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Major features:

  • Dilated cardiomyopathy (DCM), commonly starting at birth or during infancy
  • Endocardial fibroelastosis (EFE)
  • Left ventricular noncompaction (LVNC)
  • Ventricular arrhythmia, ventricular fibrillation (VF), ventricular tachycardia (VT), risk of cardiac arrest
  • Fetal cardiomyopathy and hydrops

Cardiomyopathy is the commonest feature of Barth Syndrome, although is not present in all patients. It can start whilst a baby boy is still in the womb (fetal cardiomyopathy) or be present at birth (neonatal cardiomyopathy). Other boys become unwell with dilated cardiomyopathy (DCM) in the first few years of life - this is seen in over half of all patients diagnosed. DCM is often accompanied by endocardial fibroelastosis (EFE, dense white thickening of the inner lining of the heart, shown in this paper). Another well recognised cardiac appearance is "left ventricular non-compaction (LVNC)", where there are deep pockets in the wall of the left ventricle. 

If cardiomyopathy develops during fetal life, this can lead to the death of the fetus due to "fetal hydrops" during the second and third trimester of pregnancy. A history of multiple male stillbirths is therefore present in some families (described here).

Dilated cardiomyopathy may develop rapidly and can even be triggered by viral infection. When accompanied by neutropenia (which can occur in anyone in response to viral infection) this can easily lead to confusion with "viral cardiomyopathy".

Heart failure may respond initially to cardiac medication but later relapse. It may be of such severity that cardiac transplant is required and approximately one in four boys with Barth Syndrome in the UK and one in seven worldwide have required cardiac transplantation. While the patient is awaiting cardiac transplantation it may be necessary to support the circulation using a Berlin ventricular assist device. The story of one such boy is told in the links on this page.

However, cardiomyopathy may also improve dramatically, to the point that heart scans (echocardiograms) return to normal. This improvement can either be maintained or the cardiomyopathy may recur, especially during puberty. Many boys with Barth Syndrome will go through a phase between preschool years and early puberty where cardiac symptoms mostly or completely resolve. This is sometimes called their "honeymoon phase".

Potentially dangerous disturbances of ventricular rhythm (ventricular arrhythmia, ventricular tachycardia [VT], ventricular fibrillation [VF]) can also occur in Barth Syndrome. This seems to be especially common in adolescent boys and has been recorded in up to 10% of patients. These problems with heart rhythm are particularly common in boys who have had a history of nausea, episodes of looking pale (pallor) or feeling dizzy beforehand.