OBJECTIVE: To report the case of a patient who underwent orthotopic heart transplant (OHT) and demonstrated a supratherapeutic response to ezetimibe when administered with cyclosporine. CASE SUMMARY: Ezetimibe 10 mg/day was added to the lipid-lowering regimen (atorvastatin 40 mg/day) of a 64-year-old male patient after OHT to achieve a target low-density lipoprotein cholesterol (LDL-C) level ≤97 mg/dL, as recommended by national guidelines. After 2 months of ezetimibe, the patient's LDL-C level had decreased by 60% to 51 mg/dL. Subsequently, the dose of ezetimibe was reduced to 5 mg/day and, after another 2 months, a repeat lipid panel revealed LDL-C 57 mg/dL. DISCUSSION: Hyperlipidemia is a common problem among heart transplant recipients. Combination therapy using a statin plus ezetimibe appears to be an attractive option to achieve target lipid levels in this population. However, the manufacturer warns that ezetimibe should be administered cautiously in patients concomitantly receiving cyclosporine. Unpublished data suggest a pharmacokinetic interaction between ezetimibe and cyclosporine that results in a significant 2.3- to 12-fold increase in exposure to total ezetimibe. An objective causality assessment in this case revealed that this supratherapeutic LDL-C reduction was probably related to coadministration of ezetimibe and cyclosporine. A potential mechanism to explain this interaction might be an alteration in glucuronidation induced by cyclosporine. CONCLUSIONS: When ezetimibe is prescribed for patients concomitantly receiving cyclosporine, it should be initiated at a lower than recommended dose (≤5 mg/day) and titrated upward. Careful and consistent monitoring of patients on this combination is also advised.
A series of 96 posttransplant endomyocardial biopsies taken from 11 patients was subjected to quantitative analysis of mast cells and fibrosis. Ultrastructural analysis showed that mast cell numbers were increased and there was obvious degranulation in some posttransplant hearts. Activated mast cells and their secreted products, which contain heparin and histamine, are toxic to the hearts and may contribute to interstitial and perimyocytic fibrosis. The numbers of mast cells and granules were correlated with volume of fibrosis (r=0.63, P < 0.025; r=0.73, P < 0.01). There were differences between the release of mast cell granule contents seen in the posttransplant hearts and the rapid and massive reaction of anaphylactic degranulation of mast cells. Some mast cells progressively lost their dense granule contents, displaying a variety of piecemeal degranulation that indicates a slow degranulation process. These events occurred from the first week; they lasted from weeks to months. The fibrosis developed quickly in the cases with more mast cells and degranulation. The cases with fewer mast cells and granules showed only mild increases in the volume of fibrosis. Mast cells appeared as early as the first posttransplantation week. Patients with greater numbers of mast cells underwent more severe rejection episodes. This study demonstrated that mast cells play an early and important role in the perimyocytic and interstitial fibrosis of posttransplant hearts. Mast cells may also be important in the inflammatory process of rejection reaction. The severity of fibrosis appears related to the density of mast cells and their granules.
Three-dimensional (3D) mode imaging is the current standard for PET/CT systems. Dynamic imaging for quantification of myocardial blood flow with short-lived tracers, such as 82Rb-chloride, requires accuracy to be maintained over a wide range of isotope activities and scanner counting rates. We proposed new performance standard measurements to characterize the dynamic range of PET systems for accurate quantitative imaging.82Rb or 13N-ammonia (1,100-3,000 MBq) was injected into the heart wall insert of an anthropomorphic torso phantom. A decaying isotope scan was obtained over 5 half-lives on 9 different 3D PET/CT systems and 1 3D/2-dimensional PET-only system. Dynamic images (28 × 15 s) were reconstructed using iterative algorithms with all corrections enabled. Dynamic range was defined as the maximum activity in the myocardial wall with less than 10% bias, from which corresponding dead-time, counting rates, and/or injected activity limits were established for each scanner. Scatter correction residual bias was estimated as the maximum cavity blood-to-myocardium activity ratio. Image quality was assessed via the coefficient of variation measuring nonuniformity of the left ventricular myocardium activity distribution.Maximum recommended injected activity/body weight, peak dead-time correction factor, counting rates, and residual scatter bias for accurate cardiac myocardial blood flow imaging were 3-14 MBq/kg, 1.5-4.0, 22-64 Mcps singles and 4-14 Mcps prompt coincidence counting rates, and 2%-10% on the investigated scanners. Nonuniformity of the myocardial activity distribution varied from 3% to 16%.Accurate dynamic imaging is possible on the 10 3D PET systems if the maximum injected MBq/kg values are respected to limit peak dead-time losses during the bolus first-pass transit.
