What have we learned from in vitro intravascular ultrasound?

In vitro studies have established that intravascular ultrasound is a reliable technique for accurate assessment of vascular anatomic structure and disease conditions before and after intervention. In addition, quantitative data from intravascular ultrasound studies correspond well with histologic findings, which serve as the gold standard. These in vitro studies permit the understanding and interpretation of ultrasound images obtained in vivo, although differences between the two settings should be taken into account. New ultrasound modalities currently being developed may enhance the diagnostic differentiation of plaque morphologic characteristics and facilitate on-line quantitative assessment of vessel structure.

A computerized system that uses high-frequency data for analysis of myocardial contrast echocardiograms.

Intracoronary and, more recently, intravenous injection of a contrast medium renders it possible to determine myocardial perfusion by use of ultrasound. For the analysis of the data obtained with two-dimensional phased array echocardiographic equipment, two methods can be carried out. First, in the off-line method, the images stored on video tape can be transferred to a computer memory by use of a frame grabber, after which computer analysis of the data can be performed. Second, the phased-array electronics can be directly connected to a computer. In this setup the computer controls the phased array, and the data transported consists of the high-frequency signal. Both methods are described. Some advantages of high-frequency measurements over video-densitometry are the independence of the setup of the two dimensional machine and the higher signal-to-noise ratio. Furthermore, there is the possibility to use the amplitude, phase, and frequency of the high-frequency signal. In this way a detailed study of the contrast medium is possible and the analysis can also be performed for the purpose of a combination with other methods, such as tissue identification.

Intraoperative two-dimensional echocardiography in complicated infective endocarditis of the aortic valve.

Six patients with complicated native and prosthetic aortic valve endocarditis were operated on. The data from cineangiocardiography and from precordial and intraoperative two-dimensional echocardiography were compared with the surgical findings. Surgical inspection revealed a mycotic aneurysm in six patients. In addition, a fistulous connection to the right atrium, an abscess in the interventricular septum, and mitral valve endocarditis were found in one of the patients. The pathologic conditions disclosed during the operation were correctly visualized with two-dimensional epicardial echocardiography, done before cardiopulmonary bypass. Cineangiography provided this information in one patient, and precordial two-dimensional echocardiographic analysis was correct in two patients. Thus, intraoperative two-dimensional echocardiography provides detailed information in complicated native and prosthetic aortic valve endocarditis that is of importance in the surgical management.

Intraoperative two-dimensional echocardiography in congenital heart disease.

Intraoperative epicardial two-dimensional echocardiography was used in 195 patients undergoing surgery for congenital heart disease to evaluate its potential to identify new diagnostic information immediately before and after surgical correction. In 168 patients the preoperative diagnosis was confirmed by intraoperative echocardiography. In four patients, unsuspected findings were revealed, which resulted in modification of the surgical approach. In 18 patients additional morphologic information was obtained which contributed to alteration or refinement of surgical management. The adequacy of cardiac repair was assessed before closure of the chest in all patients. In six patients this information led to immediate reoperation and in four other patients to inotropic drug therapy. During congenital heart surgery, epicardial two-dimensional echocardiography may yield important information for surgical management. The technique is an essential adjunct when preoperative diagnostic studies are not conclusive or when the initial response to repair is unsatisfactory.

Oesophageal echocardiography.

The diagnostic value of oesophageal echocardiography is most striking in patients in whom precordial studies are of inadequate quality or fail to establish a definitive diagnosis. Oesophageal studies have excellent image quality, can be completed within 10 minutes without complications and, in most instances, enables the clinical question to be answered. In 50 patients referred for suspected thoracic aorta pathology, oesophageal echocardiography correctly excluded or diagnosed the type of aortic dissection, aortic aneurysm or the site of coarctation. Of 35 patients referred with suspected infective endocarditis, oesophageal echocardiography revealed complications in 18 patients, including vegetation, mycotic aneurysm, abscess or chordal rupture. Oesophageal echocardiography is extremely helpful to visualize intracardiac mass lesions. In 27 patients with a history of systemic or pulmonary embolism, the technique confirmed the presence, size and position of a mass lesion in 11 patients. Oesophageal color Doppler flow imaging further expands the diagnostic capabilities, particularly in patients with mitral valve prosthesis. Our experience indicates that oesophageal echocardiography significantly extends the diagnostic potential of echocardiography. Detailed knowledge of cardiothoracic anatomy and its pathologic sequelae is, however, a prerequisite for the efficient and safe application of this method.

Transesophageal two-dimensional echocardiography: its role in solving clinical problems.

The diagnostic value of transesophageal two-dimensional echocardiography is described in 32 patients in whom precordial echocardiography or angiography, or both, failed to establish a definitive diagnosis. All attempted transesophageal studies were completed without complication and the referral question was definitively answered. Nineteen patients were subsequently submitted to surgery. In 18 of them, the transesophageal echocardiographic diagnoses were proven correct; in 1 patient, the diagnosis was proven partially incorrect. In the 13 unoperated patients the transesophageal echocardiographic diagnoses were not independently confirmed but were assumed correct because incontrovertible images were obtained. These results indicate that transesophageal echocardiography significantly extends the diagnostic capabilities of echocardiography.

"Offsetting" of the septal tricuspid leaflet in normal hearts and in hearts with Ebstein's anomaly. Anatomic and echographic correlation.

Apical displacement of the septal tricuspid valve leaflet is considered the most reliable criterion to diagnose Ebstein's anomaly. This feature is best assessed using 2-dimensional echocardiography. However, the anatomy in Ebstein's anomaly is highly variable; therefore, the problem arises as to how to distinguish between the abnormal displacement in borderline cases of Ebstein's disease and the lowered septal offsetting of the tricuspid valve in normal persons. To solve this problem the minimal and maximal differences in offsetting of the tricuspid and mitral valves have been studied, both anatomically and echocardiographically, in fetuses, infants, children and adults. In fetuses in the first trimester of pregnancy it was impossible to measure a difference in offsetting of the 2 atrioventricular valves. Thereafter, a gradual increase occurred with age. In normal hearts the most significant separation was usually recorded in anteriorly angulated 4-chamber views, whereas in hearts with Ebstein's anomaly maximal separation appeared to posteriorly angulated views. The anatomic and echographic measurements showed a constant relation. When the minimal distances in offsetting were measured, an overlap was found between cases with and those without Ebstein's anomaly. The maximal values, however, clearly discriminated between the 2 conditions. The critical difference in children was 15 mm, and in adults the discriminating value was 20 mm.