reliability of induced polymorphic VT or ventricular fibrillation
as end points. Recent data from subgroup analysis of the
Multicenter Unsustained Tachycardia Trial (MUSTT) suggests
that such arrhythmias may be just as important as monomorphic
VT for predicting mortality in the face of severe LV dysfunction.
Perhaps the most important role of VT study is in primary
prevention of sudden death. Two recent randomised trials have
demonstrated conclusively that patients with depressed LV
function and non-sustained VT (defined as three or more beats of
VT at a rate >120bpm) will benefit from ICD implantation if they
are inducible for sustained VT.1,2Clinical trials are in progress to
determine if ICD implantation would benefit patients with low
LVEF and heart failure alone without resorting to an EP study.
Pending their results, patients with LV dysfunction who
manifest non-sustained VT should undergo VT stimulation
studies to see if they would benefit from an ICD. This strategy
appears to be cost effective.^3
The risks of invasive electrophysiological studies are related to
venous (and rarely arterial) cannulation and from the arrhythmias
induced. Injury to the vascular structures and venous thrombosis
occurs rarely (less than 2%). Cardiac perforation from catheter
placement is equally rare (0.4%); death from the procedure
occurred in 0.12% in one study^4 and underlines the importance of
trained personnel and well equipped laboratories for these studies.
RReeffeerreenncceess
1 Buxton AE, Lee KL, Fisher JD et al. A randomized study of the
prevention of sudden death in patients with coronary artery disease. N
Engl J Med1999; 334411 : 1882–90.
2 Moss AJ, Hall WJ, Cannom DS et al. Improved survival with an
implanted defibrillator in patients with coronary disease at high risk
for ventricular arrhythmia. N Engl J Med1996; 333355 : 1933–40.
3 Mushlin AI, Hall WJ, Zwanziger J et al. The cost effectiveness of
automatic implantable cardiac defibrillators: results from MADIT.
Multicenter Automatic Defibrillator Implantation Trial. Circulation
1998; 9977 : 2129–35.
4 Horowitz L. Safety of electrophysiologic studies. Circulation
1986; 7733 ((ssuuppppll)): II28–31.