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Peri-Operative Risk Reduction


Prophylactic Coronary Revascularization

The recently completed CARP trial suggests that there is no benefit from prophylactic revascularization in high risk patients coming for elective vascular surgery. The study represents the best attempt to answer this decades old question; however, there was no control as which type of revascularization was performed. A high proportion of patients who had elective percutaneous coronary interventions (stents) had incomplete revascularization and also had a higher peri-operative infarction rate than patients who electively underwent coronary artery bypass grafting. The trial was not powered to show a difference in the short term outcomes but there was a trend to protection in patients with signs of severe multi-vessel disease. Therefore, prophylactic revascularization is usually reserved for patients who have active disease and do not have good symptomatic control on maximal medical therapy.

Revascularization Procedures

The invasive treatment of coronary disease continues to evolve. Today, revascularization may be accomplished through surgical means (CABG) or alternatively, through percutaneous coronary intervention (PCI). In regards to the surgical approach, patients may be managed either on or off pump (ie beating heart bypass surgery). There is now evidence suggesting the off pump surgery reduces perioperative stroke in high risk patients.

In regards to PCI, there are 2 major subdivisions for stents; Bare Metal Stents (BMS) and Drug Eluting Stents (DES). Presently, in North America, there are 2 types of DES in common use; the CYPHER, using the drug sirolimus and the TAXUS stent using paclitaxel. These drug eluting stents were developed in order to decrease the incidence of stent restenosis, the major cause of post PCI morbidity and mortality. Restenosis occurs secondary to inflammation and subsequent scar formation. A number of clinical trials have now shown that drug eluding stents do indeed provide longer periods of protection against thrombosis and subsequent ischemia. (43) However they require prolonged use of anti-platelet agents.

Antiplatelet Therapy in Previously Stented Patients

Post PCI, all patients are prescribed some form of anti-platelet therapy for varying periods of time. As a general rule, the DES require a longer period of anti-platelet therapy as compared to those with a BMS. In non-surgical populations, studies indicate that the cessation of ASA and/or Plavix is associated with increased rates of stent thrombosis. In fact, recent reports have found that stopping plavix as much as 1 year post PCI was associated with increased mortality. In addition, stent thrombosis can also be predicted on the basis of flow dynamics. It is intuitively obvious that longer and smaller diameter stents, as well as those placed at bifurcations, are at an increased risk of thrombosis.

In light of these issues, the acute withdrawal of anti-platelet agents in the perioperative period is a concern. Several case series have now shown that the continuation of ASA perioperatively is both safe and effective and should be mandatory in all patients who have had a recent PCI. However, the decision to continue with Plavix must be made on a cost benefit basis. The risk of major surgical bleeding must be factored into the equation. For example, in our institution, we continue plavix in selected carotid endarterectomy patients. On the other hand, in a procedure where major blood loss is anticipated, the continuation of plavix is made in concert with both the surgeon and cardiologist in order to evaluate the cardiac risk and the timing of elective surgery. As there are no practice guidelines at the present time, decisions regarding antiplatelet therapy must be made on an individual basis and may require modification in more emergent cases.

Timing of Elective Surgery After PCI

Table 1 presents the in-hospital cardiac events in the publications reviewing prophylactic revascularization preceding non-cardiac surgery. This data suggests that the interval between angioplasty and non-cardiac surgery should not be less than 6 weeks. Otherwise, PCI will increase the peri-operative cardiac event rate, probably due to increased thrombosis. Both Kaluza(14) and Posner(15) showed increased mortality in patients going for non-cardiac surgery during this time interval. Because the newer PCI and stent technology requires prolonged use of anticoagulant and anti-platelet therapy, there is the potential to increase the interval between the diagnosis and surgery. This was in fact the case in the Coronary Artery Revascularization Prophylaxis (CARP) trial, the results of which were recently reported. In this study, all patients were scheduled for elective vascular surgery and were randomized after coronary angiography to either a revascularization procedure or medical therapy Patients who were revascularized had a significant delay in the timing of their surgery.

Table 1. In hospital cardiac morbidity comparing
prophylactic revascularization to medical therapy

MYOCARDIAL INFARCTION

DEATH

STUDY

REVASC

NO REVASC

Effect
(95% CI)*

REVASC

NO REVASC

Effect
(95%)

Eagle et al [1]

8/964

16/582

.30
(0.13,0.70)

17/964

19/582

.53
(.27,1.03)

Posner et al [2]

15/686

19/686

.79
(0.38,1.63)

18/686

20/686

.90
(.46,1.77)

PTCA
( <90 DAYS)

10/142

5/142

2.0
(1.5,2.5)

3/142

4/142

.75
(.5, 2.0)

PTCA
( >90 DAYS)

5/544

14/544

.33
(.22,.67)

15/544

16/544

1

Hassan et al (BARI) [3]

CABG

2/250

NA

2/250

NA

ANGIOPLASTY

2/251

NA

2/251

NA

Kaluza et al †

Stent
( < 40 DAYS)

7/40

NA

9/40

NA

Abdelnaem et al ‡‡

24 studies
(1097 patients )

7/165/

178/932

.43
(.25,76)

NA

McFalls et al

CARP TRIAL
(mixed PCI &CABG)

30/258

36/252

.79
(.47-1.33)

8/258

9/252

.86

(33,2.28)

[1] Eagle KA Rihal CS Mickel MC et al Cardiac risk of Noncardiac Surgery: The influence of Coronary Disease and type of Surgery in 3368 operations Circulation 1997 96 1882-7

[2] Posner KL VanNorman GA Chan V Adverse outcomes after Non-cardiac Surgery in Patients with Prior Percutaneous Transluminal Angioplasty Anesthesia and Analgesia 1999 89 553-60

[3] Hassan SA Hlatly MA Boothroyd DB et al Outcomes of Non-cardiac Surgery after Coronary Bypass Surgery or Coronary Angioplasty in the Bypass Angioplasty Revascularization Investigation. Am J.Med. 2001 110 260-6

Kaluza GL Joseph J Lee JR et al Catastrophic outcomes of Non-cardiac surgery soon after coronary stenting. J Am Coll Card.2000 35 1288

‡‡ Abdelnaem E, Wijesundera D, Beattie W, Meta-analysis of Pre-operative screening tools in high risk patients Abstract ASA San Francisco ,October, 2003


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