Therapeutic effect of intermittent hypobaric hypoxia on myocardial infarction in rats.

Intermittent hypobaric hypoxia (IHH) preconditioning protects the heart against ischemic injuries. However, little is known about the therapeutic effect of IHH on myocardial infarction (MI). The aim of this study was to test whether IHH treatment influences infarct size and cardiac performance after MI. Seven days after sham operation or left anterior descending coronary artery ligation, male Sprague-Dawley rats were randomly exposed to normoxia or one 6-h period each day of IHH (5,000 m) for 14 and 28 days. Echocardiography analysis showed that IHH significantly reduced left ventricular (LV) dilation and improved cardiac performance after 14- or 28-day treatment compared with MI-normoxic groups. The improvement of LV function was further confirmed in isolated perfused MI-IHH hearts. Such protection was associated with attenuated infarct size, myocardial fibrosis, and apoptotic cardiomyocytes. IHH treatment also enhanced coronary flow and phosphorylation of heat shock protein 27 in both sham and MI groups compared with the control groups. In addition, IHH increased the capillary density and vascular endothelial growth factor expression in peri-infarcted zones compared with sham-IHH and MI-normoxic groups. Our data demonstrated for the first time that IHH treatment exerts a therapeutic effect on MI by attenuating progressive myocardial remodeling and improving myocardial contractility. IHH treatment might provide a unique and promising therapeutic approach for ischemic heart diseases.

Assessment of left ventricular segmental function after autologous bone marrow stem cells transplantation in patients with acute myocardial infarction by tissue tracking and strain imaging.

BACKGROUND: Emerging evidence suggests that stem cells can be used to improve cardiac function in patients after acute myocardial infarction. In this randomized trial, we aimed to use Doppler tissue tracking and strain imaging to assess left ventricular segmental function after intracoronary transfer of autologous bone-marrow stem cells (BMCs) for 6 months' follow up. METHODS: Twenty patients with acute myocardial infarction and anterior descending coronary artery occlusion proven by angiography were [corrected] randomized into intracoronary injection of bone-marrow cell (treated, n = 9) or diluted serum (control, n = 11) groups. GE vivid 7 and Q-analyze software were used to perform echocardiogram in both groups 1 week, 3 months and 6 months after treatment. Three apical views of tissue Doppler imaging were acquired to measure peak systolic displacement (Ds) and peak systolic strain (epsilonpeak) from 12 segments of LV walls. Left ventricular ejection fraction (LVEF), end-diastolic volume (EDV) and end-systolic volume (ESV) were obtained by Simposon's biplane method. RESULTS: (1) 3 months later, Ds and epsilonpeak over the infract-related region clearly increased in the BMCs group [Ds: (4.49 +/- 2.71) mm vs (7.56 +/- 2.95) mm, P < 0.01; epsilonpeak: (-13.40 +/- 6.00)% vs (-17.06 +/- 6.05)%, P < 0.01], but not in the control group [Ds: (4.74 +/- 2.67) mm vs (5.01 +/- 3.23) mm, P > 0.05; epsilonpeak: (-13.84 +/- 6.05)% vs (-15.04 +/- 6.75)%, P > 0.05]. At the same time, Ds over the normal region also increased, but the Ds enhancement was markedly higher in the BMCs group than that in the control group [(3.21 +/- 3.17) mm vs (0.76 +/- 1.94) mm, P < 0.01]. Parameters remained steady from the 3rd to 6th month in either group (P > 0.05). (2) LVEF in treated and control groups were almost the same at baseline (1st week after PCI) [(53.37 +/- 8.92)% vs (53.51 +/- 5.84)%, P > 0.05]. But 6 months later, LVEF in the BMCs group were clearly higher than that in the control group [(59.33 +/- 12.91)% vs (50.30 +/- 8.30)%, P < 0.05]. (3) There were no evident difference in EDV or ESV between two groups at baseline [EDV: (113.74 +/- 23.24) ml vs (129.94 +/- 32.72) ml, P > 0.05; ESV: (57.12 +/- 18.66) ml vs (62.09 +/- 17.68) ml, P > 0.05]. Three months later, EDV and ESV in the control group were markedly greater than those in the BMCs group [EDV: (154.89 +/- 46.34) ml vs (104.85 +/- 33.21) ml, P < 0.05; ESV: (82.91 +/- 35.79) ml vs (49.54 +/- 23.32) ml, P < 0.05]. But EDV and ESV did not change much from 3rd to 6th month in either group (P > 0.05). CONCLUSIONS: Emergency transplantation of autologous BMCs in patients with acute myocardial infarction helps to improve global and regional contractility and attenuate post-infarction left ventricular remodeling. Tissue tracking and strain imaging provide quick, simple and noninvasive methods for quantifying left ventricular segmental function in humans.