Transient left ventricular dysfunction syndrome: Patho-physiological bases through nuclear medicine imaging

BackgroundTakotsubo cardiomyopathy (TTC) is a novel heart disease, mimicking acute myocardial infarction. The term “transient left ventricular dysfunction syndrome” (TLVDS) seems to be more appropriate since variant forms of TTC sparing apical segments (mid-ventricular ballooning syndrome (MVBS) and inverted TTC) have been described. Patho-physiological bases of TLVDS remain poorly understood and its optimal management is until now empirical. Our aim was to characterize patho-physiological mechanisms of TLVDS by means of nuclear medicine procedures and to discuss the clinical usefulness of isotopic imaging for a non-invasive diagnosis of TLVDS.Methods and resultsDuring the sub acute phase, eighteen patients with TLVDS (13 TTC and 5 MVBS) underwent myocardial 99mTc-tetrofosmin or 201Thallium Gated Single Photon Emission Computed Tomography (G-SPECT) (n = 11), 123I-mIBG SPECT (n = 8) and 18F-FDG Gated Positron Emission Tomography (G-PET) (n = 15), assessing respectively LV perfusion, sympathetic innervation and glucose metabolism. Hypocontractile LV segments were characterized by normal perfusion but reduced uptake of 18F-FDG and 123I-mIBG. Topography and extent of metabolic defects and innervation abnormalities were largely overlapping. Follow-up 123I-mIBG SPECT and 18F-FDG G-PET were performed in selected patients showing rapid normalization of LV motion and progressive improvement of both glucose metabolism and sympathetic innervation.DiscussionWith the hypothesis of neurogenic stunned myocardium as the central causative mechanism of TLVDS, 123I-mIBG SPECT seems to be the most specific diagnostic technique. Sympathetic function and glucose metabolism seem to be strictly correlated in the hypocontractile LV segments. Finally, our results underline the role of nuclear imaging in the setting of patho-physiological mechanisms of TLVDS.