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The stimulant effects of adrenaline and noradrenaline on contractile force and adenylate cyclase, mediated through beta 1 and beta 2-adrenoceptors, are analysed in isolated atrial and ventricular myocardium of man. The tissues were obtained from patients without advanced heart failure undergoing heart surgery. Usually, both adrenaline and noradrenaline stimulated adenylate cyclase predominantly through ventricular and atrial beta 2-adrenoceptors. Because the relative density of beta 2-adrenoceptors is usually smaller than that of beta 1-adrenoceptors, stimulation of one beta 2-adrenoceptor leads to the production of up to 10 times more cyclic AMP molecules than does stimulation of one beta 1-adrenoceptor. Adrenaline and noradrenaline maximally enhance contractile force through both atrial and ventricular beta 1-adrenoceptors. Adrenaline can also maximally enhance contractile force through atrial beta 2-adrenoceptors. In the ventricle, adrenaline increases force via beta 2-adrenoceptors by up to 60% of its maximal beta 1 response. Noradrenaline can increase atrial and ventricular contractile force through beta 2-adrenoceptors but only at high concentrations. Unexpectedly, in atria from patients treated with the beta 1-selective antagonist atenolol, contractile responses to adrenaline are markedly and selectively augmented through activation of beta 2-adrenoceptors. In atria from atenolol-treated patients equi-inotropic concentrations of adrenaline and noradrenaline acting through beta 2 and beta 1-adrenoceptors, respectively, cause similar increases of cyclic AMP and of cyclic AMP-dependent protein kinase activity.

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Sub-valvular apparatus preservation after mitral valve replacement is not a new concept, yet to date there has been no quantification of its clinical effectiveness as a procedure and no consensus as to which surgical preservation technique should be adopted to achieve the best immediate and midterm clinical outcomes. This systematic review of current available literature aims to use an evidence synthesis and meta-analytic approach to compare outcomes following replacement of the mitral valve with (MVR-P) or without preservation (MVR-NP) of its apparatus. It considers all the relevant anatomical, experimental, echocardiographic, and clinical studies published in the literature and appraises all reported mitral valve sub-valvular apparatus preservation techniques. The results of this review strongly suggest that MVR-P is superior to MVR-NP with regards to the incidence of early postoperative low-cardiac output requiring inotropic support, and early or mid-term survival. They also suggest that the operative decision should be individualised based on patient's anatomy, pathology and ventricular function and therefore surgeons should be familiar with more than one surgical preservation technique. Finally, this paper highlights the need for further high quality research focusing particularly on the long-term assessment of quality of life and health utility following MVR-P.

LA dilatation leads to MVA enlargement, reduced leaflet co-aptation and MR even without LV dilatation. A co-aptation index describes this in vivo. This work provides insights into the mechanism of AMR.