Preoperative Cardiac Evaluation


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Preoperative Cardiac Evaluation


Up to 60% of patients undergoing vascular surgery have significant CAD. Two major mechanisms underlie perioperative myocardial infarction:



  1. Catecholamine surge, tachycardia, and hypertension increase coronary shear stress, which triggers plaque rupture. This is more likely to happen in plaques with a large atherosclerotic burden even if non-obstructive.1,2

    Surgery-induced procoagulant state may lead to coronary thrombosis over a ruptured or even a non-ruptured lesion, particularly if the stenosis is tight with a low flow state.


  2. Prolonged periods of demand/supply mismatch in patients with severe but previously stable CAD, without any plaque rupture.

Overall, each one of the two mechanisms is primarily responsible for ~50% of postoperative MIs.1 A combination is likely responsible for MI in a substantial proportion of patients. Most events occur in the first 24–48 hours postoperatively, the period of highest sympathetic tone. The infarct is most commonly NSTEMI/non-Q-wave MI. In a series of 21 patients who underwent preoperative coronary angiography and developed postoperative MI after vascular surgery, slightly over half of the infarcts corresponded to the territory of a totally occluded coronary artery, in which collaterals could not provide enough supply during a period of high stress; additionally, those patients had severe multivessel disease, potentially impairing collateral flow.3 The remaining infarcts occurred in the territory of a non-significant lesion, in patients who nonetheless had extensive atherosclerosis. This highlights not only the frequency of demand/supply mismatch, but also the fact that plaque rupture may very well occur at non-obstructive sites. The overall extent of CAD correlates with the risk of events and plaque rupture; however, the infarct does not necessarily occur at the actual site of severe stenosis. In fact, a non-obstructive lesion may be vulnerable (high plaque burden, thin cap). This explains why revascularization does not prevent postoperative MI.


According to the ACC/AHA 2014 preoperative guidelines,4 the cardiac evaluation for noncardiac surgery is based on the assessment of (1) active cardiac conditions, (2) known cardiovascular disease and cardiac risk factors, and (3) functional capacity in metabolic equivalents (METs).


I. Steps in preoperative evaluation


A. First step: if the surgery is emergent, no cardiac workup is performed preoperatively


B. Second step: if the surgery is not emergent, evaluate for active cardiac conditions


Active cardiac conditions:



  • Active, unstable coronary syndrome, or recent MI (<1 month) with persistent ischemic symptoms or ischemia on non-invasive stress testing
  • Severe unstable arrhythmia
  • Decompensated HF
  • Severely symptomatic valvular heart disease

These patients need to have their cardiac condition treated before surgery, depending on the urgency of the surgery (PCI for ACS, medical therapy for HF, surgical therapy for symptomatic, severe valvular disease).


In case of an emergent surgery, proceed to the high-risk surgery with maximal medical therapy.


C. Third step: in the absence of active cardiac conditions, look for clinical risk factors, and use the revised cardiac risk index or Lee index


The Lee index includes six factors:5



  • History of CAD
  • Compensated or prior HF
  • Diabetes
  • Renal insufficiency with creatinine >2 mg/dl
  • Cerebrovascular disease
  • Intermediate- or high-risk surgery

    1. In the case of a Lee risk score of 0 to 2, or in the case of a low-risk surgery regardless of risk factors, surgery is performed without any further cardiac workup. The surgery is a low-cardiac-risk surgery.
    2. In the case of a Lee risk score ≥3 and poor functional capacity <4 METs (or unknown) and intermediate- or high-risk surgery, non-invasive preoperative cardiac testing may be performed for further cardiac risk assessment (class IIa recommendation). If the functional capacity is ≥4 METs, especially ≥7 METs, stress testing is not needed even if the Lee risk score is high. Preoperative testing determines the functional capacity when it is unclear (exercise testing), and allows risk stratification of patients with a clearly reduced functional capacity <4 METs (pharmacologic testing). Four METs correspond to climbing 2 flights of stairs, walking up a hill, walking fast at ground level, dancing, or performing heavy housework or yardwork (pushing a power mower, scrubbing floors, carrying heavy groceries). Sexual intercourse corresponds to 3–5 METs.

Note that preoperative testing is mainly useful to assess how risky the surgery will be and to see whether it should be avoided or altered, if possible. Testing is only performed if it will change management, i.e., if surgery can be deferred. Preoperative testing is, therefore, much less useful in patients who require a necessary, vital surgery (e.g., cancer surgery).


A high-risk finding on preoperative testing indicates preoperative coronary angiography only if preoperative revascularization is feasible, i.e., surgery can be deferred and the patient can tolerate an antithrombotic regimen. If extensive CAD is present (left main or multivessel CAD), revascularization, typically CABG, should generally be performed before a non-vital elective surgery (class I recommendation). This revascularization is mainly meant to improve the long-term cardiac risk of the patient. Outside ACS or left main disease, preoperative revascularization does not clearly change the operative cardiac risk (CARP trial), even in high-risk ischemic patients with at least five abnormal segments on stress imaging (LV being divided into 17 segments).5,6 There is no evidence that PCI of a single- or two-vessel disease improves perioperative outcomes, outside ACS.


II. Surgical risk: surgery’s risk and patient’s risk


A. Classification of the surgery’s risk


The surgery is classified into one of three risk categories:



  • High risk: aortic or major peripheral vascular surgery
  • Intermediate risk: intraperitoneal, intrathoracic, carotid endarterectomy, common femoral endarterectomy, head and neck surgery, orthopedic surgery, prostate surgery
  • Low risk: endoscopic procedures, breast surgery, cataract surgery, ambulatory surgery

The risk of perioperative major cardiac events (death or MI) is generally ≤1% with low-risk surgery, regardless of the underlying patient’s risk; and is generally 1–5% with intermediate-risk surgery and 5% with high-risk surgery, although the actual risk of intermediate- and high-risk surgeries also depends on the patient’s intrinsic risk (Lee risk score). For example, a low-risk patient undergoing major vascular surgery has <2–5% risk of major cardiac events.


B. Classification of the patient’s overall risk (integrates the surgery’s risk with the patient’s risk factors)


In the presence of an active cardiac condition (Section I.B, above), the patient is a high-risk patient.


In the absence of an active condition, a Lee risk score ≥3 identifies high-risk stable patients, a score of 2 identifies intermediate-risk patients, while a score of 0 or 1 identifies low-risk patients. The risk of postoperative major adverse cardiac events (MACE) (MI, VF or primary cardiac arrest, or definite pulmonary edema) in high-, intermediate-, and low-risk patients is ≥9%, 4–5%, and 0.5–1.3%, respectively.7


C. Risk of MACE according to stress testing results


A high-risk stress test result (stress echo or nuclear stress test) is associated with a 10–25% risk of perioperative death or MI, while a normal stress test result is associated with a 0–4% (~2%) risk of death or MI.4 Therefore, a low-risk stress test steps down the risk in a patient with a high Lee index, but the absolute risk may remain significant.


III. CARP and DECREASE V trials


The CARP and DECREASE V trials have shown that patients with established but stable CAD, including multivessel/triple-vessel CAD, who are undergoing high-risk vascular surgery, do not benefit from revascularization preoperatively.


In the CARP trial, 509 intermediate-to-high-risk patients (by Lee risk score or stress testing) undergoing vascular surgery (33% AAA) and found to have CAD on coronary angiography were randomized to medical therapy or coronary revascularization (59% CABG, 41% PCI). Surgery was delayed a median of 6 weeks after revascularization. The postoperative risk of death was ~3% in both groups, and MI rate was ~8% (high MACE risk not modified by revascularization).6


In DECREASE V trial of patients with extensive baseline ischemia (≥ 5/17 segments), the MACE risk was high but unchanged with revascularization. This is related to the fact that postoperative MI in a CAD patient may result from a plaque rupture occurring at the site of an obstructive lesion but also frequently a non-obstructive one. Moreover, preoperative revascularization is associated with its own set of complications, such as stent thrombosis. Therefore, the usefulness of preoperative coronary revascularization in patients not having active ACS is not established, even in high-risk subgroups with strongly positive stress tests.7


Caveats



  1. Only 35% of CARP patients had three-vessel CAD and only 44% had moderate/large ischemia on stress testing. At least 25% had low-risk Lee score and nuclear imaging.6 In a post-hoc analysis of CARP, patients who underwent CABG had similar mortality but fewer MIs after vascular surgery than those who underwent PCI and probably those treated medically, despite the more extensive CAD in CABG patients.8 In another CARP analysis, patients with large anterior ischemia seemed to benefit from preoperative revascularization.9 This underlines a potential role of preoperative CABG in patients with extensive CAD undergoing elective vascular surgery.
  2. Left main disease was excluded from the CARP trial, and, in an analysis of the CARP registry, left main disease benefited from preoperative revascularization.10

Preoperative coronary testing may be useful to show the general prognosis of the patient. A high surgical risk based on preoperative stress testing may lead to a change in management but not necessarily revascularization. It should lead to a risk/benefit discussion with the patient, with a potential cancellation of non-vital surgery and consideration of percutaneous angioplasty for PAD or endovascular repair of abdominal aortic aneurysm, even if the result is expected to be inferior to surgery. Preoperative coronary testing is much less useful in patients who require a vital surgery, such as cancer surgery.


IV. Only the highest-risk coronary patients require revascularization preoperatively


The highest-risk patients are those with MI in the last month with persistent ischemia clinically or on stress testing. Stenting, however, is associated with several pitfalls:



  1. Dual antiplatelet therapy after stenting increases the surgical bleeding risk.
  2. The prothrombotic milieu created by surgery increases the risk of stent thrombosis.

Surgery soon after stenting (2 weeks) may lead to catastrophic results, with a high risk of death and MI. In one analysis, death (mostly secondary to stent thrombosis, and partly secondary to bleeding) occurred in 32% of patients who underwent surgery <2 weeks after stenting, and in four out of five patients who underwent surgery 1 day after stenting.11 One or both antiplatelet agents were only briefly interrupted before surgery (~1 day), and interruption of antiplatelet therapy may therefore not have been solely responsible for this high rate of stent thrombosis. Bleeding was also very common, and early post-PCI bleeding is known to be associated with MI and stent thrombosis.


V. Preoperative percutaneous revascularization


If percutaneous revascularization needs to be performed preoperatively, dual antiplatelet therapy is given and surgery is postponed for at least 1 month after bare-metal stent (BMS) and 3 months, preferably 6 months, after drug-eluting stent (DES) (class I for antiplatelet interruption at 6 months, IIb at 3 months). Three trials suggest that interruption of ADP-receptor antagonist at 1 month is as safe with DES as with BMS ; 2 other trials suggest that, after DES, interruption at 1 month is as safe as 6 months (Chapter 1, VI). Hence, the preference for BMS in this setting is obsolete .


If surgery is needed more urgently (<4 weeks), balloon angioplasty is performed without any stenting if possible, and stenting is only done as a bailout for complicated angioplasty. Surgery can be performed 2–4 weeks after balloon angioplasty; there is a risk of acute vessel thrombosis with earlier surgery.


VI. Surgery that needs to be performed soon after stent placement



  • If surgery needs to be performed earlier than 4 weeks after BMS placement or earlier than 3 months after DES placement, try to perform the surgery while the patient is still on dual antiplatelet therapy.
  • Dual antiplatelet therapy does not usually need to be held before dental procedures.
  • Except for aortobifemoral bypass surgery, peripheral vascular surgery (femoropopliteal bypass, CEA) may be performed under a dual antiplatelet regime.
  • Gastrointestinal endoscopic procedures:

    • Gastroscopy, colonoscopy with biopsies, and ERCP with endoprosthesis placement may be performed under dual antiplatelet regime.
    • Polypectomy or ERCP with sphincterotomy may be done under aspirin monotherapy.
    • Endoscopic gastrostomy tube may require holding both antiplatelet agents.

  • Aspirin monotherapy increases major surgical bleeding, but only mildly (<1%), and the risk is more dramatic during certain surgeries, such as intracranial surgery and posterior chamber ophthalmic surgery, where it definitely needs to be withhled, and during transurethral prostatectomy where it may nonetheless be continued.
Nov 27, 2022 | Posted by in CARDIOLOGY | Comments Off on Preoperative Cardiac Evaluation

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