ABSTRACT
The natural history and outcome of transmural [TM] and nontransmural myocardial infarction [N TM MI] was known to be significantly different many years ago. However, Neither M-mode nor 2-D Echocardiography can provide information regarding TM distribution of contractile performance. Tissue Doppler Echocardiography [TDE] provides new indices of myocardial functions such as myocardial velocity gradient [MVG] which was found to be an accurate method in the experimental assessment of TM. and N. TM. MI. The present work aims to study myocardial velocities in subendocardial and epicardial layers of the infarct segments by pulsed wave [PW] and tissue Doppler echocardiography in order to investigate the value of systolic and diastolic myocardial velocity gradient in distinguishing transmural myocardial infractions from nontransmural one. Forty patients with first attack acute myocardial infarction [MI] and significant single coronary artery disease [> 70% stenosis] were studied with conventional clinical assessment and trans thoracic Echocardiography [TTE] to assess systolic and diastolic left ventricular function, wall motion abnormalities and tissue Doppler imaging [TDI] parameters for assessment of myocardial velocities [including systolic, diastolic and myocardial velocity gradient] in the epicardial and endocardial layers of myocardium. We found a statistically significant difference in the TDI parameters in the endocardial area between the normal and the infarcted segments in patients with transmural and non transmural myocardial infarction. While in the epicardial area there is a statistical significant difference between the infarcted and the normal segments in patients with Q wave myocardial infarction but there is no significant difference in patients with non Q wave myocardial infarction. This means that TDI can detect the non-uniformity of transmural velocity denoting the presence of viable part [epicardial area] in the hypokinetic segments in the nontransmural myocardial infarction. We also found that there is significant difference in TDI parameters in the infarcted segments [either endocardial or epicardial area] between both groups with more depression of the myocardioal velocity in group I [with non Q wave myocardial infarction]. This could be explained by the presence of more viable myocardium in the area with non transmural infarction with less affection of the velocity. We conclude that TDE might be an applicable and noninvasive modality that can detect the non uniformity of transmural velocity differentiating between transmural and nontransmural MI suggesting that aggressive approaches should be taken to salvage myocardium in such patient