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Medically Clear

Survival Rate High for Cardiac Arrest Patients Treated with Percutaneous Mechanical Circulatory Support

Ballard, Dustin MD; Vinson, David MD

doi: 10.1097/01.EEM.0000574764.99968.da
Medically Clear

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Paramedics are dispatched for a 70-year-old man prone on the shower floor. He is warm but pulseless and apneic, and the monitor demonstrates ventricular fibrillation. ALS interventions are initiated, including manual CPR and immediate defibrillation at 200 joules.

With no change in rhythm, the medics continue the on-scene workup. Another shock at 200 joules is given, and then another. And then medications, mechanical CPR, and more shocks. And more shocks. Fifty minutes after EMS arrival and 13 jolts of electricity, the scribbles on the monitor are unchanged. The paramedics call for online medical control and request transport with mechanical CPR in progress. The patient decompensates to asystole during transport, and is pronounced dead upon ED arrival.

This case captures a longstanding and evolving debate about cardiac arrest in the field: Should paramedics scoop and go or stay and play? Or, in situations like this, is there a middle ground we might call quick play and go? The rationale for such an approach is that some EDs may have more effective options to treat refractory ventricular arrhythmias than electricity.

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The Evidence

Evidence supports using extracorporeal CPR for select cardiac arrest patients in the ED, but this modality may be impractical in many EDs, especially those with a low volume of cardiac arrest patients. If you are like us and do not currently have an ED equipped for extracorporeal membrane oxygenation nor a nearby cardiac arrest center, are there other means of maximizing support in the ED care for the potentially salvageable cardiac arrest patient?

The interventional cardiologists in our region have recently become bullish about using percutaneous mechanical circulatory support (MCS) devices, in particular the Impella (Abiomed, Danvers, MA), for the acute MI-induced cardiogenic shock patient, including those in active cardiac arrest.

Haven't heard of this device? Neither had we. Touted as the world's smallest heart pump, the device offers a diminutive alternative to intra-aortic balloon pumps for patients with cardiac shock or refractory ventricular rhythms eligible for emergent percutaneous coronary intervention. The Impella is inserted through the femoral artery with a 12Fr or 14Fr catheter, and it curls in the left ventricle and sucks up blood and blows it into the ascending aorta, achieving flows of 2.5-4.0 L/min, independent of native rhythm. The device has the potential to increase forward flow of oxygenated blood to vital organs and also increases coronary artery perfusion and decreases left ventricular wall tension. (Circ Cardiovasc Interv. 2018;11[4]:e005870, http://bit.ly/2YudLcK; Circulation. 2017;136[16]:e232, http://bit.ly/2Yrgl3p.)

The FDA approved the Impella in 2016 for patients with acute MI-induced cardiogenic shock, but evidence surrounding these devices is still fledgling, especially if you consider the subset of patients who are in cardiac arrest under active CPR. One of the few available entries, the Detroit Shock Trial, included 41 consecutive patients at four metro Detroit sites with moderate or better experience with MCS (>10 cases within the past calendar year) in this feasibility trial, which ran from July 2016 to February 2017. (Catheter Cardiovasc Interv. 2018;91[3]:454; http://bit.ly/2VqsbJg.) All were treated with a pathway dictating early initiation of MCS (Impella 2.5 or Impella CP) prior to PCI.

The trial excluded patients with shock of noncardiac etiology, anoxic brain injury, and unwitnessed out-of-hospital cardiac arrest or without return of spontaneous circulation within 30 minutes. Six patients (15%) of the cohort had a witnessed out-of-hospital arrest, 11 (27%) had an inpatient arrest, seven (17%) were under active CPR at the time of MCS implantation, and 35 (85%) were STEMIs. The investigators reported a door-to-MCS time of 83 minutes with significant variability (+/-58 min), improved hemodynamic measures, and lower dosages of inotropes and vasopressors within 24 hours.

Survival to explant for the entire cohort was 85 percent, a significant improvement from institutional historical controls (85% v. 51%, p < 0.001); survival to discharge was 76 percent. Consistent with prior investigation, a benefit with earlier time from shock to MCS (<1.25 hours) was suggested. (Am J Cardiol. 2017;119[6]:845; http://bit.ly/2LIKJ81.)

This study has some obvious limitations, including the absence of a control group and the potential for selection bias and other confounders in comparing survival rates with historical controls. They excluded 14 patients from the treatment algorithm; three had unwitnessed arrest or anoxic brain injury. The authors also did not report outcomes for the subset (17%) with active CPR at the time of MCS insertion. A recently published Norwegian registry study of patients receiving MCS for acute MI-induced cardiogenic shock reported a six percent 30-day survival rate in those with ongoing CPR v. 75 percent for those without. (Resuscitation. 2019 Apr 19. [Epub ahead of print].)

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The Verdict

Back to our original case. Since the day our 70-year-old patient was pronounced dead, our cardiac cath lab has become equipped and trained to use MCS. The challenge now is to figure out which patients might benefit. It seems clear that select STEMI patients with shock might, but those with ongoing cardiac arrest of presumed cardiac origin are a different matter.

For now, though, MCS is worth considering if it is an option within your system and how existing protocols might be adjusted to minimize scene-to-MCS time. Differential prehospital transport might be one option, or, as we did in our system, one might change transport criteria to quick play and go—three shocks and then immediate transport with mechanical CPR for refractory ventricular arrhythmias. It also may be worth thinking about which ED capabilities and processes should be instituted for such patients, such as mechanical CPR in the ED and a selection process or criteria for which patients to take to the cath lab.

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Dr. Vinsonis an emergency physician at Kaiser Permanente Sacramento Medical Center, a chair of the KP CREST (Clinical Research on Emergency Services and Treatment) Network, and an adjunct investigator at the Kaiser Permanente Division of Research. He also hosts Lit Bits, a blog that follows the medical literature athttp://drvinsonlitbits.blogspot.com. Dr. Ballardis an emergency physician at San Rafael Kaiser, a chair of the KP CREST Network, and the medical director for Marin County Emergency Medical Services. He is also the creator of the Medically Clear podcast on iTunes. Follow him on Twitter @dballard30, and read his past articles athttp://bit.ly/EMN-MedClear.

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