The use of acute mechanical circulatory support (AMCS) devices for patients with heart failure and/or Cardiogenic shock has grown exponentially. AMCS devices can be broadly categorized by their mechanism of action as pulsatile or rotary flow pumps. Rotary flow pumps can be further categorized as trans-valvular axial flow pumps or extracorporeal centrifugal pumps. For patients with heart failure or cardiogenic shock, the primary hemodynamic treatment objectives include: (1) providing circulatory support by increasing mean arterial pressure, (2) unloading cardiac workload by reducing left ventricular (LV) and/or right ventricular (RV) pressures and volumes, (3) increasing myocardial perfusion, and (4) facilitating decongestion of the venous system. Intra-aortic counter pulsation balloon pumps (IABPs) have remained a relatively low-cost treatment option for patients with decompensated heart failure, cardiogenic shock, and impaired coronary flow. The IABP is a catheter-mounted balloon that augments pulsatile blood flow by inflating during diastole, which displaces blood volume in the descending aorta and increases mean aortic root diastolic pressure, thereby potentially augmenting coronary perfusion. In contrast to counter-pulsation balloons, rotary flow pumps generate rotational kinetic energy, which increases blood flow. Trans-valvular axial-flow AMCS pumps for LV support are placed across the aortic valve and displace blood from the LV into the ascending aorta.

Extracorporeal centrifugal-flow pumps employ large bore arterial and/or venous cannulas to pump blood from one part of the body to another. These pumps include the Tandem Heart device and veno-arterial extracorporeal membrane oxygenation (VA-ECMO). VA-ECMO utilization has risen substantially in the last decade based on data from the Extracorporeal Life Support Organization. In contrast to VA-ECMO, by displacing blood from the left atrium, the Tandem-Heart device effectively reduces LV preload, thereby potentially reducing LV volume, wall stress, and workload, while increasing systemic mean arterial pressure and myocardial perfusion. The hemodynamic effects of VA-ECMO and Tandem Heart were evaluated in a swine model of acute myocardial injury. While the hemodynamic effects of existing AMCS platforms on cardiac physiology are well characterized the impact of AMCS devices on renal blood flow (RBF) and function remains poorly understood. In addition, non-pulsatile flow provided by VA-ECMO may not provide adequate renal blood flow, which has been demonstrated to be dependent on pulsatile flow. In a swine model comparing pulsatile and non-pulsatile cardiopulmonary bypass (CPB) support, renal blood flow measured by labelled radioactive microspheres appeared higher in the pulsatile group.

All existing studies exploring the interaction between AMCS and CRS have evaluated renal function through commonly used existing biomarkers (e.g., serum creatinine, BUN) and both invasive and non-invasive techniques of renal blood flow measurement. Potential novel renal biomarkers capable of early detection of AKI include Kidney Injury Marker 1 (KIM-1), Neutrophil Gelatinase-Associated Lipocalcin (NGAL), and Cystatin C (Cys C), among others. Ultimately, reliable renal biomarkers are necessary for assessing the complex interaction between cardiac and renal dysfunction. Predictive renal biomarkers capable of distinguishing between varying states of renal injury would potentially allow for early diagnosis and staging of cardio renal syndrome as well as aid in biomarker-guided utilization of AMCS.

Prevention and management of kidney injury across the spectrum of acute and chronic heart failure remain limited. Furthermore, the impact of existing AMCS devices on kidney function is poorly understood, yet evidence suggests each of these device based approach has a unique impact on kidney function. Innovative device-based approaches are emerging and focus primarily on modifying cardio-renal preload and afterload in heart failure. Given the direct impact of kidney function on clinical outcomes and the growing use of AMCS devices, more studies evaluating the optimal use of existing devices and the clinical utility of emerging devices are required.

Regards

Calvin Parker

Editorial Assistant

Journal of Nephrology and Urology