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Perioperative Cardiac Rsik
Perioperative Cardiac Risk
Assessment
It’s not just a “plug in the numbers” game.
James Chan MD, FRCP(C)
January 2008
Perioperative Cardiac Rsik
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Perioperative Cardiac Rsik
Objectives
• 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
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
Overview: Scope of Problem
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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;
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In studies with patients selected for CAD, risk could be
at least 2x higher
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Risk was approx 3% amongst all types of surgeries (Devereaux
CMAJ 2005:173:779-88)
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In patients going for PVD surgery or aortic surgery, the risk
varies between 3 to 38%
Perioperative Cardiac Rsik
Overview: Scope of Problem
Perioperative Cardiac Rsik
Perioperative Cardiac Rsik
Overview: Types of Surgery
Lee at al. Circulation 1999, 100:1043.
Perioperative Cardiac Rsik
Overview: Minor Surgeries
Mangano et al. NEJM 1995, Dec 28th
Perioperative Cardiac Rsik
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?
Perioperative Cardiac Rsik
Approaches: 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)
Perioperative Cardiac Rsik
Approaches: 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
Perioperative Cardiac Rsik
Overview: Detsky Index
• Detsky’s Modified Cardiac Index (1986)
Detsky et al. Arch Intern Med, 146: Nov 1986. 1986
Perioperative Cardiac Rsik
Overview: 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
Perioperative Cardiac Rsik
Overview
Perioperative Cardiac Rsik
Overview
• Detsky’s Modified Cardiac Index
Detsky et al. Arch Intern Med, 146: Nov 1986. 1986
Perioperative Cardiac Rsik
Overview
• 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
Perioperative Cardiac Rsik
Case 1
Mrs. C.
Perioperative Cardiac Rsik
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:
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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
Perioperative Cardiac Rsik
Case 1
• Physical exam today significant for:
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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
Perioperative Cardiac Rsik
What Factors Are Important to Her Cardiac
Risk?
• RISK = Clinical Predictors
x Level of Function
x Surgery Specific Risks
Perioperative Cardiac Rsik
Step 1: Is it Emergency Surgery?
Perioperative Cardiac Rsik
Step 2: R/O High Risk Cardiac Issues
Perioperative Cardiac Rsik
Step 2: R/O High Risk Cardiac Issues
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Unstable angina
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includes recent MI less than
1 month unless negative
stress test afterwards
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Decompensated CHF
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Significant arrhythmias
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Not afib
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Not LVH
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Not Q waves
Severe stenotic valve
disease
Perioperative Cardiac Rsik
Step 3: Low Risk Surgery
Perioperative Cardiac Rsik
Step 3: Low Risk Surgery
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Opthalmologic Operations 0 to 1%
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Very low risk even for patients with history of MI (Backer
Anaesth Analg 1980:59:257-62)
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Most Ambulatory Surgeries < 1%
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Warner JAMA 1993:270:1437-41
Mastectomy
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<0.128% mortality; cardiovascular events 0.06%; (Mahmoud Annals of
Surgery 2007:245(5):665-71)
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Biopsies
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Endoscopy
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Dermatologic Procedures
Perioperative Cardiac Rsik
Step 4: High-Mod Risk Surg =
Functional Capacity
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
Step 5: Risk Stratification
Perioperative Cardiac Rsik
Step 5: Lee’s Revised Cardiac Risk Index
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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)
Perioperative Cardiac Rsik
Step 5: Risk Stratification
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
Non-Invasive Testing
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ECG
Exercise Stress Test (Exercise Thallium)
Dipyridamole Thallium
Echocardiogram
Dobutamine Echo
MIBI and stress MIBI
Previous Surgery?
Perioperative Cardiac Rsik
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 2000:342:168175.
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
Dobutamine Stress Echo
Boersma E, et al. JAMA, 2001, 285:(14):1865-73
Perioperative Cardiac Rsik
Non-invasive Testing
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Stress test results are not binary but incremental
as related to risk!
– Not all positive results are significant!
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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)
Perioperative Cardiac Rsik
The internist does a dobutamine echo and
it’s very very positive! Now what?!
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
Special Topic: Surgery after PCI (Stent)
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
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?
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
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)
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
If we can’t revascularize then what?
• No time to talk about
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Euglycemia (extremely tight sugar control)
Normothermia
Effect of postoperative care
Preoperative ICU admission
• Non-cardiac Risk Factors
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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)
Perioperative Cardiac Rsik
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
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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
Perioperative Cardiac Rsik
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
Perioperative Cardiac Rsik
Infective Endocarditis
• New guidelines April 2007
– patients who have taken prophylactic antibiotics routinely in the
past but no longer need them include people with:
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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
Perioperative Cardiac Rsik
Infective Endocarditis: which conditions?
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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)
Perioperative Cardiac Rsik
Infective Endocarditis: which surgeries
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artificial heart valves
a history of infective endocarditis
certain specific, serious congenital (present from birth)
heart conditions, including
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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.