LongQTNext / RhythmNext®

Long QT syndrome, Brugada syndrome, and short QT syndrome are inherited arrhythmias that are often asymptomatic and can lead to sudden cardiac death. LongQTNext is a 17 gene panel that analyzes genes most commonly associated with LongQT, Brugada and short QT syndromes. The test can be an effective way to confirm these disorders and direct medical management and treatment decisions.

Inherited arrhythmias such as ARVD, Brugada syndrome, CPVT, LQTS, and SQTS can often lead to sudden cardiac death. RhythmNext, a 42-gene panel analyzes genes associated with these arrhythmias and can be an effective way of confirming a diagnosis. At-risk individuals in the family are identified, providing vital information for management and intervention options for both the patient and their family.

Quick Reference
Test Code: 8900 Test Name: RhythmNext™ TAT: 14-21 days Genes: 42
Test Code: 8890 Test Name: LongQTNext™ TAT: 14-21 days Genes: 17

Ordering Options

We offer family variant testing at no additional cost

for all blood relatives of patients who undergo full single gene sequencing, multigene panel testing or exome sequencing at Ambry Genetics and are found to have a pathogenic or likely pathogenic variant. No-cost testing of blood relatives must be completed within 90 days of the original report date. Whenever possible, more closely related relatives should be tested before more distant relatives.

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Why Is This Important?

Knowing if your patient has a hereditary cardiovascular disorder can help you determine their future cardiovascular disease risks and guide your medical management recommendations. Key benefits include:

  1. Clarify diagnosis and risk for sudden cardiac arrest
  2. Target cardiac event triggers, cardiac event incidence, and management plan to an individual’s genotype
  3. Adjust management in those with LQTS due to conditions like Jervell and Lange-Nielsen and Andersen-Tawil syndromes
  4. May identify the cause of a sudden unexplained death after a normal autopsy
  5. Offer family members genetic testing (for a familial mutation) and implement medical surveillance to only those that need it
  6. Reduce healthcare costs, resources, and anxiety for families

When To Consider Testing

  • Patient has a strong clinical suspicion for LQTS, based on clinical and family history and prolonged QT interval on EKG defined as QTc>480 ms (adolescents) or >500 ms (adults)*
  • Patient is asymptomatic with QT prolongation in the absence of other clinical explanations*
  • Patient has a strong clinical suspicion for BrS or SQTS, based on clinical/family history and EKG patter
  • Patient has a personal or family history of unexplained sudden cardiac arrest/death, with structurally normal heart and normal physical exam/autopsy

*Recommendations from 2011 Heart Rhythm Society (HRS) and European Heart Rhythm Association (EHRA) Expert Consensus Statement

Mutation Distribution and Detection Rates

The LongQTNext and RhythmNext tests are designed and validated to be capable of detecting >99% of described mutations in the genes represented on the tests (analytical sensitivity). The clinical sensitivity of the LongQTNext and RhythmNext test may vary widely according to the specific clinical and family history. are designed and validated to be capable of detecting >99% of described mutations in the genes represented on the tests (analytical sensitivity). The clinical sensitivity of these tests may vary widely according to the specific clinical and family history.  


Test Description

LongQTNext is an analysis of 17 genes associated with inherited arrhythmias. RhythmNext is a comprehensive analysis of 42 genes associated with inherited arrhythmias. Genomic deoxyribonucleic acid (gDNA) is isolated from the patient’s specimen using a standardized kit and quantified. Sequence enrichment of the targeted coding exons and adjacent intronic nucleotides is carried out by a bait-capture methodology using long biotinylated oligonucleotide probes, and is followed by polymerase chain reaction (PCR) and Next-Generation sequencing. Additional Sanger sequencing is performed for any regions missing or with insufficient read depth coverage for reliable heterozygous variant detection. Potentially homozygous variants, variants in regions complicated by pseudogene interference, and variant calls not satisfying depth of coverage and variant allele frequency quality thresholds are verified by Sanger sequencing. This assay targets all coding domains, and well into the flanking 5’ and 3’ ends of all the introns and untranslated regions. Gross deletion/duplication analysis is performed for all genes using a custom pipeline based on read-depth from NGS data followed by a confirmatory orthogonal method, as needed. Exon-level resolution may not be achieved for every gene.


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