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Published on: January 16, 2019
Screening of 1-Month-Old Infants With Prolonged QT Interval and Its Cutoff Value
Masao Yoshinaga1,2, Hiroya Ushinohama3, Seiichi Sato4
1Department of Pediatrics, NHO Kagoshima Medical Center.
Insights
The prevalence of prolonged corrected QT interval (pQTc) in infants is about 1 in 935. A QTc(B) cutoff of ≥0.45 at 1 month may be suitable for screening for pQTc in infants.
Area of Science:
- Pediatric Cardiology
- Clinical Electrocardiography
- Genetics
Background:
- Congenital long QT syndrome (LQTS) prevalence is established via genetic and ECG data.
- The prevalence of electrocardiographically determined prolonged corrected QT interval (pQTc) in infants remains unclear.
Purpose of the Study:
- To determine the prevalence of pQTc in 1-month-old infants.
- To identify optimal screening criteria for pQTc in this population.
Main Methods:
- Prospective ECG screening of 10,282 1-month-old infants.
- Re-examination of infants with QTc ≥0.45 (Bazett's formula [QTc(B)]).
- pQTc defined as QTc ≥0.46 on two separate infant ECGs.
Main Results:
- Prevalence of pQTc was 11/10,282 (1:935).
- Five infants were identified as high risk (QTc ≥0.50 or progressive increase).
- An abrupt QTc(B) increase occurred in high-risk infants around 6-11 weeks, often with medication initiation.
Conclusions:
- ECG-determined pQTc prevalence is approximately 1:1,000.
- A QTc(B) cutoff of ≥0.45 appears appropriate for 1-month-old infant screening.
- High-risk infants show an abrupt QTc(B) increase, primarily around 6-11 weeks post-birth.
Background:
The prevalence of congenital long QT syndrome (LQTS) (1 : 2,000) is based on genetic testing and ECG data, but the prevalence of electrocardiographically determined prolonged corrected QT interval (pQTc) in infants is unclear.
Methods And Results:
Subjects were 10,282 1-month-old infants who participated in 2 prospective ECG screening studies performed in 2010-2011 and 2014-2016. Infants with a QTc ≥0.45 using Bazett's formula [QTc(B)] at 1-month medical checks were re-examined. pQTc was defined as QTc ≥0.46 on 2 different ECGs in early infancy. Infants with QTc ≥0.50 or progressive prolongation of QTc to 0.50 were defined as at high risk. The prevalence of infants with a pQTc was 11/10,282 (1 : 935; 95% confidence interval, 1 : 588-1 : 2,283). Five infants were diagnosed as at high risk, and all infants had an abrupt increase in QTc(B) values in early infancy, mostly at 6-11 weeks after birth and when medication was started. No infants with a pQTc experienced LQTS-related symptoms. Statistical analysis showed that a cutoff QTc(B) ≥0.45 was optimal for screening infants with a pQTc.
Conclusions:
The prevalence of ECG-determined pQTc is approximately 1 : 1,000. An abrupt increase in QTc(B) values occurs in infants at high risk, mostly at 6-11 weeks after birth. A cutoff QTc(B) value ≥0.45 may be appropriate for 1-month-old screening in this population.
