Atrial tachycardia from enhanced automaticity in children: diagnosis and initial management.

Ten patients (aged 0-9 years) with the diagnosis of automatic atrial tachycardia (AAT) from August 1997 to August 2000 were reviewed. Three patients had paroxysmal (repetitive) AAT and the tachycardia was incessant in six (defined as presence of AAT for more than 90% of the time). The type of AAT in one patient was unknown. Four patients presented with congestive heart failure (CHF), one with pre-syncope, one with palpitation, and four were asymptomatic. Six patients (60%) had depressed left ventricular ejection fraction. All patients with CHF had incessant AAT with atrial rate > 220/min and ventricular rate > 200/min at admission. After treatment with antiarrhythmic medications, all patients had adequate control of the AAT (9 had complete elimination of AAT and 1 partial control). Amiodarone (alone, or in combination with digoxin) was effective in 5 of 6 cases (83%), although complete elimination of the AAT was usually delayed (median = 5 days, range 30 minutes to 17 days). Other effective medications were digoxin, digoxin + propranolol and atenolol (all in patients who did not have CHF on presentation). At the time of this report, 3 patients had no AAT off antiarrhythmic medication, 5 patients were still receiving treatment (with good control) and 2 patients died from sepsis during the same admission even though AAT was controlled. All surviving patients had normal ventricular ejection fraction on follow-up. AAT in children is rare, but when it occurs in persistent form at a fast rate, it is usually associated with CHF and is difficult to treat. Amiodarone (+/- digoxin) effectively controls the arrhythmia in the majority of cases, although full effect may take several days. With successful treatment, most patients do well and some can be taken off the medication(s) without recurrence of the arrhythmia.

Complete heart block in children at King Chulalongkorn Memorial Hospital.

The etiologies of complete heart block in thirty-one children (mean age 5.5 +/- 5.2 years, range 0-14 years) diagnosed at King Chulalongkorn Memorial Hospital between 1990-2001 were reviewed. Three main groups of patients were identified: 1) patients who presented in utero or in the newborn period (congenital heart block, n = 6), 2) patients who had complete heart block after cardiac surgery (postoperative heart block, n = 10), and 3) children outside the newborn period with a new diagnosis of complete heart block unrelated to cardiac surgery (unknown etiology, n = 15). Among 15 patients in the last group, 5 were asymptomatic (or minimally symptomatic) with complete heart block unexpectedly found. These patients probably had previously undetected congenital heart block. Two patients had complete heart block associated with mild viral illness, but no bradycardia-related symptom. The etiology for heart block in these 2 patients was unknown. Eight patients probably had recent onset heart block because of new bradycardia-related symptoms, or a previously documented normal heart rate. All patients in this group were female (mean age 4.3 +/- 4.3 years, median 3.5 years). All were diagnosed between August and January, and the majority (75%) had a history of non-specific viral illness in the preceding 2 weeks. Seven patients (87.5%) were acutely symptomatic. Syncope and/or seizure were the most common presenting symptoms. Left ventricular systolic dysfunction was found in only one patient. The etiology of complete heart block in these patients probably was an acute viral myocarditis that preferentially affected the conduction system. Two of these eight patients had complete recovery of the atrioventricular conduction. The rest had no improvement or had only partial recovery and subsequently underwent permanent cardiac pacemaker insertion.

Morbitz type I second degree AV block during recovery from dengue hemorrhagic fever.

Two patients with serologically-proven dengue virus infection and Morbitz type I second degree atrioventricular (AV) block are described. A 7 years old boy (patient 1) with grade 2 and a 7 years old girl (patient 2) with grade 3 illness were admitted to the hospital on the 3rd and the 5th day of the illness, respectively. Both had typical resentation for dengue hemorrhagic fever including fever, hepatomegaly, thrombocytopenia and signs of extravascular leakage. The 7 year old girl also had epistaxis and anemia (Hct 24%). Morbitz type I second degree and 2:1 AV block developed on day 7 (patient 1) and day 8 (patient 2) of the illness, both during recovery periods. Patient 1 also had occasional monomorphic premature ventricular contraction (PVC). There was no other abnormality in the 12-lead EKGS and echocardiograms showed normal ventricular systolic function in both. Other than mild hypokalemia (3.3 and 3.4 mgq/l), serum electrolytes were normal. Neither patients had elevation of serum creatine phosphokinase (CPK). In patient 1, exercise (on day 10) normalized AV conduction and abolished the PVC. Follow up EKG and physical examination at 10 months after the illness was normal. The rhythm in patient 2 resolved to 1st degree AV block (with occasional morbitz type I second degree at night) on day 12. In this patient, exercise resulted in shortening of the PR interval and Valsalva maneuver resulted in further PR prolongation. The patient was well at 1-month follow up with a mormal EKG. Morbitz type I second degree AV block during recovery from dengue hemorrhagic fever may be a transient functional impairment of the AV node, in which altered autonomic tone may play a role.

A Thai boy with hereditary enzymopenic methemoglobinemia type II.

Individuals with methemoglobin exceeding 1.5 g/dl have clinically obvious central cyanosis. Hereditary methemoglobinemia is due either to autosomal dominant M hemoglobins or to autosomal recessive enzymopenic methemoglobinemia. Four types of enzymopenic methemoglobinemia have been described. In addition to methemoglobinemia, individuals with type II, which is the generalized cytochrome b5 reductase deficiency, have severe and progressive neurological disabilities. Here we report a 3-year-old Thai boy with type II hereditary enzymopenic methemoglobinemia. He was born to a second-cousin couple. His central cyanosis was first observed around 10 months of age. His neurological abnormalities were seizures beginning at 1 year of age, microcephaly, and inability to hold his head up. His cardiovascular and pulmonary evaluations were unremarkable. Methemoglobin level by spectral absorption pattern was 18 per cent. A qualitative enzymatic assay confirmed the deficiency of the cytochrome b5 reductase enzyme. With this definite diagnosis, a prenatal diagnosis for the next child of this couple will be possible.

Ventricular functions in children with human immunodeficiency virus infection after ACE-inhibitors.

Nine pediatric symptomatic patients infected with human immunodeficiency virus with elevated pulmonary arterial pressure (MPA pressure) and ejection fraction (EF); and with fractional shortening, (FS) mean velocity of circumferential fiber shortening (MVCfc) and left ventricular peak systolic wall stress (PS) were prospectively evaluated using 2-dimensional and M-mode serial echocardiography and Doppler cardiography after administration of an ACE inhibitor (Inhibace 0.025 mg/kg/D orally) for 12 weeks. The MPA pressure was not decreased, however the MVCfc and PS improved significantly (p < 0.05). Further, long term evaluation is required to determine its effect in preventing dilated cardiomyopathy and elevated mean pulmonary pressure.