Cancelled Cath Lab Activations and Timely Reperfusion: A ‘Balancing Act’

(UPDATED) In a hospital system designed to activate the cardiac catherization laboratory following a prehospital ECG or emergency department diagnosis of STEMI, 65% of lab activations are ultimately cancelled after being evaluated by the on-call interventional cardiologist, according to the results of a new single-center study.

Among 1,332 consecutive cath lab activations at a high-volume, tertiary-care hospital in Los Angeles, CA, only 466 patients were found to have STEMI and underwent emergent coronary angiography. In the remaining 866 cases, the activated lab and call to the STEMI team was cancelled, with 712 patients not undergoing coronary angiography at all and 154 undergoing coronary angiography at a later date.

“Across the country, we’ve done a really good job of improving time to reperfusion, but as we do that there is always a little tension between time versus false-positive activations,” senior investigator Timothy Henry, MD (Cedars-Sinai Medical Center, Los Angeles, CA), told TCTMD. “There is huge variability across the country in terms of the scope of the problem. It turns out that across Los Angeles, not just at Cedars-Sinai, almost 60% to 70% of the time when they activate the cath lab they cancel it.”

Lead investigator David Lange, MD (Kaiser Permanente Santa Clara Medical Center, CA), said that cancelling the cath lab after an activation always feels uneasy for cardiologists given the emphasis on timely reperfusion.

“You’re programmed to respond and take the patient upstairs, and when you get into a situation of changing course you really want to be confident you’re making the right decision for the patient,” he said. “You don’t want to take them to the cath lab unnecessarily, but if it really is a STEMI that’s happening, you don’t want to do anything to delay their care.”

Every time the activated cath lab team is canceled costs the healthcare system money, but it also contributes to diminished morale and frustration among the STEMI team members, said Henry. In addition, it can be frustrating and confusing for the patient and their family, he said.

Snapshot of STEMI Care in Los Angeles Country

The new study, which was led by David Lange, MD (Kaiser Permanente Santa Clara Medical Center, CA), and published in the August 2018 issue of Circulation: Cardiovascular Quality and Outcomes, included consecutive cath lab activations between 2012 and 2014 at Cedars-Sinai Medical Center, one of the highest-volume STEMI-receiving centers in Los Angeles Country.

“Not as a criticism of the system, but just as an observation, Los Angeles County’s STEMI-receiving protocol and system was rather inefficient in that many sites that were canceled,” said Lange. “At Cedars-Sinai, I can definitively say we were inefficient because we were routinely activating the lab based on the prehospital ECG and then subsequently canceling them. Essentially we were getting the cart ready before we knew that the horse was going to pull it.”    

At the time of the study, a prehospital ECG reading of acute MI determined by computer algorithm triggered the cardiac cath lab activation with a single page to the entire STEMI team. An emergency department physician could also activate the cath lab with a diagnosis of acute MI. As part of the protocol, patients presenting as acute MI underwent an expedited evaluation from the on-call interventional cardiologist who determined whether to proceed with the emergency angiogram or whether to cancel the cath lab activation.   

The reasons for the cancellation included bundle branch block, including right bundle branch block with STEMI and prior left bundle branch block, as well as poor-quality prehospital ECG, repolarization abnormalities, and arrhythmia. “The problem is that when you look at the ECGs, they’re not always accurate,” said Henry. The prehospital ECG computer algorithm to identify acute MI was also deemed “too sensitive” as it picked up other ST-segment changes not related to STEMI, he said.

Sanjit Jolly, MD (McMaster University, Hamilton, Canada), an interventional cardiologist who was not involved in the study, acknowledged the tension between a fast response and false alarms, calling it a “balancing act.” The very high rate of cath lab cancellations suggests the acute MI protocol has gone too far in terms of prioritizing a rapid door-to-balloon time, said Jolly.

“There is a time pressure here,” he said. “You want to get the patient’s infarct artery opened as quickly as possible. And there are measures like door-to-balloon time of less than 90 minutes, so there is a real pressure to get the team in as quickly as possible. What’s interesting here is that the majority—almost two-thirds of activations where the team came in—of patients didn’t have an angiogram. That is distinctly unusual in a Canadian system.”

In the Hamilton region where he works, Jolly estimates that less than 10% of activated cath labs are cancelled. The major difference between care in Los Angeles Country and the Hamilton region is that paramedics do not activate the cath lab. In Hamilton, ischemic chest pain symptoms and a STEMI diagnosis on the ECG result in a phone call to an interventional cardiologist at the Heart Investigation Unit hotline or interventionalist on call (after hours, weekends, and holidays) to discuss the symptoms and ECG.

“If things don’t seem right, we don’t activate the cath lab, and [the patients] go to the emergency department,” said Jolly.

Lowering the Number of False Alarms

At Cedars-Sinai, the time of presentation (within vs outside of regular working hours) did not differ between patients who underwent emergent angiography and those in whom the procedure was cancelled, but those who underwent angiography were more likely to present in cardiogenic shock. Additionally, those who underwent emergent angiography had higher initial and peak troponin levels and a larger proportion of these patients had positive cardiac biomarkers.

In-hospital and 30-day mortality was significantly higher among the patients who underwent emergent angiography compared with those for whom the catheterization was cancelled, as well as compared with those who later underwent nonemergent coronary catherization. Mortality at 1 year was similar between the patients treated by the cath lab team and those for whom the procedure was canceled. After adjusting for variables associated with survival, such as age, diabetes mellitus, and cardiogenic shock, among others, a cancelled cath was associated with an increased risk of death during the study period compared with emergent angiography (HR 1.82; 95% CI 1.28-2.58).

Several changes can be made to the STEMI protocol to help lower the rate of unnecessary cath lab activations. Emergency medical services (EMS) can be taught to interpret the ECG, the ECG-interpretation algorithm can be tweaked so it is a little less sensitive, or the ECG can be transmitted to the hospital for interpretation by a cardiologist, said Henry.

No one approach is better than the other, he added, because what works effectively in one center might not be best for another hospital system. At Minneapolis Heart Institute, where Henry previously worked and helped transform the STEMI protocol to facilitate timely access to PCI, the EMS personnel were trained to interpret the ECG, which was also less sensitive for the detection of STEMI.     

“It’s not that these patients shouldn’t come to a specialized hospital,” said Henry. “They should, but we don’t need to activate the cath lab for all of them. We need to activate the cath lab for a specific group where it’s an absolutely clear-cut STEMI patient. For others, they should still come to the emergency department—we know they’re coming and we raise the alert—but we don’t call the cath lab team in. Instead, we do a more expedited evaluation in the emergency department and make a decision very quickly. That works really well.”

At Cedars-Sinai Medical Center, the ECG computer algorithm for acute MI diagnosis has since been amended to improve specificity without reducing the sensitivity of STEMI activations. Henry said the number of cath lab cancellations has been significantly reduced and they plan to publish those results soon. Adding in the second step—an expedited evaluation by an interventional cardiologist before activating the cath lab where the diagnosis is uncertain—does increase the time to reperfusion, but the time is minimal, he said.

To TCTMD, Lange said that each STEMI-receiving hospital in Los Angeles Country handles their cath-lab activation algorithm somewhat differently. Some still activate based on the prehospital ECG, while others, like Cedars-Sinai Medical Center, are now waiting for an expedited review from the interventional cardiologist based on the prehospital ECG. If the diagnosis is certain, the cardiologist activates the lab before the patient arrives. If less certain, they’ll wait for the patient to arrive in the emergency department.

“This study, in many ways, highlights the delicate balance between art and science, particularly in STEMI care,” said Lange.