Propionic acidemia is an autosomal recessive disorder caused by a deficiency in propionyl-CoA carboxylase. The disorder usually presents with episodes of metabolic acidosis. Treatment consists of a protein-limited diet and l-carnitine. Cardiomyopathy is a well-recognized complication of this condition occurring mainly at times of metabolic decompensation. However, recent literature has also highlighted the association of propionic acidemia and long QTC (>440 ms) [1, 2]. Althought both these studies report the association, this case is the first report of a child with propionic acidemia developing life-threatening complications from long QTC.

Case Report

The patient is a 13-year-old girl who was diagnosed with propionic acidemia shortly after birth. She was otherwise well and her metabolic condition was well controlled on sodium benzoate and carnitine. She presented following an episode of collapse while playing netball at school. Cardiopulmonary resuscitation had been instigated immediately and was required for 7 min. She spent 48 h in the pediatric intensive care unit (PICU) where intravenous sodium benzoate, carnitine, and 10% dextrose were commenced. On discharge from the PICU she was referred to the cardiology team.

On further history-taking, she reported previous episodes of dizziness while playing netball, at times forcing her to sit down, but she had never collapsed. She denied any history of palpitations. Examination was normal as was an echo; however, a 24-h tape showed a prolonged QTC of 450 ms. This was confirmed on exercise testing when the QTC increased further to 490–508 ms in the recovery phase (Fig. 1)

Fig. 1
figure 1

ECG trace showing prolongation of the QTC to 518 ms

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. She was commenced on 40 mg nadalol twice a day and remains under cardiology review.

Discussion

Kakavand et al. [2] were the first to publish a case demonstrating the association between propionic acidemia and long QTC. They reported an incidental finding of a long QTC in a 7-year-old propionic acidemia patient who was undergoing routine cardiology assessment because of the known association with cardiomyopathy. This patient was subsequently commenced on atenolol.

Subsequently Baumgartner et al. [1] published a case series of 10 patients with propionic acidemia who under went cardiology investigation. They found a prolonged QTC >440 ms in 70% of the children after infancy and 60% had a markedly prolonged QTC >460 ms. This prolongation of the QTC was independent of their metabolic states.

Abnormal repolarization characterized by preterminal T-wave inversion on 12-lead ECG was present in 60%, and in each case, it was associated with a QTC >460 ms. Rhythm disturbances were seen in 20%, and 40% of those with QTC >450 ms had reduced left ventricular contractility.

Our report combined with the previous two articles on this subject should lead to the consideration that all children with propionic acidemia should receive regular cardiology follow-up with a 12-lead ECG, 24-h Holter monitoring, and exercise testing. In the case of the latter, it is important that the ECG recording continues for 10 min of the recovery phase; this is a common time for QT prolongation to appear. Care should also be taken when prescribing medications known to have associations with prolongation of QTC (e.g., erythromycin).