Morphological and functional characteristics of the left atrium (LA) play a key role in the pathogenesis of atrial fibrillation (AF), which represents a global health burden as the most common cardiac arrhythmia encountered in clinical practice. For patients with drug-refractory AF, catheter-ablation may aid in a) prolonged restoration of sinus rhythm, b) decreased in total arrhythmic burden, symptomatic improvement, and c) better quality of life. However, catheter-ablation may not have a durable effect for a significant number of patients despite repeated procedures. A variety of innovative procedural technologies aim to improve patient freedom from AF. Scientific progress in the identification of patient characteristics that suggest a favorable or poor likelihood of procedural success may enhance patient selection for catheter-ablation and optimize time utilization for the cardiac electrophysiologist.

Cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement (LGE) has been shown to be a promising, non-invasive tool for the measurement of LA fibrosis, which predicts the recurrence of AF after catheter-ablation.^, While this tissue characterization of the LA represents a promising technology for patients with AF in whom catheter-ablation is being considered, it remains mostly these days at expert centers, has labor-intensive post-processing and necessitates the use of gadolinium contrast, which may exclude patients who have advanced kidney disease or allergic reactions to gadolinium. Functional assessment with intra-atrial dyssynchrony utilizing tissue-tracking represents an elegant technique to characterize LA mechanics that does not require gadolinium contrast or significant post-processing and was recently shown to correlate with the recurrence of AF after catheter-ablation.

[…]

With the advent of cardiac resynchronization therapy (CRT), and the awareness of the impairment of ventricular systolic function caused by intraventricular conduction disorders, especially left bundle branch block, after more than 50 years of routine use, conventional right univentricular artificial cardiac pacing, particularly in its classical site – the apical region – is now being questioned. In fact, conventional right univentricular pacing usually generates a large QRS (often greater than 150 ms), with electrocardiographic pattern of left bundle branch block – more significant signs for the diagnosis of ventricular dyssynchrony that may require CRT.

Some studies have shown impairment of right univentricular pacing in patients with pacemakers compared to normal ventricular activation,^– which prompted the development of algorithms of minimal ventricular pacing, favoring exclusive atrial pacing in currently available dual-chamber pacemakers, which have shown some benefits. However, when the reestablishment of heart rate requires ventricular pacing (in cases of AV blocks), these algorithms cannot be used. Other studies have shown deterioration of ventricular systolic function after initiation of right univentricular pacing.^, In order to minimize any impairment of right univentricular pacing in cases where it is necessary, multiple pacing sites have been tried: (outflow tract, mid-septal, inferior-septal, etc.) and, although no further evidence has been achieved, today, mid-septal pacing is the most commonly method in conventional pacemaker implants, to the detriment of apical pacing.

[…]