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.
A 2-year-6-month-old girl was transferred to our hospital from a primary care center for the management of tachyarrhythmia. Eight months prior to her presentation, she was found to have an increased heart rate (HR) of around 200 bpm on routine physical examination. At that time she was asymptomatic and her echocardiography was normal. Nevertheless, a week prior to her presentation to our center, an increased HR of 190 bpm was noted again on routine exam. Repeat echocardiography revealed LV dilatation along with a reduced LV systolic ejection fraction of 35%. ECG showed supraventricular tachycardia (SVT), namely atrial tachycardia. She failed a trial of adenosine and responded weakly to metoprolol. The patient was discharged on metoprolol 25 mg/day divided into two doses. She presented 2 days later to the same hospital. She had a HR of 250 bpm. She received two doses of adenosine, one dose of amiodarone and several doses of flecainide during her admission. However, no improvement was noted after 5 days of treatment, and also after direct current cardioversion. She was then transferred to our center for adequate rate control and appropriate investigation.\nUpon admission to our PICU, HR was 190 bpm. On examination, she was pale, tachypneic and hypoactive, but responsive to verbal stimulation. A third heart sound was noted on cardiac auscultation. Additionally, she had cool extremities and palpable hepatomegaly. Echocardiography was repeated, it showed worsened LV dilatation and severe LV systolic dysfunction (EF was around 20%), and moderate mitral regurgitation (see ). ECG revealed an atrial tachycardic rhythm. Patient was given adenosine. She received a second higher dose of adenosine and an infusion of amiodarone. She failed to respond adequately to these medications. Consequently, the patient was started on ivabradine at 0.15 mg/kg/day. An adequate response was noted few hours after the first dose of ivabradine. HR decreased to 90 bpm and she reverted to sinus rhythm. shows the patient's ECG pre- and post-ivabradine. The dose of ivabradine was adjusted to 0.033 mg/kg thrice daily. Adequate response was noted and the patient was discharged on ivabradine.\nOne month after the discharge, she presented to our clinic and was found to have a normocardic sinus rhythm on ECG, and an improved cardiac function on echocardiography (EF of 50%). In short, this is a case of SVT-induced DCM managed appropriately with ivabradine.