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ablation of plaques without thermal injury to the vessel. The laser treatment results in a more pliable lesion that responds better to balloon expansion. The use of laser angioplasty is limited owing to the expense

of the equipment and a high restenosis rate (>40%).·5

Directional coro/wry atherectomy can be performed by

inserting a catheter with a currer housed at the distal end on one

side of the catheter and a balloon on the other side.12 The balloon

inflates and presses the cutter against the atheroma (plaque). The

cutter can then cut the atheroma and remove it from the arterial

wall. This can also be performed with a laser on the tip of the

catheter. Rotational ablation uses a high-speed rotating bur coated

with diamond chips, creating an abrasive surface. This selectively

removes atheroma due to its inelastic properties as opposed to the

normal elastic tissue. 12 The debris emitted from this procedure is

passed into the coronary circulation and is small enough to pass

52 ACUTE CARE HANDBOOK FOR PHYSICAL THERAPISTS

through the capillary beds. Commonly, PTCA is used as an adjunct

to this procedure to increase final coronary diameter or ro allow

for stent placemenr.

Elldaillmillal stents are tiny spring-like tubes that can be

placed permanently inro the coronary artery ro increase the intraluminal diameter. Stems are occasionally necessary when initial attempts at revascularization (e.g., angioplasty) have failed.12

Clinical Tip

Refer to the Diagnostic and Laboratory Section's discussion for precautions after a catheterization procedure.

Transmyocardial Revascularization

[n transmyocardial revascularizarion, a catheter with a laser tip creates

transmural channels from patent coronary arteries into an area of the

myocardium that is thought to be ischemic. It is intended for patients

with chronic angina who, due to medical reasons, cannot have angioplasty or CABG. Theoretically, ischemia is reduced by increasing the amount of oxygenated blood in ischemic tissue. Angiogellesis (the

growth of new blood vessels) has also been proposed as a mechanism

of improvement after this procedure. Although therapists should expect

improvements in functional capacity with decreased angina, the

patient's risk status related to CAD or left ventricular dysfunction does

not change.46 Postcatheterization procedure precautions, as previously

described, will apply after this procedure.

Coronary Artery Bypass Graft

A CASG is performed when the coronary artery has become completely occluded or when it cannot be corrected by PTCA, coronary arrhrecromy, Or stenting. A vascular graft is used to revascularize the

myocardium. The saphenolls vein and the left internal mammary

artery are commonly used as vascular grafts. CABG can be performed either through a median sternotomy, which extends caudally from JUSt inferior to the suprasternal notch to below the xiphoid

process and splits the sternum longitudinally, or through a variety of

minimally i nvasive incisions.12

A minimally invasive technique that is being used for CASG

includes a CASG with a median sternoromy but without coronary

CARDIAC SYSTEM

bypass (off-pump CASG). This procedure eliminates the need for

cross clamping the aorta and is desirable in patients with left ventricular dysfunction or with severe atheroscierosis.12

If a median sternotomy is performed instead of the minimally

invasive incisions, then patients are placed on sternal precautions

for at least 8 weeks. They should avoid lifting of moderate to heavy

weights (e.g., greater than 1 0 Ib) with the upper extremities.

Clinical Tip

• To help patients understand this concept, inform them

that a gallon of milk weighs approxminately 8.5 lb.

•

Because of the sternal incision, patients are at risk of developing pulmonary complications after a CABG. The physical

therapist should be aware of postoperative complication risk

facrors as well as postoperative indicators of poor pulmonary

function. Refer to Chapter 2 and Appendix V for furrher

description of postoperative pulmonary complications.

Ablation Procedure

Catheter ablation procedures are indicated for supraventricular tachycardia, AV nodal re-entrant pathways, atrial fibrillation, atrial flurrer, and some patients with cerrain types of ventricular tachycardia. 12 The procedure anempts to remove or isolate ectopic foci in an attempt to reduce the resultant rhythm disturbance. Radiofrequency ablation uses lowpower, high-frequency AC current to destroy cardiac tissue and is the most effective technique for ablation.12 After the ecropic foci are located

under fluoroscopic guidance, the ablating catheter is positioned at the site

to deliver a current for 10-60 seconds.

Clinical Tip

•

Aftet an ablation procedure, the leg used for access

(venous puncture site) must remain straight and immobile for

3-4 hours. If an arrery was used, this time generally increases

to 4-6 hours. (The exact time will depend on hospital policy.)

•

Patients are sedated during the procedure and may

require time after the procedure to recover.

S4 AClJH. CARE HANDBOOK FOR I)HYSICAL THERAPISTS

• MOSt of the postintervenrion care is geared toward

moniroring for complications. Possible complications

include bleeding from the access site, cardiac tamponade

from perforation, and arrhythmias.

• After a successful ablation procedure (and the initial

immobility to prevent vascular complications at the access

site), there are usually no activity restrictions.

Cardiac Pacemaker Implantation and Automatic Implantable

Cardiac Defibrillator

Cardiac pacemaker implanration involves the placement of a unipolar or

bipolar electrode on the myocardium. This electrode is used to create an

action potential in the management of certain arrhythmias. Indications

for cardiac pacemaker implantation include the following'2•47.48:

• Sinus node disorders (bradyarrhythmias [HR lower than 60 bpmJ)

• Atrioventricular disorders (complete heart block, Mobitz

type 11 block)

• Tachyarrhythmias (supraventricular tachycardia, frequent ectopy)

Temporary pacing may be performed after an acute MI to help

control transient arrhythmias and after a CABG. Table 1 - 1 9 classifies

the various pacemakers.

One of the most critical aspects of pacer function for a physical therapist to understand is rate modulation. Rate modulation refers ro the pacer's ability to modulate HR based on activity or physiologic

demands. Not all pacers are equipped with rate modulation; therefore,

some patients have HRs that may not change with activity. In pacers

with rate modulation, a variety of sensors are available to allow adjustment of HR. The type of sensor used may impact the ability of the pacer to respond to various exercise modalities. For more detail, the

teader is teferred to the review by Sharp 48

Clinical Tip

• If the pacemaker does not have rate modulation, lowlevel activity with small increases in metabolic demand is