Stability of electrocardiographic classification pre- and postglucose challenge

Area of Science:

• Cardiology
• Epidemiology
• Gerontology

Background:

• Electrocardiograms (ECGs) in epidemiologic studies typically require subjects to fast due to validity concerns.
• Fasting ECGs present logistical challenges, making non-fasting recordings preferable if valid.
• Previous research has not extensively evaluated the impact of postprandial states on ECGs in older populations.

Purpose of the Study:

• To assess the stability and validity of electrocardiograms (ECGs) taken in fasting subjects compared to those taken after a glucose load.
• To determine if non-fasting ECGs are a reliable alternative for epidemiologic studies in older adults.
• To quantify the changes in ECG classifications following glucose ingestion.

Main Methods:

• A cohort of 89 older adults from the Rancho Bernardo Chronic Disease Study participated.
• ECGs were recorded from the same individuals both while fasting and approximately 1 hour after a 75-g glucose load.
• ECG tracings were classified by a blinded reader using the Minnesota code and Whitehall criteria.

Main Results:

• Among 75 initially normal ECGs, 27% shifted to 'possible ischemia' after glucose ingestion.
• Two of 12 tracings initially showing possible ischemia reverted to normal post-glucose.
• The variability in ECGs pre- and post-glucose was comparable to variability observed over 8 years of clinic visits.

Conclusions:

• Post-glucose ingestion significantly alters ECG readings in older adults, with more tracings worsening than improving.
• The observed ECG variability challenges the use of non-fasting ECGs in epidemiologic research.
• Current guidelines recommending fasting for ECGs in epidemiologic studies appear justified based on these findings.