Artificial heart

Introduction to Heart Disease

• According to the National Center for Chronic Disease Prevention, cardiovascular disease causes 1 million American deaths annually.
• Over 61 million Americans suffer from cardiovascular disease.
• There are over 6 million hospitalizations each year due to cardiovascular disease.
• Atherosclerosis in the aorta or coronary vessels are major causes of cardiac pathologies.
• Laser ablation or balloon catheter expansion alleviates coronary artery blockages and/or blockages in the aorta.
• Stents are often placed in a coronary vessel after blockage removal.
• Extensive surgery with transplanted veins or artificial vessels bypasses blockages that cannot be removed.
• A heart transplant is an option when the heart cannot be adequately repaired.
• Insufficient donor hearts are available due to the vast number of cases and the need for blood and tissue typing.
• A ventricular assist device (VAD) is a mechanical assist pumping system that serves as a stopgap mechanism.

Ventricular Assist Device (VAD)

• VADs are mechanical pumps that replace or assist the function of damaged ventricles, restoring normal blood flow.
• An LVAD (left ventricular assist device) is used when the left heart is being assisted.
• An RVAD is used when the right heart is to be assisted.
• Two devices are used in biventricular assist mode (BiVAD).
• When the left ventricle contracts (systole), blood flows into the VAD pump.
• When the heart relaxes (diastole), the left ventricle fills with blood, and the blood in the device is pumped into the aorta.
• VADs support patients in postcardiotomy recovery, and also assists as a bridge to transplantation.

Heartmate II LVAD

• The HeartMate II LVAS is an axial-flow, rotary left ventricular assist system.
• The Left Ventricular Assist Device (LVAD) is designed for long-term implantation and generates flows up to 10 liters per minute (lpm).
• Connection to the circulation of the LVAD, is achieved via an inflow conduit and outflow graft attached to the left ventricle and aorta.
• The HeartMate II LVAD uses a rotary blood pump to generate flow and assist the left ventricle.
• The artificial ventricle provides blood pressures and flows that are pulsatile, similarly to the natural, left ventricle.

Heartmate II LVAD Motor and Rotor

• The LVAD contains an electric motor that generates torque to drive the rotor.
• The motor operates with a magnetic field that spins a permanent magnet within the rotor, using the rotary motion to pump blood.
• The motor's rotor is a permanent magnet located inside a thin-walled, titanium duct measuring 12 mm in diameter.
• A magnetic field produces rotary motion and torque, which initiates blood flow.
• Three blades on the rotor impart kinetic energy to the flow field in the form of velocity.

Heartmate II LVAD Percutaneous Lead and System Controller

• The motor lead extends from the implanted LVAD through the skin to the external environment.
• DC power and control signals are carried to the LVAD via this lead.
• The LVAD is powered by two batteries through the system controller.
• A third power source is used in emergencies.
• The system controller:
  • Controls motor speed and power
  • Performs diagnostic monitoring
  • Provides hazard and advisory alarms
  • Records and stores events in memory
  • Transfers system performance data to the system monitor and display module

Heartmate II LVAD Operating Modes, Diagnosis, and Complications

• The Heartmate operates in two primary modes: Fixed Speed and Auto Speed control.
• In Fixed Speed mode, the device operates at a constant speed.
• In Auto Speed control mode, the pump speed varies to optimize flow in response to changes in the amount of flow pulse and also calculated by the pump.
• Diagnostic methods: Echocardiography and exercise test
• Complications: Bleeding, infection, thrombus formation, right ventricle failure, and device malfunction.

Total Artificial Heart

• The Total Artificial Heart replaces both failing heart ventricles and the four heart valves.
• The left and right failing ventricles are removed.
• The four native heart valves are removed.
• The atria, aorta, and pulmonary artery remain intact.
• Quick connects are sewn into the atria, aorta, and pulmonary artery.
• The Total Artificial Heart is implanted and attached via four quick connects.

Total Artificial Heart Criteria

• The total artificial heart must fit into the chest cavity and connect to atria, pulmonary artery, and aorta quickly.
• It should provide an adequate blood flow of 8 – 10 liters/min.
• Deoxygenated blood must be sent to the lungs and oxygenated blood to the body.
• Adequate warning must be provided if problems arise or if the device is going to fail.
• Blood flow should increase/decrease based on patient activity level.
• The device should not evoke an immune response, and there should be no wires or tubes that penetrate the skin.
• It should not produce blood clots or damage red blood cells.
• The artificial heart should ideally have pulsatile blood flow

Jarvik-7 Artificial Heart

• The "Jarvik-7" artificial heart, introduced in 1982, is named after its designer, Robert K. Jarvik, an American physician.
• The Jarvik-7 functions like a natural heart, having two pumps (like ventricles) that push blood from inlet to outlet valve.
• It requires an external power supply.
• The Jarvik-7 pump consists of a polycarbonate case surrounding a flexible polyurethane sac.
• The space between them allowed high-pressure air ("systolic drive pressure") to collapse the blood-containing sac, causing systolic ejection.
• A small vacuum pressure ("diastolic pressure") pulled the sac toward the casing, causing diastolic filling.
• The pumps receive power through a large external console that pushes air through percutaneous tubing.
• A heavy power console, located seven feet away from the patient, is used to adjust the patient's heart rate and cardiac output.

AbioCor Artificial Heart

• The Abiocor is a quiet, pulsatile device mimicking the natural heart's contract/relax rhythm, creating a pulse.
• The Abiocor is designed to allow patients to remain mobile and continue a productive lifestyle.
• It can provide up to 8 liters/min of blood to the lungs and body.
• It is designed with two chambers for pumping deoxygenated blood to the lungs and oxygenated blood to the body.
• An internal controller monitors operation and also increases/decreases blood flow based on blood oxygen levels.
• Materials are inert to the immune system.
• The system is completely contained within the chest, and there are no wires or tubing through the skin.
• It is made of special materials and has a special pump design to prevent clots and RBC damage.
• Pumping alternates between chambers and that creates pulsatile blood flow.
• The Abiocor heart contains: Internal pumping unit, internal rechargeable battery, internal controller, internal TET system, external TET system, external battery pack, and external console.

AbioCor Components

• Implanted battery: powers the controller and thoracic unit, continuously charged through the skin by the external TET (powered by console or external battery).
• Implanted Controller: manages the cardiac output rate of the thoracic unit for necessary blood flow and exchanges information with the console to trigger alarms.
• Implanted TET: receives electrical energy, in the form of radio waves, through the skin from the external TET.
• Console: powers the system through the implanted and external TET and also uses radio waves to send commands via the RF Antenna to the implanted Controller, receiving information about the thoracic unit's function and notifying the patient with alarms.
• External TET: transfers energy from the console to the implanted components through the implanted TET, placed over the implanted TET's location.
• External battery: provides energy to the implanted components in the absence of AC power.
• Thoracic unit: consists of two blood pumps alternating to pump blood to the lungs and body and has four valves snapped onto the aorta, pulmonary artery, left atrium, and right atrium.
• Pump: the hydraulic pump in the artificial heart's center pumps a fluid back and forth between two membranes, forcing blood alternately out of the left and right chambers.

Reasons for Heart Substitute Failure

• Immune response “rejects” transplant
• Tubes and wires passing through the skin cause infection
• Formation of clots
• Damage to red blood cells
• Device malfunction