Chronic skeletal muscle ischemia preserves coronary flow in the ischemic rat heart

Abstract

Varnavas VC, Kontaras K, Glava C, Maniotis CD, Koutouzis M, Baltogiannis GG, Papalois A, Kolettis TM, Kyriakides ZS. Chronic skeletal muscle ischemia preserves coronary flow in the ischemic rat heart. Am J Physiol Heart Circ Physiol 301: H1229-H1235, 2011. First published July 15, 2011; doi:10.1152/ajpheart.00232.2011.-Chronic skeletal muscle ischemia confers cytoprotection to the ventricular myocardium during infarction, but the underlying mechanisms remain unclear. Although neovascularization in the left ventricular myocardium has been proposed as a possible mechanism, the functional capacity of such vessels has not been studied. We examined the effects of chronic limb ischemia on infarct size, coronary blood flow, and left ventricular function after ischemia-reperfusion. Hindlimb ischemia was induced in 65 Wistar rats by excision of the left femoral artery, whereas 65 rats were sham operated. After 4 wk, myocardial infarction was generated by permanent coronary artery ligation. Infarct size was measured 24 h postligation. Left ventricular function was evaluated in isolated hearts after ischemia-reperfusion, 4 wk after limb ischemia. Neovascularization was assessed by immunohistochemistry, and coronary flow was measured under maximum vasodilatation at different perfusion pressures before and after coronary ligation. Infarct size was smaller after limb ischemia compared with controls (24.4 Ϯ 8.1% vs. 46.2 Ϯ 9.5% of the ventricle and 47.6 Ϯ 8.7% vs. 80.1 Ϯ 9.3% of the ischemic area, respectively). Indexes of left ventricular function at the end of reperfusion (divided by baseline values) were improved after limb ischemia (developed pressure: 0.68 Ϯ 0.06 vs. 0.59 Ϯ 0.05, P ϭ 0.008; maximum ϩdP/dt: 0.70 Ϯ 0.08 vs. 0.59 Ϯ 0.04, P ϭ 0.004; and maximum ϪdP/dt: 0.86 Ϯ 0.14 vs. 0.72 Ϯ 0.10, P ϭ 0.041). Coronary vessel density was markedly higher (P ϭ 0.00021) in limb ischemic rats. In contrast to controls (F ϭ 5.65, P ϭ 0.00182), where coronary flow decreased, it remained unchanged (F ϭ 1.36, P ϭ 0.28) after ligation in limb ischemic rats. In conclusion, chronic hindlimb ischemia decreases infarct size and attenuates left ventricular dysfunction by increasing coronary collateral vessel density and blood flow. chronic limb ischemia; infarct size; left ventricular function ISCHEMIC MYOCARDIAL PRECONDITIONING describes the situation where the ventricular myocardium is rendered more resistant to a prolonged ischemic insult by preceding brief periods of ischemia (22,23). In the experimental setting, a further approach of myocardial protection has been observed after short ischemic episodes of peripheral tissues, a process termed remote ischemic preconditioning (2,14). Cytoprotection in the heart has been demonstrated after ischemia in a variety of peripheral tissues, such as the mesenterium, kidney, and skeletal muscle (12, 32). Of these, skeletal muscles have attracted considerable scientific interest because they are easily accessible and can be manipulated without major risk in the clinical setting, should this method pr...

FSTL1 as a Potential Mediator of Exercise-Induced Cardioprotection in Post-Myocardial Infarction Rats

“…For example, a brief pre-MI ischemic insult of skeletal muscle is reported to decrease infarct size434445 and chronic ischemia of skeletal muscle can increase left ventricle coronary vessel density46. These results suggest that ischemic muscle may exert its cardioprotection through some neurohumoral mechanism47.…”

Endothelin-B Receptors and Left Ventricular Dysfunction after Regional versus Global Ischaemia-Reperfusion in Rat Hearts

“…The low dosage of this anaesthetic protocol, coupled with its brief duration associated with the ex vivo experimental conditions, precludes significant effects on cardiac function. After a left lateral thoracotomy, the hearts were rapidly excised and were mounted on a Langendorff apparatus (ML870B2 system, ADInstruments, Oxfordshire, UK), as previously described [27, 33]. The preparations were perfused at a constant flow of 12.5 ml/min with Krebs-Henseleit solution at the following composition (in mmol/L): NaCl: 118.1, KCl: 4.6, CaCl 2 : 2.5, MgSO 4 : 1.2, KH 2 PO 4 : 1.2, NaHCO 3 : 24.8, and glucose: 10.33.…”

“…The pH and temperature were kept stable at 7.4 and 37°C, respectively. To ensure comparable measurements, atrial pacing was performed at a rate of 300 beats per minute during the stabilization period and during reperfusion; as in previous reports, pacing was continued during regional [34], but not during global [27, 33] ischaemia. …”

Physiologic Remote Ischemic Training Offers a Cardioprotective Effect against Myocardial Infarction in a Time-Dependent Manner

“…Unlike IPC, PRIT has a more remote effect by facilitating coronary collateral formation of the myocardium by repeated short-term skeletal muscle ischemia. The cardioprotective effect of short-term skeletal muscle ischemia has been previously evaluated in experimental [20] and clinical [21] studies and the beneficial effect on the ventricular myocardium is not specific for a particular species [8]. PRIT is reversible non-invasive ischemia of normal skeletal muscles caused by tourniquet or isometric contraction, induce collateral circulation development in the myocardium (9).…”

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