Utility of Simultaneous Left Atrial Strain–Volume Relationship During Passive Leg Lift to Identify Elevated Left Ventricular Filling Pressure—A Proof-of-Concept Study

Background: The assessment of left ventricular (LV) filling pressure in heart failure (HF) poses a diagnostic challenge, as HF patients may have normal LV filling pressures at rest but often display elevated LV filling pressures during exercise. Rapid preload increase during passive leg lift (PLL) may unmask HF in such challenging scenarios. We explored the dynamic interplay between simultaneous left atrial (LA) function and volume using LA strain/volume loops during rest and PLL and compared its diagnostic performance with conventional echocardiographic surrogates to detect elevated LV filling pressure. Methods: We retrospectively reviewed 35 patients with clinical HF who underwent simultaneous echocardiography and right heart catheterization before and immediately after PLL. Patients with atrial fibrillation (n = 4) were excluded. Twenty age-matched, healthy controls were added as controls. LA reservoir strain (LASr) was analyzed using speckle-tracking echocardiography. LA strain–volume loops were generated, including the best-fit linear regression line employing simultaneous LASr and LA volume. Results: LA strain–volume slope was lower for HF patients when compared with controls (0.71 vs. 1.22%/mL, p < 0.001). During PLL, the LA strain–volume slope displayed a moderately strong negative correlation with invasive pulmonary arterial wedge pressure (PAWP) (r = −0.71, p < 0.001). At a 0.74%/mL cut-off, the LA strain–volume slope displayed 88% sensitivity and 86% specificity to identify elevated PAWP (AUC 0.89 0.76–1.00). In comparison, LASr demonstrated strong but numerically lower diagnostic performance (AUC 0.82 0.67–0.98), and mitral E/e’ showed poor performance (AUC 0.57 0.32–0.82). Conclusions: In this proof-of-concept study, LA strain–volume characteristics provide incremental diagnostic value over conventional echocardiographic measures in the identification of elevated LV filling pressure.