Right heart function in health and disease : a doppler echocardiography and doppler tissue imaging study
Abstract: Background: It is well known that performance of the right ventricle (RV) determines exercise capacity and may confer prognostic information in different cardiopulmonary diseases. To allow optimal patient management, ideal methods to assess right heart function are therefore important. Echocardiography is an attractive investigation for that purpose, although limited by the anatomical and functional complexities of the RV. The aim of the present thesis was to present applicable methods useful in clinical practice by traditional 2D/Doppler echocardiography and Doppler tissue imaging (DTI) in the assessment of global and regional RV function in both health and disease. Methods: The studies were performed on 4 different groups; (1) 255 healthy subjects (125 females), (2) 92 consecutive patients with different cardiac diseases (36 females), (3) 26 patients with systemic sclerosis, (SSc) (21 females) and (4) 26 consecutive patients with heart failure (8 females) undergoing cardiac catheterisation. Results: RV outflow tract fractional shortening (RVOT fs), which is a new method in the assessment of RV function, correlated significantly with RV systolic long axis motion (r= 0.66, p< 0.001), pulmonary artery acceleration time (r= 0.80, p< 0.001) and RV-right atrial peak systolic pressure drop gradient (r= -0.53, p< 0.001). Furthermore, RVOT fs was reduced in patients with pulmonary hypertension whereas RV systolic long axis motion was not in difference. This finding was confirmed after comparing RV function with invasive pressures. In healthy subjects, while the systolic myocardial velocities were preserved over age, the peak isovolumic contraction velocity (IVCv) was weakly increased with advanced age (r= 0.34, p< 0.01). Furthermore, both global and regional E/A ratios were reduced (r= -0.57, r= -0.67, p< 0.001 for both) with age whereas no alteration was found in the myocardial isovolumic relaxation time (IVRt). In patients with systemic sclerosis (SSc) both global (64± 23 vs. 39± 12 ms, p< 0.001) as well as regional (83± 40 vs. 46± 24 ms, p< 0.001) IVRt were prolonged. After evaluating echocardiographic parameters with invasive pressures we found a significant correlation between DTI derived IVRt and pulmonary artery systolic pressures (r= 0.83, p< 0.01) while the IVCv was related to the state of contractility (r= 0.77, p< 0.001). Furthermore, an IVCv below 6 cm/s was shown to be an accurate marker of increased right atrial pressure (>6 mm Hg). In conclusion, RVOT fs can be used as a complementary measurement of RV systolic function, being more sensitive to elevated pulmonary artery systolic pressures than the systolic longitudinal RV motion. Right heart function, mainly the diastolic function, is relatively weakly influenced by age compared to the left heart function. In patients with SSc, we found diastolic disturbances, including a prolonged IVRt and proposed the findings to be early markers related to intermittent pulmonary hypertension. This observation was strengthened after evaluating IVRt against invasive pulmonary artery systolic pressures. IVCv can be used to determine the state of RV contractility and also be used to identify patients with elevated filling pressures. The presented methods can be used to detect early signs of RV dysfunction which might prohibit right heart failure. All presented methods are non-invasive, reproducible, easy obtainable, and thus useful in clinical practice.
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