Catheter-based intravascular ultrasound discriminates bicuspid from tricuspid valves in adults with calcific aortic stenosis

The bicuspid aortic valve: Is it an immunological disease process?

Bicuspid aortic valves (BAVs) are the most common congenital cardiac condition and are characterized by a structural abnormality whereby the aortic valve is composed of two leaflets instead of being trileaflet. It is linked to an increased risk for a variety of complications of the aorta, many with an immunological pathogenesis. The aim of this study is to review and analyze the literature regarding immunological processes involving BAVs, associated common pathologies, and their incidence in the population. This study will also examine current trends in surgical and therapeutic approaches to treatment and discuss the future direction of BAV treatment.

Impact of Valvular Calcification on the Diagnostic Accuracy of Transesophageal Echocardiography for the Detection of Congenital Aortic Valve Malformation

BACKGROUND

Degeneration of congenital bicuspid or unicuspid aortic valves can progress more rapidly than that of tricuspid valves, and an early diagnosis significantly impacts decision making and outcome. We hypothesized that the extent of valvular calcification would negatively influence the diagnostic accuracy of multiplane transesophageal echocardiography (TEE) for the diagnosis of congenital aortic valve disease.

METHODS

TEE was performed in 57 patients undergoing aortic valve replacement surgery for aortic stenosis (n = 46), pure regurgitation (n = 9), or significant regurgitation with less than severe aortic stenosis (n = 2). The degree of aortic valve calcification and the number of valve cusps were determined at surgery.

RESULTS

Surgical inspection confirmed 14 bicuspid and 43 tricuspid aortic valves. Sensitivity and specificity of TEE for the diagnosis of congenital aortic valve malformation was 93% (13/14) and 91% (39/43) (P = 0.0001), respectively. In patients with no or mild aortic valve calcification (n = 13), sensitivity and specificity of TEE for the diagnosis of congenitally malformed aortic valve was 100% (5/5) and 100% (8/8) (P = 0.001), respectively. In patients with moderate or marked aortic valve calcification (n = 44), sensitivity and specificity of TEE for the diagnosis of congenitally malformed aortic valve was 89% (8/9) and 89% (31/35) (P<0.0001), respectively. In this subgroup of 44 patients, there were four false-positive and one false-negative diagnoses due to valvular calcification.

CONCLUSIONS

Although TEE is highly sensitive and specific for the detection of congenital aortic valve malformations, presence of moderate or marked calcification of the aortic valve may result in false positive and false negative diagnoses.

Sensitivity and specificity of transesophageal echocardiography for determination of aortic valve morphology

BACKGROUND

Preoperative recognition of the presence of bicuspid aortic valve can be important in the planning of procedures. Multiplane transesophageal echocardiography may allow more accurate detection of valvular morphology than does biplane transesophageal echocardiography.

METHODS AND RESULTS

The studies of 710 patients who subsequently underwent valvular or aortic surgery were reviewed in a blinded fashion. The inclusion criteria were adequate short-axis view and operative note confirmation of aortic valve morphology. Six hundred eight patients were submitted to further analysis. Four hundred three patients had aortic stenosis as the primary diagnosis. Three hundred sixty patients had biplane examinations and 248 had multiplane examinations. The sensitivity and specificity of the multiplane technique in assessing aortic valve morphology (bicuspid vs tricuspid valve) was 87% and 91%, respectively. The sensitivity and specificity of the biplane technique was 66% and 56%, respectively. Whether valves were calcified or not did not result in major changes in sensitivity and specificity for either technique.

CONCLUSIONS

Multiplane transesophageal echocardiography provides a more accurate assessment of preoperative aortic valve morphology than does the biplane approach in the majority of patients.

2-D and 3-D endoluminal ultrasound: vascular and nonvascular applications

Endoluminal ultrasound using catheter-based transducers has been used for the evaluation of a wide range of abnormalities. To date, one of the most promising areas of clinical application is its use intravascularly for quantitating the degree of arterial stenosis and for monitoring the therapeutic effects of angioplasty in peripheral and coronary arteries. Uses in the gastrointestinal tract include quantification of the size and wall thickness of esophageal varices, distinguishing between various submucosal lesions and measuring the degree of fibrosis in scleroderma. In the genitourinary system, endoluminal ultrasound provides a unique intraoperative tool allowing the addition of a third dimension (depth) to endourological procedures. The indications for, and the use of, endoluminal ultrasound within the upper urinary tract can be expected to increase with more experience, and the procedure has become an important technique that yields information not available through other modalities. In the bronchotracheal tree, endoluminal ultrasound allows imaging and subsequent biopsy of lymph nodes and tumors that cannot be visualized at routine bronchoscopy. Three-dimensional (3-D) reconstruction of two-dimensional (2-D) ultrasound imaging is a new method in the evolution of intraluminal imaging. It provides information about spatial relationships of anatomic structures that cannot be evaluated using conventional 2-D imaging. Although still in its infancy, 3-D endoluminal ultrasound has the potential to become a dynamic tool in both the research and clinical areas.

Quantitative assessment of stenotic aortic valve area by using intracardiac echocardiography: in vitro validation and initial in vivo illustration

Quantitative assessment of aortic stenosis (AS) is subject to the limitations of all current noninvasive and invasive methods. The ability to obtain a direct measure of aortic valve area with high resolution by intracardiac echocardiography (ICE) could be of great benefit to catheterized patients. To provide a fixed AS area as an ideal standard for comparison, we performed ICE in 12 sheep hearts with experimentally created AS and five human AS hearts from autopsies. ICE catheters were passed retrograde across the aortic valve, and the minimal orifice area on pullback was planimetered and compared with calibrated video imaging. The entire orifice circumference could be successfully recorded in 16 (94%) hearts. Orifice area from ICE correlated well with actual values (r=0.98; standard error of the estimate [SEE] = 0.06 cm2). To illustrate the applicability in vivo, two canine models and 10 patients with AS were studied. The limiting orifice could be imaged in both animals and in 8 of 10 patients, in whom values agreed well with invasive data (r= 0.95; SEE = 0.04 cm2). ICE can therefore accurately measure AS orifice area in vitro; it can be applied in vivo as well. These validation studies laid the foundation for subsequent clinical studies and applications.

Determination of aortic valve area in valvular aortic stenosis by direct measurement using intracardiac echocardiography: a comparison with the Gorlin and continuity equations

OBJECTIVES

This study sought to 1) show that intracardiac echocardiography can allow direct measurement of the aortic valve area, and 2) compare the directly measured aortic valve area from intracardiac echocardiography with the calculated aortic valve area from the Gorlin and continuity equations.

BACKGROUND

Intracardiac echocardiography has been used in the descriptive evaluation of the aortic valve; however, direct measurement of the aortic valve area using this technique in a clinical setting has not been documented. Despite their theoretical and practical limitations, the Gorlin and continuity equations remain the current standard methods for determining the aortic valve orifice area.

METHODS

Seventeen patients underwent intracardiac echocardiography for direct measurement of the aortic valve area, including four patients studied both before and after valvuloplasty, for a total of 21 studies. Immediately after intracardiac echocardiography, hemodynamic data were obtained from transthoracic echocardiography and cardiac catheterization.

RESULTS

Adequate intracardiac echocardiographic images were obtained in 17 (81%) of 21 studies. The average aortic valve area (mean +/- SD) determined by intracardiac echocardiography for the 13 studies in the Gorlin analysis group was 0.59 +/- 0.18 cm2 (range 0.37 to 1.01), and the average aortic valve area determined by the Gorlin equation was 0.62 +/- 0.18 cm2 (range 0.31 to 0.88). The average aortic valve area determined by intracardiac echocardiography for the 17 studies in the continuity analysis group was 0.66 +/- 0.23 cm2 (range 0.37 to 1.01), and that for the continuity equation was 0.62 +/- 0.22 cm2 (range 0.34 to 1.06). There was a significant correlation between the aortic valve area determined by intracardiac echocardiography and the aortic valve area calculated by the Gorlin (r = 0.78, p = 0.002) and continuity equations (r = 0.82, p < 0.0001).

CONCLUSIONS

In the clinical setting, intracardiac echocardiography can directly measure the aortic valve area with an accuracy similar to the invasive and noninvasive methods currently used. This study demonstrates a new, quantitative use for intracardiac echocardiographic imaging with many potential clinical applications.

Evaluation of pulmonary artery histopathologic findings in congenital heart disease: an in vitro study using intravascular ultrasound imaging

OBJECTIVES

This study aimed to 1) compare in vitro intravascular ultrasound images of human pulmonary arteries with corresponding histologic sections, and 2) correlate the relation between intravascular ultrasound findings and Heath-Edwards pathologic grade of pulmonary vascular changes.

BACKGROUND

The pathologic assessment of the pulmonary vascular bed is essential for diagnosis and management of congenital heart disease with pulmonary hypertension.

METHODS

We evaluated and compared intravascular ultrasound images with histologic findings at identical sites in 40 pulmonary artery segments from 17 autopsy studies: group 1 = 7 patients with pulmonary hypertension (Heath-Edwards grade I to V, 20 segments); group 2 = 10 patients without cardiopulmonary disease (20 segments).

RESULTS

In group 2, the pulmonary artery wall echo consisted of a single layer. In group 1, 1) all segments of pulmonary arteries from patients with pulmonary hypertension showed a three-layered appearance; 2) in patients with mild pulmonary hypertension (Heath-Edwards grades I and II), intravascular ultrasound demonstrated increased thickness of the echoluscent zone due to medial hypertrophy with no intimal reaction; 3) patients with severe pulmonary hypertension (Health-Edwards grade III or higher) had intravascular ultrasound findings of increased medial thickness and a bright inner layer from intimal hyperplasia; 4) percent wall thickness derived from intravascular ultrasound showed a significant correlation with that determined by histologic examination (r = 0.89, p = 0.0001, n = 20).

CONCLUSIONS

Changes observed with intravascular ultrasound imaging correlate well with histopathologic grade. Thus, intravascular ultrasound may have significant utility in the evaluation of pulmonary vascular morphology in patients with pulmonary hypertension.

Imaging of pulmonary vascular disease by intravascular ultrasound

To assess the ability of intravascular ultrasound (IVUS) to image changes in the pulmonary arterial wall associated with pulmonary hypertension (PHT), 10 subjects requiring diagnostic right and left heart catheterization were studied. In addition to measurements of pulmonary artery pressure and pulmonary vascular resistance and pulmonary angiography, when indicated, all underwent simultaneous IVUS imaging in the pulmonary arterial system using a 20 MHz ultrasound transducer mounted on a 2 mm diameter catheter. Four patients had normal pulmonary artery pressures and 6 had varying degrees of PHT. Satisfactory ultrasound images were obtained in 9 out of the 10 patients. In those with normal pulmonary artery pressures ultrasound showed a thin vessel wall with no distinction between separate layers. In patients with systemic PHT, a three-layered vessel wall was apparent and areas compatible with intimal proliferation were seen. In a patient with pulmonary embolic disease areas consistent with mural thrombus were detected at sites of luminal narrowing on the pulmonary angiogram. IVUS is capable of imaging some of the morphological changes in the wall of the pulmonary artery known to occur in longstanding PHT and may therefore become a useful adjunct to haemodynamic measurements and pulmonary angiography for the in vivo assessment of pulmonary vascular disease.

Intravascular ultrasound imaging: a current perspective

Catheter-based intravascular ultrasound imaging has evolved from a research tool to a device that has received Food and Drug Administration approval. Although it is currently employed as an adjunct to contrast angiography in both the peripheral and the coronary circulation, the indications for its use and its clinical utility have yet to be defined. Much of the research on the technique has explored its qualitative and quantitative capabilities to improve the assessment of atherosclerotic vascular disease. There is the hope that this imaging technique may ultimately improve the performance of endovascular interventions. This review describes the development of the technology from early in vitro validation studies to its present use in human subjects. Wherever possible, studies that validate the findings (that is, by comparison with histopathology results) of intravascular ultrasound are emphasized. Although there is great promise for this technology, limitations such as loss of image quality in severely diseased or heavily calcified vessels hinder its use. The application of imaging with endovascular intervention, imaging of intracardiac structures and the pulmonary circulation and new techniques such as computer image analysis are discussed.

Intraoperative valvuloplasty in calcific aortic stenosis: a study comparing the mechanism of a novel expandable device with conventional balloon dilatation

In selected patients with calcific aortic stenosis, balloon valvuloplasty is an intermediate alternative to surgery. The effect of balloon valvuloplasty to increase valve area, however, is limited and the restenosis rate is high during follow-up. To improve the results and reduce the complication rate, a new device for valvuloplasty of calcific aortic stenosis was developed. This system consists of three expandable prongs mounted on a freely movable catheter tip. To evaluate the efficacy of this new device, valvuloplasty was performed in 10 patients with severe aortic stenosis intraoperatively just prior to valve replacement. Comparison was made with the results of conventional balloon dilatation performed in an additional 20 patients during surgery. Using the new device, the relative orifice area increased from 10 +/- 3% before to 20 +/- 6% following intervention. However, in only one patient was a considerable increase of static valve area (greater than 15%) found. The results were comparable to the effect of conventional balloon dilatation, which led to an increase of orifice area from 12 +/- 7% to 24 +/- 10%. With both systems, the best results were achieved in patients with aortic stenosis and significant commissural fusion. In contrast, in bicuspid or tricuspid valves without fused commissures the effect of the intervention was limited. Because complete obstruction of the aortic valve does not occur during dilatation, this new device might be superior to conventional balloon dilatation. Preselection of patients according to the morphology of the valve seems mandatory to improve the success and reduce the complication rate of valvuloplasty in aortic stenosis.

Applications of intravascular scanning and transesophageal echocardiography in congenital heart disease: tradeoffs and the merging of technologies

This chapter will review the evolving role of intravascular ultrasound imaging and transesophageal echo in the care of children, infants and adults with congenital heart disease. The technologies relevant to congenital heart disease applications differ from those involving coronary disease since the intravascular structures imaged often involve visualization of large vessels and cardiac chambers. On the other hand, the requirements for transesophageal echo in children with congenital heart disease involve intraoperative (surgical) and imaging procedures in the catheterization laboratory which are performed for monitoring interventional catheterization therapy. As such, whereas the intravascular devices needed for pediatric cases involve lower frequency and sometimes larger catheters, the requirements for transesophageal echocardiography require higher frequency and smaller esophagoscopes. Applications of intravascular imaging including sizing of congenital stenoses, dilation of coarctation and valvular stenoses, imaging of intrapulmonary thrombi and monitoring of placement of ASD 'button' devices in the heart will be reviewed. The intraoperative transesophageal uses for monitoring infant surgery include procedures for tetralogy repair, transposition repair and repair of AV septal defects and other complex congenital heart disorders. Both of these 'invasive' methods of echocardiography have an important and evolving role in the management of congenital heart disease in children and infants.

Acute catastrophic complications of balloon aortic valvuloplasty. The Mansfield Scientific Aortic Valvuloplasty Registry Investigators

Among the initial 492 patients who underwent balloon aortic valvuloplasty as part of the Mansfield Investigational Device Exemption Protocol, 31 (6.3%) had acute catastrophic complications. These included ventricular perforation in nine (1.8%), seven women and two men; six cases (67%) involved serial balloon inflations and seven (78%) also involved dual balloon inflations. In six (67%) of the nine patients perforation was fatal. In four patients studied at necropsy, the perforation involved the base of the lateral left ventricular free wall. Pericardiocentesis was performed in five patients, three of whom survived with (one patient) or without (two patients) operative repair. Acute, severe aortic regurgitation developed in four patients (0.8%), all women. None had significant regurgitation before valvuloplasty; dual balloons were used in two of the four. All three patients who underwent emergency valve replacement survived. A fourth patient died 2 days after valvuloplasty without operative intervention. Fatal cardiac arrest complicated balloon aortic valvuloplasty in 13 patients (2.6%), including 7 with cardiogenic shock and 4 with refractory ventricular arrhythmias. Of the seven with shock, four had been treated with serial balloon inflations; dual balloons were used in three. In two of three patients studied at necropsy, the aortic valve was observed to be congenitally bicuspid. A fatal cerebrovascular accident occurred in two patients (0.4%); it was hemorrhagic in one, embolic in another. Both patients were treated with serial (including one dual) balloon inflations. Limb amputation was required in three patients (0.6%), two women and one man; in two patients amputation was above the knee, in the third patient it was limited to two toes.(ABSTRACT TRUNCATED AT 250 WORDS)

Transvascular intracardiac applications of a miniaturized phased-array ultrasonic endoscope. Initial experience with intracardiac imaging in piglets

BACKGROUND

Recent advances in miniaturization of phased-array and mechanical ultrasound devices have resulted in exploration of alternative approaches to cardiac and vascular imaging in the form of transesophageal or intravascular imaging. Preliminary efforts in adapting phased-array endoscopes designed for transesophageal use to a transvascular approach have used full-sized phased-array devices introduced directly into the right atrium in open-chested animals. The purpose of this study was to assess the feasibility of using a custom-made, very small phased-array endoscope for intracardiac imaging introduced intravascularly through a jugular venous approach in young piglets.

METHODS AND RESULTS

Experimental atrial septal defects created in four piglets (3-4 weeks old) had been closed with a buttoned atrial septal defect closure device consisting of an occluder in the left atrium and a counteroccluder in the right atrium. Five to 15 days after atrial septal defect closure, the piglets were returned to the experimental laboratory, where a 6.3-mm, 17-element, 5-MHz phased-array probe mounted on a 4-mm endoscope was introduced through a cutdown incision of the external jugular vein and advanced to the right atrium. From the right atrium all four cardiac chambers, their inflows and outflows, and all four valves were well imaged with minimal superior and inferior rotation. High-resolution imaging of the atrial septum defined with anatomical accuracy, later verified by autopsy, the exact placement of both the occluder and counteroccluder in the left and right sides of the atrial septal defects and the absence of any shunting across the atrial septum in any of the four animals.

CONCLUSIONS

Our efforts indicate that transvascular passage of small phased-array probes can be easily accomplished and is a promising technique for detailed visualization of cardiac structures. This approach may provide an alternative to transesophageal echocardiography, particularly for guiding interventional procedures such as placement of transcatheter closure devices in pediatric patients.