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The largest group of patients who may benefit from a
dual-chamber ICD is likely to be those with persistent ventricular
tachycardia/fibrillation (VT/VF) accompanied by AF or atrial flutter. These patients
present a particular problem, because they often require both an ICD and treatment for the
atrial tachyarrhythmia, either in the form of pacing or of medication. On one hand,
episodes of supraventricular arrhythmias can trigger inappropriate discharges of the ICD;
on the other, single chamber ventricular pacing can have undesirable consequences in these
patients, causing a deterioration in ventricular performance and often inducing AF or
atrial flutter. In such cases, a device which combines atrial and ventricular sensing with
the capacity to deliver electrical therapy in both cardiac chambers offers obvious
advantages, although the safety of low energy shocks delivered to the atria, as well as
the discomfort caused to the patient, are still a matter of some controversy.
The combination of ventricular cardioversion/defibrillation and dual-chamber pacing
would also be of benefit to patients who require an ICD and also have sick sinus syndrome
with AF or atrial flutter, atrioventricular conduction disturbances, or severe dilated or
hypertrophic cardiomyopathy. These may represent as many as 20% of patients who need an
ICD because of otherwise intractable VT/VF.
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