Page 564 - Cardiac Nursing

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540 PA R T I V / Pathophysiology and Management of Heart Disease
waves and plaque disruption. A decline in laser angioplasty oc-
curred because of significant coronary dissections and perforations
with early techniques. Laser angioplasty has been used for treat-
ment of ISR with good procedural success but disappointing
long-term results. Current guidelines conclude that there is no ev-
idence that ELCA improves long-term outcomes in coronary le-
sions that can be treated safely with stenting or PTCA alone. 3,22
Thrombectomy Devices
The presence of intracoronary thrombus with plaque rupture and
ACS or thrombotic material from degenerative saphenous vein grafts
may lead to distal embolization and a “no reflow” phenomenon dur-
ing PCI. Dislodgement of thrombotic material distally can occur
with device deployment and contribute to increased MI size. Devices
■ Figure 23-3 Rotational atherectomy catheters in different sizes. to reduce thrombotic material have produced inconsistent benefits
(Courtesy of Boston Scientific Corporation, Maple Grove, MN.) in patients with ACS. However, balloon occlusion devices and aspi-
ration systems during stenting of saphenous vein grafts have shown
reduction in major adverse events with conventional PCI. 23–25
at low pressure against one wall of the vessel to stabilize the hous-
ing chamber and the window against the opposite vessel wall of Angiojet
plaque. Plaque that protrudes into the housing unit through the The angiojet is a rheolytic thrombectomy catheter (Possis Medical
window is excised with the rotating cutter, which is advanced Inc., Minneapolis, MN) designed for the percutaneous disruption
manually. The device is then rotated and plaque is excised from and removal of thrombus from native coronary arteries and bypass
around the lumen. Combination aggressive plaque debulking grafts using high-velocity saline. It consists of a double lumen
with DCA and stenting did not improve short- or long-term clinical catheter. The smaller lumen of the catheter is used to supply the
outcomes over stenting alone; there is no well-established evidence catheter tip with saline jets that are generated by an external drive
for efficacy of DCA use in coronary arteries. 3,19,20 A modified device unit. These jets aid in the formation of a recirculation pattern that
is currently used in peripheral vascular interventions. fragments the thrombotic material and creates a “Venturi effect” that
aids in evacuation of the macerated thrombotic material. 23,26
Rotational Atherectomy
The rotational atherectomy device (Rotablator/Boston Scientific, Aspiration Thrombectomy
Maple Grove, MN) uses a high-speed, rotating, elliptical burr Aspiration thrombectomy catheters are used to manually extract
coated with diamond chips 20 to 30 microns in diameter that thrombus. These catheters are advanced into the coronary artery
form an abrasive surface (Fig. 23-3). When the burr is spun at a and, while suction is applied, pulled back through the thrombus.
high speed (140,000 to 180,000 rpm, depending on burr size), it After aspiration of the thrombus material, PCI with PTCA or
preferentially removes atheroma because of its selective differential stent is performed.
cutting of inelastic plaque rather than elastic normal tissue. The
process involves a stepwise incremental increase in burr size to pro- Distal Protection Devices
vide a “sanding effect.” Gradual advancement and withdrawal of These devices are designed to provide protection of the distal mi-
the burr in 2- to 5-second intervals for up to 20 to 30 seconds in crocirculation during PCI. One device type is a balloon occlusive
the lesion allows for heat dissipation, improved distal perfusion, and system that temporarily occludes the distal vessel during the in-
washout of particulate debris. The postablation vessel diameter is tervention followed by the aspiration of liberated atheromatous
equal to the largest burr size used. Adjunctive PTCA and stenting is and thrombotic material before it reaches that arteriolar and cap-
used to maximize final coronary artery luminal diameter. The de- illary bed. The other device type is a nonocclusive, filter-based sys-
bris emitted from the Rotablator ablation process is released into tem that preserves coronary blood flow through tiny pores, as low
the coronary bloodstream as pulverized microparticles, which can as 100 microns. Atheromatous and thrombotic material is trapped
result in “slow flow” and distal microembolization. Rotational in the filter-based systems and then removed with the retrieval of
atherectomy has been shown to be effective in the treatment of fi- the device through a retrieval catheter. These techniques can re-
brotic and calcified coronary lesions that cannot be crossed by a bal- duce the incidence of cardiac enzyme elevation post-PCI.
loon or adequately dilated before planned stent placement. The use
of rotational atherectomy is used very selectively as an adjunct to
stenting and was not supported in clinical trials for ISR. 17,21 CORONARY STENTS

Atheroablative: Excimer Laser The majority of current PCI involve coronary stenting as a primary
Coronary Angioplasty (ELCA) procedure or as an adjunct to balloon angioplasty. When PTCA was
first introduced, it was plagued by two major limitations: acute or
The concept of applying laser energy to remove, in a percutaneous subacute closure, and restenosis. Subsequently, improved intracoro-
manner, atherosclerotic coronary obstructions first emerged in the nary stent design, techniques, and pharmacological management
late 1980s. The ELCA produces monochromatic light energy to have contributed to the success of catheter-based revascularization
cause ablation of plaque via the generation of heat and shock with stents, reducing the incidence of these two major complications