Elsevier

Journal of Electrocardiology

Volume 47, Issue 3, May–June 2014, Pages 374-382
Journal of Electrocardiology

Handheld ECG in analysis of arrhythmia and heart rate variability in children with Fontan circulation

https://doi.org/10.1016/j.jelectrocard.2014.02.006Get rights and content

Abstract

Background

Our aim was to evaluate the intermittent use of a handheld ECG system for detecting silent arrhythmias and cardiac autonomic dysfunction in children with univentricular hearts.

Methods

Twenty-seven patients performed intermittent ECG recordings with handheld devices during a 14-day period. A manual arrhythmia analysis was performed. We analyzed heart rate variability (HRV) using scatter plots of all interbeat intervals (Poincaré plots) from the total observation period. Reference values of HRV indices were determined from Holter-ECGs in 41 healthy children.

Results

One asymptomatic patient had frequent ventricular extra systoles. Another patient had episodes with supraventricular tachycardia (with concomitant palpitations). Seven patients showed reduced HRV.

Conclusions

Asymptomatic arrhythmia was detected in one patient. The proposed method for pooling of intermittent recordings from handheld or similar devices may be used for detection of arrhythmias as well as for cardiac autonomic dysfunction.

Introduction

In Fontan surgery, the systemic venous blood return is redirected so the blood goes to the pulmonary arteries instead of being pumped through the ventricle. Since the introduction of this surgery [1], the technique has been modified and long-term results have steadily improved. However, arrhythmias and conduction abnormalities remain frequent complications. Known risk factors for arrhythmia in Fontan patients include older age at surgery, duration of follow-up after surgery, and worse NYHA (New York Heart Association) class symptoms. In addition, it has been suggested that autonomic nervous control plays an important role in the development of arrhythmias and that impaired cardiac autonomous nervous activity could be explained by surgery-related damage to cardiac autonomic nerves or their blood vessels. In contemporary materials with up to 15 years of follow-up time, the frequency of arrhythmia, mostly atrial re-entrant tachycardia, after Fontan operation is 4%–11% [2], [3].

Due to significant hemodynamic abnormalities, a Fontan patient is more sensitive to recurrent atrial tachycardia. Persistent tachycardia is poorly tolerated in patients with single ventricle physiology and congestive heart failure may develop within 12–36 h [4], [5].

In Fontan patients, the onset of the arrhythmia can be hard to recognize since symptoms may be vague; symptoms include fatigue, abdominal pain, nausea, edema, presyncope/syncope and respiratory symptoms. The patient may not even experience any symptoms, i.e., present silent arrhythmias. In a recent study, Czosek et al. evaluated 24-h ECG monitoring in patients with congenital heart disease, including 84 recordings from 31 Fontan patients in the age group < 18 years. The pediatric Fontan patients were asymptomatic in the majority of the recordings (79%), but arrhythmia findings led to a change in management in 2% [6].

Arrhythmias tend to occur intermittently and may be hard to detect on conventional Holter recordings [7], [8]. However, with the recent development of handheld devices to monitor ECG, home monitoring could be a viable option for detecting arrhythmias, allowing for both symptom-related recordings and multiple shorter recordings of ECG over a longer period of time than possible with a Holter monitor. One of the first clinical applications for such a device was for detection of recurrent atrial fibrillation [9]. This device easily recognizes episodes of atrial fibrillation and can also detect other types of heart rate disturbances. Doliwa et al. compared the hand-held-ECG 10 s registration for 30 days to a 24-h ECG recording in a screening for asymptomatic atrial fibrillation in a population that had suffered from ischemic stroke, and concluded that the hand-held-ECG system was significantly better than 24-h ECG [9]. However, as also pointed out by Czosek et al., systems for home monitoring need to be evaluated further in patients with congenital heart disease [6].

To find arrhythmias, patients are instructed to use the handheld ECG device both at fixed time points and when symptoms occur. The recordings are transmitted using a mobile phone connection, stored in a database and then reviewed manually. Considering that patients often perform a large number of short ECG recordings (10–30 s), the manual ECG analysis can be time consuming. Therefore, a tool is needed for efficient presentation of the heart rhythm that can assist the operator to detect signs of cardiac arrhythmia. The approach undertaken in our study is to use a graphical tool – Poincaré plot – to summarize the beat-to-beat fluctuations in heart rate occurring in all recordings in a single diagram. In these plots, the previous interbeat interval is plotted against the next one, which results in characteristic patterns for different types of normal and abnormal heart rate patterns. Poincaré plots are often based on data from 24-h ECG recordings, but they have also been applied to shorter recordings. In addition to being useful for detecting cardiac arrhythmia, they can be used to detect cardiac autonomic dysfunction [10], [11].

In adults, reduced heart rate variability (HRV) implies a shift of the sympathovagal balance toward sympathetic predominance, and reduced vagal tone has been shown to precede onset of arrhythmia [12]. Furthermore, impaired autonomic nervous activity is associated with an increased risk of sudden cardiac death in patients with congenital heart disease [13]. We, and others have earlier shown that HRV is reduced in patients with Fontan circulation [14], [15] and that HRV appears to be successively reduced over time after total cavopulmonary connection (TCPC) surgery [15]. Interestingly, in pediatric Fontan patients HRV changes can also be associated with and even precede development of arrhythmia [16]. Thus, identification of altered HRV in Fontan patients may indicate early signs of arrhythmia [16]. A potential limitation is that handheld ECG monitoring only can be performed during short-term intervals, whereas HRV parameters normally are determined over a 5-min or a 24-h period. However, the use of very short HRV recordings (10 s) has been evaluated in previous studies [17], [18]. In this study we propose a strategy where HRV is analyzed based on pooled data from all recordings that one subject performed with the handheld device.

The aim was to evaluate the applicability of intermittent ECG recordings in a pediatric Fontan population. Our hypothesis was that silent arrhythmias and impaired autonomic function can be detected in Fontan patients using handheld ECG monitoring.

Section snippets

Materials and methods

Written informed parent consent was obtained and the study was approved by the Regional Ethical Review Board, Umea University, Sweden.

Results

Recordings were used from 27 patients, 10 girls and 17 boys, mean age 9.5 years (range 2.7–16.5) who underwent intermittent monitoring with a handheld ECG device.

Age at surgery with TCPC was 2.4 ± 0.9 years (range 1.1–3.9). Postoperative follow-up time was 7.1 years (range 0.4–15.4). Thirteen patients (48 %) had a dominant LV; 12 patients (45%) had a dominant RV; and 2 patients (7 %) had a non-defined morphology of their systemic ventricle. Eight patients had hypoplastic left heart syndrome, six

Discussion

This study evaluates the applicability of using a handheld ECG device for intermittent monitoring in a pediatric Fontan population. It also presents an innovative approach to quantifying and summarizing all the obtained 30-s recordings in a single plot, with applications in detection of arrhythmia and of abnormalities in cardiac autonomic function. Furthermore, to the best of our knowledge, this is the first study using a hand-held ambulatory ECG system to analyze HRV.

Conclusions

As we hypothesized, asymptomatic arrhythmia occurred during two weeks of intermittent ECG monitoring in patients with Fontan circulation, although we recorded fewer events than we expected. We also found reduced HRV in several subjects. Poincaré plot of pooled recordings is a useful tool in visualizing the abnormalities in heart rhythm. Thus, we conclude that intermittent handheld ECG recording can be a useful method for detection of arrhythmia as well as of cardiac autonomic dysfunction.

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  • Cited by (0)

    Sources of funding: Swedish Heart–Lung Foundation and Fundings according to Agreement on Medical Education and Research, Västerbotten County Council, Sweden

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