Real-time three-dimensional transesophageal echocardiography for guiding interventional electrophysiology: feasibility study

At present, there are limited methods of acquiring three-dimensional visualization of cardiac structure and function in real-time during interventional electrophysiology procedures. Images acquired for integration of computerized tomography and magnetic resonance imaging with electroanatomic mapping systems are static and are obtained earlier in time. The purpose of this study was to test the feasibility of real-time three-dimensional transesophageal echocardiography for the guidance of interventional electrophysiological studies. A matrix array transducer with 504 channels operating at 5 MHz in a 1 cm diameter steerable esophageal probe was used in conjunction with a scanner capable of real-time 3D scanning of pyramidal volumes from 65 degrees to 120 degrees at rates up to 30 volumes per second. This device has a spatial resolution of approximately 3 mm at 5 cm depth. The authors acquired real-time three-dimensional images of anatomic landmarks of value for electrophysiological procedures in five closed chest canines. Real-time, three-dimensional ultrasound imaging was also used for visualization and guidance of interventional catheter devices within the canine heart. Real-time three-dimensional images of the atria, pulmonary veins, and coronary sinus were acquired. Real-time 3-D color flow Doppler was employed to confirm patency. Multiple image planes of image volumes and rendered views were used to track catheter position and orientation. Images of left veno-atrial junctions have been confirmed by dissection. This study has demonstrated the feasiblity of using real-time three-dimensional transesophageal echocardiography for guiding interventional electrophysiology. The technology has the potential to fill a niche as an adjunct modality for cost-effective real-time interventional guidance and assessment, providing catheter and pacing lead visualization simultaneously with functional volumetric cardiac imaging.     

Contrast superharmonic imaging: a feasibility study

Harmonic imaging provided significant improvement in image quality by taking advantage of the scattered second harmonic (2H) component from contrast bubbles. However, differentiation between contrast and tissue (usually termed contrast-to-tissue ratio, CTR) is sometimes cumbersome and this is mainly due to tissue contamination. We have previously demonstrated, using simulations and in vitro measurements, that CTR increases as a function of the order of the harmonic number. A new contrast imaging method based on the detection of the higher harmonics was developed and termed superharmonic (SH). This technique has been shown to be more sensitive to contrast by increasing the signal from contrast and suppressing that from tissue (high CTR). The purpose of this study was to determine the clinical feasibility and usefulness of SH in patients using a commercially available contrast agent (SonoVue(R)) for quantification of myocardial perfusion. A total of 10 patients with various cardiac diseases were assessed. Apical four-chamber views were acquired using SH in triggered mode before and after contrast injection. The superharmonic was performed with a newly developed probe transmitting at 0.8 MHz with a mechanical index of 0.2. Myocardial perfusion was determined visually and analyzed quantitatively using radiofrequency (RF) processing from different regions of interest. The results showed that, before contrast injection, SH was totally blinded to tissue and no superharmonic components were generated in the image view. After administration of SonoVue(R), myocardial opacification was visualized by SH after contrast entered the myocardium. An increase of more than 15 dB in the myocardial bubbles echo compared to tissue echo was measured. In addition, the technique was used to visualize myocardial perfusion after myocardial septal ablation for hypertrophic cardiomyopathy. The clinical results showed the ability of contrast SH imaging in differentiating low and normal perfusion areas, demonstrating the high sensitivity and specificity of the technique.     

Wide-field transesophageal echocardiographic tomography: feasibility study

In this report, we describe our initial investigation of wide-field ultrasonic cardiothoracic tomography utilizing a transesophageal transducer. Examination included manual rotation of an esophageal transducer 180 to 360 degrees in order to visualize contiguous related structures. Consecutive sector views were photographed and then incorporated into a digital graphics computer for smoothing. This feasibility study introduces the concept of wide-field transesophageal cardiothoracic ultrasound tomography, which holds promise for tomographic depiction of cardiothoracic and mediastinal anatomy.     

Mode vibrations of a matrix transducer for three-dimensional second harmonic transesophageal echocardiography

Transesophageal echocardiography (TEE) uses the esophagus as an imaging window to the heart. This enables cardiac imaging without interference from the ribs or lungs and allows for higher frequency ultrasound to be used compared with transthoracic echocardiography (TTE). TEE facilitates the successful imaging of obese or elderly patients, where TTE may be unable to produce images of satisfactory quality. Recently, three-dimensional (3-D) TEE has been introduced, which greatly improves the image quality and diagnostic value of TEE by adding an extra dimension. Further improvement could be achieved by optimizing 3-D TEE for harmonic imaging. This article describes the optimal geometry and element configuration for a matrix probe for 3-D second harmonic TEE. The array concept features separated transmit and receive subarrays. The element geometry was studied using finite element modeling and a transmit subarray prototype was examined both acoustically and with laser interferometry. The transmit subarray is suitable for its role, with a 3 MHz resonance frequency, a 40%-50% -3 dB bandwidth and crosstalk levels <-27 dB. The proposed concept for the receive subarray has a 5.6 MHz center frequency and a 50% -3 dB bandwidth.     

Three-dimensional transesophageal echocardiography for descending aortic atheroma: a preliminary study

Transesophageal echocardiography (TEE) is an efficient method for characterization of aortic atherosclerotic plaques (AAP). The aim of our study was to evaluate the feasibility and the additional contribution of three-dimensional (3D) TEE in the evaluation of AAPs in descending thoracic aorta. We studied 82 patients referred for TEE regardless of the indication. All patients underwent two-dimensional (2D) conventional acquisitions. A 3D TEE study was performed for all AAPs localized in the descending thoracic aorta. Thickness, degree of calcification, the presence of ulceration or mobile debris were compared for 2D and 3D modes. From 3D data, three types of AAPs were defined according to their morphological characteristics (surface and contours). Among 192 AAPs found on 2D acquisition, 189 (98.4 %) were also identified by 3D TEE. For AAP characterization, agreement was good between 2D TEE and 2D extracted from 3D with the multiplanar reconstruction mode: 83.6 % (k = 0.69) for thickness and 82.5 % (k = 0.72) for degree of calcification. All AAPs ulcerations (n = 13) and mobile debris (n = 3) seen in 2D were identified in 3D. 2D characteristics of the 3D AAPs’ morphological types were different: type I plaques were thin and rarely calcified; type III plaques were thicker and often calcified; and type II presented intermediate characteristics. There was overlap among groups and the 3D morphology could not be predicted from 2D data. 3D TEE is a feasible method for the analysis of AAPs. In addition to conventional characterization, 3D TEE provides a new morphological approach to AAPs.     

Doppler tissue velocity, strain, and strain rate imaging with transesophageal echocardiography in the operating room: a feasibility study.

OBJECTIVE: Transesophageal echocardiography (TEE) is increasingly used to monitor regional myocardial function during cardiac operation. Doppler myocardial imaging (DMI) indices can potentially provide new information on regional radial and longitudinal myocardial motion and local deformation. This study examined the feasibility of TEE acquisition of regional radial and longitudinal velocity, displacement (D), strain, and strain rate data during cardiac operation and evaluated the effects of sternotomy and pericardial opening on these indices. METHODS: After a baseline transthoracic echocardiographic study, TEE was performed in 22 patients (age 64 +/- 7 years) before sternotomy, after sternotomy with intact pericardium, and after pericardial opening. Regional DMI velocity analysis was performed for the transgastric anterior and inferior walls midpapillary segment (radial function) and the 4-chamber septum and 2-chamber inferior walls basal, mid, and apical segments (longitudinal function). For each segment, systolic and diastolic velocity were derived and D, strain, and strain rate calculated. RESULTS: Transthoracic echocardiographic study and TEE provided similar data from an equivalent number of interpretable segments. In the basal and mid septum, maximum longitudinal systolic D decreased with pericardial opening (basal septum pericardium closed: 6.6 +/- 1.5 mm, open: 4.6 +/- 1.8 mm, P =.007; midseptum pericardium closed: 4.7 +/- 2.5 mm, open: 2.7 +/- 1.5 mm, P =.028). No changes were evident in systolic or diastolic DMI indices in all other segments. CONCLUSION: DMI with TEE is feasible during cardiac operation. During pericardial opening, longitudinal D decreases in the septum, but not in the inferior wall. DMI requires further evaluation in the assessment of ventricular function and the detection of ischemia in the operating room.     

Real-time three-dimensional fetal echocardiography: initial feasibility study.

Real-time three-dimensional echocardiography acquires data as a volume rather than as a series of planar images, thereby obviating cardiac or respiratory gating and limiting artifacts generated by random motion. This study was undertaken to evaluate the feasibility of using real-time three-dimensional echocardiography to evaluate fetal cardiac anatomy and function. Ten human fetuses were evaluated in utero, four of whom had congenital heart disease. Freehand transabdominal scanning was performed on each pregnant woman using a real-time three-dimensional echocardiography system. Four volume clips at 20 volumes/s of duration 1.5 s each were obtained on each fetal heart and stored for off-line analysis. Data were displayed immediately as a series of four simultaneous planes, with the ability for the observer to manipulate the position of each plane within the acquired volume data set. Cardiac motion could be slowed, stopped, or viewed at its original speed. Most structures and views, as well as cardiac function, could be visualized consistently. Abnormal structures could be detected readily. Off-line analysis was rapid and easy. We conclude that fetal real-time three-dimensional echocardiography is a feasible, facile, and rapid new technique.     

Descending aortic mechanics and atrial fibrillation: a two-dimensional speckle tracking transesophageal echocardiography study

Vascular mechanics assessed with two-dimensional speckle tracking echocardiography (2D-STE) could be used as a new imaging surrogate of vascular stiffening. The CHA₂DS₂-VASc score is considered accurate as an estimate of stroke risk in non-valvular AF, although many potential stroke risk factors have not been included in this scoring method. The purpose of this research is to study the feasibility of evaluating vascular mechanics at the descending aorta in non-valvular AF patients using transesophageal 2D-STE and to analyze the association between descending aortic mechanics and stroke. We prospectively recruited a group of 44 patients referred for a transesophageal echocardiogram (TEE) in the context of cardioversion for non-valvular AF. A short-axis view of the descending aorta, one to two centimeters after the aortic arch was selected for the vascular mechanics assessment with the 2D-STE methodology. The vascular mechanics parameters analyzed were circumferential aortic strain (CAS) and early circumferential aortic strain rate (CASR). A clinical assessment was performed with focus on the past stroke history and the CHA₂DS₂-VASc score. The mean age of our cohort was 65?±?13 years and 75% were men; AF was known for 2.8?±?2.5 years and it was considered paroxystic in 41% of cases. Waveforms adequate for measuring 2D-STE were present in 85% of the 264 descending aortic wall segments. The mean CAS was 3.5?±?1.2% and the mean CASR was 0.7?±?0.3 s^?1. The inter- and intra-observer variability for aortic mechanics was considered adequate. The median CHA₂DS₂VASc score was 2 (2–3). As the score increased we noted that both the CAS (r?=??0.38, P?=?0.01) and the CASR (r?=??0.42, P?<?0.01) decreased. Over 16% of the AF patients had a past history of stroke. These patients had lower values of both descending aortic strain [2.2 (1.8–2.6) vs. 3.9 (3.3–4.9)%, P?<?0.01] and strain rate [0.4 (0.3–0.4) vs. 0.7 (0.6–1.1) s^?1, P?<?0.01]. CAS remained independently associated with a past history of stroke after adjustment for the CHA₂DS₂VASc score. Our data showed that non-valvular AF patients with a past history of stroke had lower values of aortic mechanics assessed with transesophageal 2D-STE.     

经食管与经胸超声心动图造影诊断卵圆孔未闭及右向左分流

目的 对比经食管超声心动图造影（cTEE）与经胸超声心动图造影（cTTE）诊断卵圆孔未闭（PFO）及右向左分流（RLS）的价值。方法 回顾性分析117例因偏头痛或隐源性卒中就诊的患者,均依次接受TTE、cTTE、TEE及cTEE检查;比较cTTE与cTEE诊断PFO的敏感度、特异度及对RLS分级的差异,观察二者诊断价值。结果 TEE联合cTEE共检出89例（76.07%,89/117）PFO;TTE、cTTE、TEE及cTEE分别检出18例（20.22%,18/89）、80例（89.89%,80/89）、75例（84.27%,75/89）及88例（98.88%,88/89）。cTTE存在9例（10.11%,9/89）假阴性、7例（25.00%,7/28）假阳性;cTEE存在1例（1.12%,1/89）假阴性,无假阳性病例。cTEE诊断PFO的敏感度（98.88%）及特异度（100%）均高于cTTE（89.89%、75.00%;χ²=6.125、5.143,P=0.008、0.016）;cTEE的PFO-RLS分级结果总体低于cTTE（Z=-3.464,P=0.001）。结论 cTEE诊断PFO的敏感度及特异度均高于cTTE,而其PFO-RLS分级总体低于cTTE。     

Contrast echocardiography

Contrast echocardiography is the technique of injecting an echo-producing, biologically compatible solution into the bloodstream and using M-mode and/or two-dimensional echocardiography to observe intracardiac bloodflow patterns revealed by the resulting cloud of echoes. This information was previously available only from angiocardiography. Contrast echocardiography has become a well-established adjunct to M-mode and two-dimensional echocardiographic examination and is valuable in the identification and validation of normal and abnormal cardiac structures, for the demonstration (and exclusion) of intracardiac as well as extracardiac shunts, and in the diagnosis of valvular regurgitation. In addition many clinical applications are being developed. Future research directions include development of videodensitometric techniques for contrast quantitation, finding contrast agents capable of passing the lung capillary bed and measurement of right heart pressures using microbubble resonance techniques.     

Detection of prosthetic mitral valve leak: a comparative study using transesophageal echocardiography, transthoracic echocardiography, and auscultation

Paravalvular leakage is a major complication of prosthetic valve dysfunction. Sixty-one subjects with valvular heart disease who had received prosthetic mitral valve replacement 5 months to 5 years before (43 received a porcine prosthesis and 18 received Bjork-Shiley valve prostheses) were evaluated for this complication. Careful auscultation was performed by two experienced cardiologists followed by transthoracic and transesophageal echocardiography. Physiologic leaks were detected in all Bjork-Shiley valves, but in only 30% of porcine valves using transesophageal echocardiography. These regurgitant jets were flame-like, with mean low velocities of 50 +/- 12.3 cm/sec and 48 +/- 18.2 cm/sec in the two types of valves. Neither transthoracic echocardiography nor auscultation could detect physiological regurgitant jets. Ten cases with paravalvular leak were detected by transesophageal echocardiography and subsequently demonstrated by left ventriculography (7 porcine, 3 Bjork-Shiley valves). Pathologic regurgitant jets were seen as high-velocity, systolic-retrograde turbulent flow across the prosthesis. However, only 6 cases of prosthetic valve dysfunction were detected by transthoracic echocardiography, 4 cases of mild paravalvular leakage went undetected. Thirteen of the 61 subjects had an apical systolic murmur and suspected prosthetic valve leakage; in 10 of the 13 cases the findings corresponded to those obtained by transesophageal echocardiography. In 3 cases of double valve replacement with Bjork-Shiley valves the magnitude of the leakage was overestimated by auscultation.     

Combined transesophageal echocardiography and transesophageal cardioversion probe: technical aspects.

A probe assembly for simultaneous transesophageal echocardiography and transesophageal cardioversion has been developed. This probe allows cardioversion with the delivery of much lower energy than the standard external approach. Details of the probe construction and its use are described, as is the prospect for future practice. The use of a combined probe may be the technique of choice for patients who require both cardioversion and transesophageal echocardiography.     

Contrast echocardiography: new agents

In this report, we review the history, rationale, current status and future directions of contrast agents in echocardiography. First, we discuss the historic development of contrast agents through a review of important physical principles of microbubbles in ultrasonography. Second, we identify attributes of an ideal contrast agent and review those that are currently available or in the "pipeline" for clinical use. Third, we review indications for contrast echocardiography, including endocardial border detection, perfusion quantification and reperfusion assessment, and validate these observations by comparisons with other imaging modalities. Then, we briefly review different methodologies of performing a contrast study, including interrupted, real-time and a hybrid modality. Finally, we identify novel future applications of the newest contrast agents. These newer concepts in contrast echocardiography should form a foundation for nearly limitless application of echocardiography in improved anatomical assessment, perfusion imaging and even special applications, such as detection of vascular inflammation and site-specific drug delivery.     

脂肪栓塞的经食管超声心动图实验和临床研究

目的经食管超声心动图观察猪脂肪栓塞模型和全髋置换术中心腔内脂肪栓子的声像图特点。方法经猪颈内静脉依次缓慢注入0.1～12．0ml的同种脂肪液，用经食管超声心动图连续观察心腔内图像变化，记录脂肪栓塞的致死量。22例全髋置换术患者术中行经食管超声心动图检查，观察术中不同时期右心房脂防栓子的表现并定量分析其平均灰阶值和超声强度。结果①在脂肪栓塞模型中，脂肪栓子表现为游动的点状强回声，可呈星点状、阵雨或雪花飞舞状，脂肪注入量大于4ml后可出现反常栓塞，累积致死量为15．8～27．8ml；②全髋置换术的各个时期均可观察到右心房呈点状强回声的脂肪栓子。B期右心房的平均灰阶值和超声强度较其他各期增大（P〈0．05）。结论经食管超声心动图可敏感发现心腔内的脂肪栓子，术中监测并定量分析有助于诊断脂肪栓塞综合征，反常栓塞的出现是脂肪栓塞综合征的可靠证据。     

Clinical utility of transesophageal echocardiography

Routine transthoracic echocardiography fails to generate images of diagnostic quality in a significant number of patients who are obese, uncooperative, or unable to be properly positioned (eg, patients receiving ventilatory assistance), and in those with severe chronic obstructive pulmonary disease, chest wall deformities, or recent thoracic surgical procedures. In addition, posterior structures in the heart such as the left atrium, left atrial appendage, atrial septum, and mitral valve are seen with poorer resolution than structures closer to the anterior chest wall. Placement of a sonographic transducer in the esophagus immediately behind the heart circumvents these limitations. Newly developed probes are well tolerated by sedated conscious patients as well as by patients receiving ventilatory assistance in the intensive care unit and those under general anesthesia. Consequently, transesophageal echocardiography is now available for further enhancement of cardiac diagnosis in outpatients, for evaluating the hemodynamic status of critically ill patients in the intensive care unit, for intraoperative assessment of cardiac repairs, and for intraoperative cardiac monitoring in noncardiac surgical procedures. A series of case examples from our practice during a recent 1-year period illustrates the clinical utility of this technique in these settings.     

Severe methemoglobinemia after transesophageal echocardiography

Methemoglobinemia, an increased concentration of methemoglobin in the blood, is an altered state of hemoglobin whereby the ferrous form of iron is oxidized to the ferric state, rendering the heme moiety incapable of carrying oxygen. This can cause hypoxia, cyanosis, or even death. Severe methemoglobinemia resulting from oral benzocaine spray before endoscopic procedures has been reported as a rare complication. We report a case of severe acquired methemoglobinemia resulting from topical benzocaine use before transesophageal echocardiography. This case serves to highlight the severity of methemoglobinemia that can result from an otherwise innocuous agent even in small doses and the fact that prompt recognition and treatment of this disorder can be lifesaving.     

经食管实时三维超声心动图的临床应用

目的探讨经食管实时三维超声心动图（RT-3D-TEE）的临床应用价值。方法应用PhilipsiE33型超声诊断仪,X7-2t经食管纯净波矩阵多平面实时三维探头,对44例患者进行RT-3D-TEE检查。其中心腔内血栓待排除患者18例,房间隔缺损7例,心瓣膜病18例（风湿性心脏病二尖瓣狭窄6例,二尖瓣脱垂10例,人工机械瓣瓣周漏1例,三尖瓣脱垂1例）,黏液瘤1例。术中监测26例。结果RT-3D-TEE能够实时直观地显示心脏立体解剖结构的三维图像;显示房间隔缺损部位和范围,在微创外科封堵术中实时全程监测,引导封堵器的植入。心脏瓣膜病术前能够清晰地显示心脏瓣膜及其病变,术后即刻可观察成形术效果或评价人工瓣膜功能。结论RT-3D-TEE操作简便、实时采集、快速成像,可同步显示三维立体影像,分辨率高,图像质量好,在临床应用,尤其在心脏外科术中应用前景广阔。