Doppler Tissue Imaging: A Noninvasive Technique for Evaluation of Left Ventricular Relaxation and Estimation of Filling Pressures

Background— Biventricular pacing has been proposed to improve symptoms and exercise capacity in patients with advanced heart failure and wide electrocardiographic wave complexes. This study investigated the effect of biventricular pacing on reverse remodeling and the underlying mechanisms. Methods and Results— Twenty-five patients with NYHA class III to IV heart failure and electrocardiographic wave complex duration >140 ms receiving biventricular pacing therapy were assessed serially up to 3 months after pacing and when pacing was withheld for 4 weeks. Tissue Doppler echocardiography was performed using a 6-basal, 6-mid segmental model to assess the time to peak sustained systolic contraction (TS). There was significant improvement of ejection fraction, dP/dt, and myocardial performance index; decrease in mitral regurgitation, left ventricular (LV) end-diastolic (205±68 versus 168±67 mL, P<0.01) and end-systolic volume (162±54 versus 122±42 mL, P<0.01); and improved 6-minute hall-walk distance and qualit...

Tissue Doppler Echocardiographic Evidence of Reverse Remodeling and Improved Synchronicity by Simultaneously Delaying Regional Contraction After Biventricular Pacing Therapy in Heart Failure

Background—Myocardial strain is a measure of regional deformation, and by definition, negative strain means shortening and positive strain, elongation. This study investigates whether myocardial strain can be measured by Doppler echocardiography as the time integral of regional velocity gradients, using sonomicrometry as reference method. Methods and Results—In 13 anesthetized dogs, myocardial longitudinal strain was measured on apical images as the time integral of regional Doppler velocity gradients. Ultrasonic segment-length crystals were placed near the left ventricular (LV) apex and near the base. Apical ischemia was induced by occluding the left anterior descending coronary artery (LAD), and preload was increased by saline. Percentage systolic strain by Doppler correlated well with strain by sonomicrometry (y=0.82x−1.79, r=0.92, P<0.01). During LAD occlusion, apical myocardium became dyskinetic, as indicated by positive strain values and negative Doppler velocities. At the LV base, myocardial strain...

Myocardial Strain by Doppler Echocardiography Validation of a New Method to Quantify Regional Myocardial Function

New Doppler echocardiographic applications for the study of diastolic function

The non-invasive quantification of regional myocardial function is an important goal in clinical cardiology. Myocardial thickening/thinning indices is one method of attempting to define regional myocardial function. A new ultrasonic method of quantifying regional deformation has been introduced based on the principles of 'strain' and 'strain rate' imaging. These new imaging modes introduce concepts derived from mechanical engineering which most echocardiographers are not familiar with. In order to maximally exploit these new techniques, an understanding of what they measure is indispensable. This paper will define each of these modalities in terms of physical principles and will give an introduction to the principles of data acquisition and processing required to implement ultrasonic strain and strain rate imaging. In addition, the current status of development of the technique and its limitations will be discussed, together with examples of potential clinical applications.

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Regional Strain and Strain Rate Measurements by Cardiac Ultrasound: Principles, Implementation and Limitations

New method for evaluating left ventricular wall motion by color-coded tissue Doppler imaging : in vitro and in vivo studies

Myocardial velocity gradient as a new indicator of regional left ventricular contraction: Detection by a two-dimensional tissue doppler imaging technique

We developed a new color Doppler system by which Doppler signals associated with tissue motion can be determined, and called it the tissue Doppler imaging (TDI) system. Using high-speed scanning, the frame rate was 26–38 F/s, and the pulse repetition frequency was 4.5–6.0 kHz. Under these conditions, the lowest measurable velocity was improved to 2 mm/s. Wall motion toward the transducer was coded as red, and that away from the transducer, as blue. To examine the accuracy and validity of the measured velocity of ventricular wall motion, we performed in vitro and in vivo studies. The results demonstrate that the present TDI system accurately represents the tissue velocity, and is applicable for creating two-dimensional images of the ventricular wall motion in real time, facilitating the visual assessment of abnormal ventricular wall motion.

Analysis of Ventricular Wall Motion Using Color-Coded Tissue Doppler Imaging System

Provided is a diagnostic ultrasound system producing an image whose brightness is enhanced by a contrast medium by implementing contrast echography based on intravenous injection. A diagnostic ultrasound system comprises a probe for converting an electrical driving signal into a corresponding transmission ultrasound wave and converting an echoed ultrasound wave into a corresponding electrical echo signal. The system still comprises a unit for transmitting the transmission ultrasonic wave to a subject by providing the probe the electrical driving signal substantially consisting of a fundamental component of a given driving frequency. The non-fundamental component is typically a second harmonic. A non-fundamental component of the driving frequency is intentionally lowered in power relative to the fundamental component by a suppressing element in the transmitting unit. The system comprises a unit for receiving the echo signal from the probe and processing the echo signal into a display image data reflecting both the fundamental and non-fundamental components and a unit for displaying the display image data.

Ultrasound imaging preferable to ultrasound contrast echography

A new method has been developed for measuring the volume flow rate of blood flowing through large vessels or outflow tracts of the heart. In this article we describe the principle of a method that can reduce the dependence of the Doppler angle of flow measurement by setting the sample points along a line to which every ultrasound beam is perpendicular. To evaluate the accuracy of this method, flow phantom experiments were made for both steady and pulsatile flows. The volume flow rate measured by this method agrees well with that observed by an ultrasound flowmeter ( r =0.99) when the vessel diameter is large (25 mm). However, this method overestimates by 40% when the vessel diameter is small (8 mm). To make this method applicable to small vessels, an improvement in the lateral resolution of Doppler measurement is necessary. It has been concluded that this method can be used to measure the cardiac output or volume flow rates in large vessels.

Makoto Hirama

Papers

New method for evaluating left ventricular wall motion by color-coded tissue Doppler imaging : in vitro and in vivo studies

Myocardial velocity gradient as a new indicator of regional left ventricular contraction: Detection by a two-dimensional tissue doppler imaging technique

Analysis of Ventricular Wall Motion Using Color-Coded Tissue Doppler Imaging System

Ultrasound imaging preferable to ultrasound contrast echography

Quantitative measurement of volume flow rate (cardiac output) by the multibeam Doppler method