Diagnostic miscues in congenital long-QT syndrome

Nathaniel W. Taggart, Carla M. Haglund, David J. Tester, Michael John Ackerman

Research output: Contribution to journalArticle

157 Citations (Scopus)

Abstract

BACKGROUND - Long-QT syndrome (LQTS) is a potentially lethal cardiac channelopathy that can be mistaken for palpitations, neurocardiogenic syncope, and epilepsy. Because of increased physician and public awareness of warning signs suggestive of LQTS, there is the potential for LQTS to be overdiagnosed. We sought to determine the agreement between the dismissal diagnosis from an LQTS subspecialty clinic and the original referral diagnosis. METHODS AND RESULTS - Data from the medical record were compared with data from the outside evaluation for 176 consecutive patients (121 females, median age 16 years, average referral corrected QT interval [QTc] of 481 ms) referred with a diagnosis of LQTS. After evaluation at Mayo Clinic's LQTS Clinic, patients were categorized as having definite LQTS (D-LQTS), possible LQTS (P-LQTS), or no LQTS (No-LQTS). Seventy-three patients (41%) were categorized as No-LQTS, 56 (32%) as P-LQTS, and only 47 (27%) as D-LQTS. The yield of genetic testing among D-LQTS patients was 78% compared with 34% for P-LQTS and 0% among No-LQTS patients (P<0.0001). The average QTc was greater in either D-LQTS or P-LQTS than in No-LQTS (461 versus 424 ms, P<0.0001). Vasovagal syncope was more common among the No-LQTS subset (28%) than the P-LQTS/D-LQTS group (8%; P=0.04). Determinants for discordance (ie, positive outside diagnosis versus No-LQTS) included overestimation of QTc, diagnosing LQTS on the basis of "borderline" QTc values, and interpretation of a vasovagal fainting episode as an LQTS-precipitated cardiac event. CONCLUSIONS - Diagnostic concordance was present for less than one third of the patients who sought a second opinion. Two of every 5 patients referred with the diagnosis of LQTS departed without such a diagnosis. Miscalculation of the QTc, misinterpretation of the normal distribution of QTc values, and misinterpretation of symptoms appear to be responsible for most of the diagnostic miscues.

Original languageEnglish (US)
Pages (from-to)2613-2620
Number of pages8
JournalCirculation
Volume115
Issue number20
DOIs
StatePublished - May 2007

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Long QT Syndrome
Vasovagal Syncope
Referral and Consultation
Channelopathies
Normal Distribution
Syncope
Genetic Testing
Medical Records
Epilepsy

Keywords

  • Electrocardiography
  • Genetic screening
  • Ion channels
  • Long-QT syndrome
  • Syncope

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Diagnostic miscues in congenital long-QT syndrome. / Taggart, Nathaniel W.; Haglund, Carla M.; Tester, David J.; Ackerman, Michael John.

In: Circulation, Vol. 115, No. 20, 05.2007, p. 2613-2620.

Research output: Contribution to journalArticle

Taggart, Nathaniel W. ; Haglund, Carla M. ; Tester, David J. ; Ackerman, Michael John. / Diagnostic miscues in congenital long-QT syndrome. In: Circulation. 2007 ; Vol. 115, No. 20. pp. 2613-2620.
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abstract = "BACKGROUND - Long-QT syndrome (LQTS) is a potentially lethal cardiac channelopathy that can be mistaken for palpitations, neurocardiogenic syncope, and epilepsy. Because of increased physician and public awareness of warning signs suggestive of LQTS, there is the potential for LQTS to be overdiagnosed. We sought to determine the agreement between the dismissal diagnosis from an LQTS subspecialty clinic and the original referral diagnosis. METHODS AND RESULTS - Data from the medical record were compared with data from the outside evaluation for 176 consecutive patients (121 females, median age 16 years, average referral corrected QT interval [QTc] of 481 ms) referred with a diagnosis of LQTS. After evaluation at Mayo Clinic's LQTS Clinic, patients were categorized as having definite LQTS (D-LQTS), possible LQTS (P-LQTS), or no LQTS (No-LQTS). Seventy-three patients (41{\%}) were categorized as No-LQTS, 56 (32{\%}) as P-LQTS, and only 47 (27{\%}) as D-LQTS. The yield of genetic testing among D-LQTS patients was 78{\%} compared with 34{\%} for P-LQTS and 0{\%} among No-LQTS patients (P<0.0001). The average QTc was greater in either D-LQTS or P-LQTS than in No-LQTS (461 versus 424 ms, P<0.0001). Vasovagal syncope was more common among the No-LQTS subset (28{\%}) than the P-LQTS/D-LQTS group (8{\%}; P=0.04). Determinants for discordance (ie, positive outside diagnosis versus No-LQTS) included overestimation of QTc, diagnosing LQTS on the basis of {"}borderline{"} QTc values, and interpretation of a vasovagal fainting episode as an LQTS-precipitated cardiac event. CONCLUSIONS - Diagnostic concordance was present for less than one third of the patients who sought a second opinion. Two of every 5 patients referred with the diagnosis of LQTS departed without such a diagnosis. Miscalculation of the QTc, misinterpretation of the normal distribution of QTc values, and misinterpretation of symptoms appear to be responsible for most of the diagnostic miscues.",
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T1 - Diagnostic miscues in congenital long-QT syndrome

AU - Taggart, Nathaniel W.

AU - Haglund, Carla M.

AU - Tester, David J.

AU - Ackerman, Michael John

PY - 2007/5

Y1 - 2007/5

N2 - BACKGROUND - Long-QT syndrome (LQTS) is a potentially lethal cardiac channelopathy that can be mistaken for palpitations, neurocardiogenic syncope, and epilepsy. Because of increased physician and public awareness of warning signs suggestive of LQTS, there is the potential for LQTS to be overdiagnosed. We sought to determine the agreement between the dismissal diagnosis from an LQTS subspecialty clinic and the original referral diagnosis. METHODS AND RESULTS - Data from the medical record were compared with data from the outside evaluation for 176 consecutive patients (121 females, median age 16 years, average referral corrected QT interval [QTc] of 481 ms) referred with a diagnosis of LQTS. After evaluation at Mayo Clinic's LQTS Clinic, patients were categorized as having definite LQTS (D-LQTS), possible LQTS (P-LQTS), or no LQTS (No-LQTS). Seventy-three patients (41%) were categorized as No-LQTS, 56 (32%) as P-LQTS, and only 47 (27%) as D-LQTS. The yield of genetic testing among D-LQTS patients was 78% compared with 34% for P-LQTS and 0% among No-LQTS patients (P<0.0001). The average QTc was greater in either D-LQTS or P-LQTS than in No-LQTS (461 versus 424 ms, P<0.0001). Vasovagal syncope was more common among the No-LQTS subset (28%) than the P-LQTS/D-LQTS group (8%; P=0.04). Determinants for discordance (ie, positive outside diagnosis versus No-LQTS) included overestimation of QTc, diagnosing LQTS on the basis of "borderline" QTc values, and interpretation of a vasovagal fainting episode as an LQTS-precipitated cardiac event. CONCLUSIONS - Diagnostic concordance was present for less than one third of the patients who sought a second opinion. Two of every 5 patients referred with the diagnosis of LQTS departed without such a diagnosis. Miscalculation of the QTc, misinterpretation of the normal distribution of QTc values, and misinterpretation of symptoms appear to be responsible for most of the diagnostic miscues.

AB - BACKGROUND - Long-QT syndrome (LQTS) is a potentially lethal cardiac channelopathy that can be mistaken for palpitations, neurocardiogenic syncope, and epilepsy. Because of increased physician and public awareness of warning signs suggestive of LQTS, there is the potential for LQTS to be overdiagnosed. We sought to determine the agreement between the dismissal diagnosis from an LQTS subspecialty clinic and the original referral diagnosis. METHODS AND RESULTS - Data from the medical record were compared with data from the outside evaluation for 176 consecutive patients (121 females, median age 16 years, average referral corrected QT interval [QTc] of 481 ms) referred with a diagnosis of LQTS. After evaluation at Mayo Clinic's LQTS Clinic, patients were categorized as having definite LQTS (D-LQTS), possible LQTS (P-LQTS), or no LQTS (No-LQTS). Seventy-three patients (41%) were categorized as No-LQTS, 56 (32%) as P-LQTS, and only 47 (27%) as D-LQTS. The yield of genetic testing among D-LQTS patients was 78% compared with 34% for P-LQTS and 0% among No-LQTS patients (P<0.0001). The average QTc was greater in either D-LQTS or P-LQTS than in No-LQTS (461 versus 424 ms, P<0.0001). Vasovagal syncope was more common among the No-LQTS subset (28%) than the P-LQTS/D-LQTS group (8%; P=0.04). Determinants for discordance (ie, positive outside diagnosis versus No-LQTS) included overestimation of QTc, diagnosing LQTS on the basis of "borderline" QTc values, and interpretation of a vasovagal fainting episode as an LQTS-precipitated cardiac event. CONCLUSIONS - Diagnostic concordance was present for less than one third of the patients who sought a second opinion. Two of every 5 patients referred with the diagnosis of LQTS departed without such a diagnosis. Miscalculation of the QTc, misinterpretation of the normal distribution of QTc values, and misinterpretation of symptoms appear to be responsible for most of the diagnostic miscues.

KW - Electrocardiography

KW - Genetic screening

KW - Ion channels

KW - Long-QT syndrome

KW - Syncope

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