Abstract
We previously determined that residual left ventricular (LV) myocardium of middle‐aged rats had sex‐related differences in regional tissue properties 4 weeks after a large myocardial infarction (MI). However, the impact of such differences on cardiac performance remained unclear. Therefore, our current study aimed to elucidate whether sex‐related changes in MI‐induced myocardial remodeling can influence cardiac function. A similar‐sized MI was induced in 12‐month‐old male (M‐MI) and female (F‐MI) Sprague–Dawley rats by ligation of the left coronary artery. The cardiac function was monitored for 2 months after MI and then various LV parameters were compared between sexes. We found that although two sex groups had a similar pattern of MI‐induced decline in LV function, F‐MI rats had greater cardiac performance compared to M‐MI rats, considering the higher values of EF (39.9 ± 3.4% vs. 26.7 ± 7.7%, P < 0.05), SW index (40.4 ± 2.1 mmHg • mL/kg vs. 20.2 ± 3.3 mmHg • mL/kg, P < 0.001), and CI (139.2 ± 7.9 mL/min/kg vs. 74.9 ± 14.7 mL/min/kg, P < 0.01). The poorer pumping capacity in M‐MI hearts was associated with markedly reduced LV compliance and prolonged relaxation. On the tissue level, F‐MI rats revealed a higher, than in M‐MI rats, density of cardiac myocytes in the LV free wall (2383.8 ± 242.6 cells/mm2 vs. 1785.7 ± 55.9 cells/mm2, P < 0.05). The latter finding correlated with a lower density of apoptotic cardiac myocytes in residual LV myocardium of F‐MI rats (0.18 ± 0.08 cells/mm2 vs. 0.91 ± 0.30 cells/mm2 in males, P < 0.01). Thus, our data suggested that F‐MI rats had markedly attenuated decline in cardiac performance compared to males due to ability of female rats to better retain functionally favorable intrinsic myocardial properties.
Highlights
Myocardial infarction (MI) remains one of the major causes of systolic heart failure (HF) in the elderly of both sexes (Hellermann et al 2002; Weir et al 2006)
Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society
Echocardiographic assessment of dynamic changes in left ventricular (LV) geometry and function Serial examinations of LV structural and functional parameters were performed in two groups of middle-aged male and female rats between baseline and eighth week following a large transmural myocardial infarction (MI)
Summary
Myocardial infarction (MI) remains one of the major causes of systolic heart failure (HF) in the elderly of both sexes (Hellermann et al 2002; Weir et al 2006). In patients with an acute MI, the impairment of left ventricular (LV) function, which is initially caused by severe ischemic myocardial damage, has often progressed to HF due to adverse LV chamber remodeling (Gaasch et al 2008). During this process, the alteration in LV geometry and mass (Gaasch and Zile 2011) has been often accompanied by significant changes in myocardial tissue properties (Beltrami et al 1994).
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