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Improvement of afterload mismatch of left atrial booster pump function with positive inotropic agent

^a Second Department of Internal Medicine, Yamaguchi University School of Medicine, Yamaguchi, Japan

View larger version (18K): [in a new window]   Figure 1 Transmitral flow velocity. Representative transmitral flow waveforms at baseline and during acute myocardial ischemia (MI) and acute MI with dobutamine (DOB). Aortic constriction (Aoc) during acute MI significantly reduced the late diastolic peak flow velocity, indicating pseudonormalization of the transmitral flow. Dobutamine infusion during acute MI with Aoc increased the late diastolic peak flow velocity, resulting in an improvement in left ventricular (LV) filling during left atrial (LA) contraction. ECG = electrocardiogram.

View larger version (56K): [in a new window]   Figure 2 The relation between transmitral flow and PV venous flow and changes of LA and LV pressures with or without DOB. Representative simultaneous recordings of the transmitral flow velocity and PV flow volume and tracings of LV pressure and magnified LV and LA pressures (arrows in right lower panel). With Aoc during MI, the pressure increase is larger and more rapid in the LV than it is in the LA at atrial systole (lower mid panel), resulting in a reduced late diastolic transmitral flow velocity and an increased PV reverse flow volume (upper mid panel). Thus, in the presence of an LA afterload mismatch, a substantial blood volume was ejected from the LA backward into the PV with atrial contraction. Dobutamine infusion markedly corrected this mismatch (upper right panel). Aoc = aortic constriction; DOB = dobutamine infusion; LA = left atrial; LV = left ventricular; MI = myocardial ischemia; PV = pulmonary vein.

View larger version (27K): [in a new window]   Figure 3 Changes in peak (minimum) PV flow volume during atrial contraction at each stage. The backward flow into the PV is represented by a negative value. Data are the mean ± standard deviation. Aoc = aortic constriction; DOB = dobutamine infusion; MI = myocardial infarction or ischemia; PV = pulmonary vein.

View larger version (25K): [in a new window]   Figure 4 Changes in diastolic LVP-volume relations and changes in LV chamber stiffness at each stage. Top: Representative diastolic LVP-volume relations at baseline, during MI and during MI with DOB all without Aoc. Bottom: Changes in LV chamber stiffness at baseline, during MI and during MI with DOB, with or without Aoc. Data are the mean ± SD. Aoc = aortic constriction; DOB = dobutamine infusion; LV = left ventricle; LVP = left ventricular pressure; MI = myocardial ischemia.

View larger version (15K): [in a new window]   Figure 5 Relationship between the time-velocity integral of the A and LV operational chamber stiffness for all the data points in this study. A = late diastolic transmitral flow velocity; LV = left ventricle.