Study Populations:
The study group included 33 β-TM patients (16 girls/17 boys, mean age 18.7±7.7 years) who were transfused every other 3-4 weeks since the early childhood and on regular chelation program. They all had normal systolic functions showed by conventional echocardiography measurements; ejection fraction (EF)>55%, fractional shortening (FS)>30%. None had thyroid, lung, renal and liver dysfunctions. Thirty-seven healthy individuals (18 girls/19 boys, mean age 19.9±8.4 years) were included into the control group.
Serum ferritin measurement: Ferritin ELISA kit (DRG-Germany) were used for serum ferritin measurements. Serum samples were obtained from both groups. The samples from the study group were taken before the transfusion. If there was any signs of infection within one week, sampling was postponed.
T2*MR imaging: T2*MRI was performed by Siemens Magneton-Avento 1.5 tesla MR device. Measurement was made from septum middle segment on short axis by using single cross-section dual echo black blood turbo field echo (TFE) sequences. TFE sequences were taken using electrocardiogram synchronization during late diastolic phase by breath-holding technic These sequence parameters were TR (time to repetition)/TE1 (time echo) /TE2:12/4.6/9.2 milliseconds (msn), flip angel:30, NEX (number of excitations): 3, FOV (field of view): 350-450, slice thickness: 10 mm, TFE factors:6. T2* MRI scan was performed only in the study group within 15-25 minutes and the findings were evaluated by the same radiologist without knowing TD imaging results. T2* MRI and TD surveys were performed on same day. The cut-off level for myocardial overload was accepted as 20 ms.
Echocardiographic evaluation: Conventional echocardiographic and pulsed-wave Doppler studies were performed using General Electric Vivid S6 system with 2.5 or 3.5 MHz transducers. Conventional echocardiographic study included two dimensional, M-mode, pulsed-wave Doppler measurements. Patients’ measurements were performed by the same cardiologist without knowing the T2*MRI results within 2 to 5 days following transfusion and on the same day with T2*MRI. Echocardiographic examination was done during normal respiration simultaneously with electrocardiogram tracing in supine or left lateral decubitus position. All patients had sinus rhythm during examination. M-mode traces were recorded at the speed of 50 mm/s and the Doppler signals 100 mm/s. Three consecutive cycles were averaged for every parameter. Left ventricle (LV) diameters, wall thicknesses, EF were measured from M-mode traces recorded from the parasternal long-axis view according to the recommendations of the American Society of Echocardiography.10 The trans mitral flow velocities were performed in the apical four-chamber view using pulsed Doppler echocardiography with the sample volume sited at the tip of the mitral leaflet. The peak early diastole (E) and late diastole (A) trans mitral flow velocities, deceleration time (DT) were measured.
For the acquisition of TD velocities; LV images were obtained from the apical four-chamber view, and a 5 mm pulsed Doppler sample volume was placed at the level of lateral and septal mitral annuluses. Myocardial velocities of the lateral tricuspid annulus were similarly obtained by placing the sample volume at the junction of the tricuspid valve annulus and the right ventricle free wall. The peak systolic velocity (Sm), early diastolic myocardial peak velocity (Em), late diastolic myocardial peak velocity (Am) and isovolumic contraction (IVC) velocity were obtained and the results were given as cm/s. The acceleration rate of isovolumic contraction (IVA) was calculated as the peak IVC velocity divided by the time interval from baseline to peak (Δt). IVA= IVC/ Δt (Figure 1). Ejection time (ET), isovolumic relaxation time (IVRT) and isovolumic contraction time (IVCT) were obtained and the myocardial performance index (MPI) were calculated by the following formulation;
MPI = (IVRT+IVCT)/ET.
The study group was divided into two subgroups according to T2*MRI results (patient with cardiac iron overload <20 ms or non-iron load group ≥ 20 ms). The results obtained from TD imaging were compared according to these subgroups.
The Uludag University Ethics Committee gave permission for the study. The written informed consents were also obtained from both patients and controls.