Impact of Holter Electrocardiogram on Diagnosis of Congenital Long-QT Syndrome

Q: What are the key findings of this study?

24-hour Holter daily average QTc >443 msec differentiated congenital LQTS from controls with an AUC of 0.98 (sensitivity 0.88, specificity 0.95) and captured nighttime QTc prolongation in LQT2.

Q: What is the clinical evidence from this study?

Study design: Case-Control. Population: Congenital long-QT syndrome (LQTS) (n=62). Intervention: 24-hour Holter electrocardiogram QTc analysis (CM5 lead, Bazett correction) vs. Resting 12-lead electrocardiogram (12ECG) and age-/sex-matched non-LQTS controls. Primary outcome: Diagnostic accuracy of daily average Holter-QTc (>443 msec) for differentiating LQTS from control subjects (AUC) and comparison of daily average Holter-QTc across groups (AUC 0.98 (sensitivity 0.88, specificity 0.95) at cut-off >443 msec, p=<0.001).

Q: What does this research mean for the field?

A 24-hour Holter daily mean QTc >443 msec accurately detects congenital long-QT syndrome (AUC 0.98) and captures nighttime QTc prolongation in LQT2 that may be missed by resting 12-lead ECG. Novelty: ClaimNovelty.CONFIRMATORY. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To evaluate the clinical utility and diagnostic accuracy of 24-hour Holter electrocardiogram QT/QTc interval analysis compared with resting 12-lead electrocardiograms in congenital long-QT syndrome.

Ayumi Daifuku; Kohei Iguchi; Yoshiyuki Sumita; Daiki Shako; Takashi Ikee; AKINORI WAKAMIYA; Satoshi Oka; Kosuke Nakasuka; Kenzaburo Nakajima; Nobuhiko Ueda; Tsukasa Kamakura; Mitsuru Wada; Kohei Ishibashi; Yuko Y. Inoue; Koji Miyamoto; Kengo Kusano; Takeshi Aiba

doi:10.5105/jse.46.224

October 31, 2026Japanese Journal of ElectrocardiologyOpen Access

Impact of Holter Electrocardiogram on Diagnosis of Congenital Long-QT Syndrome

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Key result

Daily average Holter QTc accurately identifies congenital LQTS with an AUC of ~0.98.

AUC 0.98 (sensitivity 0.88, specificity 0.95) at cut-off >443 msec
P<0.001
n=62

Why the study?

Does 24-hour Holter electrocardiogram QTc analysis improve the detection and evaluation of QT prolongation compared with resting 12-lead ECG in patients with congenital long-QT syndrome (LQT1 and LQT2)?

Key Points

To evaluate the clinical utility and diagnostic accuracy of 24-hour Holter electrocardiogram QT/QTc interval analysis compared with resting 12-lead electrocardiograms in congenital long-QT syndrome.
Analyzed 24-hour Holter recordings from 42 congenital long-QT syndrome patients (22 LQT1, 20 LQT2) and 20 age- and sex-matched control subjects.
Calculated 1-minute and 1-hour average CM5 lead QT and Bazett-corrected QTc intervals using automated detection with manual correction, comparing values against standard resting 12-lead electrocardiograms.
Holter daily average QTc increased across groups, measuring 414.4 ± 16.7 msec in controls, 468.6 ± 24.4 msec in LQT1, and 497.7 ± 31.5 msec in LQT2 (P < 0.001), with LQT2 patients showing marked nocturnal QTc prolongation.
Maximum hourly QTc values in controls and LQT1 were close to resting 12-lead electrocardiogram QTc values, whereas LQT2 displayed consistently longer QTc intervals on Holter monitoring than on resting recordings.
Receiver operating characteristic curve analysis showed that a 24-hour Holter mean QTc > 443 msec identified long-QT syndrome with an area under the curve of 0.98, sensitivity of 0.88, and specificity of 0.95.

Study Design

Type

Case-Control (n=62)

Multicenter

No

Structured PICO

Does 24-hour Holter electrocardiogram QTc analysis improve the detection and evaluation of QT prolongation compared with resting 12-lead ECG in patients with congenital long-QT syndrome (LQT1 and LQT2)?

P

Population

62 participants (42 genotype-positive congenital LQTS patients [22 LQT1, 20 LQT2] and 20 age- and sex-matched controls without structural heart disease, 80.6% female) evaluated with 24-hour Holter monitoring and resting 12-lead ECG at a single center in Japan.

E

Exposure

24-hour Holter electrocardiogram monitoring with automatic minute-averaged and hour-averaged QT/QTc interval measurement in lead CM5 (Bazett formula, tangent method for T-wave end detection) with manual correction as needed.

C

Comparator

Standard resting 12-lead electrocardiogram (12ECG) automatic QT/QTc measurement and comparison between LQTS patients (LQT1, LQT2) and age-/sex-matched non-LQTS control subjects.

O

Outcome

Diagnostic performance (ROC area under the curve, sensitivity, specificity) of 24-hour daily average Holter-QTc (Holter-meanQTc(day)) for detecting congenital LQTS, and circadian/group differences in minute-averaged, hour-averaged, and daily average QTc.surrogate

Main Result

Effect estimate: AUC 0.98 (sensitivity 0.88, specificity 0.95) at cut-off >443 msec

Absolute Event Rate: 0.98% vs 0.95%

p-value: p=<0.001

24-hour Holter ECG daily average and hourly maximum QTc measurements accurately screen for congenital LQTS and unmask substantial nighttime QT prolongation in LQT2 patients that is frequently underestimated by a standard resting 12-lead ECG.

Limitations

Retrospective single-center design with variable timing between prior cardiac events and Holter recording
Case-control design using already diagnosed LQTS patients and matched controls, so the 443 msec cut-off requires prospective validation in suspected LQTS cohorts
Complex T-wave morphologies (biphasic/notched T waves in LQT2) and external noise limited automatic T-peak and T-end detection accuracy
32% of LQT1 and 70% of LQT2 patients were taking beta-blockers during Holter recording without paired pre-/post-treatment recordings
Retrospective study design with variable timing between cardiac event occurrence and Holter recording
Case-control cohort of confirmed LQTS and matched controls means the 443 msec cut-off serves only as a screening reference and requires prospective validation in suspected LQTS patients
Measurement variability due to abnormal T-wave morphologies (biphasic, notched T waves especially in LQT2) and baseline/EMG noise affecting Tpeak and Tend detection
Concomitant beta-blocker therapy during Holter recording in 32% of LQT1 and 70% of LQT2 patients without serial pre-/post-treatment comparisons

Implication

May support Holter QTc screening when resting ECG is inconclusive; leaves open prospective validation before routine adoption.

Abstract

【目的】先天性QT延長症候群（LQTS）患者に対するホルター心電図（Holter）を用いたQT間隔（QT/QTc）解析の臨床的意義について検討した．【方法】LQTS患者42例（LQT1：22例，LQT2：20例）および年齢・性別を一致させた対照（Control）患者20例に24時間Holterを実施，CM5誘導の毎分アベレージ波形のQT間隔を自動解析し適時マニュアル補正した．またHolterの結果を安静時標準12誘導心電図（安静時12ECG）と比較した．【結果】Holter毎分あるいは毎時平均QTcは，Control，LQT1，LQT2の順で大であった．LQT2では日中に比べて深夜にQTcがより延長する傾向がみられた．Holter毎分の最大QTcはばらつきが大きく，時間平均の最大QTcではControl，LQT1で比較的安静時12ECGのQTcに近く，一方LQT2では安静時12ECGより長いQTcであった．ROC曲線解析からLQTSの診断精度は，Holterの1日平均QTc＞443msecで曲線下面積：0.98，感度：0.88，特異度：0.95であった．【結論】HolerはLQTSのスクリーニングに有用である．特にLQT2ではQTcの変動幅や延長を認める時間帯に個人差が大きく，安静時12ECGでは十分な評価ができていない可能性があり，Holterを行う意義は大きいと考えられた．

Discussion

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Cite This Study

Daifuku et al. (2026) conducted a case-control in Congenital long-QT syndrome (LQTS) (n=62). 24-hour Holter electrocardiogram QTc analysis (CM5 lead, Bazett correction) vs. Resting 12-lead electrocardiogram (12ECG) and age-/sex-matched non-LQTS controls was evaluated on Diagnostic accuracy of daily average Holter-QTc (>443 msec) for differentiating LQTS from control subjects (AUC) and comparison of daily average Holter-QTc across groups (AUC 0.98 (sensitivity 0.88, specificity 0.95) at cut-off >443 msec, p=<0.001). 24-hour Holter daily average QTc >443 msec differentiated congenital LQTS from controls with an AUC of 0.98 (sensitivity 0.88, specificity 0.95) and captured nighttime QTc prolongation in LQT2.

synapsesocial.com/papers/6ae86797b29eedd186728783 https://doi.org/10.5105/jse.46.224

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Impact of Holter Electrocardiogram on Diagnosis of Congenital Long-QT Syndrome

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Cite This Study

Impact of Holter Electrocardiogram on Diagnosis of Congenital Long-QT Syndrome

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Cite This Study

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