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Portable CPS Increases STEMI Survival

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We know that “time is muscle” and that the greatest amount of heart muscle salvage occurs if an occluded coronary artery is opened within an hour after the onset of chest pain. This has underscored the need for the rapid treatment of patients with ST elevation myocardial infarction (STEMI).

The decades-old battle over whether thrombolysis or balloon angioplasty will be recognized as the preferred treatment for STEMI has been resolved in favor of percutaneous coronary intervention (PCI) when both are available. Door-to-balloon time has replaced door-to-needle time as the standard procedure in health-care systems, which also affects EMS.

Throughout the past five years, the collaborative efforts of EMS crews, hospitals and interventional cardiologists have resulted in a decrease in average door-to-balloon times from more than 120 minutes to 60 minutes or less in San Diego County, as in many communities around the country. As a result, in-hospital mortality for STEMI patients has decreased significantly.

It has been estimated that every 60 minutes of delay from symptom onset to angioplasty increases mortality by 10%.1 Unfortunately, 25% of patients who die from STEMI do so before receiving medical attention, and the cause of death is usually ventricular arrhythmia. Refractory v fib is virtually always fatal, even in the hospital setting.

The following are two cases of STEMI patients with refractory v fib who survived neurologically intact and with near normal heart muscle function. They survived because of fast response by EMS, the use of portable cardiopulmonary support (CPS) devices in the emergency department (ED) and emergency PCI.

Case Histories
The first patient was a 59-year-old male in good health except for hypertension treated with atenolol. He developed severe anterior chest pain and called 9-1-1. During transport to Sharp Memorial Hospital, he developed v fib arrest. EMS providers started ALS and continued throughout the transport. See the ECG on presentation to the ED in Figure 1.

Despite the administration of antiarrhythmic drugs and electric shock, a stable cardiac rhythm couldn’t be maintained until CPS therapy was instituted. An ECG obtained after placement of CPS demonstrated sinus rhythm with changes of an acute anterior wall myocardial infarction. (See Figure 2)

Following stabilization, the patient was taken to the cardiac catheterization lab, where coronary angiography demonstrated a sub-total occlusion of the left anterior descending coronary artery. (See Figure 3)

Following placement of a coronary stent, the left anterior descending artery (LAD) was opened.  (See Figure 4)

A subsequent ECG demonstrated marked resolution of the ST elevation. (See Figure 5)

Although the initial left ventricular ejection fraction (LVEF) was severely reduced to 21%, heart muscle function quickly improved such that at the time of hospital discharge the LVEF was 52%. The patient was neurologically intact at discharge and continues to do well.

The second patient was a 55-year-old man with a remote history of coronary disease, prior myocardial infarction and hyperlipidemia, who continued to smoke cigarettes up to the time of admission. He presented to the ED having had chest pain since that morning. Because of his perceived need for rapid transport, he had his wife drive him to the hospital.

While being evaluated by an ED physician, he developed v fib arrest. (See Figure 6)
 
CPR, IV amiodarone and dozens of defibrillatory shocks restored sinus rhythm for only brief periods of time. An ECG recorded during a brief period of sinus rhythm was consistent with acute inferior wall infarction. (See Figure 7)

Portable CPS was initiated after placement of a 15F sheath in the right femoral artery and a 21F sheath in the right femoral vein. A flow of 4 Liters per minute was achieved, and the patient was taken to the cardiac catheterization lab in stable sinus rhythm. Shown below are the initial right coronary angiogram (Figure 8) and the angiogram obtained after stenting (Figure 9).

Following successful PCI, the patient’s cardiac rhythm remained normal and the ST elevation resolved. Left ventricular function by echo was normal at discharge, and the patient suffered no apparent neurological injury. However, surgical repair of the sternum was required due to prolonged CPR.  This post PCI ECG shows resolution of inferior ST elevation and anterior ST depression. (See Figure 10 )

Discussion
Both cases emphasize the importance of early activation of EMS and transport to a STEMI-receiving center capable of advanced circulatory support and angioplasty.
Portable CPS, though seldom used, has been lifesaving for many patients with cardiogenic shock, myocarditis and, as in these cases, refractory ventricular arrhythmia. Without the ability to provide complete circulatory support, neither of the patients presented here would have survived.

The CPS program at Sharp Memorial Hospital reported on outcomes during 1986–2006, which was recently published in the Journal of Thoracic and Cardiovascular Surgery.2 Of the 150 patients started on portable CPS for cardiac arrest (N=127) or refractory shock (N=23), 69 were weaned from CPS, and 39 (26%) were long-term survivors with a median survival rate of 9.5 years.

The success of the CPS program is grounded in training and interdisciplinary teamwork. The large 15 French (5mm) and 21 French (7mm) arterial and venous catheters are placed percutaneously, usually by a cardiologist or cardiac surgeon. Although fluoroscopy is helpful for the advancement of guidewires and to ensure the tip of the venous catheter is in the right atrium, catheter placement can be done at the bedside, as in both of these cases. The catheters are then attached to the pre-primed pump-oxygenator circuit by one of the specially trained SICU nurses. A trained and certified CPS nurse is available at all times.

Once the CPS system is running, and the patient is stabilized, a perfusionist is called in to monitor the system. Flow rates of 4 LPM are typical and sufficient to maintain normal organ perfusion.

Long-term survival is most likely to occur when the CPS is used as a bridge to a treatment that improves heart function (PCI or surgery) or when it provides time for the heart to heal on its own (myocarditis).

Conclusion
Despite significant improvements in door-to-balloon-times across the country and in San Diego County, occasional patients with refractory ventricular arrhythmia and hemodynamic collapse can’t be taken to the cath lab without first being stabilized with CPS. In selected cases, CPS can be lifesaving, but the technology isn’t widely available because its successful use requires a carefully constructed, coordinated and monitored program with close collaboration between EMS physicians and advanced practice nurses. JEMS

References
1. Terkelsen CJ, Sorenson JT, Maeng M, et al. System delay and mortality among patients with STEMI treated and primary percutaneous coronary intervention. JAMA. 2010:304;763–771.
2. Jaski BE, Ortiz B, Alla KR, et al. A 20-year experience with urgent percutaneous cardiopulmonary bypass for salvage of potential survivors of refractory cardiovascular collapse. J Thorac Cardiovasc Surg. 2010:139;753–757.

This article originally appeared in December 2010 JEMS as “The Rhythm of Survival: Using portable cardiopulmonary support to treat STEMI patients.”



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