The progression of HFpEF and its clinical course is poorly understood in comparison to HFrEF. Despite this, patients with HFrEF and HFpEF appear to have comparable outcomes in terms of hospitalization and mortality.[60][61] Causes of death in patients vary substantially. However, among patients in more advanced heart failure (NYHA classes II-IV), cardiovascular death, including heart attacks and sudden cardiac death, was the predominant cause in population-based studies.[62]