The Ischemia Trial

Posted: December 7, 2020Tags: , ,

Author: Dr Tim Glenie

Transcript:

Dr Patricia Ding:

I'm Patricia Ding, cardiologist, and I'm here with Dr. Tim Glenie, interventional cardiologists. Hi, Tim.

Dr Tim Glenie:

Hi, Patricia. How are you?

Dr Patricia Ding:

Right, so you're going to tell us about the ischemia trial. What is this trial about?

Dr Tim Glenie:

The ischemia trial was published earlier this year in the New England Journal and is one of the key trials probably of the year. It's been quite widely anticipated amongst the cardiology fraternity. It was a randomized trial that looked to compare an invasive strategy with invasive revascularization, be that PCI or bypass surgery with a medical strategy in the setting of stable coronary disease. The decision around what sort of revascularization was performed was governed by the local trial participants in a heart group setting, and a mixture of both revascularization strategies were performed.

Dr Patricia Ding:

So what are the key messages from the trial?

Dr Tim Glenie:

So, it's been interesting and it was clearly a difficult trial to enroll for. They screened around 26 and a half thousand patients to finally randomize two and a half thousand patients to each arm. All of the patients had a functional test with either stress test just with a treadmill or a stress echo. Some of them had stress MRI or perfusion scanning done, and 75% of the patients had a CT coronary angiogram done. So they were all quite well worked up for causes of chest pain right from the outset. There was some key exclusion criteria which involved significant left main stem disease, ejection fractions of less than 35%, recent infarcts, heart failure, and so none of those patients are relevant in the trial setting. And the key outcome related to fairly traditional cardiovascular events with cardiovascular death, myocardial infarction, admissions with heart failure or angina, or sudden cardiac death.

Dr Tim Glenie:

The key message from the trial, really, despite the fact there are limitations which we'll talk about in a minute, was the fact that there isn't really a difference between an early invasive strategy and a conservative medical strategy in this group of patients. There were slightly more procedural myocardial infarctions in the invasive group, but there were also more traditional myocardial infarctions in the conservatively managed group. And the interesting thing is how the curves were separating towards the end of the trial period. We've only had 3.2 years as a median follow-up at this point, and even at that point there is some hint that the trial outcomes are starting to separate in favor of an invasive strategy, but certainly it's not significant at this point.

Dr Patricia Ding:

Right, okay. And the main difference in terms of the patients that they recruited is the fact that in this particular trial, they make sure everyone's on good modern medical therapy.

Dr Tim Glenie:

Yep.

Dr Patricia Ding:

That's the main difference compared to the earlier one that-

Dr Tim Glenie:

Yeah, so certainly that's right. And so certainly they were all on good doses of statin and aspirin, smatterings of beta blockade and ACE inhibition, and they were well matched between the groups. So certainly, you could not say that these patients weren't appropriately medically treated in either arm.

Dr Patricia Ding:

Right, okay. And just to re-emphasize, to mentioning the exclusion criteria, the patients with important left main disease and significant impaired LV function, they were excluded from the trial. In other words, people with moderate to severe ischemic cardiomyopathy, they're not really in the trial.

Dr Tim Glenie:

That's right, and I think the other thing to remember is that the patients were all given appropriate diagnostic workup prior to the decision about treatment. So these patients weren't assumed to have coronary artery disease, they were tested for coronary artery disease and once that diagnosis was made, and obviously the key exclusions avoided, then they were randomized. So that's important to know that the patients all still had functional testing and they also, in the vast majority, had CT coronary angiography performed as well.

Dr Patricia Ding:

So what are the key limitations in this particular trial, given that the results are at the end? It's a negative trial.

Dr Tim Glenie:

Yeah, so one of the key things really is about the powering of the trial. As I mentioned, they had quite a problem with enrollment and you can see from the number of patients that they screen, to the ones that they actually enrolled, there's been a massive dropout, and that always is somewhat concerning. The power calculations before they started the trial obviously make certain assumptions about event rates and in actual fact, the event rates were very low, and so the trial is going to be underpowered. And on top of it, we didn't recruit as many patients as we wanted, so we're still underpowered. So that is a real concern. The other thing is that, as I mentioned before, that the follow-up so far is actually relatively short with a median of only 3.2 years. So whether this over the course of time is actually going to pan out to be a different result is yet to be seen.

Dr Patricia Ding:

Okay. And how does that relate to our current practice?

Dr Tim Glenie:

So I think in New Zealand, we're in a fortunate position where the majority of patients get good medical therapy and we don't see a lot of inappropriate investigation or procedural things undertaken. So I think this all meets our practice by reaffirming that we are in a good position to manage patients medically once we know what their functional status, and once we know what their ventricular function and their coronary anatomy is. But I think the key thing for us is to make sure that we do investigate patients with chest pain appropriately so that we know what we're dealing with from the outset so we can make informed decisions about which arm of the proposed treatment strategies the patients go down.

Dr Patricia Ding:

Right. Okay. Thank you very much, Tim.

Dr Tim Glenie:

Thank you.

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