Left Atrial Strain
Definition
Left atrial (LA) strain — specifically LA reservoir strain (LASr) — quantifies the peak longitudinal deformation of the left atrium during ventricular systole. It is the primary imaging marker for mechanical atrial dysfunction in the 2025 ESC/HFA atrial cardiomyopathy (AtCM) diagnostic framework, with an abnormality threshold of LASr <23% on echocardiography or CMR.
Key Concepts
Measurement and Phase Components
- LASr (reservoir strain): Peak LA deformation during ventricular systole (from mitral valve closure to opening). Diagnostic threshold for AtCM: LASr <23% on 2D echocardiography or CMR. (sources/atrial-cmp-esc-2025 — high)
- LA booster strain: LA deformation during active atrial contraction (atrial kick). Abnormal threshold: <8% in all age groups.
- LA conduit strain: Passive LA deformation during early ventricular diastole. Threshold: <12% (or <9% in patients >65 years).
- LA emptying fraction: Total volumetric emptying; threshold <48% (echocardiography) or <46% (CMR).
- Only LAVi and LASr are incorporated into the formal AtCM diagnostic framework — other parameters lack sufficient independent evidence. LAVi threshold: >40 ml/m² on echocardiography; >60 ml/m² on CMR. (sources/atrial-cmp-esc-2025 — high)
Clinical Significance
- Stroke and dementia prediction: LASr is more closely associated with stroke and dementia risk than the presence of AF itself — suggesting that atrial substrate quality (not just rhythm) drives thromboembolic risk. (sources/atrial-cmp-esc-2025 — high)
- HFpEF outcomes: In HFpEF, mechanical atrial dysfunction (LASr <23%) is an independent and better predictor of adverse outcomes than the presence or absence of AF. LA dysfunction captures atrial myopathy that precedes and extends beyond AF. (sources/atrial-cmp-esc-2025 — high)
- AtCM diagnosis: Abnormal LASr <23% + abnormal P-wave score ≥1 = sufficient for AtCM diagnosis (meeting the electrical + mechanical criterion pairing). (sources/atrial-cmp-esc-2025)
CMR-LGE for Atrial Fibrosis
- LA LGE ≥10–15% predicts arrhythmias, stroke, and catheter ablation recurrence. However, CMR-based atrial LGE is limited by spatial resolution and variable protocols across centres — not yet standardised for clinical use. (sources/atrial-cmp-esc-2025)
Contradictions / Open Questions
- Measurement validity during AF: LA strain is unreliable during AF due to irregular RR intervals and absent organised atrial contraction. Most diagnostic cut-offs are validated in sinus rhythm; reproducibility during AF is limited. (sources/atrial-cmp-esc-2025)
- Minimal vs maximal LA volume: Minimal LA volume (at end of atrial contraction — before atrial kick) may be more prognostic than maximal LA volume in heart failure patients — a distinction from conventional maximal LAVi used in standard echocardiography reporting. (sources/atrial-cmp-esc-2025)
- No RCT validation of AtCM cut-points: The LASr <23% and LAVi >40 ml/m² thresholds are consensus-derived approximations, not prospectively validated against hard clinical endpoints. (sources/atrial-cmp-esc-2025)
Connections
- Related to concepts/Atrial-Cardiomyopathy
- Related to concepts/Atrial-Failure
- Related to concepts/Inter-Atrial-Block
- Related to entities/HFpEF
- Related to concepts/Late-Gadolinium-Enhancement
- Related to entities/Atrial-Fibrillation