Page 572 - Cardiac Nursing

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548 PA R T I V / Pathophysiology and Management of Heart Disease
cularization procedures, exposing patients to additional cardiovas- appropriate. (Class IIb recommendation; level of evidence: B). 3
cular risks and causing substantial health care expenditures. Me- Recent randomized trials comparing DES to -emitting brachyther-
chanical devices developed to limit restenosis, such as rotational apy and PTCA for ISR have indicated superiority for long-term
atherectomy, DCA, and laser angioplasty, failed to reduce the results with DES. The better results were related to the greater acute
restenosis rate. Coronary stents were the first devices with docu- gain and late loss similar to or lower than brachytherapy. 75,76 There-
mented reduction in restenosis compared to PTCA and atherec- fore, DESs are currently the treatment of choice for ISR. 74
tomy. Restenosis rates are variable from reports of clinical trials,
but are reported to be 30% to 40% with PTCA, 35% to 50%
with atherectomy, and 20% to 30% with BMS. 19,20,69–71 Diffuse ADJUNCTIVE MODALITIES:
CHD, long lesions, small vessel size, bifurcation lesions, multiple QUANTITATIVE ANGIOGRAPHY
stents, and diabetes have shown a higher incidence of restenosis.
Restenosis after PTCA and atherectomy involves a series of Coronary angiography alone sometimes may not provide sufficient
mechanisms with vessel lumen loss due to the elastic recoil; a wound- information to distinguish ischemia-producing coronary lesions
healing process including thrombotic, inflammatory, and cell growth from non-ischemia-producing, intermediate coronary lesions. Nu-
proliferation that form neointimal hyperplasia; and remodeling of clear perfusion imaging and stress echocardiography are noninva-
the treated vessel causing shrinkage. Restenosis usually occurs within sive tests that can be used to guide treatment (Chapter 14). Invasive
3 to 6 months and rarely 12 months after PTCA and atherectomy. modalities used for diagnostic purposes are IVUS, coronary flow re-
Stents limit two of the three major mechanisms of restenosis: acute serve, and fractional flow reserve. Coronary flow reserve and frac-
elastic recoil after dilatation and vessel shrinkage due to remodeling. tional flow reserve are described in Chapter 20.
However, stents enhance neointimal proliferation. 37
Stents provide a larger arterial lumen diameter (acute gain) but
the reparative response of neointimal hyperplasia (late loss) is still Intravascular Ultrasound
present. ISR occurs when neointimal hyperplasia after stenting IVUS has become an important procedure used during PCI to
causes significant narrowing and results in a positive stress test or enhance procedure results, providing a detailed cross-sectional im-
return of symptoms. The time interval for restenosis with BMS is age of the vessel wall. This method of direct visualization of the
usually seen within the first 6 to 12 months and rarely after 1 year, arterial wall and lesion at the site of a planned intervention has
similar to PTCA and atherectomy. The antiproliferative activity improved clinical and angiographic outcomes. A miniaturized ul-
with DESs has significantly decreased the neointimal hyperplasia trasound transducer is placed on the distal end of a flexible
at the treatment site compared to PTCA, atherectomy, and BMS, catheter and advanced down the coronary artery. IVUS can be
but has a small increased risk of very late stent thrombosis. 72
used during cardiac catheterization to evaluate plaque and tissue
characteristics and during interventional procedures to verify ade-
Treatment Options quate results and stent deployment. Colombo et al. 73 recognized
for In-Stent Restenosis with the use of IVUS that stent deployment techniques were in-
adequate and that the stents frequently were not completely ex-
Treatment options for ISR initially included repeat PTCA, cutting panded in the vessel, contributing to subacute closure. As a result
balloon, atherectomy (DCA, rotational, and laser), and repeat BMS. of these findings, the use of high-pressure balloon dilatation after
These procedures provide an immediate technical success and a low stent deployment to ensure full stent expansion was instituted,
rate of ischemic events, but 30% to 60% required repeat target ves- significantly affecting stenting practices and decreasing throm-
sel revascularization secondary to recurrent neointimal hyperplasia botic complications. 77 (Fig. 23-9).
and no significant improvement in long-term results. 3,73,74
Vascular Brachytherapy NONCORONARY DEVICES FOR
Brachytherapy is a Class IIa recommendation for the treatment of
ISR (Evidence level: A). Brachytherapy is similar to PTCA but in- TREATMENT OF CONGENITAL
volves placement of a catheter containing a radioactive source ( or HEART DEFECTS
radiation) across the dilated lesion. An initial PTCA is per-
formed, the coronary lesion is dilated within the stent, and then a Percutaneous treatment of congenital heart defects (Chapter 31)
catheter containing a radioactive source is placed across the dilated requires special training by an interventional cardiologist with ex-
restenotic portion. Both and radiation reduce neointimal pro- tensive knowledge of structural cardiac anatomy. The diagnosis of
liferation associated with ISR. Although brachytherapy can be an congenital abnormalities is confirmed by trans-thoracic or trans-
effective treatment for ISR, the benefits of radiation therapy have esophageal echocardiography (Chapter 13). Use of noncoronary
been mitigated by safety concerns and late complications. The fol- devices for treatment of atrial septal defect (ASD) and patent fora-
lowing potential limitations have been observed with the use of men ovale (PFO) are described below.
brachytherapy to treat ISR: edge stenoses or geographic miss, acute
thrombosis, late thrombosis and occlusion (up to 14%), increased Atrial Septal Defect
plague burden outside the stent, IVUS echolucent areas, and very
late catch-up phenomenon or delayed restenosis. 3,72,74 Secundum ASD is the most common congenital heart defect to
present into adulthood. Untreated, ASD produces right heart
Drug-Eluting Stents volume overload, atrial arrhythmias, CHF, and pulmonary hyper-
It is reasonable to perform PCI for ISR within a DES and place a tension. Initial techniques of percutaneous ASD closure were im-
new DES for patients who develop ISR if anatomic factors are practical for younger patients because of the size of the delivery