Clinical Heart Failure
A growing body of literature supports the pivotal role of LA functional failure leading to pulmonary congestion and symptom onset. Specifically, atrial contractile failure to compensate for reservoir and/or conduit dysfunction may lead to overt clinical heart failure32 (Figures 3). Atrial fibrillation leading to failure of contractile compensation, may be large determinant of symptom onset, and compensatory enhanced conduit function becomes essential in this situation. Early exercise-induced symptoms may also be related to conduit function failure in the setting of impaired reservoir function 33. Advanced symptomatic HFpEF is characterized by an eventual impairment in all three atrial functional phases34 (Figures 2 and 3).
Hewing et al demonstrated that in patients with sinus rhythm, LA reservoir, conduit, and contractile function all inversely correlated with pulmonary capillary wedge pressure. However, LA contractile strain could independently predict invasively measured pulmonary capillary wedge pressure with a higher diagnostic accuracy than average E/E’ ratio35. Furthermore, Lundberg et al found LA strain to outperform the current guideline recommended algorithm incorporating E/e’, LA volume index, and max tricuspid regurgitation velocity in determining invasively measured elevated pulmonary capillary wedge pressure36.
Impaired LA reservoir strain may provide enhanced diagnostic accuracy beyond conventional echocardiographic measures to discriminate true HFpEF from non-cardiac dyspnea 37. Impaired resting LA reservoir strain is associated with decreased peak oxygen consumption38. LA reservoir strain normally increases during exercise, but this typical exercise related augmentation is blunted in symptomatic patients. Impaired LA reservoir augmentation with exercise leads to right ventricular-pulmonary circulation uncoupling and exercise ventilatory inefficiency39. Furthermore, resting LA reservoir strain may outperformed LV GLS in its diagnostic utility and prognostic ability for prediction of heart failure hospitalization38.