Pulmonary vascular stiffness responses are assessed using both pulmonary artery pulse pressure and intravascular ultrasound-derived pulmonary artery area changes in the cardiac cycle. The pulmonary artery stiffness responses to nitroglycerin in patients with secondary pulmonary hypertension are variable and not predicted by the change in mean pulmonary artery pressure or pulmonary vascular resistance. These data suggest that IVUS-derived measurements of pulmonary artery stiffness in pulmonary hypertension provide important information regarding functional abnormalities in the vessel wall that are not obtained with conventional measurements. other
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The focal pulmonary artery stenoses were balloon dilated, resulting in increases in lumen area. The IVUS findings were associated with an improvement in pulmonary artery hemodynamics.
Assessment of Response to Drug Therapy: Pulmonary artery IVUS has been used to detect different pulmonary vascular area responses to dobu-tamine and nitroglycerin in patients with chronic heart failure undergoing evaluation for orthotopic heart transplantation.’ buy yaz online
In one case study, despite similar calculated measurements of pulmonary vascular resistance changes to these drugs, pulmonary artery IVUS demonstrated vasoconstriction to dobu-tamine but vasodilation to nitroglycerin These responses provided additional information on the pulmonary vascular reactivity in patients with heart failure. A subsequent larger study showed a wide variety of pulmonary artery vascular responses to nitroglycerin in patients with chronic heart failure and pulmonary hypertension that were not predicted by changes in mean pulmonary artery pressure or calculated pulmonary vascular resistance.
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Secondary pulmonary hypertension may occur in response to pulmonary parenchymal disease, leftsided heart failure, or mitral valve disease. Intravascular ultrasound has been used to detect abnormalities in vessel wall thickness in pulmonary hypertension secondary to left-sided heart failure, and to determine how this correlates with wall stiffness. Pulmonary IVUS (6F 20 MHz) of vessels from 3 to 7 mm in diameter in patients with chronic congestive heart failure and secondary pulmonary hypertension revealed an increased incidence of plaque in the vessel wall when compared with an age-matched control group, as well as decreased pulsatility and increased vessel stiffness. Although patients with chronic heart failure but normal pulmonary artery pressure had an increased frequency of pulmonary artery plaque by IVUS, they continued to exhibit normal pulmonary artery pulsatility and stiffness. These studies show the usefulness of IVUS in assessing the pulmonary artery dynamics that accompany chronic heart failure. generic yaz
Chronic Pulmonary Thromboembolic Disease: Recent clinical studies have also showed the ability of pulmonary IVUS to diagnose chronic pulmonary thromboemboli. Ricou et al used an 8F 20 MHz IVUS catheter to detect abnormalities in the left and right pulmonary arteries of patients with chronic thromboemboli. These abnormalities were described as either marked thickening of the vessel wall or a crescentic layer of thickening. Using these criteria, chronic organized thrombi or tumor were identified at surgery in all of the abnormal segments of the pulmonary artery seen by IVUS. About 90% of the segments that were considered normal by IVUS were free of chronic thromboemboli at surgery. buy birth control
Using a disposable 6F 20 MHz ultrasound probe in isolated pulmonary artery segments of dogs, it has been shown that IVUS-derived measurements of pulmonary artery area, diameter, and wall thickness correlated very well with anatomic measurements in vitro (Fig 1). In this preliminary study, pulmonary IVUS images in humans were also obtained and provided detailed examinations of the changes in pulmonary artery vessel shape and pulsatility from the proximal to the distal pulmonary artery. An example of a normal human pulmonary artery using 20 MHz IVUS at end-diastole and end-systole is shown in Figure 2.
The unique features of pulmonary IVUS described above have been used for diagnostic, interventional, and pathophysiologic assessments in pulmonary vascular diseases (Table 1).
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This technique has been used to examine 1.0- to 4.5-mm diameter pulmonary arteries in humans with chronic lung disease. It has also accurately detected acute pulmonary emboli in dogs. It has been used clinically in patients suspected of having chronic pulmonary emboli where the angiogram is not conclusive. In these cases, angio-scopy has been useful in excluding other pulmonary vascular disorders, which may mimic thromboemboli, eg, plaque, and has also been used in determining operability. review
IVUS of the pulmonary artery is a new catheter-based imaging modality with high resolution and real time imaging capabilities. Its advantages over other imaging techniques include significantly better resolution of the pulmonary vessel lumen and wall, detailed description of both proximal and distal pulmonary arterial anatomy, real time imaging of the pulmonary artery throughout the cardiac cycle, and the ability to rapidly assess the effect of mechanical and pharmacologic interventions. Unlike angio-scopy, it is capable of imaging through blood and can describe disease within the vessel wall.
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Computed tomography (CT) and MR imaging provide anatomic detail in pulmonary artery disease that cannot be obtained from pulmonary angiography. In pulmonary atresia, MR imaging has shown the presence or absence of pulmonary arteries in regions that are not accessible to catheters. In a small study of 21 patients with pulmonary embolism, high resolution CT scanning was shown to be better than angiography in assessing proximal thrombi, examining pulmonary arteries distal to thrombi, and detecting pulmonary infarction. Cine MR imaging has also been clinically applied in infants to define accurately the placement of pulmonary artery banding. Cardiac and respiratory motion, as well as pulmonary artery pulsatility, limit the application of these imaging techniques in assessing intraluminal abnormalities. Recently, MR angiography has been able to compensate for cardiac motion by using electrocardiographic gating and phase velocity mapping techniques which also may be able to quantify pulmonary blood flow. Fast gradient echo-images may be able to semi-quantify the severity of pulmonary hypertension in a wide variety of pulmonary vascular diseases
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