CLINICAL
NEWS
American College of Cardiology Extended Learning
ACCEL interviews and topical summaries of cardiology’s
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Athletes with Bradycardia
How slow is too slow?
I
n athletes, a normal electrocardiogram (ECG) is
the anomaly. In Italy, where there is a nationwide
screening program for conditions causing sudden
cardiac death, the proportion of individuals 14 to 35
years of age with a completely normal ECG was 42.5%
in nonathletes but only 2.6% in athletes (p < 0.001).1
The paper, published in JACC, demonstrated that
trained athletes show ECG changes such as sinus bradycardia, first-degree atrioventricular block, and early
repolarization, all of which can result from physiological adaptation of the cardiac autonomic nervous system
to athletic conditioning (e.g., increased vagal tone and/
or withdrawal of sympathetic activity).
The ECGs of trained athletes often exhibit pure
voltage criteria (i.e. based only on QRS amplitude measurements) for left ventricular hypertrophy (LVH) that
reflect physiological LV remodeling with increased LV
wall thickness and chamber size.
Resting sinus bradycardia, as defined by a heart
rate < 60 bpm, is the most common ECG pattern
in athletes, occurring in 57.6% of 4,081 athletes
versus 26.1% of the 7,764 nonathletes in the
aforementioned Italian study by Hariharan Raju,
MBBS, St. George’s University of London, UK, and
colleagues. Prevalence varied depending on the
type of sport and the level of training/competition.
Sports that require high endurance, such as cycling,
cross-country skiing, and rowing/canoeing are
each significantly associated with a higher rate and
greater extent of physiological ECG changes compared with participation in sports that require more
strength and speed and relatively less endurance.
In highly trained athletes, Pelliccia and others have
noted that marked bradycardia < 30 bpm and asymptomatic sinus pauses > 2 seconds are not uncommon
during 24-h ECG, particularly during sleep.2
WHEN THE ABNORMAL IS
NORMAL
To listen to an
interview with
Hariharan Raju,
MBBS, on the topic
of athletes with
bradycardia, scan
the code.
ACC.org/CSWN
When Dr. Raju and his associates
reported their large analysis in
JACC in 2014, they demonstrated
that one in five young people
(athletes or nonathletes) have
group 2 ECG patterns, meaning ECG patterns suggestive of
cardiomyopathy or some sort of
structural cardiac abnormality.1
The low incidence of sudden
cardiac death in young people
suggests that, in most instances,
such patterns are non-specific.
That is important to know given
that the European guidelines recommend transthoracic echocar-
diography in individuals with group 2 ECG patterns.
According to Dr. Raju, their findings have
significant implications on the feasibility and cost
effective