ALBERT

Notes: Abstract Decreasing pleural pressure impedes the ejection of blood from the left ventricle (LV), may lead to decreased LV compliance because of interdependence effects and leads to increased transmural LV systolic and diastolic pressure. Previous work from this laboratory has shown that patients with coronary artery disease (CAD) often develop akinetic segments of the LV wall during the Mueller maneuver. In the presence of increased LV transmural pressure regional akinesis could be caused either by the development of regional ischemia or by mechanical inhibition of motion of an area of nonfunctional myocardium as would be caused by previous myocardial infarction (MI). The present study was designed to distinguish between these two mechanisms by determining if the presence of CAD alone is sufficient to lead to regional akinesis or if prior MI is necessary. We used first pass radionuclide ventriculography (RVG) in the 30° LAD supine position to measure LV ejection fraction (EF), end-diastolic (EDV) and end-systolic (ESV) volumes, heart rate and to assess regional wall motion during the Mueller maneuver. This was done in four groups of subjects: (1) 13 normal subjects, (2) 25 patients with CAD but no prior MI, (3) 13 patients with prior nontransmural MI and (4) 36 patients with prior transmural MI. All subjects had angina pectoris and underwent contrast coronary arteriography. Most also underwent routine contrast left ventriculography as well. There were no significant differences among the three patient groups as regards medications, extent and severity of CAD, and response to routine exercise tolerance testing. EF decreased significantly in the three patient groups (4%–9%, p〈0.01) but not in the normals during the Mueller maneuver. Heart rate increased (5–10 bpm, p〈0.05) in the normals and in patient groups 2 and 4. EDV decrease in all four subject groups (8%–10%, p〈0.01), while ESV remained unchanged. Akinesis of the LV wall developed during the Mueller maneuver only in one group-2 patient, but did so in 17/36 patients with prior transmural MI (group 4, p〈0.001). One-half of the akinetic LV wall segments seen during the Mueller maneuver on RVG were not seen on routine contrast ventriculography. We tested the effects of posture (supine versus upright) on the response to the Mueller maneuver in six normal subjects and found no changes in the response of EDV and ESV to the Mueller maneuver. We conclude that (1) the appearance of LV wall akinesis during the Mueller maneuver signifies the presence of prior transmural MI, and not just CAD; (2) the Mueller maneuver can enhance the sensitivity of the RVG for detecting nonfunctional myocardium; (3) regional akinesis develops even when LV volume decreases, suggesting it is due to changes in LV transmural pressure; (4) there are changes in LV function which can lead to a decrease in global EF during the Mueller maneuver; (5) the effects of the Mueller maneuver on LV volume are complex, variable and are subject to multifactorial influences.