New Minn. Protocol May Help Salvage Patients With Refractory VF/VT

Around a third of out-of-hospital cardiac arrest patients present to EMS with shockable rhythms (ventricular fibrillation/tachycardia), but that group accounts for more than 80% of OHCA survivors.^1,2 If we’re to improve cardiac arrest treatment and survival, it’s a group we might want to target.

A new strategy devised by the Minnesota Resuscitation Consortium may hold promise for the subset of that population whose VF/VT resists cardioversion in the field. Among other elements, if three shocks and amiodarone don’t do the trick, it involves a quick scene departure, LUCAS device during transport, and going directly to the cath lab.

“It’s really galvanizing for the medics and first responders,” says Marc Conterato, MD, FACEP, an emergency physician at North Memorial Medical Center and co-medical director for its ambulance service, one of three that launched the new approach last winter. “They’ve seen the power of public access to AEDs, and now we’re taking that next step for that group of patients for whom we just can’t break the rhythm. It’s frustrating to all of us when there’s a patient we keep shocking and can’t get back.”

Driving the protocol is this: Patients resuscitated from VF/VT have a high incidence of coronary artery disease, and their arrests often stem from correctable underlying causes. In cath labs, more than half receive revascularization with PCI or coronary artery bypass grafts.³ Refractory VF/VT patients, docs surmised, would have an even greater CAD prevalence, and if they could be transported with CPR ongoing, many could have their problems fixed.

Thus the LUCAS device is part of the plan. Under the protocol it’s applied for the transport, along with an impedance threshold device, and left on at the cath lab. There interventional cardiologists cannulate the femoral vessels for extracorporeal membrane oxygenation (ECMO) or support hemodynamics with an intra-aortic balloon pump. Then they perform a coronary angiography and revascularization.

“Usually we find a culprit lesion, like you would in a STEMI, and usually a hemorrhage or thrombus formation that’s causing the acute problem,” says Conterato, who described the approach at February’s Gathering of Eagles conference. “But the key is maintaining perfusion and maintaining the heart and brain while we get things fixed. That’s where the LUCAS device has been a game-changer. It can provide assisted CPR for long periods and maintain it while we’re getting the ECMO or intra-aortic balloon pump set up. You need something to maintain perfusion.

“We have seen this in other places: People will go to the cath lab with the LUCAS running, but that’s where it stops—they can’t maintain the person while they fix the lesion and after. Cardiogenic shock essentially occurs when the person’s cardiac output drops. You have to allow some time for that heart to heal, and that’s what the ECMO and intra-aortic balloon pump allow.”

The protocol’s three-month trial encompassed 27 consecutive refractory VF/VT patients, ages 18–75, who could accommodate the LUCAS and were within 30 minutes of the University of Minnesota Medical Center. Refractory was defined as failing to achieve sustained ROSC after three shocks and an antidysrhythmic agent. At that point the protocol was triggered by a simple phone call from dispatch to an on-call interventional cardiologist. Postresuscitation care at the hospital included therapeutic hypothermia in the cardiac ICU.

The results: Of the 27, 18 met inclusion/exclusion criteria. Fifteen got ECMO, 14 had significant CAD, and 12 received PCI. Fourteen (78%) survived to hospital admission, 10 (56%) to discharge, and nine (50%) with good neurological function (cerebral performance category 1 or 2). In observational data drawn from before the trial, survival to discharge with a CPC of 1 or 2 was just 8.2%.⁴

“Good neuro activity is a key part of this,” notes Conterato. “That’s where I think the ECMO has its strongest advantage: maintaining that brain perfusion until we can get the heart to come back.”

Key Aspects

In writing up its trial for the Journal of the American Heart Association, the MRC identified four key aspects to its strategy:

• Early mobilization of refractory patients;
• The simplified hospital activation process;
• The ECMO being done by an experienced core group of interventional cardiologists;
• A multidisciplinary hospital care team that comprehensively addressed patients’ medical, psychosocial and emotional needs.

Functionally favorable survivors also shared some characteristics: rapid EMS response and quick delivery to the cath lab; bystander CPR; and evidence of reversible CAD. There was a lot of CAD in this cohort, the authors noted, with multivessel disease and complicated lesions. This made interventions with CPR difficult and ECMO support necessary.

“What we’ve found in preliminary analysis of the data,” says Conterato, “is that the people who do the best from this are in their mid 50s, with no history of CAD, who are otherwise relatively healthy. When you look at our demographics so far, those are the patients we’re doing well with.”

Use of the approach continues in the Twin Cities area; the goal is to get to 40–60 patients and help start a multicenter prospective randomized controlled trial comparing the protocol to other advanced treatments.

One possible hair in the soup was a few cases of overtransport: Of the nine patients excluded from the team’s writeup, five were incorrectly judged to have had shockable rhythms. That precipitated some targeted QI but isn’t anticipated to portend a problem as the strategy continues.

“It was a very small number,” says Conterato. “We realized our paramedics are very enthusiastic about this and maybe just wanted to go that extra step and really make that extra effort for the patient. As we get more patients and our medics have more expertise with this, I expect that rate to go down. We don’t foresee it as a problem.”

Hear a survivor’s story at www.emsworld.com/video/12226179.

References

1. Aufderheide TP, Frascone RJ, Wayne MA, et al. Standard cardiopulmonary resuscitation versus active compression-decompression cardiopulmonary resuscitation with augmentation of negative intrathoracic pressure for out-of-hospital cardiac arrest: a randomised trial. Lancet, 2011; 377: 301–11.

2. Aufderheide TP, Nichol G, Rea TD, et al; Resuscitation Outcomes Consortium I. A trial of an impedance threshold device in out-of-hospital cardiac arrest. N Engl J Med, 2011; 365: 798–806.

3. Garcia S, Drexel T, Bekwelem W, et al. Early access to the cardiac catheterization laboratory for patients resuscitated from cardiac arrest due to a shockable rhythm: the Minnesota Resuscitation Consortium Twin Cities Unified Protocol. J Am Heart Assoc, 2016.

4. Yannopoulos D, Bartos JA, Martin C, et al. Minnesota Resuscitation Consortium’s Advanced Perfusion and Reperfusion Cardiac Life Support Strategy for Out-of-Hospital Refractory Ventricular Fibrillation. J Am Heart Assoc, 2016.