Xamoterol improves the control of chronic atrial fibrillation in elderly patients

Twenty digitalized elderly patients with chronic atrial fibrillation were randomized into a double-blind cross-over study. None was in overt heart failure and all were taking < 80 mg frusemide daily. They received xamoterol 200 mg b.d. for 2 months with their usual dose of digoxin for 1 month and placebo digoxin for the other month. Twenty-four-hour heart rate analysis was done at baseline and at the end of each treatment period. Compared with baseline digoxin, xamoterol alone significantly increased nocturnal minimum heart rate [85 +/- 17 vs. 62 +/- 9 (mean +/- SD), p < 0.0001] without affecting daytime maximum heart rate (132 +/- 18 vs. 122 +/- 20, p = NS). Compared with baseline digoxin, xamoterol plus digoxin significantly increased nocturnal minimum heart rate (68 +/- 8, p < 0.05) and reduced daytime heart rate (114 +/- 17, p < 0.05). The mean number of pauses > 1.5 s was significantly reduced by xamoterol alone. Walking distance in 6 minutes was 406.1 +/- 27.1 m (mean +/- SE) at baseline and improved significantly on both treatments (450.3 +/- 19.8 on xamoterol; p < 0.02 and 453.7 +/- 19.2 on xamoterol plus digoxin; p < 0.01). No significant change was found in subjective measurements of palpitations, breathlessness and well-being using visual analogue scales. Xamoterol combined with digoxin improves effort tolerance and heart-rate control by reducing diurnal tachycardia and nocturnal bradycardia and pauses.

A prospective study of the efficacy and safety of adjuvant metoprolol and xamoterol in combination with amiodarone for resistant ventricular tachycardia associated with impaired left ventricular function

Combination antiarrhythmic drug therapy may be more effective than treatment with a single agent for control of refractory cases of sustained ventricular tachycardia (VT). In a prospective randomized crossover study of 20 patients with impaired left ventricular function (ejection fraction of 28% +/- 8%) and recurrent VT in spite of treatment with amiodarone, we compared the efficacy and safety of adjuvant therapy with metoprolol, 50 mg two times daily and xamoterol, 200 mg two times daily. Metoprolol caused hemodynamic deterioration in five patients, and only one also experienced intolerance to xamoterol. Sustained VT was inducible in all 20 patients who were receiving amiodarone alone but was suppressed or rendered nonsustained in 8 of 20 patients during treatment with amiodarone plus xamoterol and in 6 of 17 patients during treatment with amiodarone plus metoprolol. Addition of xamoterol restored sinus rhythm in four patients who presented with incessant VT, and metoprolol was effective for three of them. Neither beta-blocker significantly altered tachycardia cycle length or any electrophysiologic parameter other than the slowing of the sinus rate. Both beta-blockers suppressed exercise-induced VT in 3 of 4 patients, and addition of xamoterol significantly increased treadmill exercise duration (7.1 +/- 1.8 min) compared with administration of amiodarone alone (3.8 +/- 1.5 min; p < 0.01). Fourteen patients were discharged with prescriptions for amiodarone-beta-blocker combinations. During a mean follow-up period of 13 months (range, 2 to 24 months), there were three cases of recurrent VT (in all patients VT remained inducible) and no sudden deaths.(ABSTRACT TRUNCATED AT 250 WORDS)