Postmortem long QT syndrome genetic testing for sudden unexplained death in the young.
OBJECTIVE
This study sought to determine the spectrum and prevalence of long QT syndrome (LQTS)-associated mutations in a large cohort of autopsy-negative sudden unexplained death (SUD).


BACKGROUND
Potentially heritable arrhythmia syndromes may explain a significant proportion of SUD in the young. Here, comprehensive postmortem LQTS genetic testing was performed in a cohort of SUD cases.


METHODS
From September 1998 to March 2004, 49 cases of SUD (30 male patients, average age at death 14.2 +/- 10.9 years) were referred by medical examiners/coroners to Mayo Clinic's Sudden Death Genomics Laboratory. Using polymerase chain reaction, denaturing high-performance liquid chromatography, and direct DNA sequencing, open reading frame/splice site mutational analysis was conducted for all 8 genes implicated in the pathogenesis of either LQTS (LQT1 to LQT6) or multisystem disorders involving either QT or QU prolongation.


RESULTS
Ten LQTS-associated mutations (4 novel) were discovered in 10 SUD cases (20%, 8 female patients, average age at death 18.0 +/- 11.8 years). The LQTS susceptibility mutations LQT1 (5), LQT2 (3), and LQT3 (2) were far more common among women (8 of 18, 44%) than men (2 of 30, 6.7%, p < 0.008). The activities at the time of SUD included sleep (5), exertion (2), auditory arousal (1), and undetermined (2). Sudden death was the sentinel event in two-thirds of the cases.


CONCLUSIONS
In this cardiac channel-focused molecular autopsy investigation of SUD, over one-third of decedents harbored a putative cardiac channel mutation: 7 previously reported to host mutations in the RyR2-encoded calcium release channel and now 10 with LQTS susceptibility mutations. Accordingly, postmortem cardiac channel genetic testing should be pursued in the evaluation of autopsy-negative SUD.
Tester
David J
DJ
Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota 55905-0001, USA.
Ackerman
Michael J
MJ
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001344:Autopsy; D015984:Causality; D002423:Cause of Death; D002648:Child; D015331:Cohort Studies; D016001:Confidence Intervals; D004252:DNA Mutational Analysis; D003645:Death, Sudden / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D016757:Death, Sudden, Cardiac / Q000453:epidemiology* / Q000473:pathology; D003933:Diagnosis; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D051657:KCNQ1 Potassium Channel / Q000235:genetics*; D008133:Long QT Syndrome / Q000175:diagnosis / Q000235:genetics* / Q000401:mortality*; D008297:Male; D009154:Mutation; D011110:Polymorphism, Genetic; D012189:Retrospective Studies; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics*; D012680:Sensitivity and Specificity; D017678:Sex Distribution
D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D019837:Ryanodine Receptor Calcium Release Channel