The papers were presented at the European Society of Cardiology meeting in Stockholm and published in The Lancet last week.
The first study investigated the effects of ivabradine, currently licensed to treat angina, as add-on treatment in 6,505 patients with chronic heart failure. Compared with placebo, add-on treatment with ivabradine cut the risk of cardiovascular death or hospitalisation due to heart failure by 18 per cent.
It also reduced heart rate by an average of 15bpm.
The researchers, led by Dr Karl Swedberg of Gothenburg University, said: 'Our results support the importance of heart rate reduction with ivabradine for improvement of clinical outcomes in heart failure'.
A follow-up study was conducted by a team led by Dr Michael Bohm of Saarland University Hospital, Germany. It concluded that high heart rate is an independent risk factor for heart failure, and that lowering heart rates should be an important target of therapy.
The researchers compared the risk of cardiovascular death and hospitalisation for patients with the highest and lowest heart rates after 28 days of treatment with ivabradine.
They found that patients in the placebo group with a heart rate greater than 87bpm were twice as likely to die or experience a cardiovascular event as those with a lower rate. An increase in heart rate of 5bpm led to a 16 per cent increase in the risk of negative outcomes.
Cardiovascular events occurred in 17.4 per cent of patients who had a heart rate of 60bpm after 28 days of treatment with ivabradine, compared with 32.4 per cent of patients whose heart rate was 75bpm or higher.
Professor John Teerlink, of the University of California, argues that, despite the findings, the comparative effectiveness of ivabradine needs further study.
In an editorial accompanying the papers he wrote: 'The results provide the basis for additional trials to test these important and clinically relevant questions.'
He added: 'Until these questions are answered, the place of ivabradine in heart failure remains unclear.'