michael s
(Michael S)
#1
86 Who should have a VT stimulation study? What
are the risks and benefits?
Roy M John
Contrary to conventional wisdom, a significant number of
sudden arrhythmic deaths result from re-entrant ventricular
tachycardia that occurs in patients with chronic heart disease in
the absence of acute infarction. These arrhythmias can be safely
studied in a controlled setting using electrophysiological testing.
Programmed electrical stimulation of the ventricle (also termed
VT stimulation studies) has a remarkable sensitivity for re-
producing monomorphic ventricular tachycardia associated with
infarct related myocardial scars and offers a fairly reliable means
of identifying patients at risk for sudden death. Patients with LV
dysfunction (LV ejection fraction <40%) who are inducible for
monomorphic VT have a risk of sudden cardiac death of
approximately 30% over the ensuing year.
The patients at highest risk for sudden death include those who
have survived a cardiac arrest not occurring in the context of an
acute infarction, and those presenting with sustained VT. These
patients are best treated with implantable cardiac defibrillators.
The role of VT stimulation studies in such patients is primarily to
confirm the diagnosis and exclude focal ventricular arrhythmias
or unusual supraventricular arrhythmias indistinguishable from
VT that are amenable to RF ablation. Occasionally, suppression of
VT inducibility with drugs such as amiodarone and sotalol may
be an acceptable alternative to implantable cardioverter defibril-
lator (ICD) implant.
VT stimulation studies are more valuable for patients with
severe heart disease and unexplained syncope. Such patients may
have had a self-limiting arrhythmia causing their syncope.
Inducibility of monomorphic VT is a fairly specific finding in this
patient population especially if their heart disease is based on
coronary artery disease. In addition, electrophysiological studies
can unmask severe His-Purkinje conduction disease requiring
pacemaker implantation. One major drawback of VT stimulation
studies is the low sensitivity for ventricular arrhythmia in non-
ischaemic dilated cardiomyopathy. In these patients, if the
clinical suspicion is high, a negative study may well represent a
false negative. A second problem with VT studies is the uncertain
