[Color-Doppler echocardiography in electromechanical dissociation. Study of 2 cases]

Electromechanical dissociation (EMD) is a condition of cardiac arrest occurring despite the persistence of apparently effective cardiac electric activity. Secondary EMDs are consequence of catastrophic circulatory failure (i.e. great vessel rupture, massive pulmonary embolism, cardiac tamponade), resulting in sudden and critical changes in hemodynamic load. Primary EMDs, on the other hand, occur in presence of intact circulatory system; they are known to be associated with global cardiac ischemia and contraction failure; however, the exact pathophysiologic change, triggering the onset of primary EMD, is still unknown. The current hypothesis of electromechanical uncoupling (a supposed derangement of excitation and contraction linking) has not been demonstrated. On the contrary, in a previous series of 22 2D-echocardiographic evaluations of patients with EMD, wall and valvular motion was visible in the majority of cases. In our Coronary Care Unit we had the opportunity to perform 2D and color-Doppler echocardiogram in 2 patients, developing primary EMD just while the examination was in course; we subsequently completed the examinations in the short pauses of cardio pulmonary resuscitation. Both patients died and necropsy showed in both cases recent large myocardial infarction, without hemopericardium. The analysis of the echocardiograms emphasized the presence of a residual cardiac mechanical activity: minimal segmental wall motion of left ventricle (LV); residual mitral valve motion, but no visible closure; diastolic low-velocity orthograde transmitralic flow; systolic regurgitant flow from LV to left atrium. On the other hand, we didn't observe any systolic flow directed to the LV outflow tract and to the aorta.(ABSTRACT TRUNCATED AT 250 WORDS)