Pulmonary arterial hypertension: value of perfusion scintigraphy

Records of 34 patients with established causes of pulmonary arterial hypertension were retrospectively reviewed. The ventilation-perfusion scans were blindly classified according to standardized criteria as normal or high, low, or intermediate probability of pulmonary embolism as the cause of pulmonary arterial hypertension. Twelve of 13 patients with primary pulmonary hypertension had normal or low-probability scans, but the perfusion pattern was not helpful in distinguishing between histologic subtypes. All eight patients with large-vessel thromboembolic hypertension had high-probability scans; however, three of 13 patients with nonembolic secondary pulmonary hypertension also had high-probability scans. While a normal or low-probability scan excluded proximal pulmonary emboli as a cause of pulmonary hypertension, a high-probability scan may be associated with a variety of other nonembolic causes of secondary pulmonary hypertension.     

Pulmonary arterial hypertension: an imaging review comparing MR pulmonary angiography and perfusion with multidetector CT angiography

Pulmonary hypertension (PH) is a progressive disease that leads to substantial morbidity and eventual death. Pulmonary multidetector CT angiography (MDCTA), pulmonary MR angiography (MRA) and MR-derived pulmonary perfusion (MRPP) imaging are non-invasive imaging techniques for the differential diagnosis of PH. MDCTA is considered the gold standard for the diagnosis of pulmonary embolism, one of the most common causes of PH. MRA and MRPP are promising techniques that do not require the use of ionising radiation or iodinated contrast material, and can be useful for patients for whom such material cannot be used. This review compares the imaging aspects of pulmonary MRA and 64-row MDCTA in patients with chronic thromboembolic or idiopathic PH.Pulmonary hypertension (PH) is an insidious and progressive disease that leads to substantial morbidity and eventual death. PH results from a number of diseases with different physiopathologies, treatments and prognoses [1]. One of the most frequent causes of PH is chronic thromboembolic pulmonary hypertension (CTEPH).The current classification of PH (2], resulted from a review of the previous classification developed at the 2003 3rd World Symposium in Venice, Italy. During the 4th World Symposium on PH, an international group of experts agreed to maintain the general philosophy and organisation of the Evian–Venice classifications. However, in response to a questionnaire regarding the previous classification, a majority (63%) of experts felt that modification of the Venice classification was required to accurately reflect information published in the past 5 years and to provide clarification in some areas [2].

Table 1

Classification of pulmonary hypertension according to the 4th World Symposium, Dana Point, CA, 2008 [2]

动态肺灌注显像评价特发性肺动脉高压的临床研究

目的 探讨动态PPI用于IPAH的临床应用价值.方法 2009年7月至2010年12月间20例经右心导管及肺动脉造影检查确诊为IPAH的连续病例和10名健康对照者,接受动态PPI.以双肺为ROI,得到时间-放射性曲线,计算显像剂从进入肺内到肺内放射性分布达到平衡的肺平衡时间(LET).组间比较采用t检验,LET与右心导管测得的血流动力学参数进行Pearson相关分析.结果 IPAH患者LET平均为(33.9 ±15.5)s,而健康对照组仅为(14.4±3.7)s,IPAH患者LET明显延长(t=5.340,P＜0.001).LET与mPAP、全肺阻力(TPR)间具有直线相关性(分别为r=0.566,P＜0.01和r=0.688,P＜0.05),与CI呈直线负相关(r=-0.480,P＜0.05).结论 动态PPI对于无创性评估IPAH血流动力学变化程度及右心功能具有一定的应用价值.     

Follow-up pulmonary perfusion scintigraphy pulmonary arterial embolization in two cases of familial pulmonary arteriovenous fistula

Follow-up pulmonary perfusion scintigraphy in evaluating pulmonary arterial embolization were assessed by two cases of pulmonary familial arteriovenous fistula. Pulmonary arteriovenous fistula was found for brain abscess in the older brother, and for dyspnea on effort in the younger brother. Pulmonary arterial embolizations were performed. (older brother: 4 times, younger brother: 5 times) Before embolization, pulmonary perfusion scintigram showed pale defect, clear asymmetric perfusion between right and left lung, and clear renal visualization. On the other hand, after the embolization, clear multiple defects agreed with the sites of embolization, and asymmetric pulmonary perfusion and renal visualization disappeared. We conclude that follow-up pulmonary perfusion scintigraphy is useful to evaluate in pulmonary arteriovenous fistula after embolization.     

Interventricular septal configuration at mr imaging and pulmonary arterial pressure in pulmonary hypertension

PURPOSE: To investigate whether a relationship exists between septum shape and systolic pulmonary arterial pressure (PAP) in patients with pulmonary hypertension. MATERIALS AND METHODS: Study protocol was approved by institutional ethics review committee; all patients gave informed consent. Right-sided heart catheterization with vasodilator testing was performed in 39 adult subjects suspected of having pulmonary hypertension. There were 11 men and 28 women, aged 21-75 years (mean, 46 years). Only two patients showed favorable response to vasodilators, defined by a decrease in PAP of more than 20%. Synchronous right- and left-ventricular pressure measurements and four-chamber magnetic resonance (MR) imaging were used to identify timing of maximal leftward ventricular septal bowing within cardiac cycle. Septal bowing was evaluated with MR, measured on short-axis cine heart images, and expressed as curvature (reciprocal of radius). Curvature was quantified on one image (the one that showed the most severe distortion of normal septal shape). The relationship between systolic PAP and septal curvature was tested with linear regression analysis. P <.05 was considered to indicate a statistically significant difference. RESULTS: Of 39 subjects, 37 had pulmonary hypertension. Maximal distortion of normal septal shape was found during right ventricular relaxation phase. Systolic PAP was proportional to septal curvature: r=0.77 (P < .001), slope=-114.7, and intercept=67.2. In the two vasodilator responsive subjects, a significant reduction of leftward ventricular septal bowing was observed in response to reduction of right ventricular pressure. CONCLUSION: In 37 patients with pulmonary hypertension, systolic PAP higher than 67 mm Hg may be expected when leftward curvature is observed.     

Noninvasive estimation of pulmonary arterial pressure by analysis of pulmonary blood-flow distribution

To determine whether a correlation exists between pulmonary arterial (PA) pressure (Pa) and the distribution of pulmonary blood flow, this distribution was measured in four upright dogs in the control state and during intravenous infusions of epinephrine or prostaglandin F2 alpha. During suspension of respiration, 15 mCi of Xe-133 were injected intravenously, and perfusion and equilibration lung images were recorded with a scintillation camera. The procedure was performed several times on each dog, with and without pharmacological elevation of PA pressure by 5 to 50 cm H2O. For each scintigram, the relative blood flow per unit ventilated lung volume (F) was plotted against centimeters above the hilum (h). Pulmonary arterial pressure was derived from each curve, assuming the relation F = B(Pa - hD)2, where B = constant and D = specific gravity of blood. Calculated PA pressure correlated strongly (r = 0.83) with measured PA pressure, suggesting a possible means of noninvasive estimation of PA pressure.     

Pulmonary ventilation and perfusion abnormalities and ventilation perfusion imbalance in children with pulmonary atresia or extreme tetralogy of Fallot

Xenon-133 lung ventilation and perfusion scans were done preoperatively after cardiac catheterization and cineangiocardiography in 19 children; 6 had pulmonary atresia with an intact ventricular septum and hypoplastic right ventricle, 4 pulmonary atresia with associated complex univentricular heart, and 9 extreme Tetralogy of Fallot. The four patients with discrepancies in the sizes of the left and right pulmonary arteries on angiography had marked asymmetry of pulmonary perfusion and ventilation-perfusion imbalance on scintigraphy. Similar degrees of asymmetry and imbalance were present in 6 of the 15 children with equal-size pulmonary vessels. Asymmetry of pulmonary perfusion and ventilation-perfusion imbalance were associated with a poor prognosis.     

Pulmonary arterial hypertension: diagnosis with fast perfusion MR imaging and high-spatial-resolution MR angiography--preliminary experience

PURPOSE: To determine prospectively the accuracy of a magnetic resonance (MR) perfusion imaging and MR angiography protocol for differentiation of chronic thromboembolic pulmonary arterial hypertension (CTEPH) and primary pulmonary hypertension (PPH) by using parallel acquisition techniques. MATERIALS AND METHODS: The study was approved by the institution's internal review board, and all patients gave written consent prior to participation. A total of 29 patients (16 women; mean age, 54 years +/- 17 [+/- standard deviation]; 13 men; mean age, 57 years +/- 15) with known pulmonary hypertension were examined with a 1.5-T MR imager. MR perfusion imaging (temporal resolution, 1.1 seconds per phase) and MR angiography (matrix, 512; voxel size, 1.0 x 0.7 x 1.6 mm) were performed with parallel acquisition techniques. Dynamic perfusion images and reformatted three-dimensional MR angiograms were analyzed for occlusive and nonocclusive changes of the pulmonary arteries, including perfusion defects, caliber irregularities, and intravascular thrombi. MR perfusion imaging results were compared with those of radionuclide perfusion scintigraphy, and MR angiography results were compared with those of digital subtraction angiography (DSA) and/or contrast material-enhanced multi-detector row computed tomography (CT). Sensitivity, specificity, and diagnostic accuracy of MR perfusion imaging and MR angiography were calculated. Receiver operator characteristic analyses were performed to compare the diagnostic value of MR angiography, MR perfusion imaging, and both modalities combined. For MR angiography and MR perfusion imaging, kappa values were used to assess interobserver agreement. RESULTS: A correct diagnosis was made in 26 (90%) of 29 patients by using this comprehensive MR imaging protocol. Results of MR perfusion imaging demonstrated 79% agreement (ie, identical diagnosis on a per-patient basis) with those of perfusion scintigraphy, and results of MR angiography demonstrated 86% agreement with those of DSA and/or CT angiography. Interobserver agreement was good for both MR perfusion imaging and MR angiography (kappa = 0.63 and 0.70, respectively). CONCLUSION: The combination of fast MR perfusion imaging and high-spatial-resolution MR angiography with parallel acquisition techniques enables the differentiation of PPH from CTEPH with high accuracy.     

肺灌注显像定量分析评价特发性肺动脉高压

目的探讨肺灌注显像肺血流灌注分布指数（简称P指数）定量分析法评价特发性肺动脉高压（IPAH）的应用价值。方法选取30例临床确诊的IPAH患者,行肺灌注显像和右心导管检查。应用美国国立卫生研究院开发的开源软件NIHImage进行P指数定量分析,同时选取12名年龄相匹配的健康对照者进行肺灌注显像,以得到灌注面积百分比标准曲线,并对全部30例患者的P指数和血流动力学参数进行Pearson相关性分析。按肺灌注显像特点将患者分为3组（双肺放射性分布均匀;双肺放射性分布不均匀,肺尖部放射性浓聚;双肺放射性分布明显不均匀,呈“斑片状”稀疏和缺损改变）,比较各组间P指数的差异。采用SPSS11．0软件,组间比较行student’st检验。结果P指数与平均肺动脉压（mPAP）及全肺阻力（TPR）呈直线相关性,P指数与mPAP的相关系数为0．541（P〈0．01）,与TPR的相关系数为0．573（P〈0．01）。图像定性分析3种特征性图像的P指数分别为9．47±1．06,13．77±4．57和18．97±5．93,呈递增趋势（t值分别为-2．83,-5．68和-2．65,P均〈0．05）;mPAP、TPR亦依次呈递增趋势,但差异无统计学意义（t=-1．990～0．236,P均〉0．05）。结论肺灌注显像P指数定量分析法能够准确反映肺动脉压力和TPR等血流动力学状态,对IPAH的诊断和疗效判断具有较好的应用前景。     

Effect of an iso-osmolar contrast medium on pulmonary arterial pressure at pulmonary angiography

A clinical comparison of the effects on pulmonary arterial pressure induced by contrast media with various osmolalities, iohexol 140 mg I/ml (300 mosm/kg H2O), iohexol 300 mg I/ml (690 mosm/kg H2O), and diatrizoate 292 mg I/ml (1480 mosm/kg H2O) following selective pulmonary angiography was made in 12 patients with normal pulmonary arterial pressure. A double-blind crossover study was performed and the contrast media were administered in random order. The pulmonary arterial pressure was recorded continuously before, during, and for 3 min after the injection. The effect of iohexol 140 on the pulmonary arterial pressure was significantly less marked than that of diatrizoate 292, whereas no statistical significance was shown between iohexol 140 and iohexol 300. These results indicate that iso-osmolar contrast medium (iohexol 140), as well as iohexol 300, would be better tolerated than diatrizoate 292, and is therefore a safer contrast medium for selective pulmonary angiography.     

Cardiac MR-assessed hemodynamic changes in pulmonary arterial hypertension and their relation to pulmonary artery pressure

Purpose

To demonstrate the hemodynamic changes of pulmonary arterial hypertension using cardiac MRI and to determine which parameters are best representative of the pulmonary artery pressure.

Pulmonary perfusion in acute pulmonary embolism: agreement of MRI and SPECT for lobar, segmental and subsegmental perfusion defects

Purpose: To assess prospectively the agreement of magnetic resonance (MR) pulmonary perfusion with single-photon emission computed tomography (SPECT) perfusion for perfusion defects down to the subsegmental level in patients with suspected pulmonary embolism (PE).

Material and Methods: In 41 patients with suspected PE, contrast-enhanced MR pulmonary perfusion (3D-FLASH, TR/TE 1.6/0.6 ms) was compared to SPECT perfusion on a per-examination basis as well as at the lobar, segmental, and subsegmental level.

Results: The MRI protocol was completed in all patients, and mean examination time was 3 min 56 s. MR perfusion showed a very high agreement with SPECT (kappa value per examination 0.98, and 0.98, 0.83, and 0.69 for lobar, segmental, and subsegmental perfusion defects, respectively). Of 15 patients with PE, MR perfusion detected 14 cases.

Conclusion: The very high agreement of MR perfusion with SPECT perfusion enables the detection of subtle findings in suspected PE.     

Catheter fragmentation of acute massive pulmonary thromboembolism: distal embolisation and pulmonary arterial pressure elevation

The aim of this study was to evaluate the relationship between pulmonary arterial pressure and distal embolisation during catheter fragmentation for the treatment of acute massive pulmonary thromboembolism with haemodynamic impairment. 25 patients with haemodynamic impairment (8 men and 17 women; aged 27-82 years) were treated by mechanical thrombus fragmentation with a modified rotating pigtail catheter. After thrombus fragmentation, all patients received local fibrinolytic therapy, followed by manual clot aspiration using a percutaneous transluminal coronary angioplasty (PTCA) guide catheter. Pulmonary arterial pressure was continuously recorded during the procedure. The Friedman test and Wilcoxon test were applied for statistical analysis. Distal embolisation was confirmed by digital subtraction angiography in 7 of the 25 patients. A significant rise in mean pulmonary arterial pressure occurred after thrombus fragmentation (before: 34.1 mmHg; after: 37.9 mmHg; p<0.05), and this group showed a significant decrease in mean pulmonary arterial pressure after thrombus aspiration (25.7 mmHg; p<0.05). No distal embolisation was seen in 18 of the 25 patients, and a significant decrease in mean pulmonary arterial pressure was confirmed after thrombus fragmentation (before: 34.2 mmHg; after: 28.1 mmHg: p<0.01), and after thrombus aspiration (23.3 mmHg; p<0.01). In conclusion, distal embolisation and a rise in pulmonary arterial pressure can occur during mechanical fragmentation using a rotating pigtail catheter for the treatment of life-threatening acute massive pulmonary thromboembolism; thrombolysis and thrombus aspiration can provide partial recanalization and haemodynamic stabilization. Continuous monitoring of pulmonary arterial pressure may contribute to the safety of these interventional procedures.