Cardiogenic Shock Old and New: IABPs a Thing of the Past and ECMO Under Study

PARIS, France—From intra-aortic balloon pumps (IABPs) to synchronized extracorporeal membrane oxygenation (ECMO), a moderated poster session at EuroPCR 2019 focusing on interventions for cardiogenic shock and cardiac arrest sparked discussion about technologies old and new.

Attendees and panelists there eagerly absorbed observational data from a small trial of synchronized ECMO and large-scale registry results from Sweden, among other reports that expanded the lean evidence base for these challenging conditions.

The SynCor Trial

Conventional ECMO offers continuous support, but the i-cor synchronized cardiac assist system (Xenios AG) matches the pulsing beat of the heart, said Christoph Liebetrau, MD (Kerckhoff-Klinik, Bad Nauheim, Germany), who presented the SynCor trial. Using a single i-cor console, operators can switch between synchronized flow and continuous flow, he explained, noting that the latter option is suitable, for instance, in patients with atrial fibrillation.

With continuous-flow ECMO, “you have an overload of the left ventricle. . . . The intraventricular pressure is increasing,” making it even harder for the heart to circulate blood, Liebetrau told TCTMD. Synchronized flow, on the other hand, may ease some of the strain on the left ventricle, allowing it to function better and increase coronary blood flow.

For the SynCor trial, researchers looked at use of i-cor in 47 patients: 13 had cardiogenic shock and 34 were undergoing high-risk PCI. With the ECMO device successfully delivered in all patients, most went on 1:1 synchronization and one patient each went on 1:2 and 1:3 synchronization. Mean cannulation time was 7 minutes, with a mean time to synchronization of 1 minute.

On average, the duration of assist during PCI was 1 hour and 49 minutes, with a mean flow of 2.7 L/min. No patients had to switch to continuous support to wean off the device. There were three in-hospital deaths, though none of these were deemed related to the device or procedure.

Among the PCI patients, serious adverse events related to i-cor included eight bleeds, five transfusions of at least two red blood cell units, one wound infection in the groin, one compartment syndrome, and one deterioration in bispectral index during switching between ECG-synchronized and continuous mode.

For the cardiogenic shock group, mean duration of assist was 48 hours and 46 minutes, with a mean flow of 2.7 L/min. Four of the 13 patients died in the hospital and nine were weaned off of i-cor, amounting to a survival rate of 69%. For this indication, serious adverse events related to i-cor included three red blood cell transfusions, three cases of lower limb ischemia, and one amputation.

“These data suggest that we can use this kind of ECMO device, which is successfully applicable in these patients, and . . . set the stage for further evaluation and provide the basis for a randomized trial,” Liebetrau concluded in his presentation.

Additionally, the ongoing Synchritude postmarket registry will continue to provide more details on i-cor’s effects, he noted to TCTMD. The device received CE Mark approval in 2015.

Cardiogenic Shock in SCAAR

Elmir Omerovic, MD, PhD (Sahlgrenska University Hospital, Gothenburg, Sweden), meanwhile, focused on a long-standing treatment that has lost momentum in recent years: IABP therapy in cardiogenic shock. The news for IABPs wasn’t good.

As Omerovic noted to the EuroPCR audience, European Society of Cardiology (ESC) guidelines that once gave IABPs a class I recommendation for cardiogenic shock downgraded that guidance to class III after the randomized IABP-SHOCK II trial failed to find a 1-year survival benefit in comparison to optimal medical therapy.

Omerovic and colleagues analyzed data from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR) on 2,991 patients with cardiogenic shock due to MI who underwent PCI at 31 hospitals between 2005 and 2018. Among them, 25% received IABP therapy over the entirety of the study period, though the proportion dropped rapidly after 2015, Omerovic said. The rest were given conventional treatment consisting of medical therapy only.

In-hospital complications (defined as major bleeding, minor bleeding, extended compression of the access artery, blood transfusion, surgical revision of the access artery, or neurological complications) occurred at a rate of 41%. By 30 days after PCI, 52% of patients had died.

The likelihood of complications was nearly quadrupled in patients who did versus didn’t receive IABP therapy (OR 3.74; 95% CI 1.74-8.03). Moreover, mortality didn’t decrease with circulatory support in comparison to no-IABP use (OR 0.99; 95% CI 0.46-2.14).

“Our observational study supports the class III current ESC guidelines for the use of IABP in cardiogenic shock,” Omerovic concluded.

Asked whether inherent disparities between the two treatment groups could have skewed the results, Omerovic acknowledged that this is the first question that comes to mind. “That’s why we used instrumental variable analysis, he said, as a way to correct for differences in practice among centers.

Corstiaan A. den Uil, MD, PhD (Erasmus University Medical Center, Rotterdam, the Netherlands), sitting in the audience, pointed out that previously IABP-SHOCK II showed “absolutely no difference” in complications between IABP use and conservative treatment, querying: why would IABPs fare comparatively worse here?

Omerovic said this speaks to the “limited external validity of randomized clinical trials due to the selection of the patients that are included. This is real-world data.” In fact, while IABP use has been steadily decreasing in Sweden, ECMO and Impella (Abiomed), both of which have large-bore catheters, have only recently been on the rise there for use in cardiogenic shock, Omerovic said. Thus, it will be interesting to see what future observational data reveal regarding bleeding complications.

“I would like to provoke my colleagues—balloon pump was proposed in 1968 or 1969 and used increasingly until 2015,” at which point the randomized IABP-SHOCK II trial turned the tables, Omerovic commented to TCTMD. Before the widespread adoption of ECMO and Impella, it would make sense to wait for more evidence, he suggested. “What I want to say is while of course [these devices seem] reasonable and good, and so on, why don’t we from the beginning do a proper randomized clinical trial?”

In Sweden, nothing is done hastily and outcomes are tracked carefully, Omerovic explained, adding that the goal is, as always, “first do no harm.” For the phaseout of IABP usage, this seems to be the case, he said, in that SCAAR hasn’t observed rising cardiogenic shock mortality in recent years.

Now, said Omerovic, “the subject of quarrel [among Swedish clinicians] is: are we going to use Impella instead?” He suggested that registry-nested randomized trials may be a way forward.

The DanGer trial, as reported by TCTMD, has recently expanded from Denmark for Germany. With a slated enrollment of 360, the study is comparing Impella CP with conventional therapy.