Heart failure with preserved ejection fraction (HFpEF) is a complex clinical entity that is poorly understood yet present in up to 5.5% of the general population. Proven therapies for this disorder are lacking, even though it has a similar prognosis to that of heart failure with reduced ejection fraction (HFrEF). Innovative imaging techniques have provided in-depth understanding of the unique pattern of left ventricular mechanics in patients with HFpEF who progress through preclinical (Stages A to B) and clinical (Stages C to D) American College of Cardiology/American Heart Association heart failure stages. This review highlights the mechanical basis of this disorder from the cellular and myofiber level to chamber dysfunction. As each chamber of the heart is examined, specific biomarkers and echocardiographic parameters with diagnostic and prognostic values are discussed. Finally, novel phenotyping methods including machine learning are reviewed that integrate these mechanics into clinical groups to advise and treat patients.