Role of Transesophageal Echocardiography in the Diagnosis of Paradoxical Low Flow, Low Gradient Severe Aortic Stenosis

BACKGROUND AND OBJECTIVES: Prior studies indicate that up to 35% of cases of severe aortic stenosis (AS) have paradoxical low flow, low gradient despite preserved left ventricular ejection fraction (LVEF). However, error in left ventricular outflow tract (LVOT) diameter may lead to misclassification. Herein, we determined whether measurement of LVOT diameter by transesophageal echocardiography (TEE) results in reclassification of cases to non-severe AS. SUBJECTS AND METHODS: Patients with severe AS with aortic valve area (AVA) <1 cm2 by transthoracic echocardiography (TTE) within 6 months were studied. Paradoxical low flow, low gradient was defined as mean Doppler gradient (MG) <40 mm Hg and stroke volume index (SVI) ≤35 mL/m². Preserved LVEF was defined as ≥0.50. RESULTS: Among 108 patients, 12 (15%) had paradoxical low flow, low gradient severe AS despite preserved LVEF based on TTE measurement. When LVOT diameter by TEE in 2D was used, only 5 (6.3%) patients had low flow, low gradient severe AS (p<0.001). Coefficients of variability for intraobserver and interobserver measurement of LVOT were <10%. However, the limits of agreement between TTE and TEE measurement of LVOT ranged from 0.43 cm (95% confidence interval [CI]: 0.36 to 0.5) to -0.31 cm (95% CI: -0.38 to -0.23). CONCLUSION: TEE measured LVOT diameter may result in reclassification to moderate AS in some patients due to low prevalence of true paradoxical low flow, low gradient (PLFLG) severe AS.

Left Ventricular Torsion Changes Post Kidney Transplantation

BACKGROUND: To quantify changes of left ventricular (LV) torsion in patients' pre and post kidney transplantation. METHODS: A prospective study was conducted on 48 patients who received kidney transplantation for end stage renal disease and without myocardial infarction. The rotation, twist and torsion of LV were studied pre and post kidney transplantation (6 months post transplantation) using velocity vector imaging by echocardiography. The data is expressed as mean +/- standard deviation and compared by paired t-test at the p < 0.05 significance level. RESULTS: Six months post kidney transplantation, left ventricular ejection fraction (from 40.33 +/- 11.42 to 61.00 +/- 13.68%), ratio of mitral early and late diastolic filling velocity (from 1.04 +/- 0.57 to 1.21 +/- 0.52), rotation of basal LV (from 4.48 +/- 2.66 to 5.65 +/- 2.64 degree), rotation of apical LV (from 4.27 +/- 3.08 to 5.50 +/- 4.25 degree), LV twist (8.75 +/- 4.45 to 11.14 +/- 5.25 degree) and torsion (from 1.06 +/- 0.54 to 1.33 +/- 0.61 degree/cm) were increased significantly (p < 0.05). Interventricular septum thickness (from 11.67 +/- 2.39 to 9.67 +/- 0.48 mm), left ventricular mass index (from 104.00 +/- 16.47 to 95.50 +/- 21.44 g/m2), systolic blood pressure (from 143.50 +/- 34.99 to 121.50 +/- 7.09 mmHg), serum blood urea nitrogen (from 42.40 +/- 7.98 to 30.43 +/- 13.85 mg/dL) and creatinine (from 4.53 +/- 1.96 to 2.73 +/- 2.57 mg/dL) were decreased significantly (p < 0.05). CONCLUSION: Kidney transplantation in end stage renal disease without myocardial infarction results in improvement in left ventricular structure, function and myocardial mechanics as detected by echocardiography and velocity vector imaging. Velocity vector imaging provided valuable information for detection and follow-up of cardiac abnormalities in patients with end stage renal disease.