Characteristics And Significance Of The Spectra Of SVC Flow Doppler Velocity In Pulmonary Hypertension By Echocardiography

Objective: (1) To explore the establishment and significance of a rabbit model with acute thrombo-embolic pulmonary hypertension monitored by echocardiography, to analyze their echocardiographic features and significance by two-dimensional and M-mode echocardiography, and to summarize the characteristics and regularities of the spectra of SVC flow Doppler velocity.(2) To explore the establishment and significance of rabbit models with chronic monocrotaline-induced pulmonary hypertension monitored by real-time echocardiography, and to summarize their characteristics and regular patterns of the spectra of SVC flow Doppler velocity by echocardiography.(3) To investigate the spectral wave shapes and parameters of the SVC Doppler flow patterns in patients with primary pulmonary hypertension by echocardiography.Materials and methods: (1) Imitated the patho-physiologic process of acute thrombo-embolic pulmonary hypertension in human, the rabbit model with acute thrombo-embolic pulmonary hypertension was developed by a ultrasound-guided micro-catheter put in the deep femoral vein into the pulmonary artery to detect the pulmonary artery systolic pressure and auto-thrombus injected into the contra-lateral deep femoral vein synchronously to form pulmonary embolism. The pulmonary artery systolic pressure was simutaneously detected (> 30 mm Hg was the criterion). A rabbit model with acute thrombo-embolic pulmonary hypertension was monitored and analyzed simultaneously by M-mode and two-dimensional echocardiography. Accompanied by measuring of the pulmonary artery systolic pressure by right heart catheter, an examination of the spectra of SVC had been simultaneously performed by Doppler echocardiography in the right supraclavicular fossa view before and/or after establishing of the rabbit models with acute thrombo-embolic pulmonary hypertension.(2) Synchronously monitored by real-time echocardiography, a rabbit model with chronic pulmonary hypertension was successfully developed by 99% monocrotaline solution injection into abdominal cavity. The pulmonary artery systolic pressure was then detected by pressure-guided micro-catheter put into the pulmonary artery (> 30 mm Hg was the criterion of pulmonary hypertension). Accompanied by measuring of the pulmonary artery systolic pressure by right heart catheter, an examination of SVC had been simultaneously performed by two-dimensional and Doppler echocardiography in the right supraclavicular fossa view before and/or after establishing of the rabbit models with chronic monocrotaline-induced pulmonary hypertension. At the same time, a synchronous electrocardiogram was performed and a respiratory curve recorded.(3) Twenty-three patients with primary pulmonary hypertension as the diseased group and the paired healthy subjects as the control group were recruited. Transthoracic echocardiography and an examination of the spectra of SVC flow Doppler velocities in the right supraclavicular fossa view were then performed, and the pulmonary artery pressure of the diseased subjects was assessed via tricuspid regurgitation method by Doppler echocardiography.Results: (1) Twenty-five rabbit models with acute thrombo-embolic pulmonary hypertension were successfully developed and the successful rate was 83%. The pulmonary artery systolic pressure estimated from tricuspid regurgitation was positively related to the pulmonary artery systolic pressure measured by right heart catheter ( r = 0.765, P=0.002 ).The two-dimensional and M-mode echocardiographic features of the rabbit models with acute pulmonary thrombo-embolic hypertension showed as follows:①The SVC end-diastolic diameter was positive relative with the pulmonary artery systolic pressure demonstrated by two-dimensional echocardiography(r=0.594, P=0.002).②The pulmonary artery end-diastolic dimension was significantly and positively relative with the pulmonary artery systolic pressure measured by right heart catheter(r=0.753, P=0.000);③The right ventricular end-systolic or end-diastolic cavity dimension was significantly and positively relative with the pulmonary artery systolic pressure (r=0.926, P=0.000; or r=0.849, P=0.000);④The left ventricular end-systolic or end-diastolic cavity dimension was negatively relative with the pulmonary artery systolic pressure (r=-0.444, P=0.001; or r=-0.667, P = 0.000);⑤The RVSD/LVSD or RVDD/LVDD values were significantly and positively relative with the pulmonary artery systolic pressure (r=0.869, P=0.000; or r=0.865, P=0.000);⑥Their differences between before and after acute thrombo-embolic pulmonary hypertension were significant (P<0.05).The SVC flow was evaluated by Doppler imaging in the right supraclavicular fossa view and its spectral characteristics showed as follows:①The S wave peak velocity was negative relative with the pulmonary artery systolic pressure(r=-0.692, P=0.000);②The VR wave peak velocity accelerated apparently with mild pulmonary hypertension, then decelerated with the increase of the pulmonary artery systolic pressure to the normal level till severe pulmonary hypertension, and was negative relative with pulmonary artery systolic pressure (r=-0.292, P=0.157);③The VR/S peak velocity ratio was positive relative with pulmonary artery systolic pressure(r=0.698, P=0.000), and significantly higher than the normal level(P<0.05).(2) Thirteen rabbit models with chronic monocrotaline-induced pulmonary hypertension were successfully developed and the successful rate is 65%. The results of the right heart catheterization showed that the pressures of the chambers heart except the right ventricule in the pulmonary hypertension group were distinguished from those of the control group(P<0.05). The results of the detection of color Doppler flow imaging in the pulmonary hypertension showed that the frequencies of tricuspid regurgitation and pulmonary regurgitation were 69.2% and 53.8% respectively.The characteristics of the spectra of the pulmonary artery flow Doppler velocity showed as follows:①The acceleration time (AT) and ejection time (ET) of pulmonary artery flow decurtated apparently( P<0.05);②The pre-ejection period (PEP) and the PEP/AT ratio extended apparently( P<0.05). The characteristics of the spectra of the tricuspid valve jet showed that the E/A ratios were less than 1 in the 69.2% of the pulmonary hypertension group. The characteristics of the spectra of the tricuspid annulus tissue Doppler velocity showed that the e/a ratio was less than 1 in the 100% of the pulmonary hypertension group. All the parameters of the spectra of the tricuspid valve jet and the tricuspid annulus tissue Doppler velocity except the E wave peak velocity were distinguished from those before monocrotaline solution injection (P<0.05).The SVC flow was evaluated by Doppler imaging in the right supraclavicular fossa view and its spectral characteristics were shown that the VR wave peak velocity and the AR wave peak velocity accelerated apparently than before monocrotaline solution injection (P<0.01).(3) The spectral wave-shapes of SVC flow velocity in the diseased group were distinguished from those of the control. The majority of their measurements were distinguished from those of the control. The peak velocities and VTIs of S, VR, and D waves of SVC flow Doppler velocities in the diseased group were significantly lower than those of the control (p<0.05); the peak velocities of AR wave significantly higher (p<0.05); and the ratio of peak velocities (VTIs) of AR wave and those of S wave also significantly higher (p<0.05).Conclusion: (1) The establishments of the rabbit model with acute thrombo-embolic pulmonary hypertension guided by ultrasound and the rabbit model with chronic monocrotaline-induced pulmonary hypertension monitored by real-time echocardiography are easy to operate and their successful rates are higher, which may provide a good way in the preclinical and/or clinical research on pulmonary hypertension. (2) The pulmonary artery end-diastolic dimension, SVC end-diastolic diameter and the RVSD/LVSD or RVDD/LVDD values were significantly and positively relative with the pulmonary artery systolic pressure, which maybe play an important role on the early diagnosis of acute thrombo-embolic pulmonary hypertension.(3) The S wave peak velocity of the SVC spectra of acute thrombo-embolic pulmonary hypertension was significantly negative with the pulmonary artery systolic pressure and the VR/S peak velocity ratio was significantly positive, which maybe play an important role in the diagnosis of acute pulmonary hypertension.(4) Real-time echocardiography's monitoring can give a hint on pulmonary hypertension by tricuspid regurgitation's (or pulmonary regurgitation's) presence, can judge the degree of the pulmonary hypertension by the spectra of the pulmonary artery flow Doppler velocity, and can evaluate the right heart function by tricuspid valve jet and tricuspid annulus tissue Doppler velocity. So it is the foundation of the successful establishment of the rabbit model with chronic monocrotaline-induced pulmonary hypertension.(5) The acceleration of the VR wave peak velocity and the AR wave peak velocity of Superior Vena Cana flow Doppler velocity in a rabbit with chronic monocrotaline-induced pulmonary hypertension suggests that the measurement of adterminal flow of Superior Vena Cana may be useful in the early diagnosis of chronic pulmonary hypertension.(6) Changes of wave-shape and Doppler echocardiographic variables of SVC flow can provide a sign to evaluate primary pulmonary hypertension.