What is the clinical evidence from this study?

Study design: Observational. Population: Healthy (n=72). Intervention: 12-lead ECG vs. Interlead comparison. Primary outcome: Correlation between beat-to-beat QT interval variability and T-wave amplitude (r = -0.62, p=<0.0001).

July 1, 2012Open Access

Relation between Beat‐to‐Beat QT Interval Variability and T‐Wave Amplitude in Healthy Subjects

Q: What are the key findings of this study?

In healthy subjects, beat-to-beat QT interval variability varied significantly between ECG leads and was negatively correlated with T-wave amplitude (r = -0.62, P < 0.0001).

Key Result

In healthy subjects, beat-to-beat QT interval variability varied significantly between ECG leads and was negatively correlated with T-wave amplitude (r = -0.62, P < 0.0001).

Study Design

Type

Observational (n=72)

Structured PICO

Does beat-to-beat QT interval variability differ between ECG leads and correlate with T-wave amplitude in healthy subjects?

Population

72 healthy subjects (17 females, mean age 38 ± 14 years; 55 males, mean age 39 ± 13 years) from the PTB diagnostic database.

Intervention

Short-term (approximately 2 minutes) resting 12-lead ECG recording.

Outcome

Interlead differences in beat-to-beat QT interval variability (QTV) and its relationship with T-wave amplitude.surrogate

Beat-to-beat QT interval variability differs significantly across the 12 standard ECG leads and is inversely correlated with T-wave amplitude, suggesting lead selection is critical for QTV analysis.

Main Result

Effect estimate: r = -0.62

p-value: p=<0.0001

Limitations

Focus on healthy subjects, which might not directly translate to cardiac patients with altered substrate and repolarization heterogeneity
Relatively small number of subjects for gender analysis
Relatively short duration of ECG recordings
Limited information on the subjects included in the PTB database, such as lack of BMI values

Abstract

OBJECTIVES: Elevated beat-to-beat QT interval variability (QTV) has been associated with increased cardiovascular morbidity and mortality.The aim of this study was to investigate interlead differences in beat-to-beat QTV of 12-lead ECG and its relationship with the T wave amplitude. METHODS: Short-term 12-lead ECGs of 72 healthy subjects (17 f, 38 ± 14 years; 55 m, 39 ± 13 years) were studied. Beat-to-beat QT intervals were extracted separately for each lead using a template matching algorithm. We calculated the standard deviation of beat-to-beat QT intervals as a marker of QTV as well as interlead correlation coefficients. In addition, we measured the median T-wave amplitude in each lead. RESULTS: There was a significant difference in the standard deviation of beat-to-beat QT intervals between leads (minimum: lead V(3) (2.58 ± 1.36 ms), maximum: lead III (7.2 ± 6.4 ms), ANOVA: P 0.05). CONCLUSIONS: QTV varies considerably between leads in magnitude as well as temporal patterns. QTV is increased when the T wave is small.

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