Late diastolic mitral annular velocity
a′ (A′) · Same tissue Doppler trace as e′; the late diastolic wave that follows the P wave
Normal range & thresholds
Septal a′ ≈8–11 cm/s; lateral a′ ≈9–13 cm/s in adults in sinus rhythm; a′ rises with age as the atrium compensates for impaired ventricular relaxation. a′ <5 cm/s together with s′ and e′ <5 cm/s is the ‘5-5-5 sign’ of advanced infiltrative disease.[2,30] a′ is absent in atrial fibrillation, and its absence in apparent sinus rhythm should prompt a careful look for atrial standstill or electromechanical dissociation.
Pathophysiology
a′ is the longitudinal velocity generated by left atrial contraction, so it measures atrial contractile function against the ventricular load it must overcome. It rises early in disease, as the atrium hypertrophies to compensate for a stiff, slowly relaxing ventricle, and then falls when the atrium itself fails — through fibrosis, infiltration, chronic stretch or the electrical remodelling of atrial fibrillation. That biphasic course is the atrial mirror image of the E/A ratio’s biphasic course.[2]
Raised by
- Compensatory phase of impaired relaxation — ageing, LVH, hypertension, early diastolic dysfunction
- Bradycardia and first-degree AV block with a well-timed atrial kick
- Any state in which atrial contraction is doing more of the filling work
Lowered by
- Atrial fibrillation (absent), atrial flutter, atrial standstill
- Post-cardioversion atrial stunning — recovers over days to weeks and is the reason anticoagulation must continue after rhythm restoration
- Cardiac amyloidosis — atrial infiltration produces mechanical failure even in sinus rhythm; a low a′ with a dilated atrium in sinus rhythm identifies patients at high thromboembolic risk[30]
- Advanced left atrial myopathy from long-standing hypertension, valve disease or obesity
- Markedly elevated LV end-diastolic pressure opposing atrial emptying
- After extensive left atrial ablation (scarring of the atrial myocardium)
- Mitral annular calcification and annuloplasty rings (mechanical tethering)
Technique & pitfalls
- Identical technique to e′: angle <20°, sample volume on the annulus, sweep 50–100 mm/s.
- Confirm the rhythm on the simultaneous ECG before interpreting an absent a′.
- At heart rates above ≈100/min, e′ and a′ fuse — report fusion rather than a value.
- Report septal and lateral separately; asymmetry has the same regional meaning as for e′.
- In assessing atrial function properly, prefer LA strain (reservoir, conduit and contractile components) — a′ is a single-site surrogate for the contractile component only.[2]
Pseudo-change & artefact
- e′–a′ fusion at tachycardia or with a long PR interval.
- Atrial stunning after cardioversion, ablation or a recent arrhythmia — a transient, not structural, reduction.
- Angle error and sample-volume drift, as for e′.
- Annular calcification and prosthetic material.
- Ectopy: a beat following a premature atrial complex has an abnormal a′.
Treatment thresholds
- No treatment threshold. a′ is a mechanistic and prognostic marker.
- Thromboembolic risk: a low or absent a′ with a dilated atrium in apparent sinus rhythm describes an electromechanically failing atrium, and it strengthens the case for prolonged rhythm monitoring and for anticoagulation once atrial fibrillation is documented.[40]
- Post-cardioversion: stunning with a low a′ is the physiological basis for continuing anticoagulation for at least 4 weeks after rhythm restoration, irrespective of the apparent rhythm.[40]
- Amyloidosis: part of the 5-5-5 red-flag constellation that triggers the amyloid diagnostic pathway.[30]
- Predicts post-operative and post-ablation atrial fibrillation, and ablation success — useful for counselling rather than for a decision rule.
Next step
- Next: measure LA reservoir and contractile strain, and LA volume index — the modern, better-validated description of atrial function.[2]
- Then: ambulatory rhythm monitoring if a′ is low with a dilated atrium in sinus rhythm.
- Then: if the walls are thick, take the amyloid pathway; if the atrium is large and fibrotic, review the rhythm-control strategy and stroke prophylaxis.
Drugs
- Restored by successful cardioversion or ablation — but only after atrial stunning resolves, over days to weeks.
- Improved indirectly by decongestion and by treating the ventricular disease that is loading the atrium.
- Reduced by anything that promotes atrial remodelling: uncontrolled hypertension, alcohol, untreated sleep apnoea, obesity.
- No drug targets atrial contractility directly.
Reversibility
Post-cardioversion stunning is fully reversible over days to weeks — the classic reversible cause. The compensatory rise in a′ of early diastolic dysfunction is reversible with treatment of the underlying hypertension or ischaemia. Atrial failure from fibrosis, amyloid infiltration or long-standing atrial fibrillation is essentially irreversible, and its irreversibility is one of the strongest arguments for early rhythm control and for early intervention in mitral valve disease.[30,40]