Ventricular Assist Devices are a type of Mechanical Circulatory Support (MCS) devices that are critical for people suffering from Congestive Heart Failure. They help the patient manage his/her symptoms better while living a longer, better-quality life. VADs have been around for over sixty years, and have evolved technically, becoming more reliable and efficient in cost, power-consumption and cardiac function, with time. In this article, we will learn more.
Congestive Heart Failure (CHF) is a heart condition in which the heart function deteriorates progressively with time. The condition is a lot more common than previous estimated. Risk Factors for developing this condition include coronary artery disease (CAD), hypertension, myocarditis, arrhythmias (abnormal heart-rhythm), valvular disease, obesity and type-2 diabetes. In end-stage CHF persons, heart transplantation used to be the only option in the past. However, a serious dearth of cadaver hearts makes this option unviable.
Advanced medication can restore heart function in the short-term, and also relieve symptoms. But they are not enough to restore heart function in the long-run. That is why, over time, Mechanical Circulatory Support (MCS) devices, also called Cardiac Assist Devices, have evolved to meet this demand. In an earlier article, we have covered the practice of using MCS devices. We also mentioned that MCS devices are of two types: temporary MCS for short-term use and durable MCS for long-term use. Ventricular Assist Devices are of the durable type, and extremely popular today.
Ventricular Assist Devices (VADs) are tiny pumps that are surgically implanted by heart specialists in a person’s body. They help circulate blood from one or two chambers of the heart, to rest of the body. Accordingly, there are many types of VADs but they can be broadly classified as follows:
As mentioned earlier, VADs are useful for people who are awaiting a heart transplant, or people not suited for a transplant, but both of whom require permanent support for heart function. Accordingly, they are used as:
Understanding the types of VADs will also require tracing the history of VADs. VADs may appear to be a recent techno-medical innovation but they actually have a long history. In 1812, a French physician called Le Gallios demonstrated that it is possible to maintain blood circulation using an external pump. Thereafter, for over hundred years, various experiments were conducted in Europe primarily and the US, to create such pumps. Major breakthroughs happened in the 1960s decade when various heart doctors in the US and Europe were successful in replacing the function of any one chamber of the heart, using external devices. From then, till date, we have had three generations of VADs. While some of the older models are still in use, some have been discontinued. Today, a lot of high-tech innovation is happening in this area.
In these, the native heart cycle is replicated by generating pulsatile blood-flow in pulses, that synchronize with the natural lub-dub beating of the heart. The flow is maintained using a diaphragm, and artificial valves that are unidirectional. These were heavy and bulky, which limited the person’s mobility.
LVAD: In this, blood is drawn from the top of the left ventricle and pumped into the aorta. This ensures the body gets oxygen-rich blood, and also unloads the left ventricle, which reduces pressure on the heart function. Commercial models include Novacor LVAS, HeartMate I and Thoratec PVAD.
RVAD: There are various heart conditions that require RVAD implant, and one of them is LVAD implant. Nearly half the people who have had an LVAD implant will sooner or later require RVAD implant too. In RVAD, blood is drawn from the top of the right ventricle and pumped into the pulmonary artery that carries impure blood to the lungs.
BiVAD: These balance the blood-flow in both ventricles of the heart, which acts as a life-saver. These were bulky, because of a large pneumatic driver that was required. Commercial models included AbioMed BVS5000, Berlin Heart EXCOR and Medos HIA-VAD.
TAH: These were designed to completely replace the heart function. The first such human TAH implant was done in 1969 but reliable TAHs have been built from 1982 onwards. Commercial models include CardioWest (SynCardia) which later became Jarvik 7 and Abiocor from AbioMed.
First-generation pulsatile pumps were marked by bulky size, heavy weight, high noise, low durability and malfunction issues. This helped the 2nd generation VADs to evolve. In this, the blood-flow is not pulsatile but continuous. This uses an axial pump with no valves, and a variable magnetic field. The magnetic field spins an impeller rapidly, with a continuous flow that is directed outward and in parallel to the axis of rotation.
These pumps offered the person better mobility and quality of life. However, they still required external power-sources and the person having to undergo frequent, anti-coagulation therapies to minimize the risk of blood-clots.
Popular commercial models included HeartMate II, Hemopump (Medtronic), Incor (Berlin Heart), DeBakey VAD (Micromed), Impella (Abiomed), HeartAssist-5 (Reliant Heart) and Jarvik 2000 (Jarvik Heart).
These VADs use continuous-flow, centrifugal pumps where the outflow is directed perpendicular to the axis of rotation. The impeller moves with magnetic or hydrodynamic levitation with the bearings being the non-contact type. These are smaller in size, emit less noise, cause less infection and show reduced risk of blood-clots, compared to 2nd generation VADs. This way, they offer a better quality of life.
Commercial models include HeartWare HVAD (HeartWare), DuraHeart (Terumo Heart), HeartMate III (Thoratec), Levacor (World Heart), Incor (Berlin Heart) and CentriMag (Thoratec).
Extracorporeal membrane oxygenation (ECMO) for Short-term Circulatory Support: An ECMO device uses a mechanical pump that is extracorporeal (stationed outside the body). It is capable of oxygenating the blood as well as circulation, so it is used as a BTR, BTT and MCS device. However, this is only suitable for short-term use due to certain side-effects.
AbioMed’s Impella Catheter: This is an intravascular blood-pump of the microaxial type. The inlet is placed in the left ventricle and the outlet in the ascending aorta. Efficacy of this solution depends on the proper placement of the catheter-based pumps. An Automated Impeller Controller monitors and controls the entire device. There are various models depending on how much blood-flow must be achieved. These can be used for a maximum duration of one month.
Pneumatic intra-aortic balloon pumps (IABP): These are internal devices placed inside the descending aorta. They operate by counter-pulsation. The balloon is inflated during diastole (filling-up) of the ventricle and deflated during the systole (emptying) of the ventricle. They come with a Control Unit that offers either Auto mode where the arterial-pressure waveforms are used as the guideline for settings. Or, the second option, which is Manual mode where the settings can be user-defined. Popular commercial models include the Arrow IAB Catheters from Teleflex.
Thoractec’s CentriMag acute circulatory support system: This is an external VAD that is used for temporary or short-term cardiac support. It can support left, right and both ventricles. It is a continuous-flow, magnetically-levitated centrifugal pump, without bearings or seals for a contact-free operation.
HeartMate III: This was an improvisation of the HeartMate II platform. It comes with a modular driveline (the cables and connections), a power-unit interface that is mobile, the absence of surgical pockets, reduced power consumption, and a magnetically-levitated core system called Full MagLev that is very unique.
HeartWare HVAD: This device is known for its small size and small canula which minimize invasiveness and accelerate recovery, along with offering better clinical outcomes. The impeller is of a unique, wide-blade type, a hybrid suspension system that is of magnetic-hydrodynamic type to ensure no mechanical contact inside the pump, while the pump is of a dual-motor type designed for higher reliability and efficiency.
SynCardia CardioWest TAH (SynCardia): This is the world’s first Total Artificial Heart (TAH) that is approved widely for commercial use. It delivers pulsatile flow, comes with artificial ventricles that are connected to the aorta and pulmonary artery, and blood-flow happens using a pneumatically-driven diaphragm as well as unidirectional valves.
When faced with reduced heart function or advanced heart disease, advanced medical intervention is crucial. Ventricular Assist Devices (VAD) offer a life-saving solution, boosting heart power and improving quality of life. There are several types of these devices, catering to different needs and conditions, with some serving as a bridge for those waiting for heart transplants. Kauvery Hospital, with branches across Tamil Nadu in Chennai, Hosur, Salem, Tirunelveli and Trichy, is among the leading hospitals in India equipped with state-of-the-art technology for the implantation and management of VADs. Their highly skilled team of heart specialists provides comprehensive care for heart failure patients, offering hope and improved quality of life.
A Ventricular Assist Device (VAD) is a mechanical pump implanted in the body to help circulate blood from the heart to the rest of the body, supporting heart function in patients with severe heart failure.
VADs are used to support heart function in patients awaiting a heart transplant, those not eligible for a transplant, and to provide long-term cardiac support, improving quality of life and longevity.
There are several types of VADs including Left Ventricular Assist Devices (LVAD), Right Ventricular Assist Devices (RVAD), Biventricular Assist Devices (BiVAD), and Paediatric VADs, each serving different needs based on the heart’s requirements.
First-generation pulsatile pumps replicate the natural beating of the heart by generating pulsatile blood flow, using a diaphragm and unidirectional artificial valves, but they are often bulky and heavy.
Third-generation VADs use continuous-flow centrifugal pumps with impellers that operate with magnetic or hydrodynamic levitation, offering smaller size, reduced noise, lower infection risk, and improved quality of life.
Kauvery Hospital, with its branches across Tamil Nadu, provides state-of-the-art technology and a highly skilled team of heart specialists for the implantation and management of VADs, offering comprehensive care for heart failure patients.
Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai (Alwarpet & Vadapalani), Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.
Chennai Alwarpet – 044 4000 6000 • Chennai Vadapalani – 044 4000 6000 • Trichy – Cantonment – 0431 4077777 • Trichy – Heartcity – 0431 4003500 • Trichy – Tennur – 0431 4022555 • Hosur – 04344 272727 • Salem – 0427 2677777 • Tirunelveli – 0462 4006000 • Bengaluru – 080 6801 6801
