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A morphological control for ventricular pathology in man: a morphometric and morphologic assessment of LV myofibres
1EM Unit, Faculty of Medicine, University of Natal, Durban, South Africa.
Insights
Researchers explored using left ventricular (LV) myocardium from atrial septal defect (ASD) patients as normal controls for heart muscle studies. Myofibres under 25 microns in diameter showed normal fine structure, suggesting their use in pathological research.
Area of Science:
- Cardiology
- Pathology
- Cell Biology
Background:
- Ethical constraints limit biopsies of normal human myocardium.
- Lack of normal control tissue hinders morphological studies of diseased heart muscle.
Purpose of the Study:
- To assess the suitability of left ventricular (LV) myocardium from atrial septal defect (ASD) patients as normal controls for myofiber pathomorphology.
- To investigate the fine-structure of LV myofibers in ASD patients for potential use as pathological benchmarks.
Main Methods:
- Light and electron microscopy were used to examine LV myocardial wedge biopsies from four adult ASD patients.
- Bivariant myofiber morphometry was performed to analyze myofiber diameter and morphology.
- Correlation analysis was conducted on myofiber diameter and fine-structural appearance.
Main Results:
- One of the four ASD specimens exhibited 'normal' LV myocardium; three showed varying degrees of hypertrophy.
- A correlation was observed between myofiber diameter (FD) and morphology within and between specimens.
- Myofibers with FD < 25 microns resembled normal myofibers from animal models, while those with FD > 25 microns displayed hypertrophic features.
Conclusions:
- The LV myocardium in ASD patients may exhibit mild hypertrophy.
- Myofibers with FD < 25 microns in ASD hearts are likely morphologically normal.
- These smaller myofibers can potentially serve as fine-structural controls for myofiber pathomorphology in diseased hearts.
Abstract:
Ethical considerations preclude the biopsy of normal human myocardium. As a consequence, morphological investigations of diseased human heart muscle are hampered by a lack of suitable normal control tissue. The left ventricular (LV) myocardium of patients with isolated secundum atrial septal defect (ASD) is considered to be normal. This study was designed to investigate the possibility that the fine-structure of LV myofibres in hearts with ASD could be used as normal controls for myofibre pathomorphology. Wedge biopsies from the LV of four adults undergoing elective surgery for the repair of ASD were examined by light and electron microscopy. Bivariant myofibre morphometry showed that the LV myocardium of one specimen was 'normal' while three specimens exhibited varying degrees of hypertrophy. There was a correlation between the diameter (FD) and morphology of individual myofibres within and between specimens. In general, myofibres with FD less than 25 microns were similar in fine-structural appearance to those described as morphologically normal in animal models whereas those with FD greater than 25 microns exhibited hypertrophic features that increased in 'severity' with increase in myofibre size. It is proposed that although the LV myocardium in ASD may be mildly hypertrophied, myofibres with FD less than 25 microns are probably normal and may be used as fine-structural controls for myofibre pathomorphology in hearts suspected of disease.