What is dobutamine stress echocardiography? Cardiology Basics

What is dobutamine stress echocardiography? Cardiology Basics

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. There are certain conditions like left bundle branch block in which an exercise ECG becomes uninterpretable. Some persons are unable to exercise on a treadmill due to illness or disability. In such situations dobutamine infusion is given instead of exercise, to increase heart rate and myocardial contractility, thereby increasing the workload of myocardium. Echocardiograms are taken then to assess the response of the myocardium to stress. This is known as dobutamine stress echocardiography.

Just like the graded exercise program, the dobutamine infusion is also given in a graded fashion, starting at a lower dose. Ischemic but viable myocardium will show improvement in contraction at lower dose. At higher dose of dobutamine, ischemia worsens and the contraction of such regions of myocardium will decrease. This is a biphasic response of ischemic viable myocardium to dobutamine stress.

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

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 ventricular arrhythmias like a defibrillator has to be ready while doing the test. Resuscitation tray 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 echocardiogram. For these reasons, dobutamine stress echocardiography is done only when usual exercise stress test is not feasible.

An important and emerging 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 for invasive coronary angiography, which is another way to exclude significant obstructive coronary artery disease as is done in case of valvular heart disease pre-operatively.