Cumulative sums in quantifying circadian blood pressure patterns.

Area of Science:

• Cardiology
• Biostatistics
• Chronobiology

Background:

• Circadian blood pressure patterns are crucial for cardiovascular health.
• Quantitative analysis of these patterns is essential for diagnosing and managing hypertension.
• Existing methods may lack precision in capturing dynamic blood pressure changes.

Purpose of the Study:

• To introduce a modified cumulative sums (cusums) technique for quantitative analysis of circadian blood pressure patterns.
• To establish a method for precisely identifying crest and trough blood pressures and calculating circadian blood pressure change.
• To demonstrate the utility of cusum-derived statistics in analyzing ambulatory blood pressure profiles.

Main Methods:

• Modified cumulative sums (cusums) plot generated by subtracting mean 24-hour ambulatory blood pressure from individual readings.
• Plotting the cumulative sum of products of pressure differences and time intervals.
• Calculating slopes of the cusum plot to determine mean blood pressure over specific periods.
• Identifying crest and trough pressures from steepest ascending and descending slopes.

Main Results:

• The slope of the modified cusum plot directly reflects the difference between period mean blood pressure and 24-hour mean blood pressure.
• Crest and trough blood pressures are identified by the most steeply ascending and descending 6-hour plot slopes.
• Circadian blood pressure change magnitude is calculated from the difference between crest and trough plot slopes.
• Cusum plot height serves as a measure of pressure alteration extent and duration.

Conclusions:

• The modified cusums technique offers a precise and reproducible method for quantitative analysis of circadian blood pressure.
• Cusum-derived statistics are easily calculated from raw ambulatory data.
• This approach enhances the understanding and management of circadian blood pressure variations in conditions like hypertension.