Title
Left Ventricular Outflow Obstruction From Mechanical Circulatory Support in Critical Aortic Stenosis: A Cautionary Tale
Introduction
Temporary mechanical circulatory support (MCS) is beneficial in acute myocardial infarction (AMI) with cardiogenic shock (CS). However, transvalvular MCS may have unintended consequences in critical aortic stenosis (AS).
Clinical Case
An 88-year-old male with coronary artery disease, critical AS, abdominal aortic aneurysm, diabetes, and hypertension presented with AMI with CS. ECG showed aVR elevation and diffuse ST depression. Transthoracic echocardiography revealed left ventricular ejection fraction (LVEF) of 20%, mean aortic valve (AV) gradient 35 mmHg, and estimated AV area 0.41 cm
2, consistent with low flow-low gradient critical AS. Labs showed hemoglobin of 6.8 mg/dL attributed to occult gastrointestinal bleeding. After blood transfusion, the patient remained in cardiogenic shock requiring vasopressor and inotropic support. The patient was urgently taken for coronary angiography, which demonstrated heavily calcified 90% stenosis of the left main (LM) extending into the left anterior descending (LAD) and left circumflex (LCX) (Medina 1,1,1), and 80% proximal right coronary artery (RCA) stenosis. Left ventricle (LV) end diastolic pressure was 32 mmHg. Balloon aortic valvuloplasty (BAV) was performed with an 18mm balloon. Peak transaortic pressure gradient post-BAV was 25 mmHg. Due to cardiogenic shock and need for intervention on high risk coronary anatomy, an Impella CP (Abiomed Inc, Danvers, MA) was inserted for hemodynamic support. Rotational atherectomy was performed from the LM into the proximal LAD, followed by bifurcation stenting of LM into LAD, and LCX. The Impella CP was left in place post-intervention, with heparinization through the purge solution. Post-operative invasive hemodynamics showed decreased cardiac output (CO) and cardiac index (CI) (3.2 L/min, 1.57 L/min/m
2). The Impella flow was 3.4 – 3.8 L/min with minimal native LV contribution to the CO. Peak LV-Ao pressure gradient, as reported on the Impella console, was 60-70 mmHg. For the next 36 hours, the patient was diuresed and inotropic support optimized. Due to hemolysis and concern for worsened outflow obstruction by the transvalvular MCS, the Impella CP was rapidly weaned and removed 36 hours after device placement, with improvement in hemodynamics: CO/CI 5.7 L/min, 2.8L/min/m
2. The patient was weaned off remaining inotropic support within two days of device explant, and discharged without complications. Upon hospital discharge, the patient elected to forego TAVR and was bridged to palliative care.
Discussion
Placement of an Impella CP is contraindicated in AS with an AV area less than 0.6 cm
2. In our case, while the Impella CP allowed for hemodynamic support and LV unloading in a patient needing high risk coronary intervention in the setting of AMI with CS, the device further deformed the stenotic aortic valve and added to outflow obstruction, impeding native CO recovery and contributing to significant hemolysis. Alternative MCS was either unavailable at this institution (TandemHeart, TandemLife, Pittsburgh, PA), or contraindicated due to severe PAD (intra-aortic balloon pump) or need for systemic anticoagulation (veno-arterial extracorporeal membrane oxygenation). Nonetheless, the Impella CP was beneficial in this patient’s initial recovery, and serial invasive hemodynamics were critical in the timing of device removal.