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Perioperative Cardiac Risk Assessment

It’s not just a “plug in the numbers” game.James Chan MD, FRCP(C)

January 2008

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kObjectives

• To critically appraise 2007 AHA guidelines to perioperative cardiac risk assessment (PCRA)

• to present an integrated, stepwise approach to PRCA and to use it as a framework to discuss the role of clinical judgement as it interacts with set algorithms

• To offer guidelines as to which patients should be referred to perioperative specialists and those who do not

• Offer some glimpses as to what is “state of the art” in terms of perioperative risk identification and risk reduction

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k Why Just Cardiac Risk?

• Most studied relative to pulmonary, thrombosis, endocrine, renal, etc. diseases

• Cardiac complications are the leading cause of complications in perioperative morbidity and mortality

• Clear guidelines available– 2007 ACC/AHA Perioperative Guidelines (updated from 2002)

– http://content.onlinejacc.org/cgi/content/full/j.jacc.2007.09.003

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k Overview: Scope of Problem

• In studies of consecutive non-selected patients, risk of cardiac complications is about 2-3%%, risk perioperative death is even lower (Mangano NEJM, Dec 28, 1995;

• In studies with patients selected for CAD, risk could be at least 2x higher

• Risk was approx 3% amongst all types of surgeries (Devereaux CMAJ 2005:173:779-88)

• In patients going for PVD surgery or aortic surgery, the risk varies between 3 to 38%

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k Overview: Scope of Problem

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k Overview: Types of Surgery

Lee at al. Circulation 1999, 100:1043.

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kOverview: Minor Surgeries

Mangano et al. NEJM 1995, Dec 28th

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k Overview: Why It’s Important

• if we can tell who has significant CAD we can say:– who benefits from surgery and who doesn’t– who needs a tune up and who doesn’t

would you take this car on a road trip?

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kApproaches: Goldman Index

• many different approaches to PCRA – Goldman Cardiac Index (NEJM 1977;297:845-850).

• Risk Index: Class I = 0-5 points (low), Class II = 6-12 points (intermediate), Class III = 13-25 points (high), Class IV => 25 points (very high)

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kApproaches: Goldman Index

• Goldman (1977)– Useful in predicting cardiac events in an unselected, random group of

patients but less useful as a predictor when applied to smaller subgroups, such as all those with known heart disease.  The type and extent of surgery needs to be taken into account when one is interpreting the results

• Obviously, higher risk patients going for higher risk surgeries who score low does not necessarily mean their risk is low

– Tends to overestimate risk in highest risk group– Underestimates risk for abdominal and vascular surgeries– Because it was derived retrospectively, relative risk is very

institutionally dependent

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kOverview: Detsky Index

• Detsky’s Modified Cardiac Index (1986)

Detsky et al. Arch Intern Med, 146: Nov 1986. 1986

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kOverview: Detsky Index

• Detsky’s Modified Cardiac Index (1977)– Added variables of significant angina and remote MI– Addresses problem of surgery specific risk by calculating

pretest probability based on type of surgery – More useful for high risk populations, but variable ability

to predict course of those with low scores

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kOverview

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kOverview

• Detsky’s Modified Cardiac Index Detsky et al. Arch Intern Med, 146: Nov 1986. 1986

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kOverview

• many different approaches to PCRA – Goldman (1977)– Detsky (1986), Eagle (1989), Larsen (1987), Lee (1999) etc.– Dripps-American Society of Anesthesiologists Classification 1961

• Subjective and focuses heavily on functional capacity• Sensitive predictor of death for large numbers of patients (>100,000)• Doesn’t predict cardiac complications well

– ACC/AHA Guidelines (Eagle 1996)• multi-step and considers multiple variables

– ACP Guidelines (1997)• attempts to combine Detsky and Eagle Criteria

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k Case 1

Mrs. C.

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k Case 1

• Mrs. C is a 70 year old woman referred by Dr. Qack for aortic aneurysm repair that is 6cm and “ready to blow”

• History is significant for:– DM2 with diabetic retinopathy

– remote stroke 1996 felt secondary to atrial fibrillation

– hypertension not well controlled

– severe rheumatoid arthritis

– exercise tolerance limited to very light housework, can’t do stairs

– CAD but had angioplasty 2005

– Class II angina presently

– angiogram in Jan 2000 1 vessel 70% blocked RCA

– Quit smoking 8 weeks ago

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k Case 1

• Physical exam today significant for:– BP: 150/90 right arm, sitting– ENT: normal– RESP: small bibasilar crackles– CVS: 3cm JVP, no S3, no murmurs, large apex, +2 leg edema– ABDM: pulsatile mass ~ 8cm, renal bruits

• Labs– Lytes, BUN, Cr normal, CBC microcytic anemia Hb = 98– ECG: LVH, LBBB, diffuse ST-T changes– CXR: cardiomegaly, hilar congestion

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k What Factors Are Important to Her Cardiac Risk?

• RISK = Clinical Predictors

x Level of Function

x Surgery Specific Risks

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k Step 1: Is it Emergency Surgery?

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k Step 2: R/O High Risk Cardiac Issues

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k Step 2: R/O High Risk Cardiac Issues

• Unstable angina• includes recent MI less than

1 month unless negative stress test afterwards

• Decompensated CHF

• Significant arrhythmias• Not afib

• Not LVH

• Not Q waves

• Severe stenotic valve disease

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k Step 3: Low Risk Surgery

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k Step 3: Low Risk Surgery

• Opthalmologic Operations 0 to 1%

• Very low risk even for patients with history of MI (Backer Anaesth Analg 1980:59:257-62)

• Most Ambulatory Surgeries < 1%

• Warner JAMA 1993:270:1437-41

• Mastectomy

• <0.128% mortality; cardiovascular events 0.06%; (Mahmoud Annals of Surgery 2007:245(5):665-71)

• Biopsies

• Endoscopy

• Dermatologic Procedures

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k Step 4: High-Mod Risk Surg = Functional Capacity

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k What is a MET?

• METS are a way to express VO2max

• The metabolic equivalent (MET) is an average unit oxygen uptake while resting and sitting (3.5 mL O2

per kilogram body weight per minute [mL · kg-1 · min-1]) – varies by age, gender, fitness, cardiovascular disease

1-4 METS: household activities

4-10 METS: climbing stairs, walking 4mph

> 20 METS: strenuous sports

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k Step 5: Risk Stratification

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k Step 5: Lee’s Revised Cardiac Risk Index

• History of ischemic heart disease• History of compensated or prior CHF• History of stroke• Diabetes• Renal insufficiency (Cr >177)• Surgery Type (not included)

• Give a numberic score from 1 to 5 (5 risk factors)

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k Step 5: Risk Stratification

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k Step 5: Risk Stratification

• Note that the 2 left sided arms are essential the same– Ie. If greater than 1 risk factor, consider non-invasive stress test IF it

changes management– If no stress testing then consider beta-blockade

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k Non-Invasive Testing

• ECG• Exercise Stress Test (Exercise Thallium)• Dipyridamole Thallium• Echocardiogram• Dobutamine Echo• MIBI and stress MIBI• Previous Surgery?

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k Non-Invasive Tests

• ECG– Magnitude of Q waves predict LVEF and predict long term mortality– Presence of Q waves predict postoperative cardiac complications

(MI, CHF, ventricular fibrillation) Lee Circ 1999:100:1043-9• Controversial: Liu J AM Geriatr Soc 2002:50:1186-91

• This is already incorporated into the guidelines

– Presence of LV hypertrophy or ST-segment depression preoperatively predicts adverse perioperative cardiac events

– Guidelines recommend ECG on everyone with 1 clinical risk factor• Not useful in patients undergoing low risk surgery Schein NEJM 2000:342:168-

175.

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k Non-Invasive Tests

• Exercise Stress Testing– Sensitivity 81% and specificity 66% for multi-vessel disease– probably high negative predictive value in those who can achieve

85% of predicted heart rate and a negative stress test• Positive predictive value probably only 20-30% in mod risk populations• Negative predictive value probably 90 to 99% in mod risk populations

– but up to 30% of patients can’t achieve this, and 30-70% can’t do it at all due to a variety of reasons

– high false positives in women and with LVH; patients with abnormal rest ECG

• 24 Hour Holter– conflicting data, role is unclear

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k Non-Invasive Tests

• Radionucleotide Stress Test– dipyridamole-thallium/dipyridamole MIBI

• 70%-85% sensitivity and specificity; sensitivity and specificity similar to that of exercise stress test (sensitivity approaches 100%, specificity approaches 70% in high risk patients)

– PPV between 4 to 20%; NPV 97% to 100%%• May be more inaccurate in women due to breast attenuation

– dobutamine-stress echo• Numbers are pretty much the same as dipyridamole-thallium

– Positive predictive value of 16 to 33%– Negative predictive value of 96% to 100%

• Advantages: can assess LV function, real time versus averaged image, noninvasive, no radiation (contrast), lower cost

• Like all echo it is operator dependent• The only test proven in renal failure

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k Dobutamine Stress Echo

Boersma E, et al. JAMA, 2001, 285:(14):1865-73

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k Non-invasive Testing

• Stress test results are not binary but incremental as related to risk!

– Not all positive results are significant!

• Echo– likely does not add to risk discrimination even for detection of CHF– not recommended for risk stratefication except to to rule out valvular

defects (esp. aortic stenosis)

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The internist does a dobutamine echo and it’s very very positive! Now what?!

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k The Revascularization Controversy

• Previously all evidence for CABG/PCI was from cohort studies and retrospective studies– Interesting: Data suggests that risk of death is lower if non-cardiac

surgery performed less than 4 years of revascularization NEJM 1996:335

– First RCT was published in 2004 (CARP study) which showed no morbidity or mortality benefit to revascularization in vascular sx pts

– The data for preoperative PCI is even more sketchy and benefit (if any) is probably similar to CABG

• There is not enough data to say whether bare metal stents, drug eluting stents or plain angioplasty would be better pre-operatively

– Nevertheless guidelines seem to come out in favor of PCI

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k Special Topic: Surgery after PCI (Stent)

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k Special Topic: Surgery after PCI

• Monotherapy with aspirin need not be routinely discontinued after for non-cardiac surgery with possible exception for surgeries with high risk for bleeding (eg. Intra-cranial and prostate surgery)– Cardiac surgeries and vascular surgeries routinely continue

perioperative ASA– Serious consideration should be given to continue ASA even the

clopidgrel has been stopped especially in patient with DES

• Controversy remains about risk of continuation of clopidegrel monotherapy

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k Non-Invasive Testing

• Don’t ask for a test unless it’s going to change your management– Pretend patient is not going for surgery– If you would order a stress test based on the symptoms/signs in front

of your even without surgery– Consider the delay needed to do the revascularization

• What is the risk of waiting?

• What risk is acceptable to the patient and to you?

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k If we can’t revascularize then what?

• Medical management: beta-blockers– Theory is to block catecholamine release/effects thought responsible

for many cardiac complications– Multiple conflicting poorly done studies on either side of the debate– Complicated by multiple protocols and patient populations – Suggestions that it might even harm lower risk patients– POISE results 2007 (unpublished)

• No benefit in the morbidity of mortality

• Perhaps increased incidence of death and stroke

• Perhaps due to huge dose of beta-blocker used (metoprolol 200mg po OD) and no titration of blood pressure

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k If we can’t revascularize then what?

• Beta-blockers– AHA guidelines

• Don’t stop beta-blockers perioperatively

• Vascular surgery patients who are high risk should get beta-blockers and probably for patients at moderate risk (greater than 1 risk factor)

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k If we can’t revascularize then what?

• Medical management: statins– Next frontier; statins have anti-inflammatory and plaque

stabilization effects in the short term– Statins in long term reduced cholesterol is associated

with plaque regression and long term cardiac mortality/morbidity benefit

– Almost all studies are so far retrospective and case control

– Dosage, duration, type of statin, targets of treatment all unclear

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k If we can’t revascularize then what?

• No time to talk about– Euglycemia (extremely tight sugar control)– Normothermia– Effect of postoperative care– Preoperative ICU admission

• Non-cardiac Risk Factors– Pulmonary risk (COPD, pulmonary hypertension, sleep apnea)– Thrombosis risk (VTE propholaxis, active VTE, anticoagulant)– Endocrine (thyroid, pheochromocytoma, carcinoid)– Electrolytes (Na, K, Ca)– Neurology (seizures, ETOH abuse, MS)

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k Weaknesses of This Algorithm

• Leaves out understudied risk factors– Does not recognize the metabolic syndrome (diabetes, central obesity,

hypercholesterolemia, HTN)– Does not recognize incorporate severe hypertension as risk

• Does not give incorporate recent revascularization or recent negative stress test as moderating factors

– Diel Ann Surg 1983:197– Crawford Ann Thor Surg 1978:26– Ruel J Vasc Surg 1978:26– Nielsen Am J Surg 1986:3

• does not take into account previous recent surgeries as a stress test equivalent

• does not attempt to quantify risk • Recommendations about recent MI is convoluted• No room for amelioration of risk factors

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k Strengths of This Algorithm

• incorporates multiple ways to look at risk: nature of surgery, patient risk factors, level of function, and surgical risks

• does not rely on memorization of numbers• Attempts to be evidence based (though still mostly opinion

based)• Does not address the whole patient• Recognizes ambiguity of literature but perhaps hedges too

much

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k Infective Endocarditis

• New guidelines April 2007– patients who have taken prophylactic antibiotics routinely in the

past but no longer need them include people with:• mitral valve prolapse

• rheumatic heart disease

• bicuspid valve disease

• calcified aortic stenosis

• congenital heart conditions such as ventricular septal defect, atrial septal defect and hypertrophic cardiomyopathy

• stents

• http://jada.ada.org/cgi/content/abstract/138/6/739

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k Infective Endocarditis: which conditions?

• NOT:

– Bronchoscopy (unless the respiratory mucosa is incised)GI or GU procedures (except for the above high-risk cardiac conditions when infection is present; enterococcal coverage is then recommended)

– Other procedures previously identified as not needing antibiotics (vaginal delivery, hysterectomy, ear or other body piercing, and tattooing)

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k Infective Endocarditis: which surgeries

• artificial heart valves • a history of infective endocarditis • certain specific, serious congenital (present from birth)

heart conditions, including – unrepaired or incompletely repaired cyanotic congenital heart disease,

including those with palliative shunts and conduits

– a completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first six months after the procedure

– any repaired congenital heart defect with residual defect at the site or adjacent to the site of a prosthetic patch or a prosthetic device

• a cardiac transplant that develops a problem in a heart valve.