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Continuous assessment of left ventricular shape in man
Insights
Left ventricular shape changes during the cardiac cycle were analyzed. Reduced circularity during systole and increased circularity during diastole were observed, with variations in heart disease patients.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Imaging
Background:
- Left ventricular function is crucial for cardiac health.
- Quantifying left ventricular shape dynamics provides insights into myocardial function.
- Previous methods may not fully capture shape changes during the cardiac cycle.
Purpose of the Study:
- To analyze left ventricular (LV) shape changes throughout the cardiac cycle using a novel shape index.
- To compare LV shape dynamics in healthy individuals versus patients with heart disease.
- To investigate the functional implications of altered LV shape during systole and diastole.
Main Methods:
- Frame-by-frame analysis of left ventriculograms in 10 normal subjects and 40 heart disease patients.
- Calculation of a left ventricular shape index (4π(cavity area)/perimeter²) to quantify circularity.
- Assessment of shape index changes during systole and early diastole, correlating with ejection fraction and regional wall motion abnormalities.
Main Results:
- Normal subjects showed a progressive reduction in shape index (less circular) during systole and a rapid increase during early diastole.
- Patients with low ejection fraction or regional hypokinesia (inferior/anterior) exhibited smaller systolic shape index reductions.
- Rapid diastolic shape index increase was linked to minor diameter expansion and could precede long axis changes.
Conclusions:
- Left ventricular shape undergoes significant, quantifiable changes during the cardiac cycle.
- Altered shape dynamics are associated with impaired systolic function and regional wall motion abnormalities in heart disease.
- Assumptions regarding LV cavity shape in volume estimation may need revision due to observed non-uniform wall motion during filling.
Abstract:
Frame by frame analysis of left ventriculograms has been performed in 10 normal subjects and 40 patients with heart disease. Left ventricular shape index was derived as 4 pi (cavity area)/(perimeter)2, which has a maximum value of 1 when the outline is circular. In normal subjects systole was always associated with progressive reduction in shape index, indicating that the cavity projection had become less circular. This change was smaller in patients with low ejection fraction and also when inferior or anterior hypokinesia was present, even though ejection fraction was normal. During early diastole shape index rose rapidly due to an increase in minor diameter occurring throughout the period of rapid filling. In some cases this preceded any change in long axis, which was due to upward movement of the aortic root as well as outward movement of the apex. These results have functional implications, suggesting in particular that wall movement during filling may be non-uniform and that assumptions about cavity shape used in the derivation of wall properties from estimates of ventricular volume may require modification.