Introduction
This blog is intended for physicians and staff seeking to hone their skills on Impella. This is part one of a two part blog. I will post a follow up blog that has considerations for advanced caregivers in the next few weeks.
Currently, the FDA has approved the Impella catheter for use in patients in cardiogenic shock and for patients undergoing unprotected left main PCI. I have been using Impella since 2009 and have seen the use of Impella steadily increase. The initial iteration of the device had an extremely complicated set-up and maintenance. The console screen was a third of the size of the current console screen and displayed a green background with black wave-forms and text (basically a big 1990's Texas Instrument calculator). Now the console display is much more user friendly, the set-up has easy to follow steps and the pressure wave-forms are much clearer to read. I can honestly say without reservations that several of my patients would not have made it to discharge without this device.
I still have a vivid memory of being called into the hospital at 3 am when a patient's left main closed down acutely in the CVICU. A Cardiothoracic Surgeon was standing at the bedside attending to the patient and explained to the team that he could not take the patient to surgery because of the patient's decompensated state. We rushed the patient to the cath lab and quickly placed the Impella. After the Impella was in place, the patient who I did not expect to survive, became completely stable and the cardiologist was able to stent his left main. It is moments like these that make working in the Cath Lab feel most rewarding. It makes you feel like you are on the cutting edge, forging the way for future technologies that will help improve the world. After reading this blog I hope you gain some knowledge to better take care of your patients. Enjoy!
Part One: The Basics
The Impella catheter is available in 2 sizes; 2.5 and CP. The 2.5 catheter supplies about 2.3 liters per minute of cardiac output and the CP provides about 3.2 liters of blood flow per minute of cardiac output. To know which size is right for the patient there is a simple rule; place the largest catheter that you can that won't cause limb ischemia. The outer diameter of the 2.5 catheter is 13.5 French and the outer diameter of the CP is 14 French. To make a final decision as to which catheter to use, your provider will need to shoot an angiogram of the blood vessels of the groin to see if there is enough space to place the catheter without obstructing blood flow down the leg.
The first thing you should know about the Impella is that it is a jet ski tethered to the groin by a two foot rope. The front end of the jet ski is pointed at the apex of the heart and is curled into the shape of a pig's tail. Just distal to the pig tail is the intake cage which should be positioned 3.5 cm from the aortic valve into the left ventricle of the heart. Just above the aortic valve and distal to the intake cage is the outlet cage. In between the intake and outtake cages lies a tube from which the blood flows from the left ventricle, passes over the aortic valve, and into the aorta. Distal to the outlet cage is the motor which houses a small propeller. To be exact, it is not a propeller at all but more accurately resembles an Archimedes screw. This screw is able to rotate and pull blood through the catheter by the use of rotating magnets. The magnets ensure that there is no friction present as the screw rotates to lyse blood cells and cause hemolysis. Just distal to the motor housing you will see a small hole. This is where you will get your arterial waveform (red colored placement signal on the Impella Controller). The transducer for the arterial waveform is housed in the grey part of the catheter that is outside the body. The Impella catheter autozero's itself when you go through the start up steps.
At this point I would like the reader to note that there is only a few millimeters between the outlet cage and the pressure monitor. This is extremely important since the aortic valve leaflets will be opening and closing over the catheter. If the Impella is placed too deep into the left ventricle the aortic valve leaflets could be opening and closing over the outlet cage but not over the more distal pressure monitor. This will make the placement signal look nominal but will result in the turbulent flow of blood hitting the aortic valve leaflets causing hemolysis. Clinically this will result in a decrease of the patient's hemoglobin. That being said, a 2 to 3 point drop in hemoglobin for any patient with an Impella in place for 24 hours is common.
Luckily there is an easy way to counteract this occurrence. Obtain a trans-thoracic echo with a cardiologist at the bedside and in a parasternal long axis view carefully pull the catheter back. The majority of patients I have taken care of needed the Impella to be pulled back the next day if not immediately after transport and/or re-positioning of the patient. Be aware that the Impella has a tendency to jump backwards suddenly so be extremely careful when re-positioning the catheter at bedside.
Remember the Impella is suctioning out the left ventricle of the heart like a Yankauer suction. Unless there is something catastrophic going on, the Jet Ski will always drive itself deeper into the left ventricle of the heart. This phenomenon is exacerbated over time by the heat of the body softening up the catheter, which can further help the Jet Ski drive to the apex of the heart. For Cath Lab staff, you always want to remind your cardiologist to pull the slack out of the aorta. I will provide a picture below that will illustrate what I mean by this.
In order to monitor the proper positioning and performance of the catheter, caregivers will be monitoring pressure waveforms that display on the Impella controller console. The waveform interpretations can be found in the manual. Impella provides a 24 hour hotline service if you have any questions or need help changing out the purge solution. Your Impella representative should have taped the Impella hotline number somewhere on the Impella Controller. If you have any downtime while you are taking care of the patient I would suggest calling this number. I have always found the people that run the hotline to be engaging and incredibly informative.
I will go over an in-depth explanation of how to interpret the Impella wave-forms and advanced considerations for managing the device in a future blog. Thanks for reading and see you next time!
This blog is intended for physicians and staff seeking to hone their skills on Impella. This is part one of a two part blog. I will post a follow up blog that has considerations for advanced caregivers in the next few weeks.
Currently, the FDA has approved the Impella catheter for use in patients in cardiogenic shock and for patients undergoing unprotected left main PCI. I have been using Impella since 2009 and have seen the use of Impella steadily increase. The initial iteration of the device had an extremely complicated set-up and maintenance. The console screen was a third of the size of the current console screen and displayed a green background with black wave-forms and text (basically a big 1990's Texas Instrument calculator). Now the console display is much more user friendly, the set-up has easy to follow steps and the pressure wave-forms are much clearer to read. I can honestly say without reservations that several of my patients would not have made it to discharge without this device.
I still have a vivid memory of being called into the hospital at 3 am when a patient's left main closed down acutely in the CVICU. A Cardiothoracic Surgeon was standing at the bedside attending to the patient and explained to the team that he could not take the patient to surgery because of the patient's decompensated state. We rushed the patient to the cath lab and quickly placed the Impella. After the Impella was in place, the patient who I did not expect to survive, became completely stable and the cardiologist was able to stent his left main. It is moments like these that make working in the Cath Lab feel most rewarding. It makes you feel like you are on the cutting edge, forging the way for future technologies that will help improve the world. After reading this blog I hope you gain some knowledge to better take care of your patients. Enjoy!
Part One: The Basics
The Impella catheter is available in 2 sizes; 2.5 and CP. The 2.5 catheter supplies about 2.3 liters per minute of cardiac output and the CP provides about 3.2 liters of blood flow per minute of cardiac output. To know which size is right for the patient there is a simple rule; place the largest catheter that you can that won't cause limb ischemia. The outer diameter of the 2.5 catheter is 13.5 French and the outer diameter of the CP is 14 French. To make a final decision as to which catheter to use, your provider will need to shoot an angiogram of the blood vessels of the groin to see if there is enough space to place the catheter without obstructing blood flow down the leg.
The first thing you should know about the Impella is that it is a jet ski tethered to the groin by a two foot rope. The front end of the jet ski is pointed at the apex of the heart and is curled into the shape of a pig's tail. Just distal to the pig tail is the intake cage which should be positioned 3.5 cm from the aortic valve into the left ventricle of the heart. Just above the aortic valve and distal to the intake cage is the outlet cage. In between the intake and outtake cages lies a tube from which the blood flows from the left ventricle, passes over the aortic valve, and into the aorta. Distal to the outlet cage is the motor which houses a small propeller. To be exact, it is not a propeller at all but more accurately resembles an Archimedes screw. This screw is able to rotate and pull blood through the catheter by the use of rotating magnets. The magnets ensure that there is no friction present as the screw rotates to lyse blood cells and cause hemolysis. Just distal to the motor housing you will see a small hole. This is where you will get your arterial waveform (red colored placement signal on the Impella Controller). The transducer for the arterial waveform is housed in the grey part of the catheter that is outside the body. The Impella catheter autozero's itself when you go through the start up steps.
At this point I would like the reader to note that there is only a few millimeters between the outlet cage and the pressure monitor. This is extremely important since the aortic valve leaflets will be opening and closing over the catheter. If the Impella is placed too deep into the left ventricle the aortic valve leaflets could be opening and closing over the outlet cage but not over the more distal pressure monitor. This will make the placement signal look nominal but will result in the turbulent flow of blood hitting the aortic valve leaflets causing hemolysis. Clinically this will result in a decrease of the patient's hemoglobin. That being said, a 2 to 3 point drop in hemoglobin for any patient with an Impella in place for 24 hours is common.
Luckily there is an easy way to counteract this occurrence. Obtain a trans-thoracic echo with a cardiologist at the bedside and in a parasternal long axis view carefully pull the catheter back. The majority of patients I have taken care of needed the Impella to be pulled back the next day if not immediately after transport and/or re-positioning of the patient. Be aware that the Impella has a tendency to jump backwards suddenly so be extremely careful when re-positioning the catheter at bedside.
Remember the Impella is suctioning out the left ventricle of the heart like a Yankauer suction. Unless there is something catastrophic going on, the Jet Ski will always drive itself deeper into the left ventricle of the heart. This phenomenon is exacerbated over time by the heat of the body softening up the catheter, which can further help the Jet Ski drive to the apex of the heart. For Cath Lab staff, you always want to remind your cardiologist to pull the slack out of the aorta. I will provide a picture below that will illustrate what I mean by this.
In order to monitor the proper positioning and performance of the catheter, caregivers will be monitoring pressure waveforms that display on the Impella controller console. The waveform interpretations can be found in the manual. Impella provides a 24 hour hotline service if you have any questions or need help changing out the purge solution. Your Impella representative should have taped the Impella hotline number somewhere on the Impella Controller. If you have any downtime while you are taking care of the patient I would suggest calling this number. I have always found the people that run the hotline to be engaging and incredibly informative.
I will go over an in-depth explanation of how to interpret the Impella wave-forms and advanced considerations for managing the device in a future blog. Thanks for reading and see you next time!
Comments
Post a Comment