A direct comparison between internally and externally measured left ventricular systolic time intervals

Area of Science:

• Cardiovascular Physiology
• Hemodynamics
• Non-invasive Cardiology

Background:

• Systolic time intervals (STIs) are crucial indicators of cardiac function.
• External carotid pulse tracing is a common non-invasive method for STI assessment.
• Central aortic pressure provides a more direct measure of cardiac performance.

Purpose of the Study:

• To directly compare systolic time intervals derived from external carotid pulse tracings and central aortic pressure curves.
• To investigate the transmission time of the central pulse wave's upstroke and incisura to the carotid artery.
• To determine the influence of heart rate on these measurements and transmission times.

Main Methods:

• Simultaneous recording of external carotid pulse tracings and central aortic pressure using a catheter-tip micromanometer in 38 cardiac patients.
• Analysis of systolic time intervals from both measurement sources.
• Measurement of pulse wave transmission times (upstroke and incisura) from central aorta to carotid artery.

Main Results:

• Significant differences in absolute values of systolic time intervals were observed between internal (aortic) and external (carotid) measurements, despite strong linear correlations.
• Transmission times for the pulse wave's upstroke and incisura also showed significant differences.
• Both the differences in STIs and the transmission times were found to be directly related to and dependent on the patient's heart rate.

Conclusions:

• External carotid pulse tracings provide a non-invasive estimate of STIs but exhibit significant deviations from central aortic measurements.
• Pulse wave transmission characteristics vary and are influenced by heart rate.
• Clinicians should be aware of these discrepancies when interpreting non-invasive STI data, especially in relation to heart rate.