ABSTRACT
BACKGROUND: Echocardiographic contrast media have been used to assess myocardial perfusion and to enhance endocardial definition for improved assessment of left ventricular (LV) function. These methodologies, however, have been qualitative or have required extensive offline image analysis. Power modulation is a recently developed imaging technique that provides selective enhancement of microbubble-generated reflections. Our goal was to test the feasibility of using power modulation for combined quantitative assessment of myocardial perfusion and regional LV function in an animal model of acute ischemia. METHODS AND RESULTS: Coronary balloon occlusions were performed in 18 anesthetized pigs. Transthoracic power modulation images (Agilent 5500) were obtained during continuous intravenous infusion of the contrast agent Definity (DuPont) at baseline and during brief coronary occlusion and reperfusion and were analyzed with custom software. At each phase, myocardial perfusion was assessed by calculation, in 6 myocardial regions of interest, of mean pixel intensity and the rate of contrast replenishment after high-power ultrasound impulses. LV function was assessed by calculation of regional fractional area change from semiautomatically detected endocardial borders. All ischemic episodes caused detectable and reversible changes in perfusion and function. Perfusion defects, validated with fluorescent microspheres, were visualized in real time and confirmed by a significant decrease in pixel intensity in the left anterior descending coronary artery territory after balloon inflation and reduced rate of contrast replenishment. Fractional area change decreased significantly in ischemic segments and was restored with reperfusion. CONCLUSIONS: Power modulation allows simultaneous online assessment of myocardial perfusion and regional LV wall motion, which may improve the echocardiographic diagnosis of myocardial ischemia.
Subject(s)
Coronary Circulation , Echocardiography/methods , Image Processing, Computer-Assisted , Myocardial Ischemia/diagnostic imaging , Ventricular Function, Left , Animals , Balloon Occlusion , Contrast Media , Disease Models, Animal , Echocardiography/instrumentation , Feasibility Studies , Fluorocarbons , In Vitro Techniques , Male , Microspheres , Myocardial Ischemia/physiopathology , Predictive Value of Tests , Reproducibility of Results , Swine , Ventricular Function, Left/physiologyABSTRACT
Genetically modified mice have created the need for accurate noninvasive left ventricular mass (LVM) measurements. Recent technical advances provide two-dimensional images adequate for LVM calculation using the area-length method, which in humans is more accurate than M-mode methods. We compared the standard M-mode and area-length methods in mice over a wide range of LV sizes and weights (62-210 mg). Ninety-one CD-1 mice (38 normal, 44 aortic banded, and 9 inherited dilated cardiomyopathy) were imaged transthoracically (15 MHz linear transducer, 120 Hz). Compared with necropsy weights, area-length measurements showed higher correlation than the M-mode method (r = 0.92 vs. 0.81), increased accuracy (bias +/- SD: 1.4 +/- 27.1% vs. 36.7 +/- 51.6%), and improved reproducibility. There was no significant difference between end-systolic and end-diastolic estimates. The truncated ellipsoid estimation produced results similar in accuracy to the area-length method. Whereas current echocardiographic technology can accurately and reproducibly estimate LVM with the two-dimensional, area-length formula in a variety of mouse models, additional technological improvements, rather than refinement of geometric models, will likely improve the accuracy of this methodology.
Subject(s)
Echocardiography/standards , Hypertrophy, Left Ventricular/diagnostic imaging , Hypertrophy, Left Ventricular/pathology , Myocardium/pathology , Animals , Aorta , Cardiomyopathy, Dilated/diagnostic imaging , Cardiomyopathy, Dilated/pathology , Chronic Disease , Disease Models, Animal , Echocardiography/methods , Echocardiography/statistics & numerical data , Female , Heart Ventricles/pathology , Male , Mice , Mice, Inbred Strains , Mice, Transgenic , Observer Variation , Reproducibility of ResultsABSTRACT
Power Doppler is an ultrasound technique that color-encodes the change in amplitude of the ultrasound signal, which reflects changes in the position of scatterers between ultrasound pulses. Power Doppler can be used with echocardiographic contrast agents in a harmonic imaging mode to opacify a cardiac chamber. The opacification of a cardiac chamber can aid in visualizing the silhouette of intracardiac masses and displaying blood flow patterns. Four cases are presented that demonstrate the use of harmonic power Doppler to aid in the identification of a left ventricular apical thrombus, a left atrial thrombus, and a left ventricular pseudoaneurysm.
Subject(s)
Echocardiography, Doppler/methods , Heart Diseases/diagnostic imaging , Aged , Aged, 80 and over , Albumins , Aneurysm, False/diagnostic imaging , Aneurysm, False/surgery , Contrast Media , Coronary Circulation , Female , Fluorocarbons , Heart Aneurysm/diagnostic imaging , Heart Aneurysm/surgery , Heart Diseases/surgery , Humans , Male , Middle Aged , Thrombosis/diagnostic imaging , Thrombosis/surgeryABSTRACT
An accurate echocardiographic assessment of aortic stenosis is critical for the cost-effective diagnosis and management of patients with the clinical suspicion of this diagnosis. Although the concepts involved in the echocardiographic determination of aortic pressure gradients and valve areas are relatively simple, acquisition of the data required to perform these calculations can at times be technically challenging. After reviewing the clinical signs and symptoms and the hemodynamics of aortic stenosis, this article reviews in detail the technical aspects involved in obtaining accurate gradients and valve areas emphasizing potential pitfalls.
