A Johns Hopkins study has provided the most
comprehensive description to date of people most likely to
develop a relatively rare heart condition called
arrhythmogenic right ventricular dysplasia, or ARVD, known
to be among the top causes of sudden cardiac death among
young athletes.
In their study, published in the journal
Circulation online Dec. 12, the scientists analyzed
characteristics of 100 ARVD patients, including 69 while
still alive and 31 diagnosed postmortem. The subjects
included men and women of many ethnic backgrounds, with a
median age of 31.
The subjects were part of Johns Hopkins' registry of
U.S. patients with the condition, which appears on MRI
scans as either a protruding or pouchlike bulge from the
right side of the heart or a dilated, poorly functioning
right ventricle.
As noted in numerous memorials to athletes posted to
the Internet, ARVD is composed of a range of symptoms,
including irregular heartbeat and the presence of excess
amounts of fatty tissue in the heart's right ventricle, the
lesser known of the heart's two main pumping chambers and
the one that pumps blood to the lungs. As a result, the
abnormal and often weakened and scarred right ventricle
dramatically increases the risk of harmful ventricular
arrhythmias and possible sudden cardiac death.
Estimates from researchers and the Heart Rhythm
Society suggest that ARVD accounts for up to 5 percent of
the 300,000 deaths each year in the United States from
sudden cardiac death. A family history of sudden cardiac
death at a young age is considered a major risk factor for
the disorder. Athletes are also at particular risk, but the
precise biological reasons for this remain unknown.
According to senior study investigator and cardiac
electrophysiologist Hugh Calkins, "Physicians need to know
that this is a serious disease, and they should be on the
lookout for its early signs and symptoms because it is an
important cause of sudden cardiac death in apparently
healthy young individuals."
Preventive treatment with an implantable defibrillator
appears to eliminate the risk of sudden death, Calkins
said.
Calkins, a professor of
medicine and
pediatrics
at the School of Medicine and its
Heart Institute, noted that the disease frequently
strikes people who are relatively young and that symptoms
may appear up to 15 years before diagnosis. Initial
symptoms include palpitations, dizziness and fainting.
Researchers found that symptoms usually appear after
puberty and before age 50. Eight of the 31 patients who
died before diagnosis had shown signs of the disease when
alive, including five who had passed out, suggesting they
could have been treated and saved, the researchers said.
Study lead author Darshan Dalal, a cardiology research
fellow at Johns Hopkins, said, "Our results are a sobering
reminder that if a young person faints, especially in
association with exercise, their physicians should evaluate
them carefully for cardiac diseases, including ARVD."
Diagnosis of ARVD is based on a four-point scale, and
up to 10 cardiac tests are required to confirm a diagnosis.
Electrocardiograms and echocardiograms are performed to
verify the origins of arrhythmia, and MRI tests, backed up
by tissue biopsy, are done to confirm the buildup of fat
and fibrous tissue in the right ventricle.
According to Calkins, who founded Johns Hopkins'
ARVD registry in 1998
and is also director of Johns Hopkins' arrhythmia programs,
these confirmatory tests are important because the illness
is often misdiagnosed if physicians rely on a single
diagnostic test, such as MRI.
His earlier research, in 2004, showed that more than
half of patients are misdiagnosed, with physicians
correctly diagnosing only 27 percent of true cases of
ARVD.
In the new study, of the 47 patients who were
diagnosed early and implanted with defibrillators that
shock the heart to correct irregular rhythms, only one died
of cardiac arrest, defined as when the heart suddenly stops
functioning from a runaway heartbeat. Twenty-nine of the
patients' defibrillators "fired" within two years. This
was, Dalal said, "the good news that most patients do quite
well if protected by a defibrillator."
Of 22 patients without defibrillators and maintained
on drug therapy alone, two died of cardiac arrest, in
addition to the 31 who died before diagnosis.
While the exact cause of ARVD remains unknown, the
scientists believe it to be an inherited syndrome and that
improved awareness and better diagnosis are steps toward
their goal of developing a screening test for those at
risk.
Funding for this study was provided by the Bogle
Foundation, Campanella family, Wilmerding Endowments,
National Institutes of Health and Donald W. Reynolds
Foundation. Calkins receives research support from device
manufacturers Guidant, Medtronic and St. Jude. The terms of
these arrangements are being managed by the university in
accordance with its conflict-of-interest policies.
Besides Calkins and Dalal, researchers involved in
this study, conducted solely at Johns Hopkins, were Khurram
Nasir, Chandra Bomma, Kalpana Prakasa, Harikrishna Tandri,
Jonathan Piccini, Ariel Roguin, Crystal Tichnell, Cynthia
James, Stuart Russell, Daniel Judge, Theodore Abraham,
Philip Spevak and David Bluemke.
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