Role Of Electrophysiologic Testing

Electrophysiologic testing attempts to expose a viable reentrant circuit by the delivery of premature ventricular impulses into the circuit. The goal is induction of SMVT. In ii hi aUR aUL aUF UI U2 U3 -U4 -US -U6

Fig. 12. 12-lead ECG recording during baseline (left) and after procainamide (right) in a patient with the Brugada syndrome. Note the ST-segment elevation in the right precordial leads after procainamide infusion. NSR = normal sinus rhythm.

post-infarct patients without sustained monomorphic VT, it can serve as a risk-stratifying tool. In post-infarct patients with documented SMVT, electrophysiology testing has little role in risk stratification, because these patients are already at high risk by virtue of their clinically manifest arrhythmia. It can, however, provide useful information which is important for optimal management. Electrophysiology testing can 1) exclude the presence of concomitant supraventricular ventricular tachycardia, which may result in inappropriate ICD therapy; 2) evaluate for conduction disturbances, which may warrant dual-chamber ICD implantation; 3) assist in appropriate ICD programming (tiered therapy); 4) evaluate effectiveness of antiarrhythmic drugs; 4) induce VT for catheter ablation; 5) exclude bundle-branch reentrant tachycardia that can be cured with catheter ablation; and 6) identify induction of more rapid VT, which may be associated with a greater risk of sudden death.

Electrophysiology testing has only a limited role in patients with nonischemic dilated cardiomyopathy and SMVT. Because of patchy areas of fibrosis, electrophysiology testing often results in induction of PVT. It can, however, be helpful in evaluating for bundle-branch reentrant tachycardia.

In patients who present with PVT in which the initiation of the arrhythmia is unknown, electrophysiology testing is useful in identifying patients who are susceptible to mono-morphic VT. Induction of monomorphic VT implies the presence of a fixed anatomic substrate; and inducibility in such patients suggests a high risk for sudden cardiac death. If the initiation of the arrhythmia is unknown and myocardial dysfunction is

Brugada Ecg

Fig. 12. 12-lead ECG recording during baseline (left) and after procainamide (right) in a patient with the Brugada syndrome. Note the ST-segment elevation in the right precordial leads after procainamide infusion. NSR = normal sinus rhythm.

present, a persistent risk of a life-threatening arrhythmia should be assumed; and ICD implantation is the most appropriate treatment option.

Finally, the utility of electrophysiology testing is debatable in patients who present with VF in the absence of acute MI. Most of these patients will be treated with ICDs, whether ventricular arrhythmias are inducible or not in the electrophysiology laboratory. A pre-implant may yield information important to device selection and/or programming. For example, revealing evidence of sinus or A-V conduction disease may lead to dual-chamber ICD implantation. Induction of one or more monomorphic VTs, with evaluation of VT cycle length and response of overdrive pacing, will help to optimize tachycardia detection and therapy parameters post-implant. The need for EPS in cardiac-arrest survivors should therefore be assessed on a case-by-case basis.

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