Body habitus is referring to the person's body size/structure. Sometimes with men they will have what we consider a barrel chest which makes it a little bit difficult to get great images. Typically very thin patients and obese patients are difficult to get images, but with that said I have had patient who were 400+ pounds and had wonderful images and have also had 90 pound patients with beautiful images.
When doing echoes we cannot see blocked arteries. We are looking at the structure of the heart, the valves, the ejection fraction (pumping ability) among other things. When we do stress echocardiograms we take pictures of the heart at rest and then images again when the heart rate is at peak. We cannot actually see blocked arteries, but we can see if there is any change in wall motion that is seen with blocked arteries.
Hope this helps a little.