Practice Update: Cardiology

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In risk-stratifying patients for sudden car-
diac death (SCD), my approach depends
on the following factors:
• Whether or not a patient has had cardiac
arrest due to ventricular fibrillation or
ventricular tachycardia (VT) and whether
such an event occurred in the absence
of reversible causes
• The presence of symptoms suggestive
of arrhythmias, such as syncope or
near-syncope
• The presence of systolic heart failure
with a left ventricular ejection fraction
(LVEF) ≤35% and New York Heart Asso-
ciation (NYHA) class II or III heart failure
symptoms despite guideline-directed
medical therapy (GDMT)
• The presence of other structural heart
diseases such as hypertrophic cardiomy-
opathy, arrhythmogenic right ventricular
cardiomyopathy, or cardiac sarcoidosis
• The presence of a cardiac channelo-
pathy such as long QT syndrome or
Brugada syndrome
Cardiac arrest due to ventricular fibrilla-
tion or VT portends a high risk of future
recurrence of such events. Therefore, I
recommend an ICD to such patients if the
arrhythmia occurred in the absence of
reversible causes and if I expect them to
survive for more than 1 year (the expecta-
tion of survival for more than 1 year applies
to all the scenarios below in which I recom-
mend an ICD).
In patients who present with syncope or
near-syncope, I focus my attention on
the history. Features that increase the
likelihood of an arrhythmic etiology for syn-
cope include the absence of a prodrome,
the presence of structural heart disease,
older age, and resultant injury. In patients
with syncope likely due to a ventricular
arrhythmia who do not meet other crite-
ria for an ICD (such as an LVEF ≤35% and
NYHA class II symptoms despite GDMT),
I perform an electrophysiology study to
look for sustained ventricular arrhythmia
that replicates the patient’s symptoms. If
present, then I recommend an ICD.
The risk of SCD is high in many patients
with an LVEF ≤35% due to ischemic car-
diomyopathy and NYHA class I, II, or III
symptoms despite GDMT. The risk of SCD
is also high in many patients with an LVEF
≤35% due to non-ischemic cardiomyopathy
and NYHA class II or III symptoms despite
GDMT. In such patients, I recommend an
ICD.
Risk stratification of patients with hyper-
trophic cardiomyopathy for SCD and no
prior cardiac arrest or known sustained
ventricular arrhythmias involves the fol-
lowing factors:
• Syncope presumed to be due to a ven-
tricular arrhythmia
• Family history of SCD
• Left ventricular wall thickness ≥3 cm
• Blunted blood pressure response to
exercise
• Non-sustained VT
In addition to these factors, I take into
account the presence of delayed hyper-
enhancement on a cardiac MRI. If syncope,
family history of SCD, or left ventricular wall
thickness ≥3 cm is present, then I recom-
mend an ICD. If blunted blood pressure
response to exercise or non-sustained
VT is present, then I look for risk modifi-
ers such as delayed hyperenhancement
on cardiac MRI. If present, then I recom-
mend an ICD.
Risk stratification of patients with long QT
syndrome and no prior cardiac arrest or
known sustained ventricular arrhythmias
involves the following factors:
• Syncope presumed to be due to a ven-
tricular arrhythmia
• QTc ≥500 ms
• Genotypes LQT2 and LQT3
• Females with genotype LQT2
• Age <40 years
• Onset of symptoms at <10 years of age
In patients with syncope and QTc ≥500 ms
despite treatment with a beta blocker, I rec-
ommend an ICD.
Although covering risk stratification for
other conditions is beyond the scope of
this review, a thoughtful and systematic
approach to the risk stratification of every
patient is essential. Many other tests have
been proposed for risk stratification of
patients for SCD, such as T-wave alter-
nans and measures of autonomic tone.
However, none of these tests have enough
positive and negative predictive value and
data from randomized clinical trials sup-
porting their clinical utility to justify their
routine use in clinical practice.
My Approach to the Risk
Stratification of Patients for
Sudden Cardiac Death
By Sana M Al-Khatib MD, MHS
Dr Al-Khatib is Professor
of Medicine, Duke
Clinical Research
Institute, Duke University
Medical Center, Durham,
North Carolina.
MY APPROACH 29
VOL. 2 • NO. 2 • 2017