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Background Myocardial mass increase with age, but the impact of recently discovered length reduction by age has not been taken into account. Long axis shortening is considered the main contributor to LV stroke volume. There is still disagreement about the relative contributions of cross sectional vs long axis shortening. Long axis shortening decrease with age, but EF do not. It has been postulated that this is due to increased transverse function, but this has not been demonstrated. Also, the degree of systolic myocardial compression is unresolved. Methods The HUNT study examined 1266 subjects without evidence of heart disease from a mixed urban/rural population of North Trøndelag county, Norway. Linear dimensions of diastolic left ventricular annulus to apex distance, systolic and diastolic wall thicknesses (WT), chamber diameter (LVID), and mitral annular plane displacement (MAPSE) were measured. Measurements were applied to a half-ellipsoid model of the left ventricle with assumption of 50% thinner apex than midway thickness, for calculations of left ventricular length (LVL), LV cavity volume (LVEDV), stroke volume (SV) and EF as shown in fig. 1. Results Dimensions and volumes are given in table 1. LV internal diameter was unchanged by age, and so was fractional shortening (FS). Wall thickness increased by age (p &amp;lt; 0.001), corresponding to an increase in external diameter, but LVL decreased (p &amp;lt; 0.001), so increase in myocardial volume (MyoV) although significant (p &amp;lt; 0.001), was less. Wall thickening decreased from 59 to 52% by age group (p &amp;lt; 0.001). MAPSE decreased by age (p &amp;lt; 0.001). Similarly systolic external diameter reduction (from 13.6 to 11.9%), and SV also decreased by age, while EF was unchanged. MAPSE contributed 74% to stroke volume, external diameter reduction to 26% These relative contributions did not change by age. Systolic myocardial compression was 2.5%, at all ages. Conclusion LVEDV decreases with age due to LV shortening, not wall thickening. EF is maintained by a simultaneous reduction in SV and EDV. MAPSE decreases by age, and so does transverse function. Thus, both are decreasing in proportion, and the reduction in SV is due to both, not to any increase in transverse function. Table 1 Age (years) WT (mm) LVL (mm) LVID (mm) LVEDV (ml) MyoV (ml) MAPSE (mm) SV (ml) EF (%) &amp;lt;40 8.1 (1.3) 94.2 (7.5) 50.9 (4.9) 124.0 (30.0) 101.4 (27.9) 17.3 (2.0) 83.7 (21.4) 67 (6) 40 - 60 8.9 (1.4) 92.9 (8.1) 50.9 (5.4) 122.5 (31.0) 111.2 (29.2) 15.8 (2.3) 82.4 (22.8) 67 (6) &amp;gt;60 9.5 (1.4) 89.0 (7.9) 50.3 (6.1) 113.8 (31.7) 113.9 (31.7) 14.0 (2.2) 76.0 (24.1) 66 (9) 8.8 (1.4) 92.4 (8.1) 50.8 (5.4) 121.1 (31.1) 109.2 (29.1) 15.8 (2.5) 81.4 (22.9) 67 (8) Diastolic dimensions volumes and functional measures by age. Abstract 159 Figure 1

159 LV volumes, EF, MAPSE, myocardial mass and systolic compression and relation to ageing. Results from the HUNT study