Anatomical studies have demonstrated that there are three components to the musculature of the left ventricle, which are arranged longitudinally. These are the papillary muscles, and fibres within the ventricular wall, dominantly subendocardially, and to a lesser extent subepicardially. 1 The important contribution of longitudinally arranged fibres to overall ventricular function has been recognised for many years. Surgeons now try hard to preserve papillary muscle function in both mitral valve repair and replacement, and patients do better for it. Drugs which improve longitudinal function can produce beneficial eVects in patients with ventricular disease. 2 Both the extent and timing of shortening and thickening of longitudinal fibres is essential to normal systolic function. And yet, despite the ease with which longitudinal ventricular function can be assessed, it has, until relatively recently, been neglected both in the literature and in clinical practice. In this issue of Heart, Andersson and colleagues describe a double blind trial of metoprolol treatment in patients with ventricular disease, in which they show increases in the amplitude of atrioventricular plane displacement during treatment. 3 These increases were associated with a reduction in pulmonary capillary wedge pressure and predicted increases in ejection fraction. The association with these haemodynamic improvements was greater than that with changes in short axis performance. These are intriguing findings because the subendocardial fibres are particularly at risk in patients with dilated cardiomyopathy, both from the eVects of any large or small coronary disease which may be present, but also from the indirect eVects of raised left ventricular diastolic pressures. Long axis motion of the atrioventricular rings reflects longitudinal ventricular shortening and lengthening, and the extent and timing can conveniently be assessed with M mode echocardiography. 4 The velocity of shortening and lengthening can be measured using digitised M modes or tissue Doppler. Because the majority of the longitudinally arranged fibres are located in the subendocardium, long axis function therefore largely reflects subendocardial function. This is therefore useful in assessment of the consequences of ischaemia, to which the subendocardium is particularly sensitive. 5

Cross sectionally guided M mode echocardiograms of the left ventricular long axis can be obtained by longitudinal placement of the M mode cursor through the lateral aspect of the mitral annulus and central fibrous body, visualised on the apical four chamber view. Similarly, right ventricular long axis function can be obtained by placing the cursor through the lateral aspect of the tricuspid annulus. Motion of the apex, with respect to the transducer placed at the apex, is insignificant, thus overall lengthening and shortening of the long axis of the left or right ventricles is truly reflected by atrioventricular annular motion.