologia, Dipartimento dell’Area Critica
Medico-Chirurgica, Università degli Studi, Ospedale Careggi.
Viale Morgagni n. 85, 50134
Firenze
e-mail address: g.galanti@dac.unifi.it
Exercise-induced
heart rate increase can stimulate malignant arrhythmic events in a pathological
cardiac subjet, even in absence of early symptoms. T-Wave alternans (TWA) has
been associated with malignant ventricular arrhythmias. Recently sophisticated
signal-processing techniques were able to measure TWA down to one-millionth per
volt (microvolt-TWA). Several studies confirmed the equivalence of
microvolt-TWA and electrophysiology test (EPS) in cardiopathic patients, but no
data are available in population of
competitive athletes with severe ventricular arrhythmias, where it is important
to separate a “paraphysiologic” arrhythmic training-induced subject from a
pathological one.
We selected 81 competitive athletes, aged between 12 to 46 years old,
(mean age: 24.3±4.5 yrs), 48 of them totally normal including elite type (group
A, mean age: 24.5±4.1) and 33 of them (group B, mean age: 23.9±1.5) with
important arrhythmias (ventricular ectopic beats>10/hour also complex or non
sustained and sustained ventricular tachycardia).
All athletes were evaluated by exercise-stress test (bicycle in 48 cases
or treadmill), increasing the heart rate up to 110 beats/min in about 15
minutes. Microvolt TWA have been performed using the Heart Wave System with
Micro-V Sensors (Cambridge Heart Inc.,
Boston). Analysis of the results have been performed automatically by the
Cambridge Heart system interpretation software with confirmation by an expert
(100% agreement). Group B underwent EPS in order to evaluate the inducibility
to sustained ventricular tachycardia during programmed stimulation.
In group A, TWA outcome was determinate in 45 subjects (94%) and
indeterminate in 3 cases for ECG tracing was obscured
by noise. In group B, TWA test was positive in 5 (15%) symptomatic
subjects, indeterminate or borderline for 3 (9%) subjects, and negative for the
rest of them (76%). 24/25 negative TWA-test subjects were negative in EPS too,
apart one subject with a documented ventricular tachycardia episode in
amiodarone treatment (false negative). Regarding positive TWA-test subjects: 3
(60%) were positive for ventricular tachycardia in EPS, one (20%) positive for severe atrial sustained
tachyarrhythmias, one refused EPS. We were able to state
a correct diagnosis of limphocitary myocarditis for only one positive subject,
that showed both TWA and EPS negativity after recovering. For the other positive patients, we suppose a non-documentable
micropathology. One of the 3 positive subjects became TWA
negative in amiodarone therapy. The
third positive subject received an implantable cardioverter-defibrillator.
In conclusion, microvolt TWA study seems to be a useful, non-invasive
and feasibility tool to evaluate arrhythmic risk in sporting population.
TWA-test showed a high negative predictive value, whereas positive predictive
value needs more data to confirm good concordance with EPS.
Table I:
81 athletes
48 healthy
athletes 33 arrhythmic athletes
- TWA indeter.TWA - TWA +TWA
indeter. TWA
45
3 25 5
2(+1 borderline)
- EPS + EPS no EPS -
EPS + EPS
24 1 1 1 3
Tp:Amiodarone
ICD -TWA,-EPS -TWA
1 1 1
after resolution Tp:Amiodarone
of myocarditis
TWA=T-wave alternans; EPS=electrophysiological study;
ICD=implantable cardiac defibrillator