[SCD-FORUM] 110E Threshold tests. Dr. Rondón

[SCD Symposium]

Answer to Dr. Ariel Szyszko (Argentina)

As Dr. Buxton well said, the risk of threshold tests in any patient, even with dilated cardiomyopathy and reduced EF, is very low and the possibility of a catastrophic event is pretty unimportant, even when I'm sure that in many schools, in patients with EF lower than 15%, do not administer a test shock but use maximum power in the first shock.

In our hospital, although most of our patients have chagasic cardiomyopathy with viral origin with FC III-IV (NYHA), we predominantly perform threshold tests with values of >15 J in order to make an effective first shock always, and we do not insist in looking for a minor threshold since anyway, we are interested in the patient recovering with the first shock.

We also perform threshold tests when the management plan has changed (predominantly if Amiodarone is included) since we know that threshold is quite increased; therefore we perform the test, usually, with 5 to 10 J above the first threshold with no drug.

Why is it important to measure the threshold test and why we do not use the maximal load from the beginning as first shock?

1.- How do we know that the site where we implant the electrode is of good quality to defibrillate and to stimulate post-shock?

2.- How do we know that the patient is able to recover even with maximum load?

3.- If we use maximum load from the beginning, the longevity of the system is much lower and we spend power that in many cases is unnecessary and very painful

4.- It is advisable in many cases with sustained VT, the possibility of administering ATP (anti-tachycardia pacing) in order to achieve a reversion with overdrive mechanisms without using high energy loads.

For all these reasons, the threshold test is advisable…

Regards,

Dr Mauricio Rondón
Sección de Electrofisiología y Marcapasos Hospital Universitario de Caracas
Caracas- Venezuela