You have done exceptionally well, having been a quadraplegic for so many years. The reason for the stress test is a bit puzzling, since you don't have any symptoms of coronary atherosclerosis, but this may because of your low level of exertion secondary to your disability. Of the stress test currently available, the dobutamine is the most physiological and the one I would recommend. I am not aware of any trials studying the outcomes in patients such as you, but this test will also provide information such as valvular heart disease and ejection fraction, aortic root diameter, etc.
Given your degree of paraplegia, it affects the sympathetic root of nerves which arise from the spinal cord, whereas the parasympathetic nervous system, which courses mainly with the vagus nerve. This means that at baseline you have an imbalance between the heart slowing ( parasympathetic) and heart racing ( sympathetic) and because of the decreased sympathetic stimulation present for so many years your receptors are hypersensitive to the various chemicals used for stress tests. Dobutamine, which is a sympathetic agonist is titrated slowly to a heart rate, and once this is reached it is stopped. On the other adenosine and dypiridamole which are used in the nuclear scans are weight based, and I think their response will be more difficult to predict than dobutamine.
Thank you for your helpful comments. I have a 'on demand' pacer set at 40 - pulse rate has been very low and the pacer has been kicking in more frequently. I also have a chronic pseudomonas chest infection which has been managed by nebulised colomycin. Blood pressure is currently swinging up and down, sometimes systolic reaching 200 which I believe the colomycin is the cause. The autonomic nervous system has become more sensative over the years and I'm more prone to hypereflexive (dysreflexia) responses. I'm therefore anxious that such a stress test may cause cardiac arrest!
I'm now thinking it might be safer to directly go to cardiac catheterisation (angiogram) - what do you think?