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Fractal dimension as an index of left ventricular ischaemia: a pilot study
L J Cymberknop1, W Legnani, J G Barra
1Electronics Department, Buenos Aires Regional Faculty, National Technological University, Buenos Aires, Argentina. ljcymber@electron.frba.utn.edu.ar
Insights
Fractal dimension (FD) quantifies the loss of ventricular thickness complexity. A decrease in FD indicates acute coronary ischemia, serving as a reliable marker for this cardiac condition.
Area of Science:
- Cardiology
- Biomedical Engineering
- Physiology
Background:
- Myocardial perfusion relies on coronary arteries supplying blood to ventricles.
- Ischemia, impaired arterial blood flow to cardiac muscle, is a critical condition.
- Fractal dimension (FD) has shown potential in distinguishing healthy from pathological physiological patterns.
Purpose of the Study:
- To quantify the reduction in fractal complexity of ventricular thickness.
- To determine if FD is an intrinsic biomarker for acute coronary ischemia.
Main Methods:
- Utilized five mongrel dogs for the study.
- Implanted ultrasonic microcrystals for continuous left ventricular wall thickness measurement.
- Monitored changes in ventricular wall thickness and calculated FD during induced coronary occlusion.
Main Results:
- Ischemic walls exhibited thinning during relaxation, contrasting with normoperfused walls showing thickening.
- A significant decrease in FD was observed in both posterior and anterior ventricular walls (P <0.05).
- The observed FD trend mirrored established clinical indices of myocardial ischemia.
Conclusions:
- Loss of time series fractal complexity, indicated by 'unwrinkling,' is a marker for ischemic processes.
- A single FD value can characterize the time series behavior, reflecting the presence of ischemia.
- FD serves as a sensitive and intrinsic marker for acute coronary ischemia.
Abstract:
Myocardial perfusion is performed by the left and the right coronary arteries, which deliver blood to the left and right ventricles, respectively. The impairment of arterial flow supply to the cardiac muscle by disease denotes a phenomenon known as ischaemia. Previous studies have demonstrated the ability of fractal dimension (FD) value of a physiological parameter in differentiating healthy/pathological behaviours. The aim of this study consisted in quantifying the loss of ventricular thickness fractal complexity in order to determine if FD is an intrinsic marker of acute coronary ischaemia. Five mongrel dogs weighing 18.8-26.5 kg (24.4 ± 3.3, mean ± SD) were submitted to this studio. A left ventricular pressure transducer and a fluid-filled catheter for later calibration of the pressure transducer were introduced through a stab wound near the apex. Two pairs of ultrasonic microcrystals (5 MHz) for continuous wall thickness measurements were implanted at the anterior and posterior walls of the left ventricle following a previously described technique. During coronary occlusion, the ischemic wall started to thin at the very onset of relaxation (showing abnormal motility), while the normoperfused wall displayed postejective thickening. Concomitantly, posterior ventricular wall thickness and anterior wall ventricular thickness showed a significant decrease in its FD value (P <0.05). In conclusion, loss of time series fractal complexity (waveform fine structure diminution or 'unwrinkling') constitutes a marker of the presence of an ischemic process. As a result, a single scalar value is sufficient to characterize the entire behaviour of the time series. This value manifested a similar trend compared to the most well-known clinical indices of myocardial ischaemia.
