Long-term amiodarone administration remodels expression of ion channel transcripts in the mouse heart.

BACKGROUND: The basis for the unique effectiveness of long-term amiodarone treatment on cardiac arrhythmias is incompletely understood. The present study investigated the pharmacogenomic profile of amiodarone on genes encoding ion-channel subunits. METHODS AND RESULTS: Adult male mice were treated for 6 weeks with vehicle or oral amiodarone at 30, 90, or 180 mg x kg(-1) x d(-1). Plasma and myocardial levels of amiodarone and N-desethylamiodarone increased dose-dependently, reaching therapeutic ranges observed in human. Plasma triiodothyronine levels decreased, whereas reverse triiodothyronine levels increased in amiodarone-treated animals. In ECG recordings, amiodarone dose-dependently prolonged the RR, PR, QRS, and corrected QT intervals. Specific microarrays containing probes for the complete ion-channel repertoire (IonChips) and real-time reverse transcription-polymerase chain reaction experiments demonstrated that amiodarone induced a dose-dependent remodeling in multiple ion-channel subunits. Genes encoding Na+ (SCN4A, SCN5A, SCN1B), connexin (GJA1), Ca2+ (CaCNA1C), and K+ channels (KCNA5, KCNB1, KCND2) were downregulated. In patch-clamp experiments, lower expression of K+ and Na+ channel genes was associated with decreased I(to,f), I(K,slow), and I(Na) currents. Inversely, other K+ channel alpha- and beta-subunits, such as KCNA4, KCNK1, KCNAB1, and KCNE3, were upregulated. CONCLUSIONS: Long-term amiodarone treatment induces a dose-dependent remodeling of ion-channel expression that is correlated with the cardiac electrophysiologic effects of the drug. This profile cannot be attributed solely to the amiodarone-induced cardiac hypothyroidism syndrome. Thus, in addition to the direct effect of the drug on membrane proteins, part of the therapeutic action of long-term amiodarone treatment is likely related to its effect on ion-channel transcripts.

Does the pretransplant UNOS status modify the short- and long-term cardiac transplant prognosis?

BACKGROUND: We compared the morbidity and mortality rates of patients who had urgent heart transplantation or transplantation after bridging with a ventricular assist device, with the rates of patients whose clinical stability allowed them to wait at home. METHODS: From March 1985 to December 2000, 404 patients underwent heart transplantation in a single center. There were 273 patients with UNOS status 2 (US 2), 103 patients with UNOS Status 1A (US 1A), and 28 patients with UNOS Status 1B (US 1B). We compared the groups retrospectively with respect to pretransplantation status and operative results. RESULTS: Despite more severely impaired hemodynamics and a significantly higher preoperative infection rate in US 1A and 1B patients, there were no statistically significant differences in survival rates among the three groups. Donor sex and age, cytomegalovirus and toxoplasmosis, mismatch rate, ischemic time, method of myocardial protection, and operative technique did not differ statistically among the three groups. Length of intensive care unit stay, postoperative morbidity, first year postoperative rejection rate, and graft occlusive vascular disease rate were statistically similar among the three groups. Although pretransplantation cancer assessment was less complete in US 1A and 1B than in US 2 patients, the late-cancer rate was not statistically different among the three groups. CONCLUSIONS: These data suggest that urgently transplanted patients have both early and long term morbidity and mortality similar to those of patients waiting for transplantation at home or with a ventricular assist device.