Jean-Claude Tardif

Delineation of extended lengths of coronary arteries by multiplane transesophageal echocardiography.

OBJECTIVES The purpose of this study was to evaluate the utility of multiplane transesophageal echocardiography in assessing the coronary artery tree. BACKGROUND Evaluation of coronary disease with single-plane and biplane transesophageal echocardiography is limited to the very proximal vessels. The numerous views provided by multiplane imaging may enhance visualization of coronary arteries and detection of their abnormalities. METHODS Intraoperative multiplane transesophageal echocardiography was performed in 45 consecutive adults who had recently undergone angiography. Recordings were reviewed in blinded manner. RESULTS We describe the coronary segments visualized with the different imaging planes and define new views. The left main coronary artery with its bifurcation was visualized in all 45 patients. Sensitivity and specificity for detection of coronary narrowings were 100% when results were compared with angiographic data. Visualization of proximal, mid and distal segments of the left anterior descending coronary artery was possible in 69%, 31% and 16% of patients, respectively. Among patients in whom the proximal segment was visualized, sensitivity and specificity for detection of significant narrowings were 80% and 100%. Proximal, mid and distal portions of the left circumflex coronary artery were visualized in 80%, 51% and 20% of patients. Among patients in whom the proximal portion was well seen, sensitivity and specificity were 89% and 100%. The proximal, mid and distal portions of the right coronary artery were visualized in 84%, 16% and 11% of patients. Among patients in whom the proximal segment was visualized, sensitivity and specificity were 82% and 100%. Color Doppler examination was less useful because it detected only 52% of all patients with proximal stenosis. CONCLUSIONS Multiplane transesophageal echocardiography allows enhanced visualization of extended lengths of coronary arteries and the reliable identification of coronary artery abnormalities.

Effects of variations in flow on aortic valve area in aortic stenosis based on in vivo planimetry of aortic valve area by multiplane transesophageal echocardiography

This study provides evidence that acute changes in stroke volume and cardiac output do not result in significant alterations in the anatomic AVA measured with multiplane TEE in patients with AS of moderate or severe degree. Thus, TEE could be useful in the assessment of severity of AS in both low- and high-output states.

Determination of Cardiac Output Using Acoustic Quantification in Critically III Patients

Abstract The reliability of automated acoustic quantification (AQ) in yielding real-time left ventricular (LV) area, volume, and ejection fraction has been validated. The purpose of this study was to explore the potential of AQ in providing accurate immediate determination of cardiac output in critically ill patients. A total of 48 patients were studied. One group consisted of 37 critically ill patients with indwelling Swan-Ganz catheters. In these patients, cardiac output by AQ, manual tracing of end-diastolic and end-systolic frames of 2-dimensional images, and thermodilution were measured. AQ was also compared with Doppler calculation of flow through the left and right ventricles in 11 additional patients. Adequate data for calculation of cardiac output with AQ were obtained in 78% of critically ill patients. There was an excellent correlation between AQ and off-line manual analysis for LV volumes (r = 0.94 and 0.91 for end-diastole and end-systole), ejection fraction (r = 0.85), and cardiac output (r = 0.93). AQ also correlated well with Doppler analysis (r = 0.97) and thermodilution technique (r = 0.95) in the determination of cardiac output. However, AQ slightly underestimated thermodilution measurements, with rather wide limits of agreement (−0.3 ± 1.1 liter/min). There was a similar underestimation of cardiac output with manual analysis when compared with thermodilution. Given the absence of significant differences between AQ and manual analysis, this observation suggests that the bias is related to the echocardiographic determination of stroke volume, and not to errors from the automated border detection. It is concluded that AQ, besides providing information on LV volumes and ejection fraction, also can yield rapid measurements of cardiac output in most patients who are acutely ill.

Clinical usefulness of multiplane transesophageal echocardiography: Comparison to biplanar imaging

The increased diagnostic usefulness of multiplane over biplane transesophageal echocardiography has not yet been conclusively determined. In this study the diagnostic yield of multiplanar and biplanar imaging was compared blindly by using the information content obtained from multiplane transesophageal echocardiography to that derived from biplanar type of imaging planes available in the multiplane echocardiography recordings in 80 patients with a variety of cardiac disorders. Among these patients 9 new abnormalities were identified by multiplane transesophageal echocardiography in 8 patients. Multiplane imaging yielded better delineation of 40 various lesions in 31 patients. Thus multiplane transesophageal echocardiography has a greater diagnostic yield than biplane imaging by depicting more lesions in 10% of patients and by enhanced delineation of the extent of pathologic characteristics in 39% of patients. This versatility, coupled with the ease of obtaining a vast assembly of imaging planes without undue probe manipulations, makes multiplane transesophageal echocardiography more useful than biplanar imaging.

Potential applications of intracardiac echocardiography in interventional electrophysiology

The growth of interventional electrophysiology in recent years has placed a greater demand on imaging guidance. Currently available imaging modalities to guide interventions, while useful, have significant limitations. Intracardiac echocardiography has the potential to improve on these limitations and evolve into a modality that could provide imaging guidance, aid in the prevention or instant identification of complications, help identify and quantify ablative lesions, and contribute toward visualization of normal and abnormal conduction pathways. Ongoing developments in catheter design in the form of lower frequency, smaller size, and preshaped catheters should enhance the role of intracardiac echocardiography in interventional electrophysiology. There is the potential to combine the imaging and ablative capabilities of intracardiac ultrasonography to make for an imaging and therapeutic tool.

Intravascular ultrasound imaging in peripheral arterial and coronary artery disease

Intravascular ultrasound is an emerging imaging modality that employs miniaturized transducers at the tips of catheters to provide detailed information about the morphology of small and large arteries. While there is ongoing development in technology, currently available intravascular ultrasound instrumentation already augments angiography in the assessment of structural and dynamic abnormalities of the peripheral and coronary arterial systems. Recent studies have consistently demonstrated significant underestimation of atherosclerotic disease by angiography. Demonstration by intravascular ultrasound of disease in the angiographically normal “reference” segment and of remodeling of the diseased segment may explain this angiographic underestimation. Intravascular ultrasound also has many applications during various catheter-based therapeutic procedures. In addition to contributing to our understanding of the mechanisms of interventions and restenosis, intravascular ultrasound may lead to better guidance and ultimately better outcome during various procedures such as balloon angioplasty, atherectomy, and stent placement.

Right ventricular outflow tract and pulmonary artery obstruction by postoperative mediastinal hematoma: delineation by multiplane transesophageal echocardiography.

A 53-year-old man with osteogenesis imperfecta underwent valve replacement and coronary artery bypass surgery. Unexplained symptoms of dyspnea and fatigue in the late postoperative period prompted further evaluation. Transthoracic echocardiography demonstrated obstruction of the right ventricular outflow tract and pulmonary artery by a mass, with a maximum gradient of 50 mm Hg. Multiplane transesophageal echocardiography revealed that the mediastinal hematoma was more extensive than was suggested by the transthoracic echocardiogram. This finding prompted the decision to resort to a more extensive surgical procedure. Surgical drainage continued until no residual hematoma could be visualized by multiplane transesophageal echocardiography. This case report demonstrates the value of multiplane transesophageal echocardiography in the assessment of mediastinal masses.

Intracardiac echocardiographic guidance during microwave catheter ablation.

The purpose of this study was to explore the potential of intracardiac echocardiography in monitoring lesion formation and assisting with the assessment of ablative lesions using microwave energy. Microwave energy is a promising modality for catheter ablation. Because microwave lesions may have considerable variability in dimension, the ability to assess them may be particularly useful. One hundred twenty-five microwave lesions were created in vitro in ovine left ventricles. Correct assessment of catheter-endocardial contact was possible in virtually all cases. Intracardiac imaging always identified correctly whether or not an ablation was performed. During ablation, gas formation was observed in all instances. Sensitivity, specificity, and predictive values for identification of ablation lesions were 88% to 92%. Although the correlations with pathology for lesion dimensions were relatively poor, intracardiac imaging had a predictive accuracy of 80% to 85% to discriminate small from large lesions. Intracardiac guidance for microwave ablation is useful for verifying tissue-electrode contact, monitoring lesion formation, and localizing lesions. It is also a useful tool for the assessment of lesion size. These attributes, combined with the ability to facilitate transseptal catheterization and to identify complications such as hemopericardium, make intracardiac echocardiography a potentially useful method for guiding microwave ablation of arrhythmic foci.

Evaluation of Ventricular dP/dt Before and After Open Heart Surgery Using Transesophageal Echocardiography

The mean dP/dt during isovolumetric contraction (mean dP/dtic) is a new echocardiographic index of ventricular function that has been shown to approximate and closely correlate with invasively measured peak dP/dt. It is amenable to rapid measurement via transesophageal echocardiography (TEE) and is theoretically independent of variations in ventricular anatomy and wall motion. It is therefore well suited for the assessment of ventricular function during surgery. The purpose of this study was to assess the clinical value of TEE determinations of mean dP/dtic before and after cardiopulmonary bypass (CPB). The mean dP/dtic of 50 patients undergoing open heart surgery for a variety of congenital and acquired heart defects was measured before and 15–30 minutes after CPB. Mean dP/dtic averaged 1147 ± 492 before and 1428 ± 702 mmHg/sec after CPB (P < 0.01). Mean dP/dtic was unchanged or increased in 45 patients and fell in only 5 patients. It increased significantly even among patients who did not receive supplemental inotropic agents. Mean dP/dtic correlated well with the shortening fraction, especially among patients without segmental left ventricular wall‐motion abnormalities. The general patterns observed for mean dP/dtic were also seen when the data was corrected for variations in heart rate. A preoperative mean dP/dtic < 765 mmHg/sec or a heart rate corrected mean dP/dtic < 620 mmHg/sec indicated a high likelihood that inotropic support would be needed to facilitate weaning from CPB. Mean dP/dtic may be a clinically useful, quantitative TEE index of perioperative changes in ventricular contractility.

On-line echocardiographic assessment of hemodynamic indexes by an adaptive Doppler analysis algorithm and signal/noise ratio calculation

Assessment of cardiac diseases commonly involves the use of spectral Doppler echocardiography. Its use, however, often requires manual digitization of various transvalvular flow profiles. A new approach has been developed for on-line analysis of Doppler data, which involves thresholding based on the signal/noise ratio, calculating instantaneous values, and plotting on the spectral display in real time. We examined the reliability of this new method in 32 patients with 59 various flow jets by comparing it with the data derived by manual analysis. Correlations between the algorithm analysis and manual analysis for peak velocity, peak gradient, velocity-time integral, and acceleration time were excellent. These indexes were obtained with the algorithm in a shorter time and with better reproducibility than with manual analysis. Thus this new adaptive Doppler analysis algorithm yields reliable on-line quantification of valuable hemodynamic variables and represents an advance in quantitative echocardiography.