Assessment of Left Ventricular Diastolic Function After Single Lung Transplantation in Patients With Severe Pulmonary Hypertension: Materials and Methods
Left ventricular isovolumic relaxation time was measured as a time interval from aortic closure click to the beginning of the mitral inflow in the apical five-chamber view with a continuous wave cursor positioned to straddle the left ventricular inflow and outflow tract. A sweep speed of 100 cm/s was used for this recording.
A standardized index of eccentricity, circular shape factor (CSF), was employed to determine the degree of deviation of the left ventricular cross section from a perfect circle. The planime-tered cross-sectional area (CSA) from the mid-short axis view during end-systole was used to calculate mean left ventricular diameter: d=2(CSA/’iT). The perimeter (P) for a perfect circle with this diameter was determined from P=Trd. This calculated perimeter was compared with the actual planimetered perimeter (observed perimeter) from the same echocardiographic image. Thus, the CSF was defined as follows: CSF=(calculated P/observed P)2. CSF=1.0 implies a circular shape, and CSF<1.0 implies increasing degree of eccentricity (Fig 1).
Continuous-wave Doppler was used to measure the peak velocity of tricuspid regurgitant flow for estimation of pressure gradient (mm Hg) between right ventricle and right atrium during systole: pressure gradient=4V2, where V is the peak velocity (m/s), and 10 was added as an estimate of the right atrial pressure to derive the right ventricular systolic pressure. Tricuspid regurgitation was evaluated from color Doppler flow images and graded as none, mild, moderate, or severe, depending on the maximal jet area seen from multiple views. This method is similar to that of grading mitral regurgitation. In addition, tricuspid annulus diameter as an index of right ventricular size was measured from an apical four-chamber view during end-diastole. canada viagra
Differences for each Doppler echocardiographic variable among preoperative, early, and late postoperative subgroups were analyzed by analysis of variance, and further comparisons between any two subgroups were carried out using Scheffe F test (StatView 512+; Macintosh; Agoura Hill, Calif). The unpaired t test was applied for comparing all measurements in preoperative and late postoperative subgroups, respectively, with those in control subjects. All descriptive data were expressed as mean values ±SD, and p^0.05 was considered significant.
Figure 1. Degree of the left ventricular (LV) geometric deformation determined by CSF. Top: two-dimensional echocardiographic images of LV cross-section obtained from mid-short axis view during end-systole. Bottom: measurements and calculations for CSF (see text for details). The LV image illustrated on the left appears nearly circular with a CSF of 0.99, while the one on the right is distorted by septal flattening and has a CSF of 0.74.