Loss of efficacy during long-term cifenline therapy: development of antiarrhythmic resistance?
We conclude that antiarrhythmic resistance occurred with cifenline in these patients as (1) initial efficacy was established for a minimum of two years, (2) VPD frequency was similar during cifenline therapy and placebo reintroduction, (3) cifenline therapy failure continued despite further dosage titration, and (4) alternative Class I antiarrhythmic therapy was successful in all patients. Repeat intermittent ambulatory ECG monitoring is necessary not only to assess the continued need for antiarrhythmic drug therapy, but also to establish continued long-term efficacy.
There was no correlation between respiratory function tests and NH. This study emphasizes the inability of standard respiratory function tests to predict NH that may arise early in the course of MND.