This study is a case-control research and complies with the current ethical considerations. Informed consent was obtained from each patient included in the study, and the study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki as reflected in a priori approval by the institution’s Human Research Committee. Beta thalassemia major patients and cases with thalassemia intermedia were selected from patients who referred to Ali-Asghar Hospital in Zahedan University of Medical Sciences between June 2008 and June 2009.
There are 1900 registered thalassemic patients in the south east of Iran. Of these patients,750 patients have registered records in the Center for Special Diseases of Ali-Asghar Hospital, Zahedan, Iran. In terms of age, 383 of these patients are older than 8 years. Among those 750 patients, there are only 30 cases with thalassemia intermedia, precluding a study on a larger number of patients with thalassemia intermedia.
After history taking, physical examination, chest radiography, and electrocardiography (ECG), patients with mitral valve dysfunction, hypertension, structural diseases of the heart, heart failure, metabolic diseases, endocrine or renal disorders, pulmonary hypertension, cardiac drug consumption (except for chellators), hemoglobin before transfusion less than 9 g/dl, history of irregular transfusion before two years of age, and duration of chelating therapy less than 5 years were excluded from the study. Therefore, 8 patients with thalassemia intermedia were omitted: 2 patients with pulmonary hypertension; 4 patients less than 8 years old; and 2 patients over 25 years of age. Finally, 80 patients with thalassemia major and 22 patients with thalassemia intermedia (hemoglobin > 9g/dl in both groups) were recruited into the study. The age of the patients was between 8 and 25 years old.
After the registration of the patients’ age, sex, and blood pressure, the whole study population underwent two-dimensional and Doppler echocardiography by one cardiologist, using the Challenge 7000 Instrument with 2.5, 3.5, and 5-MHz transducers (made in Italy). This device was equipped with ECG monitoring. In addition, 80 healthy individuals, between 8 and 25 years of age, who referred for routine examination or follow-up, were chosen and matched for sex with the case groups as controls.
The means of all necessary echocardiographic parameters, namely posterior wall dimension in systole (PWDS) and posterior wall dimension in diastole (PWDD) of the left side, acceleration time (AT), deceleration time (DT), myocardial performance index (MPI), peak E (early mitral valve flow velocity)/peak A (late mitral valve flow velocity) velocity (E/A ratio), isovolumic relaxation time (IRT), isovolumic contraction time (ICT) of both sides, ejection fraction (EF), fractional shortening (FS), interventricular septal dimension in diastole (IVSDD), interventricular septal dimension in systole (IVSDS), left ventricular end-diastolic dimension (LVDD), and left ventricular end-systolic dimension (LVSD) of the left side, were measured in each of the three cardiac cycles. Additionally, posterior wall dimension in systole of the left ventricle (LVPWS), posterior wall dimension in diastole of the left ventricle (LVPWD), interventricular septal dimension in systole (IVSS), EF, and FS were measured via M-mode echocardiography. Also, the velocity of the blood flow through the heart valves was measured with pulsed Doppler, and the pre-ejection time, ejection time (ET), peak A velocity (A), peak E velocity (E), E/A ratio, and pre-ejection period/ejection time ratio (PEP/ET) of both sides were measured with pulsed Doppler echocardiography.9
The sample volume was positioned at the tips of the tricuspid and mitral valve leaflets in the apical four-chamber view to enable the measurement of (a), which is the time of interval between the end and the start of trans-mitral and trans-tricuspid flow. The sample volume was thereafter relocated to the left ventricular outflow tract just below the aortic valve (apical five-chamber view) so as to measure (b), which is the left ventricular ejection time. The right ventricular outflow velocity pattern was also recorded from the parasternal short-axis view with the Doppler sample volume positioned just distal to the pulmonary valve for the measurement of (b).
MPI or the Tie Index was calculated as: a-b/b = IRT + ICT/ET.9
The left ventricular mass index (LVMI) was also calculated by the following formula:
All the parameters in the above formula were measured in the M-mode view and in diastole and were utilized for left ventricular mass evaluation.
Finally, the a statistical method for making simultaneous comparisons between two or more means (ANOVA) was employed for the normally distributed variables and the Kruskal-Wallis test was used for the non-normally distributed variables. Multiple comparisons between the groups were performed with the Tukey test. A p value < 0.05 was considered statistically significant.