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 38-year-old European woman with type I diabetes mellitus and corrected hypothyroidism and negative family history of dysrhythmias or cardiomyopathies was first noted to have a persistent asymptomatic tachycardia ∼110–120 b.p.m. during the third trimester of her first pregnancy. The 12-lead electrocardiogram (ECG) at the time confirmed P-wave morphology consistent with a sinus tachycardia with normal intrinsic atrioventricular conduction and narrow QRS complex. Reversible causes were ruled out and the tachycardia was attributed to the pregnant state. After delivery of her first son, the tachycardia persisted postpartum over several months and she was referred to Cardiology for suspected inappropriate sinus tachycardia. Apart from the elevated heart rate the physical exam was normal. A transthoracic echocardiogram (TTE) 8 months after delivery demonstrated a dilated left ventricle (LV) with severely impaired function [ejection fraction (EF) 15%], presence of an apical thrombus and an interatrial shunt. A cardiac magnetic resonance imaging (MRI) confirmed the echocardiographic findings and additionally diagnosed an ischaemic scar in the apex () but coronaries were unobstructed on ECG-gated computed tomography coronary angiogram. A genetic screen within the 100 000 Genomes project did not reveal any abnormalities in the 84 genes associated with dilated cardiomyopathy known at the time. The main differential diagnosis was a late diagnosis of peripartum cardiomyopathy with secondary LV thrombus formation complicated by embolic myocardial infarction, or myocarditis and a paradoxical coronary embolic event facilitated by the interatrial defect. With optimal medical heart failure therapy and Warfarin the left ventricular function fully recovered, the left ventricular thrombus resolved completely, and heart rate normalized within 6 months. A persistent foramen ovale closure was performed after recovery of LV function and thrombus resolution based on the differential diagnosis of paradoxical embolism. Warfarin was ceased. An attempt to wean the heart failure medication resulted in progressive LV dilatation (as documented in a routine follow-up cardiac MRI) within 3 months after stopping her betablocker and angiotensin-converting enzyme-inhibitor (ACEI) and were therefore reinstituted. The patient remained asymptomatic throughout.\nThree years later the patient became pregnant with her second child, requiring suspension of ACEI therapy. Bisoprolol was continued and she was closely monitored with clinical and echo surveillance by the Pregnancy Heart Team. Towards the beginning of the third trimester, the patient noted palpitations and a repeated TTE found a mildly impaired left ventricular EF of 46% (compared to previously 57%) and a heart rate of 120 b.p.m. No overt clinical signs of heart failure were present. The 12-lead ECG () demonstrated a regular organized atrial rhythm with 1:1 conduction to the ventricles with discrete monomorphic P waves separated by isoelectric intervals with upright P waves in the inferior leads, negative in aVL and I, and biphasic negative–positive in V1–V2. The electrocardiographical features were consistent with a left-sided FAT with suspected origin from the superior mitral annulus using the Kistler algorithm. A further up-titration of Bisoprolol to maximum dose failed to control her heart rate, worsened her fatigue, and caused loss of hypoglycaemia awareness.\nGiven the deterioration in LV function in the context of a persistent atrial tachycardia and the previous cardiomyopathy during her first pregnancy, treatment to rate control the arrhythmia was mandated; however, options in this circumstance were limited by the safety profile of commonly used antiarrhythmic drugs. Ivabradine was discussed considering the higher incidence of autonomic FATs during pregnancy and the recent evidence of its efficiency in this particular subset of arrhythmias. In view of the limited available data regarding the teratogenic risk of ivabradine, this option was reviewed with the Pregnancy Heart Team and pharmacists, as well as the patient. It was felt that the benefits would outweigh the risks and ivabradine was started at a dose of 5 mg twice daily. A three-lead 24 h Holter ECG was fitted and recording started parallel to commencing the treatment. The effect was observed ∼6 h after the first dose with a successful reduction of the average heart rate to ∼100 b.p.m. (). Ivabradine was further increased to the target dose of 7.5 mg twice daily. A repeated TTE under improved rate control demonstrated an improved left ventricular function (LV EF 55%).\nThe patient was scheduled for obstetric foetal ultrasound scans at gestation Weeks 28, 32, and 36, which revealed no abnormalities, and had an uncomplicated vaginal delivery of a 3900 g healthy male infant at term. A 12-lead ECG 1 month postpartum showed spontaneous resolution of the atrial tachycardia and confirmed normal sinus rhythm. Ivabradine was stopped and her betablocker continued. The ACEI has been reinstituted after the pregnancy. She has been symptom free since delivery.