Shock Patients Treated With MCS Devices at Referral Hospitals Have Higher Risks

Placing a temporary mechanical circulatory support (MCS) device for cardiogenic shock at a hospital that’s not a dedicated shock center is associated with a higher risk of device-related adverse events, according to an observational analysis.

Risks of bleeding, hemolysis, and vascular injury were significantly higher in patients with MCS implanted at a regional referral center before transfer to a level 1 cardiogenic shock center, raising questions around best practices for use of such devices in patients who will be transferred to a specialized hospital.

“The big question that will remain an ongoing debate, and subject for future investigation, is what is the better part of valor?” senior investigator Anthony Carnicelli, MD (Medical University of South Carolina, Charleston), told TCTMD. “Is it implanting early and helping support end-organ perfusion at a regional referral center, understanding that we’re going to be taking on a higher risk of adverse events during the transfer process? Or is it allowing for continued hypoperfusion so we can get the patient to a hub center, knowing that could risk worsening end-organ injury but also reduce the risk of having adverse events associated with MCS?”

Right now, said Carnicelli, there’s no easy answer to this challenging conundrum, but it’s one the cardiogenic shock community needs to address.

Level 1 cardiogenic shock centers are high-volume hospitals equipped with around-the-clock medical and surgical expertise, including capabilities with temporary MCS, placement of durable left ventricular assist devices (LVAD), and often heart transplantation. While regional hospitals with cardiac catheterization laboratories might also be capable of placing temporary MCS, such as percutaneous microaxial flow pumps and intra-aortic balloon pumps (IABP), to unload the left ventricle during cardiogenic shock, professional guidelines advise transfer to level 1 cardiogenic shock centers.

However, there is no formal recommendation around the placement of temporary MCS, whether that’s at the regional referral center or cardiogenic shock hub center. The general consensus is “that patients should be supported when they need support,” said Carnicelli, adding that arguments can be made in favor of MCS placed at either site.

Holger Thiele, MD (Heart Center Leipzig at University of Leipzig, Germany), an expert in cardiogenic shock who was not involved in the current study, said based on the available data, the placement of temporary MCS should not be done routinely at referral hospitals.

“However, this is usually also an individual decision based on the hemodynamic situation of a patient,” he told TCTMD. “Patients with hemodynamic collapse, or imminent collapse, will need MCS insertion before being transferred. This is a rare situation, and in all other patients with some hemodynamic stability under vasopressors or inotropes, transfer to a hub hospital is probably the preferred treatment strategy.”

The higher risk of device-related adverse events in patients treated at referring centers is likely related to inexperience with the devices, he added. “Higher volume and more experience with large-bore access and management leads to less bleeding and less limb ischemia,” said Thiele.

For example, a recent subanalysis from the ECLS-SHOCK trial in patients with acute MI complicated by cardiogenic shock showed that rates of 30-day and 12-month mortality were lowest at high-volume centers, which was defined as those who placed more than 50 venoarterial extracorporeal membrane oxygenation (VA-ECMO) devices annually.   

Sicker Patients Transferred with MCS

To TCTMD, Carnicelli said the new analysis, published last week in Circulation: Heart Failure, stemmed from their observation that patients transferred from a regional hospital tended to be more vulnerable than those who presented directly to their shock center. These referred patients also appeared to be at a higher risk of adverse outcomes and device-related adverse events.

“There are many reasons that potentially could be driving that,” he said. “MCS implant volume at referral centers tends to be lower than at major hub centers. Obviously, as with everything in medicine, the risk of adverse events is directly related to the volume of devices that you’re implanting. What drove us was primarily a quality-improvement question: is there a way that we can identify exactly what adverse events these patients are at a higher risk for so that we can work on a quality-improvement initiative across the MUSC health network knowing that MCS volume at referral centers is going to continue to increase?”

In all, 398 patients with temporary MCS—either IABP or Impella CP/5.5 (Johnson & Johnson MedTech/Abiomed)—for cardiogenic shock were included in the analysis. Of these, 307 had the MCS placed at the shock center and 91 had the device placed at the regional hospital before transfer.

The transferred patients were more likely to have ischemic cardiomyopathy and less commonly had a history of heart failure, atrial fibrillation, and chronic kidney disease than those with a device implanted at the hub center. When compared with those implanted at the specialized hub site, those with MCS placed at a referring hospital had more advanced cardiogenic shock (80% vs 46% with SCAI SHOCK stage D/E; P < 0.001), were more likely to have cardiac arrest (31% vs 10%; P < 0.001), and had higher lactate levels.

Overall, the prevalence of any device-related adverse event was 40%, with the most common events being bleeding (16%) and bacteremia (11%). At least one device-related adverse event occurred in 64% of patients treated first at the regional center compared with 33% of those with MCS placed at the hub hospital (P < 0.001). The regional hospital-implanted patients had a significantly higher risk of bleeding (29% vs 12%; P < 0.001) and vascular injury (22% vs 5%; P < 0.01). With Impella, they also had a higher incidence of hemolysis (30% vs 18%; P = 0.042) than those treated at the shock center. Rates of bacteremia were numerically higher in patients initially treated at the referral hospital.

The device-related adverse event rate was 0.33 events/patient-week, which was numerically higher when MCS was implanted at the regional referral hospital than at the shock center (0.65 vs 0.24 events/week).

The unadjusted risk of in-hospital mortality and unfavorable outcomes (death before heart transplant, durable LVAD implant, or discharge) was significantly higher in those who received MCS at the referring hospital, but the relationship with the implanting site was not statistically significant after adjusting for shock severity and pre-MCS cardiac arrest.  

“It seems like the severity of illness and the severity of cardiogenic shock are the main drivers of the discrepant outcomes when we’re looking at clinical outcomes,” said Carnicelli.

More Devices, More Risks

Carnicelli noted that patients implanted with support at outside hospitals had a greater number of temporary MCS devices during hospitalization (mean 1.6 vs 1.3; P < 0.001), but the median number of device days, at 8, was similar in the two groups.

“When patients are implanted at other centers, they tend to be implanted with devices, such as a femoral balloon pump, that may not offer the caliber or capacity of support that some of these patients need,” he said. “They end up having to get escalated to a higher-capacity mechanical support device at the hub, which confers a potentially higher risk of adverse events by having to take out one device and put in another one.”  

For Thiele, in order to avoid situations where the patient is implanted with MCS at a referral site, transfer should take place as early as possible, “not when it is too late when there is no chance of stabilization with vasopressors or inotropes.” He added that data from Germany indicate that overall care as assessed by in-hospital mortality for cardiogenic shock with and without MCS is best in experienced centers.

Right now, Carnicelli said they don’t have an answer as to the best way to treat these high-risk patients. Their hope is that by identifying the problem and defining the risks, the shock community can develop mitigation strategies to reduce the risks associated with devices implanted before transfer.