Left Ventricular Assist Devices (LVADs)

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A left ventricular assist device (LVAD) is a surgically implanted, battery-driven pump designed to augment the pumping action of a diseased left ventricle that has become too weak from heart failure to function effectively on its own.

How Do LVADs Work?

Several types of LVAD devices have been developed. Most of them pull blood from a tube inserted into the left ventricle, then pump the blood through another tube inserted into the aorta.

The pumping assembly itself is usually placed beneath the heart, in the upper part of the abdomen. An electrical lead (a small cable) from the LVAD penetrates the skin. The lead attaches the LVAD to an external control unit and to the batteries that power the pump.

LVADs are entirely portable. The necessary batteries and controller devices are worn on a belt or chest strap. LVADs allow patients to be at home and to engage in many normal activities.

Evolution of LVADs

LVAD technology has evolved significantly since these devices were first used in the 1990s. Originally, LVADs attempted to reproduce pulsatile blood flow since it was assumed that a pulse would be necessary for normal body physiology.

However, any LVAD that generates a discrete pulse requires many moving parts, uses a lot of energy, and creates ample opportunity for mechanical failure. The first generation LVADs suffered from all of these problems.

It was soon recognized that people did just as well with continuous blood flow as with pulsatile flow. This allowed a second generation of LVADs to be developed that were smaller, had only one moving part, and required much less energy. These newer LVADs last much longer and are more reliable than the first generation devices.

HeartMate II and Jarvik 2000 are second generation, continuous-flow LVADs.

A third generation of LVADs is coming on line that are even smaller and are designed to last for 5 - 10 years. The HeartWare and the Heartmate III LVADs are third generation devices.

When Are LVADs Used?

LVADS are used in three clinical situations. In all cases, LVADs are reserved for patients who are doing poorly despite aggressive medical therapy.

1) Bridge to Transplant. LVADs can be used to support patients with severe chronic heart failure who are waiting for heart transplantation.

2) Destination Therapy. LVADs can be used as "destination therapy" in people with severe end-stage heart failure who are not candidates for transplantation (because of other factors such as age, kidney disease, or lung disease), and who have an extremely poor prognosis without mechanical support. In these patients, the LVAD is the treatment; there is little reasonable expectation that the LVAD can ever be removed.

3) Bridge to Recovery. In some patients with heart failure, insertion of an LVAD device can allow a damaged left ventricle to "rest" and to repair itself by “reverse remodeling.” Examples in which the underlying cardiac problem can sometimes improve with rest include heart failure after cardiac surgical procedures, or with major acute heart attacks, or with acute myocarditis.

In patients who fall into one of these categories, LVADs are often very effective in returning the amount of blood the heart pumps back to near-normal levels. This improvement usually reduces the symptoms of heart failure, especially dyspnea and severe weakness, significantly . It also can improve the function of other organs that are often effected by heart failure, such as the kidneys and liver.

Problems With LVADs

The safety of LVADs has been greatly improved over the years, and the companies that design them have worked very hard to shrink their size to make them suitable for small adults. But there are still many problems associated with LVADs.

These include:

  • LVADs require meticulous daily maintenance, and careful monitoring to make sure they are always attached to a good power source. So the patient - or family members - must be able to cope with the chronic demands that will be placed upon them.
  • Serious bloodstream infections still occur in up to 25% of patients with LVADs, and these infections are often fatal.
  • Significant bleeding problems occur in a substantial minority of patients.
  • The risk of stroke (from blood clots) is between 10% and 15% per year.

These problems are obviously very serious, so the decision to insert an LVAD is truly a monumental one. This decision should be taken only if early death appears to be the most likely outcome without one.

Whether to use an LVAD as "destination therapy" is a particularly difficult decision, because in that case, there is little hope of ever being able to remove the device. In the largest clinical trial conducted to date using LVADs as a destination therapy, only 46% of LVAD recipients were both alive and stroke-free at two years.

Even with the problems that remain with LVADS, these devices offer a realistic hope to many patients with end-stage heart failure who would have had no hope just a few years ago.

Birks EJ, George RS, Hedger M, et al. Reversal of severe heart failure with a continuous-flow left ventricular assist device and pharmacological therapy: a prospective study. Circulation 2011; 123:381.

Sources:

Rose, EA, Gelijns, AC, Moskowitz, AJ, et al. Long-term use of a left ventricular assist device for end-stage heart failure. N Engl J Med 2001; 345:1435.

Birks EJ, George RS, Hedger M, et al. Reversal of severe heart failure with a continuous-flow left ventricular assist device and pharmacological therapy: a prospective study. Circulation 2011; 123:381.

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