Abstract 15279: Understanding a Paradox in Patients with Myocardial Ischemia with Increased Diastolic Wall Stress. A Dobutamine Stress MR study

Abstract

BACKGROUND DSMR is a valuable tool to diagnosis ischemia in a wide spectrum of patients. The population with concentric geometry (either hypertrophy or remodeling) have unexpected lower sensitivities. Based on Laplace theory relatively increased wall thickness preserves lower wall stress (LVDWS). A reduced LVDWS (seen in the concentric LV geometries) could explain the normal wall motion even in the presence of significant coronary stenosis. The aim of the study is to investigate weather LVDWS could explain this phenomenon.

MATERIALS 155 patients with suspected or known coronary artery disease were evaluated with DSMR and invasive angiography. LVDSW was calculated using LV end-diastolic volume, LV Myocardial Volume and LV End-Diastolic Pressure. False negative (FN) patients in the wall motion analysis were detected and the level of LVDSW was compared to the rest of the population. 4 Quartiles were defined according to the LVDSW (Q1 being the lowest level). Sensitivity and specificity of DSMR for each quartile were separately calculated for each quartile and comparisons were performed.

RESULTS 20 FN cases were detected in the overall population. A significantly higher level of LVDSW In the FN cases was detected vs. Non-FN population (3,22 ±1.07kPa vs. 3.81 ±1,45kPa; p=0.04). Wall-motion-DSMR sensitivities through Q1-Q4 obtained were 0.71; 0.79; 0,83 and 0,88, respectively, showing ascending behavior (the higher level of LVDSW, the better sensitivity) Specificities through Q1-Q4 were 0.86; 0.9; 0.87 and 0.83, respectively, showing descending behavior.

CONCLUSION The LVDSW determined as subrogate variable of LV geometry and intracavitary pressures (Laplace theory) is a mayor determinant of a wall motion in stress conditions. The LVDSW parameter could explain the myocardial paradox described earlier in this text. Calculation of the LVDSW could be clinically useful selecting patients before DSMR improve the accuracy of the test.