Ivabradine in combination with metoprolol succinate in the treatment of inappropriate sinus tachycardia.

BACKGROUND: Inappropriate sinus tachycardia (IST) is a clinical syndrome characterized by excessive resting heart rate (HR) or a disproportional increase in HR during exercise. ß-blocker or calcium channel-blocker therapy is often noneffective or not well tolerated. The HR reduction on ivabradine is similar to ß-blockers but in some patients its efficacy to resolve all IST-related symptoms is limited. The aim of the study was to assess the efficacy and safety of combining ivabradine with metoprolol succinate in patients with refractory highly symptomatic IST. METHODS: Twenty patients (36 ± 10 years; 16 women) with IST were enrolled. All patients received metoprolol succinate 95 mg single dose during the first month of the study. After 4 weeks of treatment with metoprolol, ivabradine was administered as adjuvant therapy up to 7.5 mg twice daily. Holter monitoring and treadmill stress test were performed at baseline, after 4, and 8 weeks of the study, respectively. RESULTS: We observed significant and similar reduction in resting HR both for metoprolol and for combined therapy compared to the baseline. The mean HR during daily activity was significantly lower on ivabradine and metoprolol compared to monotherapy with ß-blocker. The combined treatment yielded a significant increase in exercise capacity as assessed by treadmill stress test. After 4 weeks of combined therapy a significant reduction in IST-related symptoms, measured by means of the European Heart Rhythm Association score, was observed. CONCLUSION: Combining ivabradine with metoprolol is an effective and well-tolerated treatment option for IST in patients with refractory to monotherapy.

How to do exercise-induced T-wave alternans testing using the spectral method.

The present review summarizes current aspects on how to perform noninvasive microvolt T-wave alternans (mTWA) testing in clinical practice. The focus is on methodologic issues such as patient-related, or technical aspects, and interpretation of the results. Special attention is given to the different sources of noise that may interfere with mTWA assessment. The role of beta-blocker therapy and its potential effect on mTWA is discussed as well. In the first clinical studies of mTWA, a high rate of indeterminate test results was observed. In this respect, patient-related indeterminacy has been demonstrated to be associated with an increased mortality and such tests are thus regarded as "abnormal" whereas technically inadequate tests are classified as indeterminate. Since mTWA evolves over time in patients with structural heart disease, the "optimal timing" for mTWA assessment is rather in the chronic phase than in the acute setting of heart disease.