i bc27f85be50b71b1 (261 page)

832 AClITE CARE HANDBOOK FOR I'HYSICAL THERAPISTS

•

Refractory ventricular dysrhyrhmias

•

Anticipated heart transplantation

The ratio of heart beats to counterpulsations of the [ABP indicates the

amount of circulatory suppOrt an individual requires (e.g., 1 to I is

one counterpulsation to one heart beat; 1 to 4 is one counterpulsation

to every fourth heart beat; a ratio of 1 to 1 provides maximum circulatory suPPOrt). Weaning from IABP involves gradually decreasing the number of counterpulsarions to heart beats, with the goal being one

counterpulsation for every fourth heart beat, as tolerated, before discontinuing the IABP. Although weaning from the lABP is generally performed by decreasing the number of counterpulsations, weaning

can also be performed by gradually decreasing the amount of inflation

pressure of the balloon in the aorta.',2

The following are complications of IABP:

•

Ischemia of the involved limb secondary to occlusion of femoral

artery from compression or from thrombus formation

•

Slippage of the balloon, resulting in occlusion of subclavian or

renal arteries

Clinical Tip

•

During IABP, the lower extremity in which femoral

access is obtained cannot be flexed at the hip, and the

patienr's head cannot be raised higher than 40 degrees in

bed.

•

Depending on the amount of time spent on the pump,

the patient may require active-assistive range of motion

exercises for hip flexion after the IABP is removed.

Ventricular Assist Device

A VAD is a mechanical pump that provides prolonged circulatory

assistance in patients who have ventricular failure from myocardial

infarction or are awaiting transplantation because of severe cardiomyopathy. The mechanical pump can be internal or external to the

APPENDIX III-C: CIRCULATORY ASSIST DEVICES

833

patient. An internal VAD consists of a pump that is surgically placed

extra peritoneally within the patient's abdominal cavity with access

lines leading to an ex ternal control device. An external VAD consists

of a pump that is completely ex ternal to the patient, bur with access

lines shunting blood from the heart to the great vessels.2"

Figures III-C.2 and III-C.3 illustrate an example of an internal

VAD and an ex ternal VAD, respectively. Generally, the left ventricle is

most commonly assisted (left VAD [LVADO, but occasionally, the

Left Battery

omitted for clarity

External

Battery

Pack

/

XVE

LVAD

Skin

Vent Adapter

Line

& Vent Filter

XVE System

Controller

Figure IU-C.2. The HeartMate implantable left ventricular assist device

(LVAD). (XVE extended lead vented electric.) (Reprinted with permission

=

{rom Thoratec Corporation, Woburn, MA.}

834 ACUTE CARE HANDBOOK FOR PHYSICAL THERAPISTS

Figure m-C.3. The Thoratec paracorporeal ventricular assist device.

(Reprinted with permission from Thoratec Corporation, Wobunt, MA.)

right ventricle also needs assistance (right VAD). In more severe situations, both ventricles need to be assisted (bivenrricular assist device) .

The various types and general characteristics of internal and external

VADs are described briefly in Table Ill·c.l. It is beyond the scope of

this appendix to describe in detail all the aspects of each type of VAD;

however, physical therapists working with patients on a VAD need to

be familiar wirh the type of machine that the patient is on, as well as

the safery features of the VAD.

Weaning from VAD involves a gradual decrease in flow rates,

which allows the patient's ventricle to contribute more to rotal systemic circulation. Complications of VAD include thrombosis, bleeding, and infection at or near the insertion sites of the access lines.

The combination of technological advancements and a lack of donor

organs has increased the use of VADs in patientS with cardiomyopathy.

Therefore, physical therapists are more likely to encounter rhis equip·

ment in the hospital. Research has demonstrated that patients with a

VAD can be mobilized safely in the hospital and that their exercise tolerance can be improved while awaiting transplantation.�