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Παρασκευή 25 Αυγούστου 2017

Functional capacity in a rat model of heart failure: impact of myocardial infarction size

Abstract

Oxygen uptake (VO2) and exercise tolerance in rats classified by myocardial infarction (MI) size are underexplored. The aim of this study was to evaluate VO2/carbon dioxide production (VCO2) and exercise tolerance in rats that have undergone MI. Fourteen weeks after MI or sham surgery, rats underwent an integrated approach to left ventricular function and VO2/VCO2, exercise tolerance and skeletal muscle weight evaluation. Based on MI size determination, rats were assigned to sham operated controls (Sham, n = 12), small myocardial infarction (SMI, n = 8), and large myocardial infarction (LMI, n = 5) groups. LMI rats showed lower systolic (ejection fraction and fractional shortening) and diastolic (E/A ratio) left ventricular function compared with SMI. VO2max (∼24%, P < 0.05), VO2reserve (∼30%, P < 0.05), time to exhaustion (∼36%, P < 0.05) and maximal velocity (∼30%, P < 0.05) was lower in LMI compared with sham operated controls, with no difference between SMI rats and sham operated controls. VCO2max and respiratory exchange ratio (RER) showed no significant difference between MI rats and sham operated control rats. LMI rats demonstrated lower gastrocnemius weight (∼12%, P < 0.05) and soleus weight (∼19%, P = 0.07) compared with sham operated control rats. Significant correlations between MI size, left ventricular end-diastolic pressure, right ventricle hypertrophy, pulmonary congestion, ejection fraction, and fractional shortening with VO2max and run distance were observed. O2 uptake and exercise intolerance are MI size dependent.

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