Role of Impella 2.5 Heart Pump in Stabilizing Diastolic Aortic Pressure to Avert Acute Hemodynamic Collapse (Full title below)

Role of Impella 2.5 Heart Pump in Stabilizing Diastolic Aortic Pressure to Avert Acute Hemodynamic Collapse during Coronary Interventions

_______________________________________________

From the University of Chicago Medical Center, Chicago, Illinois. The author is a member of Scientific Advisory Board of Abiomed, the makers of the Impella 2.5. Manuscript submitted January 2, 2009, provisional acceptance given April 20, 2009, and final version accepted April 21, 2009. Address for correspondence: Neeraj Jolly, MD, 5841 South Maryland Avenue, MC 5076, Chicago, IL 60637. E-mail: njolly@medicine.bsd.uchicago.edu

_______________________________________________

J INVASIVE CARDIOL 2009;21:E134-E136 Percutaneous ventricular assist devices have recently been introduced to support patients with cardiogenic shock or those undergoing high-risk coronary interventions.1,2 They provide circulatory support by unloading the left ventricle in addition to maintaining adequate forward blood flow.3 A case of an elderly patient who benefited by the support provided by one such assist device as he underwent a high-risk coronary procedure is presented to highlight an important mechanism by which these novel mechanical pumps support the arterial circulation and provide clinical benefit. Case Presentation. An 82-year-old male with unstable angina was referred for a high-risk coronary intervention. He had undergone coronary artery bypass surgery with a left internal mammary artery (LIMA) anastamosed to the left anterior descending (LAD) artery and a radial “T-graft” anastamosed in a sequential manner to two obtuse marginal branches of the left circumflex artery. The left main trunk was totally occluded, thereby making the internal mammary the sole conduit of blood flow to his codominant left coronary distribution. There was a 70% stenotic lesion at the LIMA anastamotic site and another lesion of a similar severity involving the side-to-side anastamosis of the radial graft onto the first obtuse marginal branch. A codominant right coronary artery had no significant stenosis. The patient underwent attempted coronary intervention through the mammary artery at another institution and had sustained cardiac arrest due to a wire-induced spasm of the LIMA graft, despite intra-aortic balloon pump support. He suffered a myocardial infarction as a result of that intervention and his left ventricular ejection fraction was reduced to 40%. The patient refused repeat surgical intervention. Repeat coronary angiography was performed, which revealed the previously described anatomy and highlighted the extremely tortuous mammary graft that presented a challenge in navigating a steerable guidewire through its length (Figure 1). The LIMA-to-LAD anastamotic site lesion was the primary interventional target. In view of the past history of hemodynamic collapse during an attempted coronary intervention via the mammary graft, an Impella 2.5 cardiac assist device was introduced prophylactically to support cardiac hemodynamics during this high-risk intervention. A PT2 moderate-support wire (Boston Scientific Corp., Natick, Massachusetts) was used to negotiate the severely tortuous LIMA graft (Figure 2). Significant wire-induced pseudo-lesions were exacerbated every time a balloon catheter was advanced over the wire (Figure 3) to attempt angioplasty of the target lesion. The patient’s systolic pressure dropped significantly during each attempt at angioplasty. However the diastolic pressure was maintained due to the support provided by the Impella 2.5 (Figure 4). Balloon angioplasty was successful in reducing the target lesion to a 20% stenosis, and the patient tolerated the intervention very well. At the completion of the procedure, the patient was weaned from the Impella circulatory support system and the device was successfully explanted. The 13 Fr sheath was removed and manual compression was applied to the groin. Discussion. The TandemHeart® (CardiacAssist, Inc., Pittsburgh, Pennsylvania) and the Impella® 2.5 (Abiomed, Danvers, Massachusetts) are the two commercially available percutaneous left ventricular assist devices in the United States. With the TandemHeart, the left ventricle is supported by pumping blood out of the left atrium and ejecting it into the iliac artery. The Impella 2.5 aspirates blood from the left ventricle and ejects it into the ascending aorta. Our case pertains to the use of an Impella 2.5, which incorporates a 12 Fr pump mounted on a 9 Fr catheter. The catheter is introduced via the femoral artery and placed across the aortic valve such that the tip and inflow are in the left ventricle, and the catheter-mounted pump and outflow are just above the aortic sinuses. When activated, the pump can provide up to 2.5 L per minute of flow from the left ventricle directly into the ascending aorta, over and above the intrinsic cardiac output of the native heart. This clinical case demonstrates the advantage of using the Impella 2.5, a minimally invasive left circulatory support device, in a patient who had known hemodynamic instability following manipulation of his last remaining significant conduit. From the patient’s past experience at another institution, it was evident that mechanical circulatory support greater than that provided by an intra-aortic balloon pump was required to avoid a similar catastrophic result. Maintenance of stable diastolic blood pressure despite significant drops in systolic pressure, likely secondary to myocardial stunning, resulted in adequate mean systemic pressure and avoided any procedural complications. Prior studies of the Impella 2.5 for high-risk percutaneous coronary intervention (PCI) have emphasized increased cardiac output and ventricular unloading as the principal mechanisms by which this device assists in the performance of these high-risk procedures.2–5 Positive effects on aortic pressure have also been cited as a likely benefit, primarily acting by increasing coronary blood flow.4,5 To our knowledge, no study has stressed the effect on diastolic versus systolic pressure, hence the maintenance of mean blood pressure as an important mechanism by which this device provides hemodynamic support to the systemic circulation. This mechanism is particularly important during the performance of these high-risk coronary interventions if and when myocardial stunning and resultant hypotension develop during the procedure. Our case demonstrates a potent effect of the Impella on diastolic pressure maintenance as a mechanism of benefit during high-risk PCI. Although unloading the left ventricle is an important mechanism of action of such pumps,3 this is likely to be more useful when providing support on a continuous basis for patients with cardiogenic shock or severe heart failure.1,6 Acute support during a high-risk coronary intervention in clinical situations as exemplified by this case is achieved by maintenance of mean systemic blood pressure despite a significant drop in systolic pressure. Hemodynamic stability provided by this mechanism allows for the safe performance of coronary interventions that could be life-threatening without such a “safety net”.

2. Henriques JPS, Remmelink M, Baan J Jr, et al. Safety and feasibility of elective high-risk percutaneous coronary intervention procedures with left ventricular support of the Impella Recover LP 2.5. Am J Cardiol 2006;97:990–992.

3. Valgimigli M, Steendijk P, Sianos G, et al. Left ventricular unloading and concomitant total cardiac output increase by the use of percutaneous Impella LP2.5 assist device during high-risk coronary intervention. Catheter Cardiovasc Interv 2005;65:263–267.

4. Remmelink M, Sjauw KD, Henriques JPS, et al. Effects of left ventricular unloading by Impella recover LP2.5 on coronary hemodynamics. Catheter Cardiovascular Interv 2007;70:532–537.

5. Dixon SR, Henriques JPS, Mauri L, et al. A Prospective feasibility trial investigating the use of the Impella 2.5 system in patients undergoing high-risk percutaneous coronary intervention (The PROTECT I trial): Initial U.S. experience J Am Coll Cardiol Interventions 2009;2:91–96.

6. Reesink K, Dekker A, van Ommen V, et al. Miniature intracardiac assist device provides more effective cardiac unloading and circulatory support during severe left heart failure than intraaortic balloon pumping. Chest 2004;126:896–902.