This was a cross-sectional monocentric study that included patients with heart transplantation < 10 years previous who were undergoing heart transplantation monitoring from January 2017 to December 2019. Exclusion criteria were age < 18 years, multiorgan transplantation and dialysis. All patients were evaluated by a senior rheumatologist. The following data were systematically collected: 1) demographic characteristics including sex, age, smoking status, excessive alcohol consumption (>20 g/day for women and >30 g/day for men), and diabetes; 2) the etiology of heart disease and treatment received after the transplant; 3) previous history of fractures and previous treatments for osteoporosis (calcium, vitamin D and osteoporotic therapies). Dietary calcium intake was evaluated with a specific questionnaire (12).

BMD was measured by dual-energy X-ray absorptiometry (Hologic Inc., Waltham, MA) at the lumbar spine (second to fourth vertebrae and vertebral fractures were excluded for BMD evaluation) and the upper part of the left femur (total femur and femoral neck). The results were given as BMD (g/cm²) and T-scores (standard deviation). Sex-specific T-scores were based on female and male reference curves. The device was controlled by measuring a spine phantom at least three times per week throughout the study. All examinations were performed according to the manufacturer’s recommendations. Osteoporosis was defined for patients ≥50 and <50 years as a T-score ≤-2.5 SD and Z-score ≤-2 SD at the lumbar spine (L1-L4), femoral neck or total femur. Osteopenia was defined for patients ≥50 and <50 years old as a T-score ≤-1 SD and Z-score ≤-1 SD at the lumbar spine (L1-L4), femoral neck or total femur (13).

Data on previous fractures (location, date) were collected. All patients underwent radiography with anteroposterior and lateral views of the dorsal and lumbar spine to establish the presence of vertebral fractures. Vertebral fracture diagnosis was confirmed in the presence of a reduction > 20% of the height of the vertebra (14). An experienced rheumatologist analyzed the radiographs.

At inclusion, all patients were assessed for calcium, phosphorus, creatinine, parathyroid hormone, 25 hydroxy-vitamin D, ß C-terminal propeptides of type I procollagen (ßCTX), osteocalcin (N-Mid osteocalcin) and bone-specific alkaline phosphatase levels (B-ALP). Serum for biochemical analysis was obtained in the morning under fasting conditions in the same laboratory. Serum calcium (normally 2.20-2.55 mmol/l), phosphorus (normally 0.81-1.5 mmol/l) and creatinine (normally <84 μmol/l) were measured by standard automated techniques (Cobas Pro, Roche). Intact parathormone 1-84 (normally 15-65 ng/l) was measured by electrochemiluminescence immunoassay (Cobas Pro, Roche), 25 hydroxy-vitamin D (normally 75-200 nmol/l), ßCTX (normally <0.635 μg/l), osteocalcin (normally 10.4-45.6 μg/l) and B-ALP (normally 4.7-27.0 μg/l) were measured by immunoassay (IDS-iSYS). Vitamin D deficiency was defined as serum level of 25 hydroxy-vitamin D < 50 nmol/l, insufficiency 50 to 75 nmol/l (15).

The Institutional Review Board (No. 12-011) of Paris North Hospitals approved this study. Written informed consent was obtained from all participants in agreement with French bioethics laws.

All data are expressed as mean ± SD and were compared by Mann Whitney test. Categorical data are described with number (%; percentages were calculated excluding missing data) and were compared by chi-square test or Fisher exact test, as appropriate. Univariate analysis (p<0.15) was performed to select potential explanatory variables that were then tested in the multivariable model (stepwise method). Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated. P < 0.05 was considered statistically significant.

From January 2017 to December 2019, 161 patients who underwent heart transplantation were screened for inclusion; 15 were excluded (age < 18 years, n=1; multiorgan transplantation, n=1; dialysis, n=13), 39 patients died and 28 were lost to follow-up ( Figure 1 ). The baseline characteristics of the 79 patients are summarized in Table 1 . Briefly, 61 were male (77.2%), the mean age was 54.1 ± 10.8 years, the mean body mass index (BMI) was 27.2 ± 4.99 kg/m², 49 (62%) were ever-smokers and 7 (8.9%) were current smokers. Twelve (15.2%) had excessive alcohol consumption and 29 (37%) had diabetes mellitus. Among 18 women, 15 had been menopausal for 5.3 years. The heart disease leading to transplantation was dilated cardiomyopathy for 34 (43%) patients, ischemic for 31 (39.2%), valvular cardiopathy for 6 (7.6%) and idiopathic or other cardiopathies for 8 (10.1%). The mean time from heart transplantation to inclusion was 32.3 ± 35.0 months. All patients except 2 received corticosteroids, with a mean dose of 10 ± 4.21 mg per day of prednisone. All patients received vitamin D supplementation. A total of 59 (75%) patients received ciclosporin, 67 (86%) mycophenolate mofetil, 14 (18%) tacrolimus and 24 (31%) everlimus. Two patients received osteoporotic treatment: alendronate, n=1, and zoledronic acid, n=1.

Osteopenia and osteoporosis were diagnosed in 38 (48%) and 22 (28%) patients, respectively. Diabetes mellitus was less prevalent in patients with than without osteoporosis: 4 (18%) versus 24 (44%), p=0.036 ( Table 2 ). Pre-transplant osteoporotic fractures were noted for 2 patients (2 femoral neck fractures). At the time of the visit, 21 (27%) patients had fractures diagnosed after transplantation. Vertebral fractures were the most frequent (15, 71.4%). In total, 15 patients had 30 vertebral fractures (11 thoracic and 19 lumbar vertebral) ( Figure 2 ). For 7 patients, vertebral fractures were unknown and were diagnosed on systematic X-rays. The other sites of fractures were femoral neck (n=2), pelvic (n=1), humeral (n=1), fibula (n=1), ad clavicular (n=1). Mean ages of patients with and without fracture after transplantation were 57.6±9.84 and 52.9±10.9 years, respectively (p=0.04). Estimated glomerular filtration rate (eGFR) was lower with than without fracture (44.8 ± 14.8 vs 53.3 ± 18.6, p=0.011), but osteoporosis was more frequent (9 [43%] vs 13 [22%], p=0.073) ( Table 3 ). The prevalence of osteopenia did not significantly differ between the 2 groups. Mean BMD at the femoral neck and total hip was lower with than without fracture (femoral neck: 0.777 ± 0.125 vs 0.892 ± 0.174 g/cm², p<0.01; total hip: 0.892 ± 0.165 vs 0.748 ± 0.07 g/cm², p<0.001). The mean femoral neck and total hip T-scores were lower in patients with than without fractures: -1.79 ± 0.987 vs -0.955 ± 1.33 SD (p=0.01) and -2.07 ± 0.556 vs -0.976 ± 1.26 SD (p<0.001), but the difference was not significant for spine BMD. We performed a logistic regression analysis including age at transplantation eGFR and confirmed lower femoral neck BMD and total hip BMD for patients with fracture (OR 0.939 [95% CI 0.891–0.980], p<0.01, and OR 0.924 [95% CI 0.873–0.967], p<0.01, respectively). Age at transplantation and eGFR were not associated with fractures on multivariate analysis. The mean time from transplantation to the first fracture was 8.0 ± 7.6 months. Only two patients with fracture were < 50 years old at the time of transplantation (39 and 44 years) and 9 (43%) had a T-score <-2.5 SD at at least one site.

Biochemical variables are described in Table 1 . At the time of the visit, 58 (77%) patients had vitamin D deficiency and 44% (n=34) had increased level of parathyroid hormone. Patients with and without fracture and with and without osteoporosis did not differ in 25 hydroxy-vitamin D level, percentage of vitamin D deficiency, or secondary hyperparathyroidism (p>0.05). Bone turnover was assessed with ßCTX, osteocalcin and B-ALP levels. Bone turnover did not differ between patients with and without fracture or those with and without osteoporosis. Only 9.7% of patients had an increased ßCTX level.

All patients received 2 or 3 immunosuppressant therapies. Overall, 90% (n=71) received calcineurin inhibitors and 86% (n=77) mycophenolate mofetil. Patients with and without fracture and with and without osteoporosis did not differ in immunosuppressant therapies. Dietary daily calcium intake was lower than recommended levels in 58% (n=35) of patients, with no difference between groups (with and without fracture or with and without osteoporosis).

After global bone fragility evaluation, calcium and/or vitamin D therapy was initiated in 58 (73.4%) patients. Specific osteoporosis treatment was started for 56 (70.9%): zoledronic acid (n=42), denosumab (n=8), alendronate (n=4), and teriparatide (n=2).