[Considerations on differential diagnosis of syndrome of initial retardation of ventricular depolarization traced to myocardial infarction from branch block; electro- and vectocardiographic findings].

Introduction. Ivabradine is an agent that selectively decreases heart rate (depending on the dose) and does not affect other cardiovascular parameters. In particular, it does not influence left ventricular ejection fraction and does not inhibit vascular relaxation during exercise. Due to these properties, ivabradine can be used in those patients in whom beta-blockers are contraindicated or their dose escalation is not possible. These properties also suggest that use of ivabradine during cardiac rehabilitation in patients with contraindications to beta-blockers or beta-blocker intolerance might increase exercise tolerance. The aim of the study was to evaluate whether administration of ivabradine (in addition to or instead of beta-blockers) during a cardiac rehabilitation program improved exercise tolerance in comparison to patients receiving only beta-blockers. Materials and methods. Fifty patients treated with ivabradine during cardiac rehabilitation were enrolled into this retrospective study. The control group was matched for gender, age and other comorbidities and consisted of 50 subjects. The improvement in exercise tolerance was compared between the group receiving beta-blockers alone and those on ivabradine treatment. Results. The study included 100 patients — 60 males and 40 females. Our analysis of exercise test results expressed in metabolic equivalents of task (MET) suggested a positive effect of ivabradine on the improvement of exercise tolerance. The percentage improvement was significantly higher in patients on ivabradine compared to the control group (26.8% ± 27.73% vs. 11.64% ± 19.34%, p = 0.002). In addition, a larger increase in the duration of exercise test was noted in patients treated with ivabradine (52.76% ± 47.29% vs. 32.59% ± 42.94%, p = 0.0101). No difference was found between patients who were already treated with ivabradine before cardiac rehabilitation and those in whom ivabradine was initiated during the cardiac rehabilitation program. Conclusions. Treatment with ivabradine during a cardiac rehabilitation program was associated with a better improvement in exercise tolerance compared to patients receiving beta-blockers alone.