The core hemodynamic case

The atrial "kick" supplies roughly 10-30% of LV filling normally, but in a stiff, non-compliant ventricle (exactly the HFpEF substrate) that contribution can rise to ~40%, because passive early filling is already curtailed. So AF is doubly damaging in HFpEF: it abolishes the booster contribution the stiff ventricle most depends on, and it shortens diastolic filling time. This is why AF is tolerated far worse in HFpEF than in HFrEF (where the dilated ventricle fills passively and the dominant AF harm is rate-related). AF carries a worse prognosis in HFpEF than HFrEF, and baseline AF prevalence in HFpEF is ~42%.

The strongest direct evidence that restoring the atrial contribution helps comes from the small dedicated ablation RCTs in AF-HFpEF (Aldaas, JACC Heart Failure 2023; the STALL program). Restoring sinus rhythm cut peak exercise PCWP (~30→25 mmHg), raised resting and peak cardiac output, improved peak VO2, and in half of ablated patients eliminated the exercise-hemodynamic HFpEF signature. These are the cleanest invasive demonstrations that returning organized atrial mechanics improves output.