The 85% minimum is well known for administering a stress test, but is it really achieving what you need? Are we best serving our patients if we push for that 85% minimum and no more?

There are many reasons for a patient to go through an MPI stress test, with each patient having their own story and set of circumstances. Our view is that the best possible stress tests are planned in collaboration with the patient and take their individual case into consideration.

There are other important factors to look at and some good reasons to go beyond minimums – let’s take a closer look:

The 85% minimum for stress tests

The main part of a stress test is the treadmill exercise portion, where the patient progresses through levels of difficulty. At a minimum, they need to reach 85% of their predicted heart maximum. This maximum is calculated using a formula based on their age and heart rate.

85% is the minimum expected to achieve an adequate test and for the technologist to give the injection of the radioactive isotope. In the field, most technologists tend to follow this 85% rule, give the injection immediately, then terminate the test.

However, there are so many other things besides that 85% that you should be watching. For example, the EKG, how well the patient is doing, their blood pressure and their METS. Also, if you can reach 90% or more instead, why not go for what you can? 85% is just a minimum and you have the potential to learn more and get better data to make better-informed decisions for the patient if you go for more (within reason, of course!)

When I posted some of my thoughts on this on LinkedIn, I got this response from Gautham Ravipati, Interventional Cardiologist at Texas Health Resources:

“The validity of an exercise stress test with and without imaging regarding true sensitivity [negative predictive value] for ischemic heart disease is

1]Not only dependent on THR achieved/and or double product above intermediate hemodynamic response

2] But robust data clearly shows the significance of METS achieved and this must be reported in results so a provider can realize that despite negative imaging…METS <7 decreases sensitivity to rule out IHD, and clinical pre test probability should truly dictate whether invasive strategy is necessary for definitive diagnosis and prognosis”

These are some great points that can support the idea that there is more to it than meeting that minimum.

Here are some aspects that are vital to a successful stress test outside of that 85% minimum:

Communication with the patient

One of the most vital facets outside of that 85% minimum is your communication with the patient. In fact, how well you communicate can aid in achieving better than minimum results. For example, your preparation of the patient ahead of the test can make a big difference.

This includes communicating all of the information that will make them better prepared for the test and more comfortable during it. For example, here are some things you should talk with them about or help them with in preparation for the test:

• The clothing and footwear they should wear. Sometimes people are coming to a stress test straight from work and may not be wearing the most appropriate items. Let them know they will need clothing and footwear suitable for a treadmill.
• The procedure itself and how it will work. Patients are often nervous or feeling stressed over having to be tested. It can help if they feel confident that they know what will happen during the test.
• Set their expectations for what a stress test can and can’t tell them. For example, an abnormal result may point to a risk of CAD, but then again, a normal result doesn’t rule out the risk of a plaque later rupturing.
• How the treadmill works and getting a feel for it. Patients are usually much more comfortable if you give them the chance to spend a little time on the treadmill before actually starting the test. Some people will never have used a treadmill before and this can be a source of anxiety.
• A target heart rate for the test. See if you can get them to go for a stretch target, rather than simply a minimum, otherwise there is often a tendency for people to reach the minimum and decide they are done.
• Give them some level of control to help them feel comfortable. You can talk with them about their part and what they can do to have some control over the situation. For example, point out the emergency stop button and explain that they can hit it any time they feel the need. You can also help them out during the test by letting them know before the transition to each stage.

Communicating with the patient can also help for pushing them that little bit farther to get a good test done. Here’s what Andrea Brumfield, Lead Certified Cardiovascular Technician at Digirad has to say:

“Patients can reach the 85% mark easily within a few minutes if the patient is out of shape, but that doesn’t mean you get a good study by injecting at that point. Most won’t even have symptoms at all, so why not push them a little? Make them feel short of breath and fatigue. See how far they can push themselves (within reason). Personally, I won’t have the patient injected until at least 7.0-10.1 METS and that’s only if they are visibly working hard.

Communication is the key though. Talk with the patient about anything other than what they are doing at that moment and you’ll be surprised to see how much farther they can go.”

Give the patient something to focus on

It can help the patient to go further if they have something they can focus on while they do their test. Too many clinics have blank walls for patients to stare at with nothing to keep them occupied.

If you don’t have the option of facing equipment toward a window, put something engaging on the wall. We recommend interesting posters with scenery that might hold their attention, such as the one shown below.

Want a poster for your office? We are happy to send you a print of our posters if you don’t have any. Contact us here to request your poster.

Final thoughts

There is more to MPI stress tests than simply meeting that 85% minimum. In fact, you may have a better test if you’re able to push above minimums, as well as monitor important aspects such as METs and EKG readings.

Communication with the patient is the key ingredient for a successful stress test. You can do a lot to prepare the patient ahead and ease any fears they may have about doing the test. You can also keep them informed during the test so that they are as comfortable as possible.

Often you can achieve much better than the 85% minimum just by communicating with the patient and giving them something else to focus on during the test other than their current situation.

Should you push past the 85% minimum? If you can do so safely, yes, absolutely.