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A case of long QT syndrome associated with familial occurrence of persistent patency of the arterial duct

Published online by Cambridge University Press:  03 May 2005

Subramanian Jothi Murugan ,
Jonathan M. Parsons  and
Chris Bennett
Subramanian Jothi Murugan
Affiliation:
Department of Congenital Heart Disease and Clinical Genetics, Leeds General Infirmary, Leeds, United Kingdom
Jonathan M. Parsons
Affiliation:
Department of Congenital Heart Disease and Clinical Genetics, Leeds General Infirmary, Leeds, United Kingdom
Chris Bennett
Affiliation:
Department of Congenital Heart Disease and Clinical Genetics, Leeds General Infirmary, Leeds, United Kingdom
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Abstract

We describe an occurrence of long QT syndrome in association with persistent patency of the arterial duct in members of a family. Patency of the arterial duct was diagnosed in family members of 4 successive generations. The index case had long QT syndrome associated with such a patent duct. Another patient had long QT syndrome, but associated with a ventricular septal defect. We postulate that there may be a common genetic mechanism for long QT syndrome and persistent patency of the arterial duct.

Keywords

Arrhythmiasductus arteriosusgenetics

Information

Type
Brief Report
Information
Cardiology in the Young , Volume 15 , Issue 3 , June 2005 , pp. 309 - 311
Copyright
© 2005 Cambridge University Press

Isolated patency of the arterial duct accounts for up to one-tenth of all types of congenital heart disease.1 The median incidence of such isolated patency is estimated as 567 per million live births.2 Polygenic inheritance has been implicated as its etiology. The long QT syndrome is caused by defect in the genes controlling the sodium and potassium channels. This can be inherited as an autosomal dominant or recessive disorder. Familial occurrence of these two disorders individually has been reported in the literature.3–6 Long QT syndrome, however, has not to the best of our knowledge been reported in association with familial occurrence of persistent patency of the arterial duct. To our knowledge, there is only one report of long QT syndrome in association with syndactyly, in three children from unrelated families, all of whom had a patent arterial duct.6 We report here the occurrence of long QT syndrome in association with patent arterial duct in a family.

Case report

A three month old baby girl, presented to a cardiology unit in heart failure at the age of three months (Fig. 1: III:2). She was found to have a large patent arterial duct requiring surgical ligation. After a delay of 12 years, she presented with two episodes of syncope. An electrocardiogram showed sinus bradycardia, with a rate of 50 per minute with corrected QT interval of 480 milliseconds (Fig. 2a). A diagnosis of long QT syndrome was made, and she was commenced on nadolol. At the age of 20, she delivered a baby boy, who was found to have a patent arterial duct (Fig. 1: IV:1). His corrected QT interval is thus far within normal limits, and he is being followed up regularly.

Figure 1. Pedigree of the family. Shaded upper right quadrant – patent arterial duct, shaded upper left quadrant – ventricular septal defect, shaded lower left quadrant – long QT syndrome.

Figure 2. The electrocardiograms showing (a) the prolonged QT interval in patient III:2 and (b) the prolonged QT interval in patient III:1.

Her twin brother was referred to the cardiology unit with a heart murmur (Fig. 1: III:1). He was found to have a small perimembranous ventricular septal defect. During a routine follow up examination at the age of 10 years, his electrocardiogram showed a sinus bradycardia and a prolonged QT corrected interval of 600 milliseconds (Fig. 2b). Although he remained asymptomatic, he was started on beta adrenergic blocker therapy with nadolol.

Their mother had ligation of a patent arterial duct at the age of three years, and died suddenly at the age of 41 years (Fig. 1: II:2). The exact cause was uncertain, but the post mortem ruled out structural cardiac abnormalities of the heart. This could presumably be due to arrhythmia related to long QT syndrome. Their maternal grandmother also underwent surgical ligation of patent arterial duct at younger age (Fig. 1: I:2).

Discussion

We have described the occurrence of long QT syndrome associated with patency of the arterial duct in a family. In this family, 4 members had persistent patency of the arterial duct, out of whom one died suddenly with presumed arrhythmia, one member had a patent arterial duct and long QT syndrome, and another member had ventricular septal defect and long QT syndrome. Isolated patent arterial duct was reported in 52 families with more than one affected relative.4 Genetic linkage analysis of the long QT syndrome has identified five locuses located on chromosomes 11p15.5, 7q35-36, 3p21-24, 4q25-27 and 21q22. We have not yet genotyped this family.

Presence of long QT syndrome associated with patency of the arterial duct occurring together in members of a family is unlikely to be by chance alone, suggesting a possible genetic mechanism. The association may provide insight into the mechanisms underlying both disorders. One postulated hypothesis for closure of the arterial duct suggests that this may be accomplished by mechanisms working through ion channels. Studies on the rabbit arterial duct suggested that increasing oxygen stimulates contraction of smooth muscle partly by closing oxygen sensitive delayed rectifier potassium channels.7 As long QT syndromes also involve abnormal ion channels, there may be a common mechanism for persistence of arterial duct.

Conclusion

We identified long QT syndrome in association with familial occurrence of persistent patency of the arterial duct. We postulate that there may be a common genetic mechanism for these two disorders occurring together.

References

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Figure 0

Pedigree of the family. Shaded upper right quadrant – patent arterial duct, shaded upper left quadrant – ventricular septal defect, shaded lower left quadrant – long QT syndrome.

Figure 1

The electrocardiograms showing (a) the prolonged QT interval in patient III:2 and (b) the prolonged QT interval in patient III:1.