Long-Term Cardiac Assist Devices

Long-Term Cardiac Assist Devices

Cardiac assist devices are mechanical pumps that work in tandem with the heart to improve pumping efficiency and keep the blood flowing with enough force throughout the body. Because the chambers of the heart that are responsible for pumping are called the ventricles, cardiac assist devices are often referred to as ventricular assist devices. They've come a long way since Michael E. DeBakey designed and implanted the first ventricular assist device in 1966.

Depending on which chamber they are designed to help, cardiac assist devices can be left ventricular assist devices, right ventricular assist devices, or biventricular pacemakers, or CRT devices, (which pace both the left and the right ventricles, thus coordinating the beating of the heart). Unlike artificial hearts, assist devices do not require removal of the heart.

A Bridge to Recovery -- or Transplant 

Patients may be eligible for a cardiac assist device if they're not improving with other treatments. Cardiac assist devices can be used for short-term support (defined as under a week) -- for example, during surgery or in the recovery period just after surgery. Longer-term implantation occurs when a cardiac assist device is used as a so-called "bridge to transplant." In this case, the cardiac assist device keeps the patient alive while awaiting the availability of a compatible donor heart.

As a "bridge to recovery," long-term use of a cardiac assist device may be planned in hopes that the heart muscle will have a chance to heal and become strong enough to take back over the work of pumping. In these cases, the cardiac assist device can then be removed.

When recovery isn't expected, and where transplantation is not planned, a cardiac assist device is considered "destination therapy," or permanent placement. Because donor hearts are so hard to get, and so many people die without ever receiving a needed heart transplant, there is hope that cardiac assist devices will continue to improve to the point that they become the first choice for patients with critical heart failure.

How They Work

The pump portion of a cardiac assist device can be surgically placed into the body (specifically, into the abdomen), set up outside of the body or partially implanted. The pump is attached by wires to a computerized control panel and to an external battery that serves as a power source. The computer allows customization of a variety of settings, such as pump rate. Wherever the patient goes, so must the device.

Some of the battery packs are designed to be small enough to be worn in a waist pack; others are pushed on a little cart about the size of a portable cooler. Some fully implanted cardiac assist devices have a tiny battery that is implanted along with the pump, which allows the individual to disconnect briefly from the larger power source, making it possible (for example) to shower untethered.

Because the most recent models have lighter, more portable power supplies, patients who receive cardiac assist devices can usually return home to live. New technology is also producing ever smaller, more efficient devices.

Decreasing Risks, Increasing Lifespans

Implantation requires open-heart surgery, and the highest rates of complication occur around the time of this operation. The most common complications of the surgery include infection, right heart failure and multi-organ failure. The new, smaller devices decrease these risks and others, including blood clotting within the tubes and the pump with ongoing use.

These improvements mean that patients who receive cardiac assist devices have a greater likelihood of a longer lifespan and a better quality of life. The latest studies suggest that survival with a cardiac assist device has improved greatly over time -- a paper from 2008 stated that over 86% of patients were still living one year after implantation, and over 82% were still alive five years after implantation.

Sources: