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Am J Cardiol. 2015 Sep 15;116(6):894-9. doi: 10.1016/j.amjcard.2015.06.030. Epub 2015 Jun 27.

Diagnostic Approach to Unexplained Cardiac Arrest (from the FIVI-Gen Study).

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Cardiology Clinical Management Unit, Granada University Hospitals, Granada Institute of Biohealth Research, Granada, Spain. Electronic address:
Cardiology Department, La Paz University Hospital, Madrid, Spain.
Cardiology Department, La Fe University Hospital, Valencia, Spain.
Cardiology Department, Gran Canaria Island Hospital, Las Palmas de Gran Canaria, Spain.
Cardiology Department, Juan Ramón Jiménez Hospital, Huelva, Spain.
Cardiology Department, Virgen de la Arrixaca University Hospital, Murcia, Spain.
Cardiology Department, Reina Sofía University Hospital, Córdoba, Spain.
Cardiology Department, Virgen de Macarena University Hospital, Seville, Spain.
Cardiology Department, Virgen de Valme University Hospital, Seville, Spain.
Cardiology Department, Health in Code SL, A Coruña, Spain.
Cardiology Department, Virgen de la Victoria University Hospital, Málaga, Spain.
Cardiology Clinical Management Unit, Granada University Hospitals, Granada Institute of Biohealth Research, Granada, Spain.


Unexplained cardiac arrest (UCA) can be caused by low-penetrance genetic disorders. The aim of this cross-sectional study is to assess the usefulness of a new diagnostic protocol: Thirty-five patients were recruited from 9 Spanish centers. Electrocardiogram, echocardiogram, and coronary catheterization were used to rule out electrical or structural heart disease in all subjects. Patients underwent pharmacologic tests with epinephrine and flecainide, followed by assessment of family members using electrocardiogram and echocardiogram, and next-generation genetic sequencing to analyze 126 genes if all the other test results were negative. A firm diagnosis of channelopathy required phenotypic proof of the condition in unmasking tests, the presence of a pathogenic variant consistent with the phenotype observed, and/or co-segregation of the mutation found in a family member's phenotype. A firm diagnosis was made in 18 cases. The diagnoses were 7 Brugada syndrome, 5 catecholaminergic polymorphic ventricular tachycardia, 3 long QT syndrome, 2 early repolarization syndrome, and 1 short QT syndrome. Pharmacologic testing was the most frequent method of diagnosis. In 5 cases, the diagnosis was made based on positive genetic testing without phenotypic alterations. In conclusion, this sequential diagnostic protocol allows diagnoses to be made in approximately half of the UCA cases. These diagnoses are low clinical penetrance channelopathies. If interpreted carefully, genetic tests can be a useful tool for diagnosing UCA without a phenotype.

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