Evaluation of stunned and infarcted canine myocardium by real time myocardial contrast echocardiography

Abstract

Differentiation between stunned and infarcted myocardium in the setting of acute ischemia is challenging. Real time myocardial contrast echocardiography allows the simultaneous assessment of myocardial perfusion and function. In the present study we evaluated infarcted and stunned myocardium in an experimental model using real time myocardial contrast echocardiography. Sixteen dogs underwent 180 min of coronary occlusion followed by reperfusion (infarct model) and seven other dogs were submitted to 20 min of coronary occlusion followed by reperfusion (stunned model). Wall motion abnormality and perfusional myocardial defect areas were measured by planimetry. Risk and infarct areas were determined by tissue staining. In the infarct model, the wall motion abnormality area during coronary occlusion (5.52 ± 1.14 cm 2 ) was larger than the perfusional myocardial defect area (3.71 ± 1.45 cm 2 ; P < 0.001). Reperfusion resulted in maintenance of wall motion abnormality (5.45 ± 1.41 cm 2 ; P = 0.43 versus occlusion) and reduction of perfusional myocardial defect (1.51 ± 1.29 cm 2 ; P = 0.004 versus occlusion). Infarct size determined by contrast echocardiography correlated with tissue staining (r = 0.71; P = 0.002). In the stunned model, the wall motion abnormality area was 5.49 ± 0.68 cm 2 during occlusion and remained 5.1 ± 0.63 cm 2 after reperfusion (P = 0.07). Perfusional defect area was 2.43 ± 0.79 cm 2 during occlusion and was reduced to 0.2 ± 0.53 cm 2 after reperfusion (P = 0.04). 2,3,5-Triphenyl tetrazolium chloride staining confirmed the absence of necrotic myocardium in all dogs in the stunned model. Real time myocardial contrast echocardiography is a noninvasive technique capable of distinguishing between stunned and infarcted myocardium after acute ischemia.

Evaluation of Risk Area by Myocardial Contrast Echocardiography with a New Computer-aided Method

“…In addition, in Groups I and II, MCE with the new technique did not find the infarct size, indicating that short coronary occlusion was not enough to produce myocardial infarction. The results were confirmed by TTC and consistent with previous studies showing that short occlusions in the myocardium (＜45 min) followed by reperfusion resulted in myocardial stunning [3,4].…”

“…One possible explanation is that the presence of collateral flow from adjacent vascular beds allowing some degree of myocardial perfusion in the margins of regions supplied by the occluded coronary artery [4]. Although the risk area measured by color-coded map of the computer-aided software was also smaller than the anatomical risk area, the correlation between the above measurements was better than that between MPD and staining.…”

“…Myocardial contrast echocardiography (MCE) has been used to gain new insight into diagnosis of myocardial infarct (MI) and/or myocardial ischemia [1][2][3][4]. Because contrast agent has similar rheology as red blood cells within the microcirculation, MCE can also assess the myocardial capillary perfusion after thrombolytic therapy or percutaneous coronary intervention [5][6][7].…”

Bioeffects of albumin-encapsulated microbubbles and real-time myocardial contrast echocardiography in an experimental canine model

“…In recent years, myocardial contrast echocardiography has been demonstrated to be a feasible and accurate method for the evaluation of myocardial perfusion in many clinical settings (2)(3)(4)(5). In addition, the combination of intravenous contrast agents and RTMCE with application of high-mechanical index impulses for microbubble destruction followed by myocardial replenishment has permitted the quantification of myocardial blood flow (19,20).…”

“…The development of low-mechanical index imaging techniques that cause minimal microbubble destruction has permitted simultaneous analysis of myocardial perfusion and function in real time (2). Real-time myocardial contrast echocardiography (RTMCE) increases the sensitivity of dobutamine stress testing for the detection of coronary artery disease (3,4) and can distinguish between stunned and infarcted myocardium after acute ischemia (5). However, some concerns regarding the safety of this new imaging modality remain, mainly because some animal studies have demonstrated damage to the endothelial system in the presence of microbubbles and ultrasound (6)(7)(8)(9).…”