Mechanical circulatory support





In addition to standard cardiopulmonary bypass during cardiac surgery, there now are several options for longer-term mechanical circulatory support ranging from a simple intraaortic balloon pump to a total artificial heart. Some of these devices are used in the hospital setting because of the external components of the device and need for continuous monitoring, including the intraaortic balloon pump (IABP), percutaneous assist devices, and use of an external corporal membrane oxygenator (ECMO). Others are designed for long-term use in the outpatient setting, including implanted ventricular assist devices and a total artificial heart (TAH).



Fig 12.1


Although all forms of mechanical circulatory support return blood to arterial system, they differ with respect to site from which they draw blood. These differences underlie differences in their hemodynamic effects. Percutaneous axial flow devices (A) (Impella®) and durable ventricular devices (B) (surgically implanted LVAD) that take blood from the LV have similar physiology. Extracorporeal membrane oxygenation (ECMO) withdraws blood from right atrium or venous system and utilizes a blood gas exchange unit (C) . Percutaneous devices can also achieve LA sourcing of blood (without need for gas exchange unit) (D) (TandemHeart®). LA = left atrium/atrial; LV = left ventricle/ventricular.

(From Burkhoff D, Sayer G, Doshi D, Uriel N: Hemodynamics of mechanical circulatory support, J Am Coll Cardiol 66:2663–2674, 2015.)




CASE 12-1


Intraaortic balloon pump


An intraaortic balloon pump (IABP) may be positioned before surgery in patients with hemodynamic compromise or with critical coronary artery disease or may be placed at the end of the procedure to facilitate weaning from cardiopulmonary bypass in patients with severely impaired left ventricular systolic function. The catheter is inserted via a femoral artery, and positioned in the descending thoracic aorta, with the catheter tip just distal to the left subclavian artery.



Fig 12.2


IABP is positioned distal to left subclavian origin and inflates in diastole (A) , increasing aortic root and coronary perfusion, then deflates in systole (B) , reducing LV afterload. (C) Hemodynamic tracing of proximal aortic pressure at time of IABP activation shows reduction in systolic pressure and augmented diastolic pressure. Reduced aortic systolic pressure is an indicator of mechanical unloading of left ventricular pressure.

(A and B reproduced with permission from Jones HA, et al: J Invasive Cardiol 24(10):544–550, 2012. C reproduced with permission from Kapur NK, Esposite M: Hemodynamic support with percutaneous devices in patients with heart failure, Heart Fail Clin 11:215–230, 2015.)



Fig 12.3


Photograph of an intraaortic balloon pump (IABP), demonstrating tip and length of balloon that is placed in the descending aorta. IABP tip has a radiopaque marker to aid in positioning. Proximal end of catheter is off the image at left.



Fig 12.4


Chest radiograph demonstrating the tip of the IABP just distal to the aortic arch. Right heart catheter is also present.



Fig 12.5


This view of the aortic arch and left subclavian artery is obtained from a very high TEE position, with probe turned to patient’s left side and image plane rotated to about 90 degrees. This view is helpful for confirming correct positioning of the IABP, which will be seen if the tip is advanced too far into the aorta.



Fig 12.6


This view of the descending thoracic aorta reveals typical appearance in short-axis view (left) and long-axis view (right) of intraaortic balloon pump. In real time, the device is seen to pulsate in synchrony with the heartbeat. There are multiple reverberations from inflated balloon (red arrow).



Fig 12.7


Technique for determining position of the IABP. With balloon preferably suspended and descending thoracic aorta visualized in the long axis, operator withdraws probe until tip is in middle of sector, and places a finger where probe meets patient’s teeth (upper two images). Probe is slowly withdrawn with finger held in place until left subclavian artery is seen, at which point the operator stops and measures distance from finger to teeth ( lower two images ). (With the assistance of Heather Reed MD).




Comments


The purpose of an IABP is to improve both forward cardiac output in systole and coronary flow in diastole. The balloon inflates during diastole and deflates during systole, with timing based on an arterial pressure waveform and/or the electrocardiogram. Balloon inflation in diastole improves coronary artery blood flow, which occurs mainly in diastole, by increasing the coronary perfusion pressure. Balloon deflation in systole effectively decreases left ventricular afterload resulting in an increase in forward cardiac output.


An IABP is contraindicated in patients with significant aortic regurgitation, as diastolic balloon inflation increases the volume of backflow across the aortic valve.


Suggested reading




  • 1.

    De Silva K, Lumley M, Kailey B, et al: Coronary and microvascular physiology during intraaortic balloon counterpulsation, JACC Cardiovasc Interv 7:631–640, 2014.





CASE 12-2


External centrifugal pump devices


This patient was taken to the cardiac catheterization laboratory for placement of a TandemHeart® percutaneous assist device (Cardiac-Assist®, Pittsburgh, PA) for circulatory support after an acute myocardial infraction and percutaneous coronary intervention with acute heart failure.



Fig 12.8


Schematic of device. Oxygenated blood is removed from left atrium via multiorifice transseptal cannula (black arrow), and with use of centrifugal pump (red arrow) is delivered to a cannula in the femoral artery.

(From Myat A, Patel N, Tehrani S, et al: Percutaneous circulatory assist device for high-risk coronary intervention, J Am Coll Cardiol Interv 8:229–244, 2015. With permission.)



Fig 12.9


Transseptal puncture. Interatrial septum is first tented with needle (left), and then punctured (right). White arrows indicate puncture needle.



Fig 12.10


In left frame, cannula with color flow is seen to cross interatrial septum into LA. On right, cannula is seen in cross section.



Fig 12.11


Close-up of end of inflow cannula in left atrium. Multiple orifices are seen. Position of distal end of inflow cannula is important; if too close to interatrial septum, it may retract into right atrium causing flow of right atrial blood to device and significant shunt.



Fig 12.12


3D TEE of left atrium shows cannula crossing interatrial septum (red arrow). Multiorificed tip is indicated by black arrow.



Fig 12.13


On x-ray, position of LA cannula crossing interatrial septum to provide inflow into TandemHeart® is visible. This patient also has IABP with radiopaque tip in descending aorta, behind LA. In real time normal inflation–deflation of IABP can be appreciated.



Fig 12.14


In different case, this 50-year-old man with preexisting heart failure was brought to cath lab following major myocardial infarction. In real time, profound hypokinesis is seen in all major ventricular segments. Left ventricle is seen in transgastric short axis and long axis. Arrow indicates collection of pericardial effusion. In real time, ventricles are severely hypokinetic.



Fig 12.15


In same patient as seen in Fig 12.14 , TandemHeart® cannulae were placed and flow from LA to aorta was initiated. After initiating flow, significant echo contrast in left ventricle and aortic root was seen, which did not clear. This phenomenon was secondary to extremely low native left ventricular stroke volume. The arrow indicates pericardial fluid.



Fig 12.16


In same patient as Fig 12.14 , because of concern for risk of left-sided thrombosis, even with anticoagulation, patient was taken to OR where implanted left ventricular assist device was placed and percutaneous device removed. Arrow indicates inflow cannula to device.



Fig 12.17


Another example of support with TandemHeart® is this 57-year-old man who suffered right ventricular infarction resulting in cardiogenic shock. He was taken urgently to the cath lab where a right-sided TandemHeart® device was placed. Inflow cannula to the device, a multiorifice catheter similar to femoral venous cannula used for bypass, was placed via right internal jugular vein (left) . Outflow cannula to patient was placed via femoral vein, and through right atrium, tricuspid valve, and pulmonic valve into main PA (middle, arrows) thereby passing failing right ventricle.




Comments


Cardiac mechanical support with an external centrifugal pump devices or percutaneous axial flow assist device is primarily used for acute heart failure in the hospital setting where rapid recovery of ventricular function is likely, such as with a high-risk percutaneous coronary intervention. This approach also may be utilized for acute support, followed by placement of a device intended for longer term support or as a bridge to heart transplantation.


Suggested reading




  • 1.

    Kowalczyk AK, Mizuguchi KA, Couper GS, et al: Use of intraoperative transesophageal echocardiography to evaluate positioning of TandemHeart® percutaneous right ventricular assist, Anesth Analg 118:72–75, 2014.


  • 2.

    Kirkpatrick J: Cardiac assist devices: normal findings, device failure and weaning parameters. In Otto CM, editor: The Practice of Clinical Echocardiography, ed 5, Philadelphia, 2016, Elsevier.





CASE 12-3


Percutaneous axial flow assist devices


Newer percutaneous or centrally placed axial flow assist devices are available for temporary ventricular support (Impella®, Abiomed, Danvers, MA). Placement is retrograde through the aortic valve. These devices offer temporary support for a failing heart as a bridge to recovery, transplant decision, or a more durable device. They are also placed during some procedures such as high-risk percutaneous coronary intervention (PCI) or ventricular tachycardia ablation procedures.



Fig 12.18


Schematic shows device being passed retrograde through aortic valve. Inlet port to device is seen in left ventricle (white arrow) , and outflow port in ascending aorta (red arrow) .



Fig 12.19


On left, ventricular side of device (arrow) is seen passing through aortic valve, and on right, device is advanced to its final position. In order to ensure that outlet is positioned optimally just above aortic valve, inlet should be 3–4 cm on LV side of aortic annulus. Inlet is identified on echocardiography as discontinuity in parallel lines of cannula with echoes from cannula tip and pigtail visible more apically in LV chamber.



Fig 12.20


A model of the device (A) and an image from cardiac catheterization (B) illustrates the components of the device: The driveline that is attached to the motor housing, the inlet and outlet ports, and the cannula itself. The 2D TEE (C) shows flow in the device; the positions of the ports relative to the aortic valve can be ascertained as can the depth into the left ventricle. It is imperative that the outlet port (white arrow) be above the aortic valve. The 3D TEE (D) is a closer look at the outlet port (white arrow) and its relationship to the aortic annulus (black arrows) .



Fig 12.21


Modification of original Impella® allows use on right side of heart for up to 14 days, delivering 4 L/min of flow. Inflow comes from the right atrium, and outflow is delivered to the main pulmonary artery. These findings are illustrated in different patient with acute right heart failure. At left, high esophageal TEE shows cannula to be in pulmonary artery (arrow), and on right, color flow Doppler shows outflow to pulmonary artery.

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Jan 2, 2020 | Posted by in CARDIOLOGY | Comments Off on Mechanical circulatory support

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