Reversal of the pattern of respiratory variation of Doppler inflow velocities in constrictive pericarditis during mechanical ventilation.

BACKGROUND: Spontaneous inspiration causes a characteristic decrease of the mitral valve (MV) and pulmonary venous (PV) flow velocities obtained by Doppler echocardiography in patients with constrictive pericarditis (CP). This has been explained by the decrement it causes in the intrathoracic pressure. Positive pressure ventilation (PPV) causes an increment of intrathoracic pressure with mechanical inspiration. Therefore the pattern of respiratory variation produced during PPV may differ from that seen during spontaneous breathing. OBJECTIVE: Our goal was to describe the effect of PPV on the pattern and magnitude of respiratory variation of MV and PV flow velocities in CP. METHODS: We performed intraoperative pulsed Doppler transesophageal echocardiography on 15 patients (13 men, mean age 52+/-15 years) with CP after general anesthesia and before sternotomy and pericardial stripping. The peak velocity and time-velocity integral (TVI) of the mitral inflow E and A waves and the PV systolic and diastolic waves were measured at onset of inspiration and expiration for 3 to 6 respiratory cycles. Respiratory phase was monitored with a heat-sensitive nasal thermistor. The percent change in Doppler flow velocities from mechanical inspiration (INS) to mechanical expiration (EXP) was calculated with the formula %change = INS - EXP / INS x 100. RESULTS: The peak velocity of the mitral inflow E wave was significantly higher during mechanical inspiration than expiration (57 +/-14.5 versus 47+/-13.9 cm/s, P<.001). This represented a percent change of 18%+/-7.9% from expiration to inspiration. The mean TVI of the mitral inflow E was also higher during mechanical inspiration than expiration (P = .02). The peak velocity of the PV D wave was higher during mechanical inspiration than expiration (39+/-17.8 versus 28+/-14.7 cm/s, P<.001). This represented a mean percent change of 28%+/-13.8%. The mean value of the TVI for the PV D wave was also significantly greater during mechanical inspiration than expiration (P <.05). CONCLUSIONS: Positive pressure ventilation reverses the pattern of respiratory variation of the MV and PV flow velocities in CP. The percent change in the peak velocities of the MV and PV flows produced by PPV is the same range reported in CP during spontaneous breathing.     

胸压对三尖瓣反流速度和肺动脉压测定的影响

目的 应用超声心动图观察平静呼吸情况下胸压对三尖瓣反流速度的影响及规律,为超声心动图准确测定肺动脉压和验证呼吸影响心功能机制新假说提供依据.方法 对50例三尖瓣反流患者,利用二维及多普勒超声心动图记录不同呼吸时相三尖瓣反流速度和跨瓣压,观察不同呼吸时相时三尖瓣反流速度的变化规律.结果 呼吸对三尖瓣反流速度有确定影响,反流速度与呼吸时相关系表现有三种类型:第一种为吸气相速度增加,呼气相速度减小;第二种表现与第一种相反;第三种为速度变化表现为随机性.结论 呼吸性胸压变化对三尖瓣反流速度有明确影响,提示用多普勒法无创测定肺动脉压时需要将呼吸停止在呼吸时相的中期,并保持测定过程中胸压稳定,以提高测定准确性.     

The value of Doppler echocardiography findings in selecting patients with aortic stenosis for surgical intervention

Doppler echocardiographic and catheter measurements of pressure gradients were compared in 29 patients (61 +/- 11 a) with isolated aortic stenosis. In addition we retrospectively evaluated which easily obtained Doppler echocardiographic parameters might indicate severe aortic stenosis requiring surgery. Catheter-derived peak to peak and mean gradients correlated well with maximum systolic Doppler gradient (r = 0.78, p less than 0.01) and mean Doppler gradient (r = 0.73, p less than 0.01). Using the continuity equation, the aortic valve area was assessed in 14 patients by Doppler echocardiography. A good correlation was found with catheter-determined aortic valve area (r = 0.83, p less than 0.01). Surgical intervention was recommended in 19 patients after left heart catheterisation. Doppler determined maximum transvalvular flow velocity (Vmax.) was greater than 4.5 m/s in 10 patients, all ultimately considered to be surgical candidates. None of the 7 patients with Vmax. less than 3.8 m/s proved to have critical aortic stenosis. In 12 patients Vmax. was between 3.8 and 4.5 m/s. In this group aortic valve replacement was advised in 9 patients after catheterisation. In 5 surgical candidates echocardiography showed reduced left ventricular function (systolic shortening fraction less than 0.27). Hence, the Doppler derived peak flow velocity greater than 4.5 m/s or peak flow greater than 3.8 m/s in the presence of reduced left ventricular function indicate severe aortic stenosis requiring surgery.     

Stentless bioprostheses have ideal haemodynamics, even in the small aortic root

Objective: To determine normal Doppler and 2D gradients and flow characteristics of the Freestyle^® stentless aortic bioprosthesis related to valve size. Background: The Freestyle^® stentless aortic bioprosthesis is one of the newer aortic xenografts. Only limited data are available of the echocardiographic flow characteristics during a mid-term follow-up period of this valve. Therefore valve performance related to valve size was measured during a follow-up period of two years. Methods: 175 consecutive patients with a Freestyle^® aortic bioprosthesis underwent an echocardiographic and Doppler examination according to a common protocol. Investigations were done within 4 weeks after operation, after 3 to 6 months, and after 1 and 2 years. Results: With a valve size from 19 to 27 mm mean gradients decreased from 8.0 ± 5.1 mmHg at discharge to 5.8 ± 3.8 mmHg after 3–6 months (p < 0.001). Thereafter gradients remained stable. The performance index, the ratio of the measured effective orifice area in the patient divided by the effective orifice area measured in vitro increased from 69 ± 20% at discharge to 79 ± 29% after one, two and three years. Performance index was especially very high in the smaller sized valves with a performance index of 85 ± 17% for the 21 mm valve. During follow-up mean gradients remained below 10 mmHg even in the 21 mm valve. Conclusion: Stentless xenografts have ideal haemodynamics, even in the small aortic root.     

呼吸对右心衰竭患者三尖瓣反流速度和肺动脉压测定的影响

目的 探讨平静呼吸对右心衰竭患者三尖瓣反流速度和肺动脉收缩压测定的影响.方法 选取32例右心衰竭患者(病例组)和28例右心功能正常而三尖瓣反流患者(对照组)行超声心动图检查.观测三尖瓣反流速度,根据反流法计算肺动脉收缩压,比较两组吸气相与呼气相之间的差异.结果 病例组三尖瓣反流速度、肺动脉收缩压吸气相均小于呼气相(P＜0.001);对照组三尖瓣反流速度、肺动脉收缩压吸气相与呼气相比较差异无统计学意义.结论 使用超声心动图估测肺动脉收缩压时,应注意平静呼吸对右心衰竭患者三尖瓣反流速度和肺动脉收缩压测定的影响,尽量在呼气末或呼气末屏气状态下进行.     

What role for echocardiography in primary pulmonary hypertension? New ultrasound methods accurately estimate pulmonary pressures

Several echocardiographic techniques provide accurate, noninvasive estimates of peak or mean pulmonary artery pressure and can aid in diagnosing primary pulmonary hypertension. One such method involves converting peak tricuspid velocity to an estimated peak right ventricular minus right atrial gradient; peak pulmonary artery pressure is roughly equal to the sum of the tricuspid gradient estimate and estimated mean right atrial pressure. A second technique evaluates the contour of the transpulmonary Doppler velocity profile; a third measures the interval between pulmonary valve closure and tricuspid valve opening. An M-mode method can be used to assess wedge pressure. Echocardiographic variables can also help evaluate prognosis in primary pulmonary hypertension.     

超声心动图观察室间隔运动新方法研究

目的 利用室间隔运动时曲率半径的变化,观察正常人呼吸性胸压变化对室间隔摆动和形变的影响,评价新方法 观察室间隔运动的敏感性.方法 应用Acuson Sequoia 512型超声仪对21例健康志愿者进行检查.分别获取呼气相和吸气相左室腱索短轴观图像;同步记录各瓣口血流速率、心电图和呼吸曲线.两名医师在双盲条件下采用自制的测量软件.分别测量吸气相与呼气相室间隔曲率半径.结果 二尖瓣E峰血流速率和主动脉血流速率在呼气相均高于吸气相;三尖瓣E峰血流速率和肺动脉瓣血流速率则相反.吸气相室间隔曲率半径为(25.14±6.082)mm.呼气相室间隔曲率半径为(22.296±4.398)mm,二者差异有统计学意义(P<0.0001).结论 曲率半径可以评估室壁摆动和形变,具有良好的重复性,为临床评价呼吸性胸压变化提供一种敏感而可靠的新方法 .     

超声心动图检测上腔静脉血流评价肺动脉高压的临床研究

目的:通过应用超声多普勒检测慢性阻塞性肺疾病(COPD)患者上腔静脉(SVC)收缩期正向血流速度随呼吸的变化,来评价肺动脉压力。如果肺动脉压力大于30mmHg可定义肺动脉高压。方法:检测64例COPD患者的SVC收缩期正向血流速度随呼吸的变化,并应用三尖瓣返流法计算肺动脉压力。结果:根据肺动脉压力结果将患者分为两组:病例组22例(肺动脉压力>30mmHg), 对照组42例(肺动脉压力<30mmHg)。吸气时两组的SVC收缩期正向血流速度(Vins)无显著差异,呼气时病例组的SVC收缩期血流速度(Vexp)明显高于对照组。且Vexp/Vins和肺动脉压力相关良好。结论:SVC收缩期正向血流的呼吸变化性是检测COPD患者肺动脉高压的敏感指标。     

Comparison of simultaneous invasive and noninvasive measurements of pressure gradients in congenital aortic valve stenosis

PURPOSE: Congenital aortic valve stenosis is a common problem in pediatric cardiology. The catheter peak to peak systolic gradient is the accepted standard used for prognosis and intervention, but noninvasive correlation in pediatric patients is frequently associated with underestimation or overestimation of this gradient. The purpose of this study was to compare different noninvasive measurements with simultaneous catheter gradients to identify which best predicts the catheter peak to peak gradient. METHODS: Twenty-five simultaneous Doppler and catheter measurements of aortic stenosis gradient were performed in 14 children (all 14 before valvuloplasty and 11 after valvuloplasty). Noninvasive estimates of pressure gradient were compared with catheter measurements with linear regression and Bland-Altman analysis. RESULTS: The Doppler peak instantaneous pressure gradient overestimated the catheter peak to peak gradient but correlated well with the catheter peak instantaneous gradient. The Doppler mean systolic gradient correlated well with the catheter peak to peak gradient at low gradients and underestimated higher catheter gradients but agreed well at all levels with the catheter mean gradient. The modification of a catheter-derived correlation equation produced good correlation with the catheter peak to peak gradient (slope, 1.14; intercept, -1.8; R, 0.92), as did the use of estimated pressure recovery (slope, 1.04; intercept, 5.0; R, 0.94), calculated from a defined fluid mechanic equation. CONCLUSION: The catheter peak to peak gradient can be accurately estimated noninvasively using estimated pressure recovery or correlation equations incorporating Doppler measurements.     

In aged men,central vessel transmural pressure is reduced by brief Valsalva manoeuvre during strength exercise

A brief Valsalva manoeuvre, lasting 2–3 s, performed by young healthy men during strength exercise reduces transmural pressure acting on intrathoracic arteries. In this study, we sought to verify this finding in older men. Twenty normotensive, prehypertensive and moderately hypertensive otherwise healthy men 46–69 years old performed knee extensions combined with inspiration or with brief Valsalva manoeuvre performed at 10, 20 and 40 mmHg mouth pressure. Same respiratory manoeuvres were also performed at rest. Non‐invasively measured blood pressure, knee angle, respiratory airflow and mouth pressure were continuously registered. In comparison to inspiration, estimated transmural pressure acting on thoracic arteries changed slightly and insignificantly during brief Valsalva manoeuvre at 10 and 20 mmHg mouth pressure. At 40 mmHg mouth pressure, transmural pressure declined at rest (?8·8 ± 11·4 mmHg) and during knee extension (?12·1 ± 11·9 mmHg). This decline ensued, as peak systolic pressure increase caused by this manoeuvre, was distinctly <40 mmHg. Only a main effect of mouth pressure was revealed (P<0·001) and neither exercise nor interaction between these factors, what suggests that transmural pressure decline, depended mainly on intrathoracic pressure developed during brief Valsalva manoeuvre. Resting blood pressure did not influence the effect of brief Valsalva manoeuvre on transmural pressure.     

呼吸对慢性阻塞性肺病左心室充盈的影响及其机制的超声心动图研究

目的探讨超声心动图检测慢性阻塞性肺病（COPD）患者左心室功能和COPD病程的可行性。方法采用Sequoia512彩色超声诊断仪,记录21例COPD患者及50名健康人自然呼吸时二尖瓣口E峰、A峰血流速度,同步记录心电图和呼吸曲线,计算二尖瓣舒张早期E峰血流速度呼吸性波动指数（RVI）及E峰与A峰血流速度比值（E/A）呼吸变化率。结果两组均表现为E峰血流速度、E/A吸气相低于呼气相（P〈0.001）;COPD组A峰血流速度吸气相与呼气相差异无统计学意义（P=0.076）,而健康对照组A峰血流速度吸气相低于呼气相（P〈0.001）。COPD组二尖瓣E峰血流速度RVI及E/A呼吸变化率均较对照组增大（P=0.002）。结论自然呼吸对COPD患者二尖瓣血流影响具有规律性,进一步验证了呼吸影响心功能机制新假说,同时也为利用多普勒技术评价COPD患者左室功能损害程度和肺实质病变严重程度的进一步研究提供更多信息。     

Exaggerated increase of exercise-induced pulmonary artery pressure in systemic sclerosis patients predominantly results from left ventricular diastolic dysfunction

Objective

High prevalence of exaggerated pulmonary artery pressure response to exercise (EPAPR) was reported in patients with systemic sclerosis (SSc). However, pathophysiology of this phenomenon has not been well defined. Therefore, we evaluated the frequency and potential aetiology of EPAPR in SSc patients.

Methods

We included 85 patients (79 female, 6 male, mean age 54.3 ± 13.9 years) with SSc. Transthoracic echocardiography followed by exercise Doppler echocardiography (EDE) were performed. A positive EDE was defined when at least 20 mmHg increase of tricuspid regurgitation peak gradient (TRPG) was recorded. Right heart catheterization (RHC) with exercise was performed in positive EDE patients and in subjects with resting TRPG >31 mmHg.

Results

Resting TRPG >31 mmHg and/or positive EDE was found in 30 patients and they were referred to RHC. Finally, RHC was performed in 20 patients (16 pts resting TRPG >31 mmHg and 4 others normal resting TRPG and positive EDE). In 12 (60 %) of them an EPAPR with elevated pulmonary capillary wedge pressure (PCWP) was observed. Interestingly, mean left atrium (LA) diameter was greater in an EPAPR with elevated PCWP patients than in subjects with normal exercise response (39.36 ± 5.6 vs. 35.53 ± 3.48, p = 0.03). In EPAPR with elevated PCWP group greater mean value of E/E′ of mitral lateral annulus was observed (7.98 ± 3.35 vs. 6.27 ± 1.94, p = 0.03). In the univariate logistic regression analysis increased LA diameter was significant predictor of EPAPR with elevated PCWP (OR 1.199, 95 % CI 1.029–1.396, p = 0.019).

Conclusions

Despite very well-known risk of PAH in systemic sclerosis patients, the excessive increase of PAP during exercise is more commonly caused by left ventricular diastolic dysfunction than pulmonary arterial vasculopathy.     

Assessment of the normal adult right ventricular diastolic function using M-mode echocardiographic measurement of tricuspid ring motion

Right ventricular function can be evaluated echocardiographically by assessing the longitudinal motion of the tricuspid ring recorded in the apical four chamber view. In this study, we applied this technique to assess the right ventricular diastolic function in 10 healthy Japanese men (mean age : 28±6 years; age range : 20–43 years). Echocardiographic studies were performed with a phased-array imaging system using a 2.5 MHz probe. Tricuspid ring motion was measured by two-dimensional echo guided M-mode echocardiogram of the right lateral tricuspid ring. The excursion of the tricuspid ring during early diastole (dS; mm) and the peak rate of change of the excursion (dS/dt; mm/sec) were measured. We also assessed the right ventricular function by cine magnetic resonance imaging (MRI). Cine gradient echo images were obtained along the short axis of the right ventricle. The right ventricular volume at each phase of the cardiac cycle was calculated by Simpson's method and time–volume curves were constructed. The peak filling rate (dV/dt; ml/s) was determined from these time–volume curves. The dS was 12.8±2.5 mm, dS/dt was 132±27 mm/sec and dV/dt was 269±66 ml/s. There were significant positive correlations between dS and dV/dt (r=0.80, P<0.01), and between dS/dt and dV/dt (r=0.45, P<0.05). Based on our results, M-mode echocardiographic measurements of tricuspid ring motion may be used to assess the right ventricular diastolic function.     

Echocardiographically estimated left ventricular end-diastolic and right ventricular systolic pressure in normotensive healthy individuals

Aim To study the effect of aging on and the relationship between echocardiographically estimated left ventricular (LV) filling pressure and estimated right ventricular (RV) systolic pressure among healthy normotensive individuals.Methods We analyzed 249 healthy individuals (aged 18–82 years, 52% men) with normal echocardiographic findings and reliably measurable tricuspid regurgitation gradients. Subjects with blood pressure >140/90 mmHg and/or LV hypertrophy were excluded. LV & RV dimensions and LV mass were measured with M-mode echocardiography. Atrial (A) volumes were determined with the area-length method. Diastolic function was assessed with transmitral Doppler and mitral annulus tissue Doppler. The ratio of transmitral early peak velocity to early diastolic mitral annulus velocity (E/E′) was used as estimation of LV filling pressure. The transtricuspid Doppler gradient was used to estimate RV end-systolic pressure.Results Even in normotensive individuals aging was accompanied by an increase in LV mass and LA dimensions and an increase in relaxation abnormalities. E/E′ increased with every decade: from 7.8 for age 18–35 years to 10.9 for age ≥75 years (p<0.0001) as did the transtricuspid gradient: from 18.3 mmHg for age 18–35 years to 25.8 mmHg for age ≥75 years (p<0.0001). Linear regression showed that estimated RV systolic pressure was independently predicted by age, LA volume, LV systolic function and E/E′.Conclusion Among normotensive healthy individuals both E/E′ and tricuspid regurgitation gradients increase significantly with aging. Moreover the E/E′ ratio was independently predicting the tricuspid regurgitation gradient. These findings support the need for further studies defining age specific normal values.     

Morphologic bases for establishing end-points for early plaque detection and plaque instability

The aim of the present study was to investigate which factors could influence the accuracy of aortic stenosis severity assessment by Doppler echocardiography in an unselected population. Doppler echocardiographic determination of mean transvalvular pressure gradient and aortic valve area by continuity equation was performed in 101 patients before catheterization. According to the catheterization data, aortic stenosis was classified into 2 categories: mild to moderate (orifice area [Gorlin formula] > 0.75 cm², mean transvalvular gradient < 50 mmHg) and severe (orifice area < 0.75 cm², mean transvalvular gradient ≥ 50 mmHg). The influence of eight factors on the absolute difference in aortic valve area and mean transvalvular pressure gradient and on the concordant classification in the same category by both methods was investigated.Results. By multivariate analysis, the absolute difference in aortic valve area by both methods was significantly associated with poor image quality, absolute difference between mean catheterization and Doppler transvalvular gradient and inversely related to body mass index. Absolute difference in mean transvalvular gradients by both methods was significantly associated only with image quality. Poor image quality emerged as the only significant factor influencing the concordant classification between invasive and noninvasive studies according to orifice area (but not according to transvalvular pressure gradient).Conclusion. Echographic image quality significantly influences the accuracy of Doppler echocardiographic determination of aortic valve area and, to a lesser extent, of transvalvular pressure gradient. Therefore, the mere noninvasive approach is not suitable to every consecutive patient with aortic stenosis. Qualifications concerning overall image quality should identify patients most likely to benefit from catheterization.     

Aortic prosthetic valve design and size: relation to Doppler echocardiographic findings and pressure recovery- an in vitro study.

The extent to which Doppler echocardiography information can be used in the assessment of prosthesis hemodynamic performance is still controversial. The goals of our study were to assess the importance of valve design and size both on Doppler echocardiography findings and on pressure recovery in a fluid mechanics model. We performed Doppler and catheter measurements in the different orifices of the bileaflet St Jude (central and side orifices), the monoleaflet Omnicarbon (major and minor orifices), and the stented Biocor porcine prosthesis. Net pressure gradients were predicted from Doppler flow velocities, assuming either independence or dependence of valve size. The peak Doppler estimated gradients (mean +/- SD for sizes 21 to 27) were 21 +/- 10.3 mm Hg for St Jude, 18 +/- 9.3 mm Hg for Omnicarbon, and 37 +/- 14.5 mm Hg for Biocor (P <.05 for St Jude and Omnicarbon vs Biocor). The pressure recovery (proportion of peak catheter pressure) was 53% +/- 8.6% for central-St Jude, 29% +/- 8. 9% for side-St Jude, 20% +/- 5.6% for major-Omnicarbon, 23% +/- 7.4% for minor-Omnicarbon, and 18% +/- 3.6% for Biocor (P <.05 for central-St Jude and side-St Jude vs Omnicarbon and Biocor). Valve sizes (x) significantly influenced pressure recovery (y in percentage) (central-St Jude: y = 3.7x - 35.9, r = 0.88, P =.0001; major-Omnicarbon: y = 2.1x - 30.3, r = 0.85, P =.0001). By assuming dependence of valve size, Doppler was able to predict net pressure gradients in St Jude with a mean difference between net catheter and Doppler-predicted gradient of -3.8 +/- 2.5 mm Hg. In conclusion, prosthetic valve design and size influence the degree of pressure recovery, making Doppler gradients potentially misleading in both the assessment of hemodynamic performance and the comparison of one design with another. The preliminary results indicate that net gradient can be predicted from Doppler gradients.     

Mixed venous blood temperature response to exercise in heart failure patients treated with short-term vasodilators

Summary. Deep-body or core temperature decreases during exercise in patients with heart failure, primarily due to the circulatory inadequacies associated with the pathophysiology of this condition. Vasodilators are commonly used to treat patients suffering from heart failure because these drugs improve total cardiac output and blood-flow to the regional circulations. In heart failure patients, the core temperature response to exercise should also be affected if the circulation is improved by vasodilators. Patients with severe heart failure were studied at rest and during upright bicycle exercise before, and after, short-term treatment with vasodilators (2-minoxidil, 3-hydralazine, 5-captopril). Their heart rate increased significantly (P<005) from rest to exercise before (87±15–109±14 beats/min), and after 89±13–112±15 beats/min) vasodilators, but there was no drug-related affect on these changes. Mean arterial and pulmonary capillary wedge pressures were significantly (P<0–05) decreased at rest and after the administration of vasodilators (mean arterial pressure 88±7 mmHg before; 77±8 mmHg after; pulmonary capillary wedge pressure 25±8 mmHg before, 19±9 mmHg after). During exercise, the increases in mean arterial and pulmonary capillary wedge pressures were not significantly different from the before vasodilator values (mean arterial pressure 92±14 mmHg before, 87±14 mmHg after; pulmonary capillary wedge pressure 31±11 mmHg before, 29± 11 mmHg after). Vasodilators increased cardiac output significantly (P<0–05) at rest (3-1 ±0–6 litre/min to 4-1 ± 1 1 litre/m) and during exercise (4–8±-2 litre/min-5–6±l-7 litre/min). The core temperature (mixed venous blood temperature) decreased significantly (P<0–05) during exercise from 37-04±0–62^oC to 36–65±0–65^oC, before treatment with vasodilators. After administration of vasodilators, resting core temperature was not significantly different (36–95±0–54^oC) and still decreased significantly (P<0–05) during exercise to 36–73±0–53^oC. This decrease was significantly (P<0–05) different from the core temperature response before the administration of vasodilators. We conclude that heart failure patients, treated with short-term vasodilators, have an     

健康成年新西兰兔肺动脉、肺静脉血流频谱分析及右心系统压力检测

目的 利用超声心动图及右心导管测量新西兰兔肺动脉、肺静脉频谱指标及右心系统压力指标,了解其频谱特点及右心系统压力的正常值范围。 方法 选择健康成年新西兰兔24只,用彩色多普勒超声诊断系统测量其肺动脉、肺静脉频谱,并同步记录心电图及呼吸曲线。通过右心导管记录并测量其右心房、右心室、肺动脉的收缩压及舒张压。 结果 频谱多普勒结果显示新西兰兔肺静脉频谱的峰值血流速度吸气相与呼气相的差异均无统计学意义(P均>0.05),肺动脉频谱峰值血流速度吸气相高于呼气相,差异有统计学意义(P<0.001)。右心导管压力测值结果显示新西兰兔肺动脉收缩压范围为16.07~23.99 mmHg、肺动脉舒张压为11.18~19.22 mmHg。 结论 超声心动图可清晰显示新西兰兔肺动脉、肺静脉血流;其肺动脉血流频谱随呼吸周期呈规律性变化。     

Expanded PTFE-covered stent-grafts in the treatment of transjugular intrahepatic portosystemic shunt (TIPS) stenoses and occlusions

Background We evaluated the efficacy of the VIATORR endoprosthesis for the management of transjugular intrahepatic portosystemic shunt (TIPS) dysfunction. Methods Twelve consecutive patients (10 men and two women, mean age 52.7 years) with recurrent TIPS dysfunction underwent TIPS revision with use of the VIATORR endoprosthesis. Nine patients were asymptomatic and three patients had developed recurrent variceal bleeding. All patients had previous shunt revisions (mean 2.1 revisions per patient) with angioplasty or bare stents. Follow-up included clinical assessment, Doppler ultrasound, and portal venography. Results TIPS revision was successful in all patients, without complications. The mean portosystemic pressure gradient decreased from 16.8 ± 2.7 mmHg to 6.5 ± 2.6 mmHg. Hemostasis was achieved in all three patients who had recurrent variceal bleeding at the time of the procedure. Mean follow-up was 21.9 ± 10.7 months. In two patients TIPS dysfunction occurred at 14 and 30 months after stent-graft placement, respectively. The primary patency rates were 100% after 12 months and 88.8% after 24 months. Two patients (16.6%) developed encephalopathy after stent graft placement. Conclusion TIPS revision using the VIATORR endoprosthesis appears to be an effective and durable method to control shunt dysfunction.     

超声心动图研究正压通气对犬心功能的影响及其机制

目的观察正压通气时心内瓣口血流速度和左、右心功能的变化,研究正压通气影响血流动力学机制的新理论。方法11条杂种犬,用超声心动图测定正压通气时心内各瓣口的血流速度,右室、左室每搏量,左室容积和射血分数的变化。结果三尖瓣和肺动脉瓣口血流速度正压吸气相减低,呼气相增加;二尖瓣和主动脉瓣口血流速度变化与之相反(P<0.05)。与自主呼吸相比,正压吸气时,右室每搏量减少,左室舒张末和收缩末容积减小,射血分数降低(P<0.05)。结论正压通气使室间隔趋于右移,同时,肺血管床回心血量增加,但与自主呼吸时相比,腔静脉回心血量相对减少,故心功能降低。