Regional remodeling strain and its association with myocardial apoptosis after myocardial infarction in an ovine model

Abstract

Objective: Progressive left ventricular remodeling after myocardial infarction has been viewed as an important contributor to progressive heart failure. The objective of this study was to investigate the relationship between myocardial apoptosis and strain during progressive cardiac remodeling.

Methods: Before creation of an anterolateral left ventricular infarction by ligation of diagonal arteries, 16 sonomicrometry transducers were placed in the left ventricular free wall of 8 sheep to assess regional deformation in the infarct, adjacent, and normally perfused remote myocardial regions over 8 weeks' duration. Hemodynamic, echocardiographic and sonomicrometric data were collected before infarction and then 30 minutes and 2, 6, and 8 weeks after infarction. At the end of the study, regional myocardial tissues were collected for apoptotic signaling proteins.

Results: At terminal study, an increase in left ventricular end-diastolic pressure of 8.1 +/- 0.1 mm Hg, a decrease in ejection fraction from 54.19% +/- 5.68% to 30.55% +/- 2.72%, and an end-diastolic volume increase of 46.08 +/- 5.02 mL as compared with the preinfarct values were observed. The fractional contraction at terminal study correlated with the relative abundance of apoptotic protein expressions: cytochrome c (r(2) = 0.02, P < .05), mitochondrial Bax (r(2) = 0.27, P < .05), caspase-3 (r(2) = 0.31, P < .05), and poly (adenosine diphosphate-ribose) polymerase (r(2) = 0.30, P < .05). These myocardial apoptotic activities also correlated with remodeling strain: cytochrome c (r(2) = 0.02, P < .05), mitochondrial Bax (r(2) = 0.28, P < .05), caspase-3 (r(2) = 0.43, P < .05), and poly (adenosine diphosphate-ribose) polymerase (r(2) = 0.37, P < .05).

Conclusion: Increase in regional remodeling strain led to an increase in myocardial apoptosis and regional contractile dysfunction in heart failure.