An one-year old girl presented a persistent tachycardia during a routine visit at the local pediatrician and was immediately transferred to KUNO university hospital. There had been a benign febrile infection 1 week prior to admission. Personal and family history was non-contributory to the tachycardia. Six months before, the previous check at the pediatrician had been uneventful. On admission she had mild signs of heart failure with delayed capillary refill time (3 s) and an enlarged liver. She had a tachycardia with 240 beats/min. Echocardiography showed structural normal anatomy with moderately reduced contractility while tachycardia. Laboratory studies including blood count, inflammatory biomarkers and cardiac troponin were normal but NT-proBNP was significantly elevated (maximum 2,685 pg/ml, lab reference <130 pg/ml).\nThe initial 12-lead electrocardiogram (ECG) showed a regular, sustained small-QRS-complex-tachycardia (mean heart-rate 240 beats/min). The tachycardia demonstrated a 1:1 atrio-ventricular conduction (P-P cycle length 250 ms) with a monomorphic P-wave configuration characterized by a superior axis (P-vector of −60°) and sinus tachycardia was therefore not possible. RP interval was significantly longer than PR—interval (i.e., long-RP-tachycardia) and we thought about a permanent orthodromic supraventricular tachycardia first (such as permanent junctional reciprocating tachycardia) () and gave Adenosine intravenously. This did not stop atrial tachycardia and ruled out a reentry-tachycardia dependent on the AV-node. We therefore hypothesized a focal ectopic atrial tachycardia. Infusion of Flecainide (1 mg/kg/30 min) did not affect the atrial rate or atrioventricular conduction. Synchronized electric cardioversion with 0.5 and 1 J/kg was performed due to signs of hemodynamic instability but this just interrupted the tachycardia for seconds. Medical cardioversion and rate control were attempted starting Amiodarone with a bolus. After 30 min the girl developed a second-degree AV-block (type Wenckebach) with ongoing QRS-amplitude alternans, eventually resulting in a bradycardia with 70 beats/min. Amiodarone infusion was stopped and the AV-block resolved. While persisting EAT, Esmolol infusion was started and slowly increased to a maximum rate of 75 mcg/kg/min. This lowered the atrial tachycardia rate to 160 beats/min without affecting the blood pressure. Ivabradine was started with a dose of 0.25 mg (0.025 mg/kg) every 12 h and increased to 0.5 mg (0.05 mg/kg) per dose on the second day. This led to a persistent heart rate reduction to a physiologic level (80–100 beats/min at rest) with alternating periods of restored sinus rhythm and ectopic atrial rhythm. Subsequent ECG recordings showed sinus rhythms with regular AV conduction and no abnormalities of de- or repolarization (). No adverse effects attributable to Ivabradine were registered. After stabilization Esmolol infusion was discontinued and the beta-blocker therapy was switched to Metoprolol administered orally (1 mg/kg/d). Holter evaluation before discharge (1 week after admission) showed sinus rhythm with short times of ectopic atrial rhythm and a regular diurnal pattern and heart rate.\nIn the follow up visits 2 and 10 weeks later echocardiography showed normal left-ventricular function and dimension. The 12-lead-ECG and Holter evaluation showed alternating ectopic atrial and sinus rhythm with a physiologic diurnal heart rate spectrum and a regular response to physical activity (). Combination of Metoprolol and Ivabradine did not cause bradycardia and no other side effects attributable to medication were noticed.
A 60-day-old male weighing 5 kg was referred for cardiac evaluation in view of suspicion of dilated cardiomyopathy. Physical examination revealed tachycardia and tachypnea with decreased pulses and peripheral perfusion. Chest radiograph showed a cardiothoracic ratio of 70%. The 12-lead electrocardiogram (ECG) showed a regular narrow QRS tachycardia with a rapid ventricular rate of 250 bpm with a long RP interval and abnormal peaked P-wave morphology. Differential diagnosis of ectopic atrial tachycardia (EAT) and permanent junctional reciprocating tachycardia were considered. The P waves were negative in V1 and aVR and positive in leads II, III, and aVF suggestive of EAT of superolateral crista terminalis origin []. Echocardiography showed severe left ventricular (LV) dysfunction with an ejection fraction (EF) of 17% with significant LV dilatation (LVIDd 3.58 cm [Z score + 5.60]).The coronary artery origins and aortic arch were normal. Serum electrolytes and renal function were normal. Severe acute respiratory syndrome coronavirus 2 polymerase chain reaction was negative and antibodies levels were normal. All serum inflammatory/cardiac markers were normal (C-reactive protein, ferritin, troponin I, and CK MB). The NT pro-BNP level was grossly elevated (31,500 pg/ml [normal <125]). Adenosine given during the tachycardia resulted in transient slowing of the heart rate from 250 to 187 bpm followed by reappearance of the tachycardia [Figure and ]. The tachycardia persisted despite giving three doses of bolus intravenous metoprolol and metoprolol infusion. The infant was hemodynamically unstable with poor perfusion, decreased urine output, and low blood pressure (mean 20 mmHg). Hence, synchronized cardioversion with 5J was given with no benefit. Intravenous digoxin 15 μg/kg given over 30 min resulted in decrease in heart rate (107 bpm) followed by severe bradycardia (65 bpm) and cardiac arrest. ECG during the time of bradycardia showed multiple P waves with periods of flat isoelectric line confirming EAT []. After cardiopulmonary resuscitation (0.4 ml of 1 in 10,000 dilution adrenaline single dose) and mechanical ventilation, heart rate picked up and tachyarrhythmia persisted. Furosemide (1 mg/kg/day), milrinone (0.5 mcg/kg/min), and amiodarone infusion (25 mcg/kg/min for 4 h followed by 15 mcg/kg/min for 24 h) were started in view of severe LV dysfunction and persistent tachyarrhythmia. There was no improvement in the hemodynamics and tachycardia persisted even after continuous metoprolol and amiodarone infusion for 2 h. Hence, enteral sotalol (1 mg/kg) was started. Despite all the above pharmacological interventions for 10 h since admission, the tachyarrhythmia persisted and the mean blood pressure was persistently low with poor urine output. Repeat synchronized cardioversion with 5J resulted in conversion of the rhythm to ventricular fibrillation. Unsynchronized cardioversion 10J thrice resulted in termination of VF and the EAT restarted. The child remained with a poor urine output (<0.3 ml/kg/hr) and hypotension, with mean blood pressure <25 mmHg for >6 h.\nConsidering the hemodynamic instability and persistence of tachyarrhythmia despite using most of the conventional antiarrhythmic drugs, we administered enteral ivabradine. Within 45 min of the initiation of ivabradine (0.15 mg/kg), the heart rate slowed down to 190 bpm with significant improvement in the hemodynamics and perfusion (mean BP 40 mmHg). Metoprolol infusion was stopped and amiodarone infusion was continued for 24 h and then stopped. The heart rhythm became sinus after 12 h of enteral ivabradine and digoxin []. The LVEF improved from 17% to 33% after 24 h of ivabradine. The LVIDd started decreasing (LVIDd Z score + 4.26). He was extubated after 48 h of ventilation and put on high flow nasal cannula in view of respiratory distress and moderate LV dysfunction. He had one transient episode of tachyarrhythmia (250 bpm) which lasted for 2 min and terminated by itself. Hence, oral propranolol was added. Milrinone infusion was tapered and stopped with subsequent addition of enalapril. The LV function and LVIDd recovered completely (EF 58%; LVIDd 2 cm (Z score-0.22) after 7 days of achievement of sinus rhythm. The timeline of events which happened during the first 24 h was shown in . He was discharged after 10 days of hospitalization on oral ivabradine (0.15 mg/kg twice a day), digoxin (5 μg/kg twice a day), and propranolol (0.5 mg/kg twice a day). The efficacy of the treatment was monitored by patch ambulatory ECG (aECG) recorder for 7 days after discharge. The aECG recordings were predominant in sinus rhythm with short episodes of ectopic atrial rhythm. The average heart rate was 132 bpm (58–163). At follow-up after 3 months, ECG was in sinus rhythm and the LV function (EF 70%) is normal. The developmental milestones are appropriate for the age.