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Anatomically and physiologically based reference level for measurement of intracardiac pressures
M Courtois1, P G Fattal, S J Kovács
1Cardiovascular Division, Washington University School of Medicine, St Louis, Mo 63110, USA.
Circulation
|October 1, 1995
Summary
A new reference level (H) for measuring intracardiac pressure, aligned with the uppermost blood in the left ventricle, accurately measures diastolic pressure. This method corrects for hydrostatic pressure errors common with midchest referencing.
Area of Science:
- Cardiology
- Medical Instrumentation
- Physiology
Background:
- Established reference levels for intracardiac pressure measurement lack universal acceptance.
- Hydrostatic pressure significantly influences fluid-filled catheter measurements of intracardiac pressures.
- Understanding of hydrostatic pressure effects on intracardiac measurements varies among clinicians.
Purpose of the Study:
- To evaluate cardiologists' understanding of hydrostatic pressure's influence on intracardiac pressure measurements.
- To propose and validate a novel zero reference level (H) for left ventricular (LV) pressure measurement.
- To compare LV diastolic pressure measurements using the new reference level (H) versus the traditional midchest level.
Main Methods:
- Two-dimensional echocardiography was used to determine the H reference level in seven normal patients.
- H was defined as the uppermost blood level in the LV relative to the anterior chest wall in the supine position.
- Micromanometer and fluid-filled catheters compared LV minimum diastolic pressure (LVPmin) referenced to H versus midchest.
Main Results:
- LV minimum diastolic pressure referenced to H was -0.6 +/- 0.6 mm Hg, significantly lower than 5.1 +/- 1.6 mm Hg referenced to midchest (P < .001).
- A strong linear relationship (r = .88; P < .01) was found between anterior-posterior chest diameter and hydrostatic pressure effects at the midchest reference.
- The new reference level (H) demonstrated a more accurate measurement of LVPmin, approaching subatmospheric levels.
Conclusions:
- External fluid-filled transducers should be aligned with the uppermost blood level in the chamber to eliminate hydrostatic pressure influences.
- Referencing LV diastolic pressure to the midchest level systematically overestimates pressure due to hydrostatic effects.
- Accurate measurement of diastolic intracardiac pressure, including subatmospheric levels, requires referencing to the chamber's uppermost blood level.