In this article, we discuss coronary artery stenting and its complications, use of anticoagulation therapeutics and the management of dental patients with these stents.

	CORONARY ARTERY STENTING

TOP ABSTRACT CORONARY ARTERY STENTING STENT PLACEMENT POSTOPERATIVE... ANTICOAGULATION AND ANTIPLATELET... DENTAL MANAGEMENT CONSIDERATIONS CONCLUSIONS REFERENCES

 
In many cardiac care centers, coronary artery stenting now is the recommended treatment over PTCA,^12,13 and many cardiac catherization laboratories use stents in as many as 60 percent of all cases.^14,15

Internationally, there are approximately 25 different stent designs being tested or used clinically. Of these, seven stents are commercially available for use in the United States.¹⁵ Stents may be categorized by their type of delivery system (self-expanding, balloon-expandable),¹² composition (stainless steel, cobalt-based alloy, tantalum,¹² nitinol, platinum iridium,¹⁴ biodegradable-polymeric¹²) or configuration (tubular mesh, slotted tubes, coils).^12,14

The majority of stents approved by the FDA and presently undergoing FDA evaluation are balloon-expandable.¹⁴ These stents are mounted on an angioplasty balloon catheter and delivered either with or without a protective sheath.² There are two major groups of balloon-expandable stents: metallic coils and slotted tubes.

The GRII coronary stent (Cook Cardiology), successor to the Gianturco-Roubin Flex-Stent (Figure 1), is a balloon-deployed, flat-wire coil stent with a single, longitudinal strut designed to hold the position of the coils while maintaining flexibility.¹⁶ This surgical stainless steel stent has an interdigitating coiled structure of 0.127 millimeters and is radiopaque. The Wiktor Coil stent (Medtronic) is a balloon-delivered, radiopaque tantalum single-wire configured as semi-helical coil.¹⁶ It is 16-mm long with interval diameters from 3.0 to 4.5 mm. Wiktor Hepamed stents (Medtronic) are the same stents with biologically active heparin permanently and covalently bound to the stent surface.¹⁶ The heparin coating is designed to prevent the incidence of stent stenosis after placement.¹⁶ Although a heparin-coated stent has shown promising results,¹⁷ randomized clinical studies need to be conducted to assess the effectiveness of this coating.^4,18

The prototype slotted-tube design stent was the Palmaz-Schatz stent. It has been placed in more than 600,000 patients worldwide and has been used in multiple randomized controlled trials.¹⁶ The original Palmaz-Schatz stent was a 15-mm long surgical stainless steel slotted tube. The newest design is the Palmaz-Schatz Crown stent (Figures 2 and 3). Other Palmaz-Schatz designs that are being evaluated outside the United States include shorter stent devices, articulated designs to improve flexibility, spiral strut designs and stents with covalently bonded heparin coatings.¹⁶

View larger version (22K): [in this window] [in a new window]   Figure 2. Palmaz-Schatz Crown Stent (Cordis Corp.) unextended on balloon catheter. Photo credit CRDUS Inc., used with permission.

View larger version (24K): [in this window] [in a new window]   Figure 3. Extended Palmaz-Schatz Crown Stent (Cordis Corp.). Photo credit CRDUS Inc., used with permission.

	STENT PLACEMENT POSTOPERATIVE COMPLICATIONS

TOP ABSTRACT CORONARY ARTERY STENTING STENT PLACEMENT POSTOPERATIVE... ANTICOAGULATION AND ANTIPLATELET... DENTAL MANAGEMENT CONSIDERATIONS CONCLUSIONS REFERENCES

In 1991, U.S. and European investigators initiated randomized trials to compare stenting with PTCA in selected patients who had new-onset atherosclerotic lesions. These trials were reported in 1994 and were the first to show a reduction in the restenosis rate.^19,20 Until 1994, early stent thrombosis was a major complication. In 1991, a 20 percent incidence of early stent closure was reported in a multicenter European registry,⁴ but only up to a 3.5 percent reduction restenosis was reported in 1994.^19,20

A new era of reduced stent complications began in 1994 due to two stent protocol modifications: the introduction of ticlopidine as an antiplatelet agent instead of other oral anticoagulation^21,22 and the use of a high-pressure stent deployment technique.²³ After these modifications were made, controlled studies of elective stenting reported early stent thrombosis rates as low as 1 percent, which suggests a clinical outcome more predictable than conventional angioplasty.^4,24

Although more than 1 million stents have been implanted worldwide, long-term follow-up has been reported for less than 0.5 percent of the cases.⁴ Analysis of the value of an interventional treatment in patients with ischemic heart disease is difficult due to the natural evolution of the disease and the multiple factors that may influence the disease’s progression or regression. Also, comparison of clinical studies may be difficult due to differences in study design and methodology.⁴ Despite these difficulties, clinical studies of postoperative stenting outcomes have been published. Pooled data on one stent design showed a 6 percent death rate and a 4 percent incidence of myocardial infarction, or MI, at 32 months’ follow-up.^4,25 Although stenting in emergent situations is associated with better clinical and radiographic outcomes than PTCA, studies show potentially higher cardiac postoperative complications when stents are placed during an emergent cardiac event vs. elective stenting.^2,25–29 Specifically, as many as 12 to 20 percent of patients in various studies experienced major cardiac events (for example, MI, death) or long-term adverse cardiac events 60 to 90 days after emergency stenting.^2,27–29

	ANTICOAGULATION AND ANTIPLATELET THERAPIES

TOP ABSTRACT CORONARY ARTERY STENTING STENT PLACEMENT POSTOPERATIVE... ANTICOAGULATION AND ANTIPLATELET... DENTAL MANAGEMENT CONSIDERATIONS CONCLUSIONS REFERENCES

 
Anticoagulation and antiplatelet therapies have been standard adjuncts in the United States during stent placement to prevent postoperative restenosis.² This regimen consisted of pre-procedural aspirin and dipyridamole, as well as additional heparin during the placement procedure. As part of this protocol, warfarin was initiated on hospital discharge and was continued for up to three months postoperative; aspirin (with or without dipyridamole) is continued indefinitely.² Several studies, however, now indicate that such an intense anticoagulation regimen is not routinely necessary, and both restenosis and postoperative complications are reduced with a regimen of aspirin and ticlopidine,^{4,14,21–23,30,31} or ticlopidine alone.³²

Most recently, developments include in-hospital use of newer platelet antagonists such as abciximab, the use of ß-particle–emitting stents, or the use of brachytherapy with either ß- or - radiation to reduce the rate of stent restenosis.¹⁸

	DENTAL MANAGEMENT CONSIDERATIONS

TOP ABSTRACT CORONARY ARTERY STENTING STENT PLACEMENT POSTOPERATIVE... ANTICOAGULATION AND ANTIPLATELET... DENTAL MANAGEMENT CONSIDERATIONS CONCLUSIONS REFERENCES

 
Dental management for patients who have received coronary artery stents should parallel established management standards of nonstented cardiac patients. Most importantly, the dental professional should be aware that cardiac stenting cannot be considered a "cure" for atherosclerotic coronary artery disease. Although the patient may, in general, exhibit clinical improvement, adverse cardiac events (for example, MI, ischemia, coronary artery restenosis) still can occur after successful stent placement.^2,25–29

Dentists should consult with the patient’s physician, cardiologist or both to obtain specific details of the patient’s cardiac history and present status. For example, dentists should determine if stenting was an elective or an emergent procedure. Patients with stents placed on an emergent basis should be viewed as being at a higher risk of experiencing further cardiac complications than are patients whose stents were placed on an elective basis. Patients who had a stent placed during an MI should be managed using the established guidelines for patients who experienced an MI and did not receive a stent.

The patient’s medication status should be ascertained. Most patients with stents are maintained on an antiplatelet regimen of aspirin or a combination of aspirin and ticlopidine.¹⁸ Such medications may cause a slight increase in bleeding time during surgical procedures. Because these medications do not affect overall coagulation status,³³ the bleeding usually can be managed by local measures. Dentists should be judicious in prescribing other medications, such as nonsteroidal anti-inflammatory drugs, that may potentiate antiplatelet actions,³³ and they should be aware that ticlopidine has caused acute neutropenia in up to 2.4 percent of patients in some clinical trials.^31,33,34

There is little in the medical literature about bacteremias and the possible need for antibiotic prophylaxis with stents,³⁵ but one source advises administering antibiotic prophylaxis per AHA recommendations for up to six months after the stent is implanted.³⁶ This source did not cite a specific rationale for the six-month recommendation; perhaps it is to allow suitable time for endothelium coverage, as that author included stents in the same narrative passage as surgical repair of cardiac defects.³⁶ During surgery, stents are placed into intimate contact with the endothelial wall of the vessel using high-pressure techniques. Recent studies have revealed that once they are embedded in the artery wall, stents are covered with a neointima in as little as 72 hours.³⁷ By 28 to 30 days, the neointima covering each stent has organized into smooth muscle cells and is completely endothelialized.^37,38

Due to such rapid adaptation of the stent into the artery wall, it is the authors’ opinion that patients with stents do not require antibiotic prophylaxis to prevent possible endarteritis from bacteremia-inducing dental treatment. During the first 30 days after stent placement, however, dentists should consult with the patients’ cardiologists about the need for any antibiotic prophylaxis as per established AHA recommendations.

	CONCLUSIONS

TOP ABSTRACT CORONARY ARTERY STENTING STENT PLACEMENT POSTOPERATIVE... ANTICOAGULATION AND ANTIPLATELET... DENTAL MANAGEMENT CONSIDERATIONS CONCLUSIONS REFERENCES

 
Prosthetic stenting of coronary arteries has shown clinical promise in the management of atherosclerotic coronary artery disease. Coronary artery stents are becoming a more commonly used treatment modality in the general population, and dental professionals are likely to treat patients with such devices. Dental management of these patients should consist of the following:

– identification of patients with cardiac conditions and cardiac stents through their medical histories;

– consultation with the patient’s physician;

– awareness of potential cardiac morbidity;

– awareness of patient’s antiplatelet regimens, knowledge of possible adverse drug affects and drug interactions, and avoidance of potentiating medications;

– consideration of prophylactic antibiotics for bacteremia-producing dental procedures for up to 30 days after the stent has been placed.