AT was regularly divided into focal and reentrant tachycardia according to the electrophysiological mechanism [7]. Its occurrence is linked to changes in atrial electrical characteristics, the presence of undifferentiated autonomic cells or reentry loops in the atrium, and respiratory illnesses [8]. However, the accurate diagnosis and classification of neonatal AT can be challenging because of its diverse clinical presentations and overlapping ECG characteristics. In this study we retrospectively analyzed the dynamic electrocardiographic and clinical data of 96 patients with new-onset AT at our hospital and compiled their LP features. We firstly summarized the morphological characteristics of the LPs derived from electrocardiographic monitoring and founded that they could be divided into 3 categories: multifocal, parasystole, and atrial premature beat-induced atrial tachycardia. Notably, this is the first LP analysis to include AT in a large sample of 96 newborns. In particular, we evaluated the clinical characteristics, treatment and outcomes of children and elucidated the difference of 3 kind of neonatal atrial tachycardia classified by the LP analysis.
The highest percentage of APB-ATs was detected in the present study. The ECG showed that the P-wave morphology of APB-AT was identical to that of single premature atrial tachycardia. Atrial activation starting rhythmically at a small focus contributes to the occurrence of APB-AT, which may mechanistically correspond to focal AT [9]. Furthermore, the majority of APB-AT cases were admitted to the NICU due to respiratory diseases, metabolic diseases, or infection, and structural heart disease is relatively uncommon compared with children with MAT. We discovered that the most common comorbidity in the APB-AT group was respiratory illness. When underlying disorders are treated without the use of antiarrhythmic medicines, the clinical course is typically benign, and some individuals are restored. Younger children generally respond to antiarrhythmic therapy [8, 10] and recurrent or persistent episodes can quickly result in tachycardia cardiomyopathy, heart failure, or even life-threatening conditions [2]. Therefore, patients with frequent episodes of tachycardia or severe signs of myocardial injury are treated with β-blockers or adenosine. Our data demonstrated a 76.6% success rate and no recurrence during the follow-up period, similar to a previous study that found a 72% spontaneous regression rate in children under 6 months of age following medication cardioversion [11].
The parasystolic rhythm was first reported decades ago [12]. When a secondary atrial pacemaker fires simultaneously with the sinoatrial node but is prevented from depolarizing by the sinus node because of an entry block, two simultaneous atrial rhythms that resemble atrial premature beats are created, which could jointly or alternately control the atrium, this condition is known as atrial parasystole. It has fusion beats, mathematically connected interectopic intervals, and variable coupling; however, it is difficult to detect using standard electrocardiography. The typical Lorenz plot, which has a pattern like a tricycle and is akin to the inverted "Y" shape of ventricular parasystole, is easy to spot on 24-hour Holter recordings [13]. Our data revealed that viral infections were more common than were anatomical cardiac problems in the APT group. In addition, this form of atrial tachycardia in newborns is associated with stable hemodynamics and is less prone to heart failure. Only symptomatic management of the underlying condition resulted in spontaneous recovery in the majority of cases (12 instances [63.2%]).
Antiarrhythmic medications are the primary line of therapy in neonates because their blood arteries have small diameters and radiofrequency ablation is challenging in this population [14]. However, the effectiveness and consequences of various varieties of AT categorized by LPs, on the other hand, were demonstrated to be unique. APB-ATs and APT are often associated with infectious illnesses, are easily controlled, and are less frequently associated with cardiac failure or myocardial injury. However, MAT is more difficult to perform.
Neonatal MAT is not rare, and some cases can be inherited from the fetus. Maternal hypertension and diabetes are risk factors for fetal MAT [15]. The development of MAT can be facilitated by abnormal shunting in congenital heart abnormalities and ion channel failure [16]. In our investigation, the MAT group also revealed greater comorbidities. Seventeen patients had structural abnormalities in the heart. In addition, more serious fundamental conditions such as pulmonary illnesses and electrolyte problems were detected. The results for newborns with MAT are generally good, with the documented exception of cases with structural heart abnormalities or persistent rapid ventricular rate [17]. Our results also revealed that the MAT group had a greater risk of heart failure and stayed in the hospital longer than the other two groups. Its management can be problematic owing to poor pharmaceutical response. Hence, increased focus has been placed on handling underlying diseases and symptomatic treatment. There were 14 instances of MAT that could not be properly controlled in the hospital; however, the basic underlying condition was treated, and the hemodynamics were stable. During the follow-up period, these patients were administered up to six different antiarrhythmic medications. Four patients were lost to follow-up, and six had therapeutic control of MAT at a median of 8.5 months. Radiofrequency catheter ablation was used in the remaining four cases, and proved to be effective.
Our single-center cohort was small, and the treatment strategy was exclusive. To address these limitations, future research will involve a larger number of patients from multi-centers. However, all cases were treated with the most consistent treatment principles, as they were assessed and managed by the same department throughout the study. there are also inherent limitations of the study owing to its retrospective design. Further randomized controlled study has been ongoing to address these limitations.