Alan C. Cameron, BSc (Hons), MB ChB, PhD, MRCP
Atrial fibrillation (AF) is a common comorbidity in patients with acute ischaemic stroke and a dilemma frequently encountered in clinical practice is whether we should aim for stringent or lenient rate control in patients with AF. Lee and colleagues sought to address this question by assessing associations between mean heart rate, heart rate variability and clinical outcomes in more than 2,000 patients with acute ischaemic stroke and AF included in a prospective, multi-centre, Korean-based stroke registry. The authors demonstrate a J-shaped association between heart rate and mortality, with heart rates in the region of 80 beats per minute associated with lowest risk of mortality at 24 hours or 3 to 7 days after stroke onset and heart rates above or below this sweet-spot associated with increased mortality. Similar results were observed for a composite endpoint of stroke recurrence, myocardial infarction and all-cause mortality, although no effect was observed on stroke recurrence alone, nor from heart rate variability on mortality, stroke recurrence or the composite endpoint.
Studies assessing the optimal heart rate in a range of patients with AF have produced conflicting results. The ORBIT-AF registry of almost 3,000 patients demonstrated a J-shaped relationship between heart rate and mortality with a nidus of 65 bpm, whereas the RACE-II trial randomized around 600 patients with AF to lenient (<110 bpm) versus strict (<80 bpm) rate control and demonstrated that target heart rates <110 bpm are as effective and easier to achieve. Results from the study by Lee and colleagues are more aligned with results from ORBIT-AF, although the nidus of 80 bpm in the current study is higher than that in ORBIT-AF. Thus, optimal heart rate may vary in different populations of patients with AF, although confounding effects from post-stroke complications may have contributed to the results observed by Lee and colleagues.
Overall, heart rates in the region of 80 bpm appear to be associated with a lower risk of mortality in patients with AF and acute ischemic stroke, and the results would support a randomized evaluation of target heart rates in this population.