Echocardiographic Evaluation of left Ventricular Function and Geometry in Pediatric Patients with Kidney Transplantation

Extended abstract Echocardiographic Evaluation of Left Ventricular Function and Geometry in Pediatric Patients with Kidney Transplantation Cardiovascular disease (CVD) is an important, leading cause of mortality and morbidity in patients with chronic kidney disease (CKD) as well as in renal transplant recipients. Cardiovascular complications become more important in children because of the improved life span of children after kidney transplantation (KT).  Recent research programs are looking into the initial stages of renal failure to diagnose early and subclinical cardiac impairment. It has been shown that abnormalities in LV geometry which start early during renal impairment are one of the key mechanisms for developing progressive cardiac complications. Despite improving LV function following KT, cardiac complications are still defined as the main risk factor for mortality in renal recipients. (2,7) New echocardiographic techniques using Tissue Doppler Imaging (TDI) have been proven to be sensitive and accurate methods for recognizing the initial phase of ventricular dysfunction in a variety of diseases. (6) To our knowledge, there is a little information on severity of cardiac involvement including structural and functional changes in children with KT who have a short duration of renal impairment. This study aimed to evaluate ventricular systolic and diastolic functions by using TDI parameters in a group of post-transplant children who had no symptoms of heart failure before KT.  Materials and Methods: Clinical and echocardiographic data were prospectively obtained from 18 patients with CKD before kidney transplantation. The inclusion criteria consisted of the following: (1) age under 18 years old, (2) no limitation in ordinary physical activities (NYHA functional class I), (3) LV ejection fraction ≥ 55%, and (4) absence of co-existing disease. The transthoracic echocardiographic study was performed within 3 months before the transplantation by an experienced physician, who was unaware of the status of the subjects. All patients of the study were followed up, and the post-transplant data were obtained during one to three years. The obtained echocardiographic data were analyzed and compared with the control group consisting of 37 age-matched, healthy children.  LV hypertrophy (LVH) was defined as LV mass index >51 g/m2.7. (13) LV systolic function was assessed by measuring ejection fraction (LVEF) using modified Simpson’s method.(12) Tissue Doppler Imaging was used for the assessment of both systolic and diastolic LV functions, and the TDI derived MPI (TDI-MPI) was considered to be a marker of global LV function. (5))In addition, tissue Doppler derived parameters were used for assessing regional longitudinal performances of the left ventricle. Peak early diastolic velocity (e’), peak late diastolic velocity (a’), and peak systolic velocity (s’) were obtained from the septal and lateral sides of the mitral annulus. According to the current guidelines, we evaluated the diastolic function by calculating E/e´ ratio. (14) Results. The mean age at KT was 12.2+2 years. Five patients received maintenance dialysis before KT. Median follow-up after KT was 2.3 (1.3-3) years.  LVEF was within the normal range for all of the patients. LV mass decreased significantly after KT (51 ± 1.5g/m2.7 vs. 43.1±1.6 g/m2.7، p<0.05), but it was still greater than the controls (p<0.05). LVH was found in 8(44%) patients. We observed a positive correlation between pre-transplant hypertension and post-transplant LVMI (r=0.41, p<0.05).  The TDI-MPI, as a marker of global LV function, was significantly greater in the post-transplantation patients than that in control group (0.36 ± 0.13 vs. 0.31 ± 0.01, p <0.05). Using ROC curve analysis, the TDI-MPI yielded an area under the curve of 0.86 to discriminate the patients against those without subclinical LV dysfunction. Using a TDI-MPI > 0.32 as the cut point, LV dysfunction was identified with a sensitivity of 75% and specificity of 48%. We observed a significant correlation between the values of TDI-MPI and the presence of LVH before transplantation (r=0.41,p<0.05).  Regarding the LV longitudinal systolic function, the myocardial systolic velocity (s´) was significantly different between the post-transplantation patients and the ones in the control group (6.5 ± 0.9cm/s vs. 7.3±0.7cm/s, p<0.05), while the myocardial diastolic velocities did not differ between them. Moreover, an inverse relationship was observed between the values of s´ wave velocity and LVMI (r= -0.46, p<0.05). This association is in favor of the potential role of LV remodeling on the reduced longitudinal function of the myocardium. None of the patients had a ratio of E/e’> 14 as an index of high LV filling pressure. The values of E/e ratio were correlated to LV end- diastolic and systolic diameters (r= 0.36, r= 0.34, p<0.05, respectively). There was no relationship between E/e’ ratio and LV mass. Discussion. Assessment of the LV function with accurate echocardiographic methods showed subtle LV dysfunction in patients who were asymptomatic for heart failure and with a short pre-transplant duration of renal impairment. Moreover, LVH was the most commonly observed cardiac abnormality in post-transplant pediatric patients. In concordance with previous studies, we found that the restoration of renal function by renal transplantation improved global ventricular function and also reduced the LV mass.(7,8) However, a higher LV mass was often present in KT patients and may lead to a poor outcome. (2) Furthermore, the LV longitudinal systolic function, assessed by measurement of s’ wave velocity, improved significantly after KT. Our findings regarding a correlation of elevated LV mass with both of the TDI-MPI and impaired systolic indices of myocardial function highlight the basic role of LV remodeling on myocardial dysfunction even in the subgroup of the patients with a short period of renal failure. Moreover, its association with pre-transplant hypertension suggests that more complete control of the blood pressure in CKD patients is important for reducing cardiac risk factors. Conclusion. Subtle abnormalities of the LV systolic- diastolic function and LVH are present in children after renal transplantation who have no symptoms for heart failure within the pre-transplant period. Although our study is limited by the small group of the patients, the data might imply that high LV mass may substantially influence the post-transplant cardiac function.These findings confirm the importance of early initiation of therapeutic interventions to modify permanent cardiac dysfunction. ABSTRACT Echocardiographic Evaluation of left Ventricular Function and Geometry in Pediatric Patients with Kidney Transplantation Background. Cardiovascular complications become more important in children with chronic kidney disease (CKD) because of the improved life span of children after kidney transplantation (KT). This study aimed to evaluate ventricular function in pediatric patients with KT, who were asymptomatic for heart failure by using new echocardiographic parameters.  Methods. We investigated possible differences in echocardiographic parameters between a population of 18 patients (12.2±2 years) before and after KT and 37 age-matched healthy subjects. Transmitral flow velocities, mitral annular velocities and myocardial performance index (MPI) were determined by pulsed Doppler echocardiography and Tissue Doppler Imaging (TDI).  Results. Left ventricular (LV) hypertrophy was found in 44%. The values of TDI derived MPI of the patients after KT were significantly different from those of the control subjects (0.36 ± 0.13 vs. 0.31 ± 0.01, p<0.05). The peak velocities of s´ wave, as a marker of LV longitudinal systolic function, were significantly different between the transplant recipients and controls. We found an inverse correlation between s’ wave values and LV mass in the patients (r=0.46, p<0.05). The values of myocardial diastolic velocity (e’) did not differ between the patients after KT and control subjects. Based on obtained E/e’, a non-invasive index of LV filling pressure, none of the patients had high filling pressure. Conclusion. Subtle abnormalities of LV systolic and diastolic function are present in asymptomatic children after renal transplantation. LV hypertrophy is a predictor for myocardial dysfunction. These findings confirm the importance of early initiation of interventions to modify permanent cardiac dysfunction in children with CKD.