The normal P-R interval in infants and children

Accelerated atrial pacing reduces left-heart filling pressure: a combined clinical-computational study

BACKGROUND AND AIMS

Accelerated atrial pacing offers potential benefits for patients with heart failure with preserved ejection fraction (HFpEF) and atrial fibrillation (AF), compared with standard lower-rate pacing. The study investigates the relationship between atrial pacing rate and left-heart filling pressure.

METHODS

Seventy-five consecutive patients undergoing catheter ablation for AF underwent assessment of mean left atrial pressure (mLAP) and atrioventricular (AV) conduction delay (PR interval) in sinus rhythm and accelerated atrial pacing with 10 bpm increments up to Wenckebach block. Computer simulations (CircAdapt) of a virtual HFpEF cohort complemented clinical observations and hypothesized the modulating effects of AV coupling and atrial (dys)function.

RESULTS

In the study cohort, 49(65%) patients had a high HFpEF likelihood (H2FPEF ≥ 5.0), and 28(37%) an elevated mLAP ≥ 15 mmHg at sinus rhythm. Optimal pacing rates of 100 [70-110]bpm (median [IQR]) significantly reduced mLAP from 12.8 [10.0-17.4]mmHg in sinus rhythm (55 [52-61]bpm) to 10.4 [7.8-14.8]mmHg (P < .001). Conversely, higher pacing rates (130 [110-140]bpm) significantly increased mLAP to 14.7 [11.0-17.8]mmHg (P < .05). PR interval and, hence, AV conduction delay prolonged incrementally with increasing pacing rates. Simulations corroborated these clinical findings, showing mLAP reduction at a moderately increased pacing rate and a subsequent increase at higher rates. Moreover, simulations suggested that mLAP reduction is optimized when AV conduction delay shortens with increasing rate.

CONCLUSIONS

Accelerated pacing acutely reduces left-heart filling pressure in patients undergoing AF catheter ablation and computer simulations with HFpEF features, suggesting it as a potential therapeutic strategy to alleviate congestion symptoms. Virtual HFpEF patient cohorts hypothesize that AV sequential pacing may further optimize this therapy's beneficial effects.

Paediatric/young versus adult patients with long QT syndrome

INTRODUCTION

Long QT syndrome (LQTS) is a less prevalent cardiac ion channelopathy than Brugada syndrome in Asia. The present study compared the outcomes between paediatric/young and adult LQTS patients.

METHODS

This was a population-based retrospective cohort study of consecutive patients diagnosed with LQTS attending public hospitals in Hong Kong. The primary outcome was spontaneous ventricular tachycardia/ventricular fibrillation (VT/VF).

RESULTS

A total of 142 LQTS (mean onset age=27±23 years old) were included. Arrhythmias other than VT/VF (HR 4.67, 95% CI (1.53 to 14.3), p=0.007), initial VT/VF (HR=3.25 (95% CI 1.29 to 8.16), p=0.012) and Schwartz score (HR=1.90 (95% CI 1.11 to 3.26), p=0.020) were predictive of the primary outcome for the overall cohort, while arrhythmias other than VT/VF (HR=5.41 (95% CI 1.36 to 21.4), p=0.016) and Schwartz score (HR=4.67 (95% CI 1.48 to 14.7), p=0.009) were predictive for the adult subgroup (>25 years old; n=58). A random survival forest model identified initial VT/VF, Schwartz score, initial QTc interval, family history of LQTS, initially asymptomatic and arrhythmias other than VT/VF as the most important variables for risk prediction.

CONCLUSION

Clinical and ECG presentation varies between the paediatric/young and adult LQTS population. Machine learning models achieved more accurate VT/VF prediction.

Ventricular Tachyarrhythmia Risk in Paediatric/Young vs. Adult Brugada Syndrome Patients: A Territory-Wide Study

Introduction: Brugada syndrome (BrS) is a cardiac ion channelopathy with a higher prevalence in Asia compared to the Western populations. The present study compared the differences in clinical and electrocardiographic (ECG) presentation between paediatric/young (≤25 years old) and adult (>25 years) BrS patients. Method: This was a territory-wide retrospective cohort study of consecutive BrS patients presenting to public hospitals in Hong Kong. The primary outcome was spontaneous ventricular tachycardia/ventricular fibrillation (VT/VF). Results: The cohort consists of 550 consecutive patients (median age of initial presentation = 51 ± 23 years; female = 7.3%; follow-up period = 83 ± 80 months), divided into adult (n = 505, mean age of initial presentation = 52 ± 19 years; female = 6.7%; mean follow-up period = 83 ± 80 months) and paediatric/young subgroups (n = 45, mean age of initial presentation = 21 ± 5 years, female = 13.3%, mean follow-up period = 73 ± 83 months). The mean annual VT/VF incidence rate were 17 and 25 cases per 1,000 patient-year, respectively. Multivariate analysis showed that initial presentation of type 1 pattern (HR = 1.80, 95% CI = [1.02, 3.15], p = 0.041), initial asymptomatic presentation (HR = 0.26, 95% CI = [0.07, 0.94], p = 0.040) and increased P-wave axis (HR = 0.98, 95% CI = [0.96, 1.00], p = 0.036) were significant predictors of VT/VF for the adult subgroup. Only initial presentation of VT/VF was predictive (HR = 29.30, 95% CI = [1.75, 492.00], p = 0.019) in the paediatric/young subgroup. Conclusion: Clinical and ECG presentation of BrS vary between the paediatric/young and adult population in BrS. Risk stratification and management strategies for younger patients should take into consideration and adopt an individualised approach.

R-wave synchronised atrial pacing in pediatric patients with postoperative junctional ectopic tachycardia: the atrioventricular interval investigated by computational analysis and clinical evaluation

Background

R-wave synchronised atrial pacing is an effective temporary pacing therapy in infants with postoperative junctional ectopic tachycardia. In the technique currently used, adverse short or long intervals between atrial pacing and ventricular sensing (AP–VS) may be observed during routine clinical practice.

Objectives

The aim of the study was to analyse outcomes of R-wave synchronised atrial pacing and the relationship between maximum tracking rates and AP–VS intervals.

Methods

Calculated AP–VS intervals were compared with those predicted by experienced pediatric cardiologist.

Results

A maximum tracking rate (MTR) set 10 bpm higher than the heart rate (HR) may result in undesirable short AP–VS intervals (minimum 83 ms). A MTR set 20 bpm above the HR is the hemodynamically better choice (minimum 96 ms). Effects of either setting on the AP–VS interval could not be predicted by experienced observers. In our newly proposed technique the AP–VS interval approaches 95 ms for HR > 210 bpm and 130 ms for HR < 130 bpm. The progression is linear and decreases strictly (− 0.4 ms/bpm) between the two extreme levels.

Conclusions

Adjusting the AP–VS interval in the currently used technique is complex and may imply unfavorable pacemaker settings. A new pacemaker design is advisable to allow direct control of the AP–VS interval.

Drug-induced brugada syndrome in children: clinical features, device-based management, and long-term follow-up

OBJECTIVES

The goal of this study was to investigate the clinical features, management, and long-term follow-up of children with drug-induced Brugada syndrome (BS).

BACKGROUND

Patients with BS <12 years of age with a spontaneous type I electrocardiogram have a higher risk of arrhythmic events. Data on drug-induced BS in patients <12 years of age are lacking.

METHODS

Among 505 patients with ajmaline-induced BS, subjects ≤12 years of age at the time of diagnosis were considered as children and eligible for this study.

RESULTS

Forty children (60% male; age 8 ± 2.8 years) were included. Twenty-four children (60%) had a family history of sudden death. Two (5%) had a previous episode of aborted sudden death, and 8 (20%) had syncope. Children experienced more frequent episodes of sinus node dysfunction (SND) compared with older subjects (7.5% vs. 1.5%; p = 0.04) and had a comparable incidence of atrial tachyarrhythmias. Children more frequently experienced episodes of ajmaline-induced sustained ventricular arrhythmias (VAs) compared with older patients (10.0% vs. 1.3%; p = 0.005). Twelve children (30%) received an implantable cardioverter-defibrillator (ICD). After a mean follow-up time of 83 ± 51 months, none of the children died suddenly. Spontaneous sustained VAs were documented in 1 child (2%). Among children with ICD, 1 (8%) experienced an appropriate shock, 4 (33%) had inappropriate ICD shocks, and 4 (33%) experienced device-related complications.

CONCLUSIONS

Drug-induced BS is associated with atrial arrhythmias and SND. Children are at higher risk of ajmaline-induced VAs. The rate of device-related complications, leading to lead replacement or inappropriate shocks, is considerable and even higher than with appropriate interventions. Based on these findings, the optimal management of BS in childhood should remain individualized, taking into consideration the patient's clinical history and family's wishes.

Electrocardiographic effects of dexmedetomidine in patients with congenital heart disease

OBJECTIVE

Assessment of electrocardiographic (ECG) effects of dexmedetomidine.

DESIGN

Prospective observational study including children 0-17 years of age with congenital heart disease (CHD) and children following cardiothoracic surgery. Patients who did not receive dexmedetomidine were used as a control group. All patients had two ECGs: one baseline, pre-dexmedetomidine (T1) and one during dexmedetomidine infusion (T2).

MEASUREMENTS AND RESULTS

Fifty-one patients, median age of 0.5 years (IQR = 3.4), and 25 patients, age 0.25 (IQR = 2.9), were included in the dexmedetomidine and control groups, respectively. Forty received a dexmedetomidine-loading dose of 1 microg/kg (IQR = 0.5). At T2, the dexmedetomidine infusion was 1 microg/kg/h (IQR = 0.5). In the dexmedetomidine group, heart rate (HR) decreased from 140 +/- 22 to 115 +/- 23 (P < 0.001); PR, PRc and PR index changed from 115 +/- 28 to 122 +/- 29 ms (P = 0.01), 174 +/- 38 to 167 +/- 35 ms (P = 0.07) and 15,882 +/- 3,565 to 13,792 +/- 3,311 (P < 0.001), respectively. QRS decreased from 84 +/- 21 to 80 +/- 21 ms (P = 0.02), and QTc had no change (433 +/- 47 to 435 +/- 36 ms). When compared to the control group, none of the ECG intervals had any difference other than a trend towards lower HR (P = 0.08). Neonates and infants had a bigger drop in the HR compared to older children (P < 0.001), while other parameters were similar. At T2 none of the dexmedetomidine group patients had atrioventricular block or other arrhythmia. Four patients in the control group had accelerated junctional rhythm.

CONCLUSIONS

Use of dexmedetomidine in patients with CHD and patients following cardiothoracic surgery is not associated with any significant ECG interval abnormalities other than a trend towards lower HR.

Electrocardiographic changes after recovery from measles

Children with measles seen at our hospital had an initial electrocardiogram (ECG) and a repeat after 3 months. The patients were aged 5 months to 8 years (mean 19 months). The ECG changes observed after clinical recovery included T-wave inversion in eight patients (16%), flattening in eight patients (16%), prolonged PR interval in six (12%), prolonged Q-Tc in three (6%) and low QRS amplitude in four (8%). At least one ECG change was present in 18 patients (36%) after recovery, 14 of these were due to persistence of the changes noted during measles. The implication of above findings and the need for a longer-term follow-up study are discussed.

Electrocardiographic changes in measles

Electrocardiograms (ECGs) were recorded in 100 Nigerian children with measles admitted to our paediatric wards or treated on an out-patient basis. The patients were aged 5 months-8 years (mean, 19 months) and the male:female ratio was 1.3:1. Similar recordings were obtained in 100 age- and sex-matched controls. The electrocardiographic changes observed include T wave inversion in 28 patients and prolonged P-R interval in 22. Other changes are prolonged Q-Tc (13 patients), low QRS amplitude (13 patients), abnormal QRS axes in the frontal plane (5 patients) and T wave flattening (4 patients). A statistically significant difference between patients and controls with respect to the above changes was demonstrated in T wave inversion and prolonged P-R interval--the latter in the 5 months-1 year age group. Hence, 35 patients had at least one statistically significant ECG change, giving a prevalence rate of 35%. The implications of the above findings are discussed and the need to intensify efforts aimed at immunizing all children against measles is stressed.

Electrophysiologic studies in patients with ventricular inversion and "corrected transposition"

We evaluated the intracardiac conduction intervals using His bundle recordings in 40 patients with ventricular inversion and 1-transposition of the great arteries. Twenty-nine subjects had 1:1 atrioventricular (AV) conduction. In 15 of those with normal PR intervals and QRS durations, the conduction intervals were not different from those of subjects with normal hearts. In the 14 patients with first-degree AV block, the block was located between the sinus node and AV node in four, between the low right atrium and bundle of His in seven, and below the common bundle of His in four. In 11 subjects with complete AV block, the stie of block was above the site of the His potential in four, below in two and within the His bundle in one. In four patients we could not record a His potential and thus could not localize the site of block. Complete block below the His recording site was associated with syncope in one patient and sudden death in another. His bundle recording is a safe technique for studying the conduction system in children with ventricular inversion and 1-transposition of the great arteries.

Intracardiac electrography in endocardial cushion defects

Conduction of the sino-atrial impulse from the high right atrium to the ventricles was studied by intracardiac electrography in 21 unoperated patients, age 3 months to 11 years, with endocardial cushion defects (ECD). The high right atrium-to-low right atrium conduction time was prolonged in 15 of 18 subjects (mean 57 +/- 20 msec). The low right atrium-to-His bundle conduction time (LRA-H) was normal in 16 of 17 subjects (mean 82 +/- 30 msec), prolonged in one. The His-to-ventricle conduction time (H-V) was normal in 16 of 17 subjects (mean 37 +/- 8 msec), equivocally short in one. Nine patients with ECD, age 3 to 21 years, were studied postoperatively. One had an acquired complete atrioventricular block in the His bundle. Two had prolonged LRA-H and two prolonged LRA-H and two prolonged H-V. The surface ECG failed to identify accurately either prolonged atrioventricular conduction or the site of prolongation.

Assessment of cardiovascular side effects of therapeutic doses of tricyclic anti-depressant drugs

An assessment of the side effects of therapeutic doses of tricyclic anti-depressant drugs was attempted in 32 patients with depressive illness. The patients studied had no evidence of clinical heart disease or hypertension and were not receiving any other drugs. Moderate increase in heart rate and mild prolongation of atrioventricular conduction occurred. No significant effect on the corrected QT interval or blood pressure was found. There was no correlation between the increased heart rate, prolongation of the atrioventricular conduction time (PR interval) and plasma nortriptyline levels measured in 20 out of 32 patients.

Electrocardiographic findings in Iranian children with severe chronic anemia. Observations in iron deficiency, thalassemia major, and miscellaneous other anemic states

The electrocardiograms of 60 children with severe chronic anemia of vari ous etiologies are reviewed. Twenty-five had repeated electrocardiograms during or after treatment. Abnormal electrocardiograms consistent with mild ischemia secondary to impaired oxygen delivery were found in 11 patients, ten of whom belonged to a low socioeconomic group. The elec trocardiographic changes were variable, relatively infrequent, and mild. They improved or disappeared in eight of the 11 patients, after treatment.

His bundle electrogram in children. Statistical correlation of the atrioventricular conduction times in children with their age and heart rate

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Atrioventricular conduction in acute rheumatic fever

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Electrocardiographic correlation of anatomical and haemodynamic data in ostium primum atrial septal defects

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Congenital heart disease with arrhythmia in a family

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Pulmonary Stenosis

The electrocardiographic, vectorcardiographic, and right heart catheterization data of 100 patients with isolated or complicated pulmonary stenosis were analyzed.

All but two patients had normal sinus rhythm. One patient, age 62, had atrial fibrillation; the other, age 8, had the Wolff-Parkin-son-White syndrome.

In isolated pulmonary stenosis, P-wave enlargement was far more frequently seen in those patients with right ventricular systolic pressures above 100 mm. Hg as compared to those with pressures less than 100 mm. Hg. This relationship was not observed in patients with complicated pulmonary stenosis.

The incidence of rsR' in V 1 , QRS widening, and the vectorcardiographic evidence of conduction delay was significantly lower in pulmonary stenosis, isolated or complicated, when compared to atrial septal defects alone. There was one instance of terminal conduction delay of the right bundle-branch block type and one diffuse slowing of the QRS sÊ loop in the present series.

The correlation between the amplitude of the R wave in V 1 and right ventricular systolic pressure was better in the group of isolated pulmonary stenosis as compared to the groups complicated by interatrial communications or ventricular septal defects.

The average right ventricular systolic pressures in patients with type 3 right ventricular hypertrophy was significantly higher than those with either type 1 or type 2 right ventricular hypertrophy on the basis of vectorcardiographic criteria discussed. In the presence of pulmonary stenosis, the electrocardiographic and vectorcardiographic evidence of left ventricular hypertrophy or combined ventricular hypertrophy suggests coexisting lesions such as ventricular septal defect with left-to-right shunts. However, it was not possible to differentiate between isolated pulmonary stenosis and pulmonary stenosis complicated by interatrial communication by either electrocardiograms or vectorcardiograms.

The vectorcardiographic features of combined ventricular hypertrophy are discussed.

Atrial Septal Defect

The results of the electrocardiographic, vectorcardiographic, and hemodynamic studies of 70 patients with atrial septal defects are analyzed. Serial electrocardiograms and vectorcardiograms were obtained in 16 patients following surgery.

The incidence of the rSR' and rSr' patterns in the right precordial leads was 60 per cent.

To a limited extent, the configuration of the electrocardiogram is related to right ventricular pressure and PBF/SBF. However, no quantitative assessment could be made by determining the magnitude of R or R' in lead V 1 .

The vectorcardiogram is an important adjunct to the electrocardiogram in detecting right ventricular hypertrophy. As the right ventricular pressure increases, the QRS sÊ loop tends to shift more to the right and anteriorly.

Although it can be generally stated that the rSR' configuration in atrial septal defects is usually due to right ventricular hypertrophy, this configuration is also due to terminal conduction delay or terminal conduction delay associated with right ventricular hypertrophy in a significant number of instances.

The vectorcardiogram is useful in detecting terminal conduction delay in patients with rSR' in the right precordial leads. It was also of value in determining the presence of right ventricular hypertrophy in combination with terminal conduction delay.

The evidence of terminal conduction delay may disappear after successful repair of atrial septal defects.

Left axis deviation, superior displacement, and counterclockwise direction of inscription of the QRS sÊ loop in the frontal plane are valuable signs for differentiating ostium primum defects from ostium secundum defects. Each of the eight proved instances of ostium primum defects had these typical features.