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Right and left ventricular compliance in the hereditary cardiomyopathy of the Syrian hamster
Insights
In cardiomyopathic hamsters, the oedematous stage shows decreased ventricular compliance and increased elastic modulus, suggesting myocardial failure rather than just congestion. This impacts cardiac function and ventricular remodeling.
Area of Science:
- Cardiovascular Physiology
- Myocardial Pathophysiology
- Animal Models of Heart Disease
Background:
- Cardiomyopathy progression in Syrian hamsters involves pre-oedematous and oedematous stages.
- Previous research indicated normal filling pressures and cardiac output in the pre-oedematous stage.
- The oedematous stage presents elevated filling pressures and increased cardiac output, questioning its underlying mechanism (myocardial failure vs. circulatory congestion).
Purpose of the Study:
- To investigate ventricular pressure-volume relationships in pre-oedematous and oedematous cardiomyopathic hamsters.
- To determine if the oedematous stage represents true myocardial failure or circulatory congestion.
- To analyze ventricular compliance and left ventricular tissue elastic modulus in different stages of cardiomyopathy.
Main Methods:
- Examination of ventricular pressure-volume curves in pre-oedematous (120 d) and oedematous (210 d) cardiomyopathic Syrian hamsters and age-matched controls.
- Derivation of ventricular compliance (dV/dP) from post-mortem pressure-volume curves (0–2.66 kPa).
- Calculation of left ventricular tissue elastic modulus (E) from compliance curves and heart dimensions.
Main Results:
- Ventricular compliance was similar between control and myopathic ventricles at isobaric intervals.
- Myopathic ventricles showed significant dilation at physiological end-diastolic pressures in both stages.
- End-diastolic compliance was normal in pre-oedematous hamsters but significantly decreased in oedematous hamsters; left ventricular elastic modulus was elevated in both myopathic groups.
Conclusions:
- The oedematous stage of this hamster cardiomyopathy is characterized by decreased ventricular compliance and increased ventricular dilation.
- Elevated left ventricular elastic modulus suggests intrinsic myocardial stiffening.
- Findings support the interpretation of the oedematous stage as representing true myocardial failure with associated circulatory congestion.
Abstract:
Ventricular pressure-volume curves were examined in 10 pre-oedematous cardiomyopathic Syrian hamsters, aged 120 d, and 10 oedematous cardiomyopathic hamsters, aged 210 d, and compared with 10 and 8 age-matched controls, respectively. Previous studies had shown filling pressures and cardiac output to be normal in the pre-oedematous stage. In contrast, the oedematous stage was characterised by elevated filling pressures and increased cardiac output, raising the question whether this stage represents true myocardial failure or circulatory congestion associated with decreased ventricular compliance. Compliance, defined as dV/dP, was derived simulataneously for both ventricles from post-mortem pressure-volume curves from 0 to 2.66 kPa (0 to 20 mmHg). Left ventricular tissue elastic modulus, E, defined as dsigma/depsilon or the incremental stress (sigma) for an increment of strain (epsilon), was derived from the compliance curves and certain linear dimensions of the heart. At isobaric intervals, compliance did not differ between control and myopathic ventricles. At pressures corresponding to previously measured, naturally prevailing end-diastolic pressures, the myopathic ventricles were significantly dilated in both stages; end-diastolic compliance was normal in pre-oedematous hamsters, but was significantly decreased in the oedematous animals. Left ventricular elastic modulus was elevated at all values of sigma in both groups of myopathic animals.