Adynamic cardiomyoplasty: effect on cardiac efficiency and contractile reserve in dogs with adriamycin-induced cardiomyopathy

Animal models of heart failure: what is new?

Heart failure is the major cause of mortality in Western countries. Medical treatment of heart failure is associated with 50% survival at 5 years. Experimental models are required to better understand the progression of the disease and elaborate new therapy. Heart transplantation, left ventricular assist devices, artificial hearts, and cardiac bioassist techniques require animal models for testing and optimizing before they are implemented on human patients. The perfect model of heart failure that reproduces every aspect of the natural disease does not exist. Acute and chronic heart failure models have been developed to reproduce different aspect of the pathology.

Passive ventricular constraint

Heart failure (HF) is a progressive degenerative and malignant syndrome with a large number of aetiologies including coronary artery disease, chronic hypertension, exposure to toxins, bacteria and viruses and in a significant percentage of HF patients, the causal mechanism is unclear. The HF trail of morbidity and mortality is well documented and is characterised by step-like periods of relative symptomatic stability, compensation, separated by decompensatory episodes. The homeostatic response to the decline in cardiac function is diverse and involves most organs. There is an increase in resting rate, intra-cardiac hormone production (catecholamines, aldosterone, etc.) and in particular structural changes occur with increased mass and dilatation (dilated cardiomyopathy, DCM). DCM is associated with decreased cardiac output, contractility and energy efficiency and an increase in pro-arrhythmia and conduction defects. Kass et al. (Circulation 91(9) (1995) 2314) first demonstrated in patients who had undergone a dynamic cardio-myoplasty procedure, that, preventing further dilatation in DCM was beneficial and that the improved cardiovascular status was largely independent of muscle stimulation. We hypothesised that this outcome could be achieved by implanting a fabric cardiac support device around both ventricles to the AV junction. Subsequently, it was shown by us and others (Kass et al., 1995) (Cardiovasc. Res. 44(3) (1999) 549); (Ann. Thorac. Surg. 70(4) (2000) 1275) (in different animal models of DCM) that passive ventricular constraint prevented further dilatation, initiated left ventricular volume reduction and reversed the decline in ejection fraction, mitral valve integrity and left ventricular contractility, when compared with untreated controls. Subsequent European and North American clinical trials in patients with DCM of varying aetiologies have shown equal promise and an absence of device related complications (Circulation 104(12 Suppl. 1) (2001) I270); (Ann. Thorac. Cardiovasc. Surg. 7(5) (2001) 278). The mechanisms behind this improvement have yet to be fully clarified however the support generated by the device upon the right and ventricular freewall would lower wall tension. Not only is passive ventricular constraint a very promising treatment modality for heart failure and DCM it should provide a useful research tool for the study of the role of ventricular dilatation in the progression of heart failure.