Coronary flow reserve dysfunction in hemodialysis and kidney transplant patients

Background: The assessment of coronary flow reserve (CFR) by trans-thoracic echocardiography has recently been introduced into clinical studies. Impairment of coronary microvascular functions and decreased CFR detected by trans-thoracic Doppler harmonic echocardiography (TTDE) has recently been reported in hemodialysis (HD) patients, but there is no comparative study between HD patients and renal transplant recipients. Methods: The aim of our study was to evaluate coronary microvascular circulation in chronic HD patients and renal transplant recipients. Forty-eight chronic HD patients, 27 renal transplant patients and 39 normotensive healthy controls were studied for the assessment of CFR by TTDE. The carotid artery intima media thickness (IMT) and areas of focal plaque formation were also evaluated in all subjects. Results: CFR values were significantly lower in both the HD and renal transplant groups than in the control group (p = 0.00). CFR values (1.57 ± 0.32 vs. 1.89 ± 0.50, p = 0.01) were also significantly lower in the HD group than in the renal transplant group. In 43 of 48 (89.6%) HD patients, CFR was <2.0; however, in 16 of 27 (59.3%) renal transplant recipients it was <2.0 (p = 0.00). When the HD and renal transplant groups were divided into two subgroups, according to CFR measurements (CFR < 2 and ≥2), no significant differences were found with respect to coronary risk factors and left ventricular echocardiographic measurements. The IMT of the control group (0.586 ± 0.163 mm) was significantly lower than the HD (0.799 ± 0.218 mm) and renal transplant groups (0.681 ± 0.148 mm; p = 0.00). The IMT of the HD patients (0.799 ± 0.218 mm) was significantly higher than the renal transplant recipients (0.681 ± 0.148 mm; p = 0.01). Conclusions: Renal transplant and HD patients had lower CFR values detected by TTDE, which may be regarded as an early finding of an affected cardiovascular system. CFR is more impaired in HD patients than renal transplant recipients. Uremia-associated microvascular disease may be responsible for CFR impairment in HD patients.