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Integrated wall stress: a new methodological approach to assess ventricular workload and myocardial contractile reserve.

Dong H, Mosca H, Gao E, Akins RE, Gidding SS, Tsuda T - J Transl Med (2013)

Bottom Line: IWS was calculated over one minute through simultaneous measurement of LV internal diameter and wall thickness by echocardiography and LV pressure by LV catheterization.At rest, the MI group showed concentric LV hypertrophy pattern with preserved LV cavity size, LV systolic function, and IWS comparable with the sham group.IWS showed good correlation with a product of peak-systolic wall stress and heart rate.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nemours Cardiac Center and Nemours Biomedical Research, Alfred I, duPont Hospital for Children, 1600 Rockland Rd, Wilmington, DE 19103, USA.

ABSTRACT

Background: Wall stress is a useful concept to understand the progression of ventricular remodeling. We measured cumulative LV wall stress throughout the cardiac cycle over unit time and tested whether this "integrated wall stress (IWS)" would provide a reliable marker of total ventricular workload.

Methods and results: We applied IWS to mice after experimental myocardial infarction (MI) and sham-operated mice, both at rest and under dobutamine stimulation. Small infarcts were created so as not to cause subsequent overt hemodynamic decompensation. IWS was calculated over one minute through simultaneous measurement of LV internal diameter and wall thickness by echocardiography and LV pressure by LV catheterization. At rest, the MI group showed concentric LV hypertrophy pattern with preserved LV cavity size, LV systolic function, and IWS comparable with the sham group. Dobutamine stimulation induced a dose-dependent increase in IWS in MI mice, but not in sham mice; MI mice mainly increased heart rate, whereas sham mice increased LV systolic and diastolic function. IWS showed good correlation with a product of peak-systolic wall stress and heart rate. We postulate that this increase in IWS in post-MI mice represents limited myocardial contractile reserve.

Conclusion: We hereby propose that IWS provides a useful estimate of total ventricular workload in the mouse model and that increased IWS indicates limited LV myocardial contractile reserve.

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Related in: MedlinePlus

Changes in IWS, peak systolic WS, and end diastolic WS with dobutamine stimulation. A: IWS changes with incremental dobutamine stress. The IWS were comparable between MI (n = 5) and sham group (n = 5) at the baseline. However, IWS in MI hearts increased significantly with dobutamine stimulation, whereas there was no noticeable increase of IWS in the sham hearts. ms: millisecond. Changes in peak systolic WS (B) and end diastolic WS (C) with incremental dobutamine stress after small MI. Both peak systolic WS and end diastolic WS in MI hearts were significantly higher than those in sham hearts with dobutamine stimulation. * p < 0.05 vs. sham, # p < 0.05 vs. 0 mcg/kg/min, § < 0.05 vs. 5 mcg/kg/min.
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Figure 5: Changes in IWS, peak systolic WS, and end diastolic WS with dobutamine stimulation. A: IWS changes with incremental dobutamine stress. The IWS were comparable between MI (n = 5) and sham group (n = 5) at the baseline. However, IWS in MI hearts increased significantly with dobutamine stimulation, whereas there was no noticeable increase of IWS in the sham hearts. ms: millisecond. Changes in peak systolic WS (B) and end diastolic WS (C) with incremental dobutamine stress after small MI. Both peak systolic WS and end diastolic WS in MI hearts were significantly higher than those in sham hearts with dobutamine stimulation. * p < 0.05 vs. sham, # p < 0.05 vs. 0 mcg/kg/min, § < 0.05 vs. 5 mcg/kg/min.

Mentions: IWS changes in both MI and sham groups, before and after dobutamine stimulation (5 and 10 μg/kg/min), are shown in Figure 5A. IWS was comparable between the two groups at the baseline. But with dobutamine stimulation, IWS was significantly increased in MI group, whereas IWS was relatively unchanged in sham group. Increased IWS implies increased external ventricular work load that is not absorbed by the intrinsic myocardial contractile reserve. The difference in myocardial reserve capacity in the two groups was reflected in IWS changes with dobutamine stimulation. Increased IWS by dobutamine stimulation in MI mice indicates increased ventricular workload in MI mice in a stressed condition.


Integrated wall stress: a new methodological approach to assess ventricular workload and myocardial contractile reserve.

Dong H, Mosca H, Gao E, Akins RE, Gidding SS, Tsuda T - J Transl Med (2013)

Changes in IWS, peak systolic WS, and end diastolic WS with dobutamine stimulation. A: IWS changes with incremental dobutamine stress. The IWS were comparable between MI (n = 5) and sham group (n = 5) at the baseline. However, IWS in MI hearts increased significantly with dobutamine stimulation, whereas there was no noticeable increase of IWS in the sham hearts. ms: millisecond. Changes in peak systolic WS (B) and end diastolic WS (C) with incremental dobutamine stress after small MI. Both peak systolic WS and end diastolic WS in MI hearts were significantly higher than those in sham hearts with dobutamine stimulation. * p < 0.05 vs. sham, # p < 0.05 vs. 0 mcg/kg/min, § < 0.05 vs. 5 mcg/kg/min.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750700&req=5

Figure 5: Changes in IWS, peak systolic WS, and end diastolic WS with dobutamine stimulation. A: IWS changes with incremental dobutamine stress. The IWS were comparable between MI (n = 5) and sham group (n = 5) at the baseline. However, IWS in MI hearts increased significantly with dobutamine stimulation, whereas there was no noticeable increase of IWS in the sham hearts. ms: millisecond. Changes in peak systolic WS (B) and end diastolic WS (C) with incremental dobutamine stress after small MI. Both peak systolic WS and end diastolic WS in MI hearts were significantly higher than those in sham hearts with dobutamine stimulation. * p < 0.05 vs. sham, # p < 0.05 vs. 0 mcg/kg/min, § < 0.05 vs. 5 mcg/kg/min.
Mentions: IWS changes in both MI and sham groups, before and after dobutamine stimulation (5 and 10 μg/kg/min), are shown in Figure 5A. IWS was comparable between the two groups at the baseline. But with dobutamine stimulation, IWS was significantly increased in MI group, whereas IWS was relatively unchanged in sham group. Increased IWS implies increased external ventricular work load that is not absorbed by the intrinsic myocardial contractile reserve. The difference in myocardial reserve capacity in the two groups was reflected in IWS changes with dobutamine stimulation. Increased IWS by dobutamine stimulation in MI mice indicates increased ventricular workload in MI mice in a stressed condition.

Bottom Line: IWS was calculated over one minute through simultaneous measurement of LV internal diameter and wall thickness by echocardiography and LV pressure by LV catheterization.At rest, the MI group showed concentric LV hypertrophy pattern with preserved LV cavity size, LV systolic function, and IWS comparable with the sham group.IWS showed good correlation with a product of peak-systolic wall stress and heart rate.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nemours Cardiac Center and Nemours Biomedical Research, Alfred I, duPont Hospital for Children, 1600 Rockland Rd, Wilmington, DE 19103, USA.

ABSTRACT

Background: Wall stress is a useful concept to understand the progression of ventricular remodeling. We measured cumulative LV wall stress throughout the cardiac cycle over unit time and tested whether this "integrated wall stress (IWS)" would provide a reliable marker of total ventricular workload.

Methods and results: We applied IWS to mice after experimental myocardial infarction (MI) and sham-operated mice, both at rest and under dobutamine stimulation. Small infarcts were created so as not to cause subsequent overt hemodynamic decompensation. IWS was calculated over one minute through simultaneous measurement of LV internal diameter and wall thickness by echocardiography and LV pressure by LV catheterization. At rest, the MI group showed concentric LV hypertrophy pattern with preserved LV cavity size, LV systolic function, and IWS comparable with the sham group. Dobutamine stimulation induced a dose-dependent increase in IWS in MI mice, but not in sham mice; MI mice mainly increased heart rate, whereas sham mice increased LV systolic and diastolic function. IWS showed good correlation with a product of peak-systolic wall stress and heart rate. We postulate that this increase in IWS in post-MI mice represents limited myocardial contractile reserve.

Conclusion: We hereby propose that IWS provides a useful estimate of total ventricular workload in the mouse model and that increased IWS indicates limited LV myocardial contractile reserve.

Show MeSH
Related in: MedlinePlus