In:
American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 284, No. 6 ( 2003-06-01), p. H2295-H2301
Abstract:
Maximal left ventricular (LV) hydraulic power output (PWR max ), corrected for preload as PWR max /(V ed ) β (where V ed is the end-diastolic volume and β is a constant coefficient), is an index of LV contractility. Whereas preload-adjusted maximal power (PAMP) is usually calculated with β = 2, there is uncertainty about the optimal value of β (β = 1 for the normal LV and 2 for the dilated LV). The aim of this work is to study the determining factors of β. The data set consisted of 245 recordings (steady state and vena cava occlusion) in 10 animals in an ischemic heart pig model. The occlusion data yielded the slope ( E es ; 2.01 ± 0.77 mmHg/ml, range 0.71–4.16 mmHg/ml) and intercept (V 0 ; −11.9 ± 22.6 ml; range −76 to 39 ml) of the end-systolic pressure-volume relation, and the optimal β-factor (assessed by fitting an exponential curve through the V ed -PWR max relation) was 1.94 ± 0.88 (range 0.29–4.73). The relation of β with V ed was weak [β = 0.60 + 0.02(V ed ); r 2 = 0.20]. In contrast, we found an excellent exponential relation between V 0 and β [β = 2.16[Formula: see text] r 2 = 0.70]. PAMP, calculated from the steady-state data, was 0.64 ± 0.40 mW/ml 2 (range 0.14–2.83 mW/ml 2 ) with a poor correlation with E es ( r = 0.30, P 〈 0.001). An alternative formulation of PAMP as PWR max /(V ed − V 0 ) 2 , incorporating V 0 , yielded 0.47 ± 0.26 mW/ml 2 (range 0.09–1.42 mW/ml 2 ) and was highly correlated with E es ( r = 0.89, P 〈 0.001). In conclusion, correct preload adjustment of maximal LV power requires incorporation of V 0 and thus of data measured under altered loading conditions.
Type of Medium:
Online Resource
ISSN:
0363-6135
,
1522-1539
DOI:
10.1152/ajpheart.01110.2002
Language:
English
Publisher:
American Physiological Society
Publication Date:
2003
detail.hit.zdb_id:
1477308-9
SSG:
12
Bookmarklink
