The evaluation of systemic ventricular function of patients who undergone Fontan operation via cardiopulmonary exercise test and tissue doppler study and the relationship with NT-proB type natriuretic peptide levels

For the first time in 1971, Fontan described a palliative operation named Fontan circulation for complex congenital heart disease which showed single ventricular physiology or for which biventricular repair is not possible. Pulmonary and systemic venous return is separated via this operation technique. By the prevention of early ventricular function loss and insufficient blood oxygen level because of volume load over functional single ventricle with this technique, survival ratios and quality of life of patients were increased. As the survival ratio was increased, problems that endanger the life quality and the patients' life were seen in the long term. This result speeded up the researches on determination of factors affecting the outcoming problems. In our study, functional status, life quality, systemic ventricle status of patients with Fontan operation were evaluated via conventional echocardiograpy, tissue Doppler Imaging (DTI), and PW Doppler measurements with the aim of the determination of the relation between the resulting data and execise capacity, dyssynchrony, NT-proBNP levels. 28 patients with exercise capacity who underwent Fontan operation between January 1991 and December 2008 in Cardiovascular surgery Department of Baskent University Medical Faculty were included in the study. Patients with neurupsychomotor developmental problems and permanent pace were excluded from the study. 27 healthy children who attended with cardiac murmur and chest pain with normal telecardiography, ECG and echocardiography were chosen as the control group. Detailed physical examination, ECHO, ECG, TELE and 24-hour holter monitorization of the patients were performed and blood was drawn for analysis. Cardiopulmonary exercise test was performed via bicycle ergometer method. 17 of the patients were male and 11 were female. The average age of operation was 5.6 ± 3.06 years ( range 1.9-14, median 5.35 years). The duration of follow up was 1.8 ± 14.8 years ( mean 6.85 ± 3.67 years, median 5,75 years). The mean age of patients was 12.8 ± 4.36 years (range 7.5-25 years, median 12.7 years). The mean age of control group was 12.5 ± 3.76 years (range 8-25.3 years, median 11.9 years) There was a significant difference between patients and controls in realtion to weight, height and BMI z scores (p< 0.05). Cardiac output (CO), stroke volume ( SV), systemic valve E measured with PW, E/A ratio, tissue systolic myocardial velocity (Sm), tissue early diastolic myocardial velocity (Em), functional vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), maximum voluntary ventilation (MVV), peak work, work at anaerobic threshold, peak heart rate, chronotropic index, peak oxygen consumption, peak carbondioxide production were all decreased in patients when compared with control group (p<0.05). ). Left ventricle myocardial performance index (MPI), septum MPI, right ventricle MPI, systemic valve PW MPI, dyssynchrony measurements, NT-proBNP levels were significantly higher in patients (p<0.05). Systemic valve isovolemic relaxation time (IRT) measured with PW, IRT measured with DTI, and isovolemic contraction time(ICT) were significantly prolonged in the patient group (p<0.05). There was a positive correlation with dyssynchrony measurements and mass/volume ratio, MPI calculated with PW, MPI calculated with TDI, NT-proBNP. A negative correlation was found between dyssynchrony measurements and chronotropic index, peak heart rate, basal-peak oxygen saturation, peak work measurements. While a negative correlation was present between NT-proBNP levels and FVC, FEV1, MVV, peak work, peak heart rate, respiratory reserve, chronotropic index, SV, and CO; a positive correlation was found between NT –proBNP and TDI, MPI,PW MPI, mass/volume ratio. A positive correlation was present between respiratory reserve, SV and CO. NT-proBNP cutoff level between patients and controls was 90 pg/ml ( sensitivity 89,3 %, spesitivity 81,5 %). A significant difference was found with NT pro BNP level ≥ 90 pg/ml in relation to height, weight, BMI z score, basal and peak O2 value, MPI value calculated with TDI, myocardial tissue velocities, mass/volume ratio, left atrium volume, E/A ratio, dyssynchrony measurements, respiratory function tests, chronotropic index (p<0.05). As a conclusion, no superiority could be found between exercise capacity, NT-proBNP dyssynchrony and DTI measurements for the evaluation of clinical and functional status of the patients. When these methods were compared with conventional echocardiography, the superiority of dyssynchrony and DTI measurements in the evaluation of patients was undebatable. The negative correlation between NT-proBNP, dyssynchrony, DTI measurements and exercise capacity demostrated that these measurements in Fontan patients should be studied in a more detailed way. For this reason, serial measurements of NT-proBNP, dyssynchrony and DTI measurements of patients before and after operation and also during follow up should be performed, cutoff values be constituted and the relationship of the clinical and functional status with these parameters should be searched.