diastolic heart failure

Every heartbeat has two halves: squeeze (systole) and relax-and-fill (diastole). Diastolic heart failure is when the squeeze still works but the relaxing-and-filling half breaks down — the ventricle is too stiff to draw in blood easily, like trying to fill a jar whose walls will not flex.

The left ventricle has become thick or stiff, so it cannot relax and fill at normal pressures. To get enough blood in, filling pressure must rise, and that pressure backs up into the lungs and causes breathlessness and congestion — even though the ejection fraction looks normal. This is why diastolic heart failure largely overlaps with HFpEF (heart failure with preserved ejection fraction). Common contributors include long-standing high blood pressure, left ventricular hypertrophy, aging, diabetes, and infiltrative diseases such as cardiac amyloidosis.

The terms ‘diastolic heart failure’ and HFpEF are often used interchangeably, though they are not perfectly identical: diastolic dysfunction names the mechanism, while HFpEF names the clinical syndrome defined by a preserved ejection fraction. Many patients have a mix of impaired relaxation and other abnormalities, so modern practice leans toward the broader HFpEF label.