The Role of Advanced Echocardiography in Predicting Atrioventricular Synchrony in Leadless Pacemakers: A3, a Still Underrecognized Parameter

Introduction Leadless cardiac pacemakers represent an alternative to conventional transvenous pacemakers and are capable of providing atrioventricular synchrony. The accelerometer of the Micra–AV leadless device detects mechanical atrial activity and uses this information to deliver ventricular pacing with AV synchrony. Considerable efforts have been made to identify predictors of adequate A4 signal amplitude, which determines the ability of the Micra–AV to maintain AV synchrony. The MARVEL 2 study demonstrated that A4 wave amplitude is crucial to ensure a high percentage of AVS. In recent years, in addition to traditional echocardiographic parameters, left atrial function has been investigated using a novel functional parameter, left atrial strain (LAs). Objectives This study aimed to evaluate the correlations between echocardiographic parameters and A3–A4 signal amplitudes in patients implanted with a Micra–AV pacemaker. Methods Eight patients (75 ± 13 years; 5 women) implanted with a Micra–AV device underwent comprehensive echocardiographic evaluation focused on left atrial assessment. Morphological and functional parameters were analyzed using both 2D and 4D techniques, with dedicated advanced echocardiography software (GE Vivid E95 – AFI LA, 4D Auto LAQ). After implantation, all patients underwent complete device interrogation to assess A3 and A4 wave amplitudes across all sensing vectors. Results Our data suggest that the A3 parameter, together with A4, may play a role in identifying patients with a high likelihood of achieving adequate AV synchrony following Micra–AV implantation. A3 amplitude showed an inverse correlation with mean E/e′ ratio, indexed left atrial volume assessed by 2D echocardiography, and left atrial volume measured by 4D echocardiography (p ‹ 0.05). A direct correlation was observed between A3 amplitude and left atrial reservoir strain, calculated using both 2D and 4D software, whereas an inverse correlation was found between A3 amplitude and left atrial contraction strain (in both 2D and 4D). Finally, the inverse correlation between A4 amplitude and left atrial contraction strain—previously reported by our group—was further confirmed. Conclusions Appropriate patient selection is crucial to achieve favorable clinical outcomes. In this context, echocardiographic parameters appear promising for identifying patients most likely to benefit from leadless pacemaker implantation with optimal atrioventricular synchrony.