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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

Echocardiographic and hemodynamic changes with dubutamine stimulation after small MI. A: Echocardiographic findings at 7 weeks after MI with dobutamine stimulation (baseline, 5, and 10 μg/kg/min for MI [n = 5] and sham groups [n = 5]) under xylazine/ketamine anesthesia. Significant heart rate increases were noted in MI group at 10 μg/kg/min, but not in sham group. %FS did not significantly change in response to dobutamine in either group, although there is a mild dose-dependent positive trend in sham mice. #p < 0.05 vs. baseline. B: Hemodynamic data by cardiac catheterization at 7 weeks in MI (n = 5) and sham group (n = 5) with dobutamine stimulation (baseline, 5 μg/kg/min, and 10 μg/kg/min). LVSP was comparable between MI and sham at the baseline but became significantly higher in sham than in MI with maximum dobutamine stimulation. LVEDP was significantly higher in MI than in sham group at the baseline, and these values did not significantly change with dobutamine stimulation. Maximum response in (+)dP/dTmax and (−)dP/dTmax by dobutamine infusion from baseline were shown. Even at the baseline, sham hearts showed better systolic and diastolic LV function than MI hearts. In addition, sham hearts had better response to dobutamine stimulation for both systolic and diastolic function. * p < 0.05 vs. sham; # p < 0.05 vs. baseline.
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Figure 4: Echocardiographic and hemodynamic changes with dubutamine stimulation after small MI. A: Echocardiographic findings at 7 weeks after MI with dobutamine stimulation (baseline, 5, and 10 μg/kg/min for MI [n = 5] and sham groups [n = 5]) under xylazine/ketamine anesthesia. Significant heart rate increases were noted in MI group at 10 μg/kg/min, but not in sham group. %FS did not significantly change in response to dobutamine in either group, although there is a mild dose-dependent positive trend in sham mice. #p < 0.05 vs. baseline. B: Hemodynamic data by cardiac catheterization at 7 weeks in MI (n = 5) and sham group (n = 5) with dobutamine stimulation (baseline, 5 μg/kg/min, and 10 μg/kg/min). LVSP was comparable between MI and sham at the baseline but became significantly higher in sham than in MI with maximum dobutamine stimulation. LVEDP was significantly higher in MI than in sham group at the baseline, and these values did not significantly change with dobutamine stimulation. Maximum response in (+)dP/dTmax and (−)dP/dTmax by dobutamine infusion from baseline were shown. Even at the baseline, sham hearts showed better systolic and diastolic LV function than MI hearts. In addition, sham hearts had better response to dobutamine stimulation for both systolic and diastolic function. * p < 0.05 vs. sham; # p < 0.05 vs. baseline.

Mentions: At 7 weeks after MI, echocardiography and cardiac catheterization were performed simultaneously at rest and with continuous intravenous infusion of dobutamine (first 5 and then 10 μg/kg/min) under ketamine/xylazine anesthesia (Figure 4). Heart rate increase with dobutamine stimulation was more prominent in the MI group than in sham group. %FS by echocardiogram showed positive response by dobutamine, more in the sham group than in the MI group, although the increase was not statistically significant (Figure 4A). In hemodynamic evaluation, LVSP increased significantly with 10 μg/kg/min of dobutamine infusion in sham, whereas the increase was only modest in the MI group (Figure 4B). LVEDP was notably higher in MI than in sham, but the value did not change throughout dobutamine stimulation in either group. At the baseline, the absolute values of both (+)dP/dTmax and (−)dP/dTmax were significantly higher in the sham group than in the MI group (6820 ± 573 vs. 4115 ± 485 [p < 0.05], and –6144 ± 614 vs. –3824 ± 540 [p < 0.05], respectively); further difference was observed with the 10 μg/kg/min of dobutamine infusion (15681 ± 2128 vs. 8118 ± 1144 [p < 0.05] and –11986 ± 1257 vs. –5542 ± 920 [p < 0.05], respectively), suggesting that both systolic and diastolic ventricular reserve capacities were significantly diminished in MI compared with sham. Three of 5 MI mice developed hemodynamic instability at 20 μg/kg/min of dobutamine infusion. Of these 3, 2 mice subsequently died of cardiovascular collapse. Echocardiographic measurements at 7 wk were not included in Figure 2 because the method of anesthesia was different, which caused a significantly lower heart rate than under isoflurane anesthesia. Nevertheless, the measured echocardiographic parameters at 7 wks for both MI and sham were comparable from those obtained at 5 wks (data not shown).


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)

Echocardiographic and hemodynamic changes with dubutamine stimulation after small MI. A: Echocardiographic findings at 7 weeks after MI with dobutamine stimulation (baseline, 5, and 10 μg/kg/min for MI [n = 5] and sham groups [n = 5]) under xylazine/ketamine anesthesia. Significant heart rate increases were noted in MI group at 10 μg/kg/min, but not in sham group. %FS did not significantly change in response to dobutamine in either group, although there is a mild dose-dependent positive trend in sham mice. #p < 0.05 vs. baseline. B: Hemodynamic data by cardiac catheterization at 7 weeks in MI (n = 5) and sham group (n = 5) with dobutamine stimulation (baseline, 5 μg/kg/min, and 10 μg/kg/min). LVSP was comparable between MI and sham at the baseline but became significantly higher in sham than in MI with maximum dobutamine stimulation. LVEDP was significantly higher in MI than in sham group at the baseline, and these values did not significantly change with dobutamine stimulation. Maximum response in (+)dP/dTmax and (−)dP/dTmax by dobutamine infusion from baseline were shown. Even at the baseline, sham hearts showed better systolic and diastolic LV function than MI hearts. In addition, sham hearts had better response to dobutamine stimulation for both systolic and diastolic function. * p < 0.05 vs. sham; # p < 0.05 vs. baseline.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 4: Echocardiographic and hemodynamic changes with dubutamine stimulation after small MI. A: Echocardiographic findings at 7 weeks after MI with dobutamine stimulation (baseline, 5, and 10 μg/kg/min for MI [n = 5] and sham groups [n = 5]) under xylazine/ketamine anesthesia. Significant heart rate increases were noted in MI group at 10 μg/kg/min, but not in sham group. %FS did not significantly change in response to dobutamine in either group, although there is a mild dose-dependent positive trend in sham mice. #p < 0.05 vs. baseline. B: Hemodynamic data by cardiac catheterization at 7 weeks in MI (n = 5) and sham group (n = 5) with dobutamine stimulation (baseline, 5 μg/kg/min, and 10 μg/kg/min). LVSP was comparable between MI and sham at the baseline but became significantly higher in sham than in MI with maximum dobutamine stimulation. LVEDP was significantly higher in MI than in sham group at the baseline, and these values did not significantly change with dobutamine stimulation. Maximum response in (+)dP/dTmax and (−)dP/dTmax by dobutamine infusion from baseline were shown. Even at the baseline, sham hearts showed better systolic and diastolic LV function than MI hearts. In addition, sham hearts had better response to dobutamine stimulation for both systolic and diastolic function. * p < 0.05 vs. sham; # p < 0.05 vs. baseline.
Mentions: At 7 weeks after MI, echocardiography and cardiac catheterization were performed simultaneously at rest and with continuous intravenous infusion of dobutamine (first 5 and then 10 μg/kg/min) under ketamine/xylazine anesthesia (Figure 4). Heart rate increase with dobutamine stimulation was more prominent in the MI group than in sham group. %FS by echocardiogram showed positive response by dobutamine, more in the sham group than in the MI group, although the increase was not statistically significant (Figure 4A). In hemodynamic evaluation, LVSP increased significantly with 10 μg/kg/min of dobutamine infusion in sham, whereas the increase was only modest in the MI group (Figure 4B). LVEDP was notably higher in MI than in sham, but the value did not change throughout dobutamine stimulation in either group. At the baseline, the absolute values of both (+)dP/dTmax and (−)dP/dTmax were significantly higher in the sham group than in the MI group (6820 ± 573 vs. 4115 ± 485 [p < 0.05], and –6144 ± 614 vs. –3824 ± 540 [p < 0.05], respectively); further difference was observed with the 10 μg/kg/min of dobutamine infusion (15681 ± 2128 vs. 8118 ± 1144 [p < 0.05] and –11986 ± 1257 vs. –5542 ± 920 [p < 0.05], respectively), suggesting that both systolic and diastolic ventricular reserve capacities were significantly diminished in MI compared with sham. Three of 5 MI mice developed hemodynamic instability at 20 μg/kg/min of dobutamine infusion. Of these 3, 2 mice subsequently died of cardiovascular collapse. Echocardiographic measurements at 7 wk were not included in Figure 2 because the method of anesthesia was different, which caused a significantly lower heart rate than under isoflurane anesthesia. Nevertheless, the measured echocardiographic parameters at 7 wks for both MI and sham were comparable from those obtained at 5 wks (data not shown).

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