Laptop-sized Echocardiography Machine Versus Full-sized Top-of-the-Line Machine: A Comparative Study

Echocardiography has become an essential part of the evaluation of patients in a wide variety of clinical settings 1 and an invaluable tool in the treatment of patients who are critically ill in the intensive care unit (ICU) and emergency department. Echocardiography can be performed at the bedside, thus, avoiding the need to transport patients who are acutely ill. However, there still remain obstacles to using portable echocardiography. The current commonly available echocardiography machines are bulky and heavy (400 lb). Bringing the echocardiography machine to the bedside is time-consuming and may cause damage to valuable equipment and personnel in that process. Often the images obtained are suboptimal secondary to faulty positioning of the machine as a result of space constraints, difficult positioning of patients, and poor lighting conditions. There have been prior attempts to design a small, truly portable echocardiography machine. Several products have been previously manufactured. The sizes ranged from laptop-sized devices to even smaller units (hand-carried devices) of less than 6 lb in weight. The earliest models had limited functionality; however, newer models have nearly all the standard features present on full-sized echocardiography equipment. Nonetheless, the performance of these units has proved to be inferior to that of the standard, bulky echocardiographic machines. 2-8 Several studies were done to evaluate the diagnostic quality of these hand-carried ultrasound systems. Although information obtained with these studies helped patient care and treatment, the sensitivity of these units to accurately identify different cardiac pathologies, compared with standard echocardiography machines, was lower (70%-80%). Thus, the use of these hand-carried ultrasound machines seemed promising and appropriate (in adequately trained hands) for limited studies with a clear, predefined clinical question. 9-12 Recently a new, laptop-sized echocardiography machine has been introduced into the market (Vivid I, GE, Milwaukee, Wis). This machine is the size of an average laptop computer and weighs approximately 10 lb. It is easily transported and can be used comfortably in every department in the hospital. It has been approved by the Food and Drug Administration for clinical use. The machine has all the modalities of a standard echocardiography machine: M-mode, 2-dimensional imaging, spectral Doppler, continuous wave and pulsed wave Doppler, harmonic imaging, and tissue Doppler. There is also a prototype that carries unique software for speckle tracking, non-Doppler 2-dimenstional strain analysis. Automated speckle tracking is a new means by which endocardial border and ventricular myocardium can be detected. It analyzes motion by tracking speckles (natural acoustic markers) in the ultrasonic image in two dimensions. These markers are statistically equally distributed throughout the myocardium. The size of these elements is 20 to 40 pixels. Each speckle can be identified and followed accurately over a number of consecutive frames. These markers, within the ultrasonic image, are tracked by calculating frame-to-frame changes using a sum of absolute difference algorithm. Novel software is now available that allows automatic speckle tracking with subsequent calculation of ejection fraction (EF), tissue velocities, strain, and strain