Vlt Tachycardia

4 8 12 16 20 24 Follow-up (months)

Fig. 5. Survival in patients with nonsustasined VT, coronary disease, and left ventricular dysfunction, stratified by results of electrophysiologic testing. (From: Wilber DJ. Circulation 1990;82:350-358.)

Electrophysiology study (EPS) has been used to assess risk of life-threatening arrhythmias in patients with NSVT. The use of such testing is based on the premise that if a sustained, potentially life-threatening, ventricular arrhythmia is induced in the electro-physiology laboratory, it may occur spontaneously. After extensive study, it appears that this approach has no important predictive value in patients without CAD (63,64). In the absence of CAD, even if there is a high risk for sudden arrhythmic death, the likelihood of inducing such an arrhythmia in the electrophysiology laboratory is small. Thus, EPS is not generally recommended to assess risk in patients with NSVT who do not have CAD.

Electrophysiologic testing for NSVT has prognostic value when CAD and left ventricular dysfunction are present. In the MUSTT trial, about one-third of the patients with impaired ventricular function, coronary disease, and NSVT had inducible sustained ventricular tachyarrhythmias. No clinical parameters predicted inducibility (50). Several studies have assessed the efficacy of electrophysiology testing to predict the risk of sustained VT or ventricular fibrillation (VF) in post-MI patients with mixed results (65-73). Prior to the era in which ICD implantation was commonplace, we evaluated 100 patients with NSVT, CAD, and a LVEF less than 0.40 (74). Forty-three had inducible sustained VT at electrophysiology testing. Of these, 20 became noninducible with serial antiarrhythmic drug testing, and 20 patients remained inducible, but with a slower ventricular tachycardia (VT) rate. The 1- and 2-yr mortality in the inducible group, despite drug treatment, was 38% and 50%, respectively (see Fig. 5). Patients who did not have inducible VT fared better.

More recent data call into question the value of EPS to define risk in this population (75). In MUSTT (Multicenter Unsustained Tachycardia Trial), patients with prior myo-

Risk Stratification—Electrophysiologic Testing

Atrial Fibrillation Tachycardia

Fig. 6. Data from the MUSTT trial—Kaplan-Meier mortality curves:

(A) Total mortality in patients who met trial inclusion criteria, but were noninducible at EPS (registry) compared with patients who were inducible but randomized to no arrhythmic therapy. (From: Buxton A. N Engl J Med 2000;342:1942.)

(B) Total mortality in patients randomized to EP-guided therapy vs no antiarrhythmic therapy. (From: Buxton A. N. Engl J Med 1999;341:1855.)

Fig. 6. Data from the MUSTT trial—Kaplan-Meier mortality curves:

(A) Total mortality in patients who met trial inclusion criteria, but were noninducible at EPS (registry) compared with patients who were inducible but randomized to no arrhythmic therapy. (From: Buxton A. N Engl J Med 2000;342:1942.)

(B) Total mortality in patients randomized to EP-guided therapy vs no antiarrhythmic therapy. (From: Buxton A. N. Engl J Med 1999;341:1855.)

cardial infarction, EF < 0.40, and NSVT underwent EPS. The 1-yr mortality in such patients who had a negative electrophysiology test and received no specific antiarrhythmic treatment was 12% (76) (see Fig. 6A). Although this was better than the 18% risk if the EPS were positive and no antiarrhythmic therapy was administered, all such patients with NSVT, CAD, and left ventricular dysfunction are at risk. A

Mustt Trial

Fig. 6. (Continued) Data from the MUSTT trial—Kaplan-Meier mortality curves:

(C) Total mortality in patients randomized to EP-guided therapy vs no antiarrhythmic therapy, stratified by whether the patient eventually received an ICD or not. (From: Buxton A. N Engl J Med

1999;341:1886.)

Fig. 6. (Continued) Data from the MUSTT trial—Kaplan-Meier mortality curves:

(C) Total mortality in patients randomized to EP-guided therapy vs no antiarrhythmic therapy, stratified by whether the patient eventually received an ICD or not. (From: Buxton A. N Engl J Med

1999;341:1886.)

generous interpretation was that EPS differentiated high-risk from moderate-risk patients in this study. Some have advanced the position that EPS is of little benefit in this population (77).

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