Ultrasonic myocardial tissue characterization in the operating room: initial results using transesophageal echocardiography

Quantitative texture analysis and transesophageal echocardiography to characterize the acute myocardial contusion

Myocardial contusion (MC) is a common injury following blunt chest trauma without any specific symptoms.

Several techniques such as electrocardiogram, estimation of myocardial band fraction of creatine phosphokinase, chest radiography and the scintiscanning missed efficiency to characterize the MC.

Another technique based on transesophageal echocardiography [TEE] allows to visualize the structures of the heart with a good spatial resolution.

We postulated that the quantitative texture analysis of regional image texture in two- dimensional [2D] TEE echocardiograms would be an accurate method to differentiate normal from abnormal myocardial wall.

This preliminary experimental study demonstrated the feasibility of the proposed technique.

Influence of respiration on myocardial signal intensity

Echocardiographic quantification of myocardial perfusion after IV contrast is possible, based on the intensity of the received intermittent second harmonic signal. To investigate the influence of respiration on the intensity of myocardial signals, we examined nine patients with normal coronary angiograms. At baseline, end-expiratory and end-inspiratory images were obtained in broadband radiofrequency (RF) and intermittent second harmonic modes, the latter repeated during IV contrast at rest and at peak stress. In mid-septum at baseline, end-inspiratory integrated backscatter intensity was 4 dB higher (p < 0.05, both in second harmonic and fundamental domains) than end-expiratory intensity. In second harmonic imaging, contrast increased signal intensity by 4 dB (p < 0.05) in six examined segments, but the increase in the midseptal region (2 dB) was not significant. Contrast-enhanced intensity at end-inspiration was higher (3 dB, p < 0.01) than baseline intensity at end-expiration. We conclude that the increase in myocardial signal intensity during inspiration may resemble the contrast effect in intermittent second harmonic mode. The respiratory variation persists after contrast and may mask or exaggerate the effect of myocardial contrast.

Transesophageal Echocardiographic Evaluation of Patients Receiving Mechanical Assistance from Ventricular Assist Devices

Ventricular assist devices (VADs) have been successfully used to provide circulatory support for patients with cardiogenic shock after cardiac surgery. Transesophageal echocardiography plays a vital role in the evaluation of patients on VAD support: it is used to verify the correct positioning of the VAD hardware; to diagnose complications, including intracardiac thrombus and tamponade; and to assess right and left ventricular function when VAD flow is decreased to determine the correct timing for weaning from the device. Future developments may allow us to prospectively identify patients with stunned but viable myocardium who would benefit the most from VAD support.

Myocardial ultrasonic tissue characterization in patients with different types of left ventricular hypertrophy: a videodensitometric approach

Although analysis of the radio frequency signal is the most accurate approach to myocardial tissue characterization, clinical diffusion has been limited because of the complex technology required. Much easier to perform, videodensitometric analysis could represent a valuable alternative. Previous works carried out on radio frequency data have shown that the absolute value of ultrasonic back scatter increases while its diastole-to-systole variation decreases in the hypertrophied myocardium. This study was aimed at clarifying whether alterations in characterization indexes of ultrasonic tissue can be detected by means of a videodensitometric approach, whether a specific type of left ventricular (LV) hypertrophy can be identified with this method, and finally what possible relationships exist between parameters of contractile function and tissue characterization indexes. Myocardial echo intensity (MEI), its cyclic variation (CV), and the dynamic relationship between myocardial signal and wall thickness variations during the cardiac cycle were assessed in 20 healthy subjects, 11 patients with essential hypertension and LV hypertrophy, 15 patients with hypertrophic cardiomyopathy, and 4 patients with primary amyloidosis. The CV was lower in the interventricular septum of patients with cardiac hypertrophy as a group, compared with that of control subjects (13.0% +/- 5.6% versus 18.8% +/- 5.5%, p < 0.001), but it was similar among patients with different types of hypertrophy. In control subjects, a significant inverse correlation was found between the progressive decrease of the myocardial signal and the parallel increase in wall thickness during systole; this correlation was lost in 60% of patients with hypertrophic cardiomyopathy and 50% of those with amyloidosis, but only in 9% of patients with essential hypertension (chi square analysis 12.68, p < 0.01). The CV was associated with systolic wall thickening (r = 0.53, p = 0.0001) and fractional shortening (r = 0.44, p = 0.0014). MEI and its CV per se cannot distinguish among different types of LV hypertrophy; however, the loss of an inverse relationship between the myocardial signal and wall thickness may suggest abnormal myocardial conditions in individual patients with the same disease or comparable wall thickness.

Cyclic variation of integrated ultrasound backscatter: normal and abnormal myocardial patterns in children

Cyclic variation of integrated backscatter (CVIBS) is altered in adults with myocardial infarction, allograft rejection, and cardiomyopathy. Its utility in children has not been tested. We studied 99 normal subjects: 16 fetuses, 13 newborns, 47 children, and 23 teenagers. Fifteen children with cardiomyopathy (13 dilated and two infiltrative) were studied to define abnormal CVIBS. CVIBS was measured in the anterior septum and the left ventricular posterior wall from a two-dimensional ultrasound image with an acoustic densitometry software package. CVIBS was similar in the anterior septum (3.7 +/- 1.9 dB) and the posterior wall (4.1 +/- 2.4 dB) of all children after birth. CVIBS was significantly lower in the fetus (septum: 2.8 +/- 1.6 dB) and in children with cardiomyopathy (septum: 0.6 +/- 1.6 dB, dilated; -1.2 +/- 4.2 dB, infiltrative; p < 0.01). Four children, studied after recovery from cardiomyopathy, had diminished CVIBS despite the return of normal systolic function. The pattern and extent of CVIBS in children is similar to that of adults. CVIBS is diminished in children with cardiomyopathy.

Stress echocardiography, contrast echocardiography, and tissue characterization: applications for the future

During the last three decades the application of ultrasonography has expanded rapidly. The information available to the clinician from ultrasound imaging today is vastly more significant than it was in the early years of the development of this technology. In addition to automatic information, there is an increasing potential to provide functional, dynamic perfusion and even cellular information about the heart. This article attempts to summarize briefly the advances in these areas.

Quantitative Echocardiography, Part 1

The quantitative applications of echocardiography in clinical practice are well known. The measurements of cardiac chamber dimensions, wall thickness, and overall performance have been uniformly adopted. An important emerging ultrasound modality known as tissue characterization of the myocardium has evolved from experimental studies to clinical investigation. The ability to quantitate myocardial acoustic properties by the measurement of integrated backscatter (in decibels) provides direct assessment of myocardial structural characteristics and contractile performance, to complement conventional two-dimensional imaging of ventricular wall motion and wall thickening. Despite the considerable amount of work that has been done, there are several areas of research that need to be further investigated before widespread clinical use of these techniques is possible. Specifically, absolute values of myocardial backscatter are not yet obtainable with the current instrumentation; only the relative change in backscatter during the cardiac cycle (cyclic variation) has been defined and employed in clinical studies. This review summarizes the principles of tissue characterization and the results of several clinical studies, specifically those carried out in patients with coronary artery disease and cardiomyopathies.