What is dobutamine stress echocardiography?

What is dobutamine stress echocardiography?

Echocardiography is ultrasound imaging of the heart. Usual stress test for the heart is exercise ECG in which serial ECG recordings are done during a graded exercise protocol, usually on a treadmill. ECG is the recording of the electrical activity of the heart. There are certain conditions like left bundle branch block in which an exercise ECG becomes uninterpretable. Left bundle branch block is the lack of signal conduction in left bundle branch taking signals to the lower left chamber of the heart. In that case, a medication known as dobutamine is given as drip into the blood vessels and serial echocardiograms done to assess the response of heart to stress. This is known as dobutamine stress echocardiography. It is also useful in those who cannot exercise due to medical problems or physical disability.

Just like the graded exercise program, the dobutamine drip is also given in a graded fashion, starting at a lower dose. Heart muscle which has decreased blood supply, but not totally damaged, that is viable, will show improvement in contraction at lower dose. At higher dose of dobutamine, the contraction of such regions of heart muscle will decrease.

If a region of heart muscle is scarred and non-viable, it will not contract at all and there is no response to dobutamine infusion. A region of heart muscle which is not contracting is technically known as akinetic. The abnormality seen on echocardiography in that region of heart is called akinesia. If a region of heart muscle is contracting less than the normal regions, it is called hypokinesia. Part of the heart muscle which bulges out when rest of the heart is contracting is called dyskinesia.

Though dobutamine stress echocardiography is an excellent test for those who cannot exercise, it is quite cumbersome to do in a usual echo room with limited space. Emergency equipment to treat life threatening heart rhythm disorders like a defibrillator has to be ready while doing the test. All emergency medications and personnel to deal with emergencies should be ready, as in case of treadmill exercise test. Dobutamine stress echocardiography takes much more time than a usual echo test. For these reasons, this test is done only when usual exercise stress test is not feasible.

An important role for dobutamine stress echocardiography is as part of workup for liver transplantation. These patients are too sick to do an exercise treadmill test. Due to liver failure, they have higher bleeding risk while doing invasive coronary angiography, which is another way to exclude significant blocks in blood vessels of heart. Coronary angiography is a test in which small tubes known as catheters are introduced through blood vessels of wrist or groin and guided to the blood vessels of the heart. The blood vessels of the heart are then visualized by injecting radiocontrast medications under continuous X-ray imaging.