Ventricular Assist Device

Ventricular Assist Device

A Ventricular assist device, or VAD, is a mechanical circulatory device that is used to partially or completely replace the function of a failing heart. Some VADs are intended for short term use, typically for patients recovering from heart attacks or heart surgery, while others are intended for long term use (months to years and in some cases for life), typically for patients suffering from congestive heart failure.

VADs need to be clearly distinguished from artificial hearts, which are designed to completely take over cardiac function and generally require the removal of the patient's heart.

VADs are designed to assist either the right (RVAD) or left (LVAD) ventricle, or both at once (BiVAD). Which of these types is used depends primarily on the underlying heart disease and the pulmonary arterial resistance that determines the load on the right ventricle.

LVADs are most commonly used, but when pulmonary arterial resistance is high, right ventricular assistance becomes necessary. Long term VADs are normally used to keep patients alive with a good quality of life while they wait for a heart transplantation (known as a "bridge to transplantation"). However, LVADs are sometimes used as destination therapy and sometimes as a bridge to recovery.

In the last few years, VADs have improved significantly in terms of providing survival and quality of life among recipients.



The pumps used in VADs can be divided into two main categories - pulsatile pumps, that mimic the natural pulsing action of the heart, and continuous flow pumps.

Pulsatile VADs use positive displacement pumps. In some of these pumps, the volume occupied by blood varies during the pumping cycle, and if the pump is contained inside the body then a vent tube to the outside air is required.

Continuous flow VADs normally use either centrifugal pumps or an axial flow pump. Both types have a central rotor containing permanent magnets. Controlled electric currents running through coils contained in the pump housing apply forces to the magnets, which in turn cause the rotors to spin. In the centrifugal pumps, the rotors are shaped to accelerate the blood circumferentially and thereby cause it to move toward the outer rim of the pump, whereas in the axial flow pumps the rotors are more or less cylindrical with blades that are helical, causing the blood to be accelerated in the direction of the rotor's axis.

An important issue with continuous flow pumps is the method used to suspend the rotor. Early versions used solid bearings; however, newer pumps, some of which are approved for use in the EU use either electromagnetic or hydrodynamic suspension. These pumps contain only one moving part.


The early VADs emulated the heart by using a "pulsatile" action where blood is alternately sucked into the pump from the left ventricle then forced out into the aorta. Devices of this kind include the HeartMate IP LVAS, which was approved for use in the US by the FDA in October 1994. These devices are commonly referred to as first generation VADs.

More recent work has concentrated on continuous flow pumps, which can be roughly categorized as either centrifugal pumps or axial flow impeller driven pumps. These pumps have the advantage of greater simplicity resulting in smaller size and greater reliability. These devices are referred to as second generation VADs. A side effect is that the user will not have a pulse, or that the pulse intensity will be seriously reduced, and will need to carry documentation saying that the lack of a pulse does not mean that they are dead.

Third generation VADs suspend the impeller in the pump using either hydrodynamic or electromagnetic suspension, thus removing the need for bearings and reducing the number of moving parts to one.

Another technology undergoing clinical trials is the use of trans cutaneous induction to power and control the device rather than using percutaneous cables. Apart from the obvious cosmetic advantage this reduces the risk of infection and the consequent need to take preventative action. A pulsatile pump using this technology has CE Mark approval and is in clinical trials for US FDA approval.

A very different approach in the early stages of development is the use of an inflatable cuff around the aorta. Inflating the cuff contracts the aorta and deflating the cuff allows the aorta to expand - in effect the aorta becomes a second left ventricle. A proposed refinement is to use the patient's skeletal muscle, driven by a pacemaker, to power this device which would make it truly self contained. However a similar operation (cardiomyoplasty) was tried in the 1990s with disappointing results. In any case, it has substantial potential advantages in avoiding the need to operate on the heart itself and in avoiding any contact between blood and the device. Interestingly this approach involves a return to a pulsatile flow.

Studies and outcomes

Recent developments

* In July 2009 in England, surgeons removed a donor heart that had been implanted in a toddler next to her native heart, after her native heart had recovered. This technique suggests mechanical assist device, such as an LVAD, can take some or all the work away from the native heart and allow it time to heal.

* In July 2009, 18-month follow-up results from the HeartMate II Clinical Trial concluded that continuous-flow LVAD provides effective hemodynamic support for at least 18 months in patients awaiting transplantation, with improved functional status and quality of life. (see below).

* Heidelberg University Hospital reported in July 2009 that the first HeartAssist5, known as the modern version of the DeBakey VAD, was implanted there. The HeartAssist5 weighs 92 grams, is made of titanium and plastic, and serves to pump blood from the left ventricle into the aorta.

* A phase 1 clinical trial is underway (as of August 2009), consisting of patients with coronary artery bypass grafting and patients in end-stage heart failure who have a left ventricular assist device. The trial involves testing a patch, called Anginera(TM) that contains cells that secrete hormone-like growth factors that stimulate other cells to grow. The patches are seeded with heart muscle cells and then implanted onto the heart with the goal of getting the muscle cells to start communicating with native tissues in a way that allows for regular contractions.

* In September 2009, a New Zealand news outlet, Stuff, reported that in another 18 months to two years, a new wireless device will be ready for clinical trial that will power VADs without direct contact. If successful, this may reduce the chance of infection as a result of the power cable through the skin.

* The National Institutes of Health (NIH) awarded a $2.8 million grant to develop a "pulse-less" total artificial heart using two VADS by Micromed, initially created by Michael DeBakey and George Noon. The grant was renewed for a second year of research in August 2009. The Total Artificial Heart was created using two HeartAssist5 VADs, whereby one VAD pumps blood throughout the body and the other circulates blood to and from the lungs.

* HeartWare International announced in August 2009 that it had surpassed 50 implants of their HeartWare Ventricular Assist System in their ADVANCE Clinical Trial, an FDA-approved IDE study. The study is to asses the system as bridge-to-transplantation system for patients with end-stage heart failure. The study, Evaluation of the HeartWare LVAD System for the Treatment of Advance Heart Failure, is a multi-center study that started in May 2009.

Information above was compiled from Wikipedia

If you or a loved one have been affected by a Faulty Ventricular Assist Device and/or experienced cardiac device malfunctions, failure or injury, you should contact us immediately. You may be entitled to compensation by filing a lawsuit.