Introduction
Cystic fibrosis (CF) is an autosomal recessive hereditary disease with a
chronic, progressive, multisystemic course (1,2). The patients show a
deficiency of the gene coding for the transmembrane conductance
regulator protein (CFTR) (2,3). CF is a systemic disease causing
multiple organ malfunctions (5). The classical triad of signs include
suppurative chronic obstructive pulmonary disease, pancreatic
insufficiency and high sweat electrolyte levels (7). Pulmonary injury
developing out of chronic lung infection and inflammation is the most
important morbidity and mortality factor (4). Pulmonary vasoconstriction
develops following alveolar hypoxia resulting from pulmonary damage.
This, in its turn, contributes to the development of cor pulmonale, its
most frequent cardiac complication (7,8). Pulmonary hypertension,
myocardial fibrosis and chronic infection combine to cause right
ventricular (RV) dysfunction. Left ventricular (LV) dysfunction has also
been identified in CF as a result of the cellular and molecular changes
caused by the disease (5,9,22). Alterations of the structure in both
ventricles have been reported in 20-47% of the cases in postmortem
studies (5,6). Even though CFTR-related cardiac effects are not entirely
elucidated, a commonly proposed hypothesis is a disturbance of
regulatory functions over calcium channel-related resting membrane
potentials and action potentials (9).
Conventional transthoracic echocardiography (TTE) and Doppler
echocardiography performed as standard assessments of cardiac function
may help identify cardiac involvement in patients with CF. These
examinations are, however, often insufficient to demonstrate the
presence of early-stage, subclinical cardiac dysfunction. Tissue Doppler
echocardiographic imaging (TDI) and two-dimensional speckle tracking
echocardiography (STE) are helpful in detecting the presence of
subclinical cardiac dysfunction in the early stages of CF (10,11,12).
The objective of this study was to investigate the possibility of a
superiority of TDI and STE over standard echocardiography techniques for
studying cardiac function in CF patients.