Preoperative cardiac risk assessment

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Mohammed A. Sbeih, M.D. [2]; Kashish Goel,M.D.

Pre-operative cardiac risk assessment Microchapters
Stepwise approach to preoperative cardiac assessment
Estimated energy requirements for various activities
Cardiac risk stratification for noncardiac surgical procedures
ACC / AHA recommendations for perioperative cardiac assessment
Preoperative cardiac risk assessment On the Web

Stepwise approach to preoperative cardiac assessment

Adapted from Fleisher et al. Circulation. 2009 Nov 24;120(21):e169-276; HR, Heart rate

^§,∧ Noninvasive testing is not useful for patients with no clinical risk factors undergoing intermediate-risk or low-risk noncardiac surgery (AHA guidelines Class III, Level of Evidence: C).

^¶ Clinical risk factors: Ischemic heart disease, compensated or prior heart failure, diabetes mellitus, renal insufficiency, and cerebrovascular disease

Cardiac Risk Index

Original / Goldman Index

Goldman et.al devised a cardiac index for preoperative evaluation in 1977.

Risk Factors	Points
History
Age > 70 years	5
Recent MI (6 months)	10
Aortic Stenosis	3
Physical Examination
Signs of Chronic Heart Failure	11
Electrocardiogram
Rhythm other than Sinus Rhythm	7
PVC's > 5/ min	7
Poor General Medical Condition
PO2 < 60mmHg; PCO2 > 50mmHg; K < 3mmol/l; HCO3 < 20mmol/l; urea >18mmol/l (BUN > 50mg/dl); Creatinine > 260umol/l (3mg/dl); bedridden from non-cardiac cause	3
Surgery
Emergency	4
Intrathoracic	3
Total Points	53

Goldman Classification	Total Points
1	0 - 5
2	6 - 12
3	13 - 25
4	> 25

Revised Cardiac Risk Index

• Identification of patients at high rate of complications who are undergoing elective no cardiac surgery.
• Risk stratification with non invasive techniques.

Revised Cardiac Risk Index
1. History of Ischemic Heart Disease
2. History of Congestive Heart Failure
3. History of Cerebrovascular Disease
4. Insulin Therapy for Diabetes
5. Renal Insufficiency
6. High Risk Type Surgery

• Rates of major cardiac complications increased with 2 or more risk factors of revised cardiac risk index.

Surgery specific risk - 2007 ACC/AHA guidelines

• Vascular surgery has a risk more than 5%
  • Aortic surgeries
  • Peripheral vascular surgery

• Intermediate risk surgeries are as follows:(1- 5% risk)
  • Intraperitoneal
  • Intrathoracic
  • Carotid endarterectomy
  • Head and neck surgery
  • Orthopedic surgery
  • Prostate surgery

• Low risk:(< 1%)
  • Endoscopic procedures
  • Superficial procedures
  • Cataract surgery
  • Breast surgery
  • Ambulatory surgery

Cardiac conditions of increased pre-operative risk

1. Unstable coronary syndromes

• Unstable or severe angina (Canadian Cardiovascular Society class III or IV): May include “stable” angina in patients who are unusually sedentary.
• Recent MI: Greater than 7 days, but less than or equal to 1 month (within 30 days)

2. Decompensated HF

• NYHA functional class IV
• Worsening or new-onset heart failure

3. Significant arrhythmias

• High-grade atrioventricular block
• Mobitz II atrioventricular block
• Third-degree atrioventricular heart block
• Symptomatic ventricular arrhythmias
• Supraventricular arrhythmias (including atrial fibrillation) with uncontrolled ventricular rate (HR greater than 100 bpm at rest)
• Symptomatic bradycardia
• Newly recognized ventricular tachycardia

4. Severe valvular disease

• Severe aortic stenosis (mean pressure gradient >40 mm Hg, aortic valve area <1.0 cm2, or symptomatic)
• Symptomatic mitral stenosis (progressive dyspnea on exertion, exertional presyncope, or heart failure)

Estimated energy requirements for various activities^#

The metabolic equivalent of task (MET), or simply metabolic equivalent, is a physiological concept expressing the energy cost of physical activities as multiples of resting metabolic rate (RMR) and is defined as the ratio of metabolic rate (and therefore the rate of energy consumption) during a specific physical activity to a reference rate of metabolic rate at rest, set by convention to 3.5 ml O2·kg-1·min-1 or equivalently 1 kcal·kg-1· h-1 or 4.184 kJ·kg-1· h-1. By convention 1 MET is considered as the resting metabolic rate obtained during quiet sitting . MET values of physical activities range from 0.9 (sleeping) to 18 (running at 17.5 km/h or a 5:31 mile pace).

Calculating the weekly energy expended in recreational-time physical activity using METs (Metabolic equivalent task) .

Physical Activity	MET
Light Intensity Activities	< 3
Sleeping	0.9
Watching television	1.0
Writing, desk work, typing	1.8
Walking, 1.7 mph (2.7 km/h), level ground, strolling, very slow	2.3
Walking, 2.5 mph (4 km/h)	2.9
Moderate Intensity Activities	3 to 6
Bicycling, stationary, 50 watts, very light effort	3.0
Walking 3.0 mph (4.8 km/h)	3.3
Calisthenics, home exercise, light or moderate effort, general	3.5
Walking 3.4 mph (5.5 km/h)	3.6
Bicycling, <10 mph (16 km/h), leisure, to work or for pleasure	4.0
Bicycling, stationary, 100 watts, light effort	5.5
Vigorous Intensity Activities	> 6
Jogging, general	7.0
Calisthenics (e.g. pushups, situps, pullups,jumping jacks), heavy, vigorous effort	8.0
Running jogging, in place	8.0
Rope jumping	10.0

Cardiac risk stratification for noncardiac surgical procedures

High (Reported cardiac risk often greater than 5%)

• Aortic and other major vascular surgery.
• Peripheral vascular surgery.
• Anticipated prolonged surgical procedures associated with large fluid shifts and/or blood loss.

Intermediate (Reported cardiac risk generally 1% to 5%)

• Carotid endarterectomy.
• Head and neck surgery.
• Intraperitoneal and intrathoracic surgery.
• Orthopedic surgery.
• Prostate surgery.

Low (Reported cardiac risk generally less than 1%)

• Endoscopic procedures.
• Superficial procedure.
• Cataract surgery.
• Breast surgery.

• Ambulatory surgery

ACC / AHA 2007 Recommendations for Preoperative Cardiac Assessment

Risk Factors	Functional Capacity	Vascular Surgery (High Risk)	Intermediate Risk Surgery	Low Risk Surgery
0	< 4	Proceed with surgery	Proceed with surgery	Proceed with surgery
0	>= 4	Proceed with surgery	Proceed with surgery	Proceed with surgery
1 or 2	< 4	Proceed with surgery and Heart rate control	Proceed with surgery and Heart rate control	Proceed with surgery
1 or 2	>= 4	Proceed with surgery and Heart rate control	Proceed with surgery and Heart rate control	Proceed with surgery
>= 3	< 4	Non invasive Stress Test (NST)	Proceed with surgery and Heart rate control	Proceed with surgery
>= 3	>= 4	Proceed with surgery and Heart rate control	Proceed with surgery and Heart rate control	Proceed with surgery

Adapted from lecture of Robert B.McCully,M.D.;

Class I recommendation

Class IIa recommendation

Key points about NST

• No Class I recommendation
• Class IIa recommendation in patients with
  • >= 3 risk factors
  • Functional capacity of < 4 METs
  • High risk surgery (Vascular surgery)

ACC / AHA 2007 Guidelines for Perioperative Cardiac Assessment (DO NOT EDIT)

This table below contains the ACC/AHA 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery.

Class I

1.Patients who have a need for emergency noncardiac surgery should proceed to the operating room and continue perioperative surveillance and postoperative risk :stratification and risk factor management. (Level of Evidence: C)

2.Patients with active cardiac conditions* should be evaluated and treated per ACC/AHA guidelines and, if appropriate, consider proceeding to the operating room. (Level of Evidence: B)

3.Patients undergoing low risk surgery are recommended to proceed to planned surgery.† (Level of Evidence: B)

4.Patients with poor (less than 4 METs) or unknown functional capacity and no clinical risk factors should proceed with planned surgery.† (Level of Evidence: B)

Class IIa

1.It is probably recommended that patients with functional capacity greater than or equal to 4 METs without symptoms‡ proceed to planned surgery.§ (Level of Evidence: B)

2.It is probably recommended that patients with poor (less than 4 METs) or unknown functional capacity and 3 or more clinical risk factors who are scheduled for vascular surgery consider testing if it will change management.¶ (Level of Evidence: B)

3.It is probably recommended that patients with poor (less than 4 METs) or unknown functional capacity and 3 or more clinical risk factors who are scheduled for intermediate risk surgery proceed with planned surgery with heart rate control.¶ (Level of Evidence: B)

4.It is probably recommended that patients with poor (less than 4 METs) or unknown functional capacity and 1 or 2 clinical risk factors who are scheduled for vascular or intermediate risk surgery proceed with planned surgery with heart rate control.¶ (Level of Evidence: B)

Class IIa

1.Noninvasive testing might be considered if it will change management for patients with poor (less than 4 METs) or unknown functional capacity and 3 or more clinical risk factors who are scheduled for intermediate risk surgery. (Level of Evidence: B)

2.Noninvasive testing might be considered if it will change management for patients with poor (less than 4 METs) or unknown functional capacity and 1 or 2 clinical risk factors who are scheduled for vascular or intermediate risk surgery. (Level of Evidence: B)

§Noninvasive testing may be considered before surgery in specific patients with risk factors if it will change management. Clinical risk factors include ischemic heart disease, compensated or prior heart failure, diabetes mellitus, renal insufficiency, and cerebrovascular disease. ¶Consider perioperative beta blockade for populations in which this has been shown to reduce cardiac morbidity/mortality.

Pre-operative stress testing

• For patients who are able to exercise : Treadmill Exercise ECG.
• For patients who are unable to exercise : Pharmacological Stress Imaging.

Electrocardiogram - Treadmill Exercise ECG

Risk Assessment

Risk	METs	Heart rate
High Risk - Ischemia induced by low level of exercise	< 4	< 100 or 70% age pred. max
Intermediate Risk - Ischemia induced by moderate exercise	4 - 6	> 100 - 130 or 70 - 85% of age pred. max
Low Risk - No ischemia or ischemia induced at higher level of exercise	> 7	> 130 or > 85% of age pred. max

Inadequate test : In patients undergoing non cardiac surgery ,the inabilty to exercise to a level of 4 - 6 METs without out ischemia should be considered as inadequate test. (Stage II Bruce protocol)

Electrocardiogram - Preoperative 12 lead ECG

• The time frame for ECG testing is fixed, it can be done within 30 days of planned surgery when indicated.
• The resting 12-lead ECG did not identify increased perioperative risk in patients undergoing low-risk surgery.
• In patients with coronary disease, the resting 12-lead ECG may have contains important prognostic information relating to long-term morbidity and mortality.

ACC / AHA 2007 Guidelines for Preoperative Resting 12 - Lead ECG (DO NOT EDIT)

Shown below are the ACC/AHA guidelines for preoperative 12 lead ECG testing.

Class I

1. Preoperative resting 12-lead ECG is recommended for patients with at least 1 clinical risk factor who are undergoing vascular surgical procedures. (Level of Evidence: B)

2. . Preoperative resting 12-lead ECG is recommended for patients with known CHD, peripheral arterial disease, or cerebrovascular disease who are undergoing intermediate-risk surgical procedures. (Level of Evidence: C)

Class III (No Benefit)

1. Preoperative and postoperative resting 12-lead ECGs are not indicated in asymptomatic persons undergoing low-risk surgical procedures. (Level of Evidence: B)

Class IIa

1. Preoperative resting 12-lead ECG is reasonable in persons with no clinical risk factors who are undergoing vascular surgical procedures. (Level of Evidence: B)

Class IIb

1. . Preoperative resting 12-lead ECG may be reasonable in patients with at least 1 clinical risk factor who are undergoing intermediate-risk operative procedures. (Level of Evidence: B)

Non invasive Stress Testing (NST)

These are used for preoperative evaluation of patients undergoing non cardiac surgery. These are used in patients who cannot exercise.

Techniques

• Increasing oxygen demand of the heart either by pacing or inotropes
• Increasing blood supply (hyperemic response) by vasodilators

Dobutamine Stress Echocardiography

• Increasing doses of supratherapeutic doses of dobutamine are infused , which increases myocardial contractility and heart rate. This leads to significant coronary stenosis which can be identified by regional wall-motion abnormalities within the distribution of the affected vessels.
• It has high negative predictive value (93-100%)
• It has low positive predicitive value (5 - 33%)
• Extent of regional wall motion abnormality and low threshold of ischemia is an important predictor of post operative events.

Radionuclide Myocardial Perfusion Imaging

• Stress nuclear myocardial perfusion imaging has a high sensitivity for detecting patients at risk for perioperative cardiac events.
• It has high negative predictive value (95-100%)
• It has low positive predictive value (5- 20%)
• Perioperative cardiac risk is directly proportional to the myocardium at risk detected by the extent of reversible defects found on imaging.
• It is of high clinical value when used for selective population of high clinical risk.

In Left Bundle-Branch Block

• Exercise may at times induce reversible septal defects in the absence of LAD disease. Specificity of exercise myocardial perfusion imaging in presence of LBBB is low.
• Pharmacologic strss testing with perfusion scintigraphy or DSE is preferred over exercise stress testing.

ACC / AHA 2007 Guidelines: Recommendations for Noninvasive Stress Testing Before Noncardiac Surgery

Class I

1. Patients with active cardiac conditions (see Table 2) in whom noncardiac surgery is planned should be evaluated and treated per ACC/AHA guidelines before noncardiac surgery. (Level of Evidence: B)

Class III (No Benefit)

1. Noninvasive testing is not useful for patients with no clinical risk factors undergoing intermediate-risk noncardiac surgery. (Level of Evidence: C)

2. Noninvasive testing is not useful for patients undergoing low-risk noncardiac surgery. (Level of Evidence: C)

Class IIa

1. Noninvasive stress testing of patients with 3 or more clinical risk factors and poor functional capacity (less than 4 METs) who require vascular surgery is reasonable if it will change management. (Level of Evidence: B)

Class IIb

1. Noninvasive stress testing may be considered for patients with at least 1 to 2 clinical risk factors and poor functional capacity (less than 4 METs) who require intermediate-risk noncardiac surgery if it will change management. (Level of Evidence: B)

2. Noninvasive stress testing may be considered for patients with at least 1 to 2 clinical risk factors and good functional capacity (greater than or equal to 4 METs) who are undergoing vascular surgery. (Level of Evidence: B)

Perioperative Therapy

Preoperative Revascularization

Routine prophylactic coronary revascularization is not recommended. (Class III)

• Extensive ischemia is a risk factor for increased peri-operative events
• Pre-op coronary revascularization does not prevent death or MI.

Pre-operative CABG

• Patients who have high-risk coronary anatomy and in whom long-term outcome would likely be improved by CABG should generally undergo coronary revascularization before a noncardiac elective vascular surgical procedure or noncardiac operative procedures of intermediate or high risk.

• The cumulative mortality and morbidity of both the coronary revascularization procedure and the noncardiac surgery should be weighed carefully. The individual patient’s overall health,functional status, and prognosis have to be taken into consideration.

Pre-operative PCI

• Prophylactic preoperative PCI in non cardiac surgical procedures is of no value in preventing perioperative cardiac events.
• Unscheduled noncardiac surgery in a patient who has undergone a prior PCI presents special challenges, particularly with regard to management of the dual-antiplatelet agents required in those who have received coronary stents.
• Following flowchart depicts the approach based on expert opinion in patients who have undergone successful coronary intervention with or without stent placement before planned or unplanned noncardiac surgery.

Prior PCI

Balloon Angioplasty

Bare Metal Stent

Drug

Time since PCI < 14 days

Time since PCI > 14 days

Time since PCI > 30-45 days

Time since PCI < 30-45 days

Time since PCI < 365 days

Time since PCI > 365 days

Delay for elective surgery

Proceed to operating room with aspirin

Delay for elective surgery

Proceed to operating room with aspirin

Perioperative Medical Therapy

Beta Blockers

• Shown below are the ACC/AHA recommendations fore preoperative beta blocker therapy.

Class I

Continue beta blocker in patients already taking them.

Class IIa

Titrate beta blocker to heart rate, blood pressure in patients undergoing vascular(high risk) or intermediate risk surgery who are at high risk(CAD, >= 2 risk factors).

Key points about perioperative beta blocker therapy

• Start well before surgery. ( minimum of 1 week - don't start on the day of surgery)
• Use is in high or intermediate risk population only.
• Titrate dose to heart rate and blood pressure starting with a low dose. (Fixed doses shouldn't be used)
• Long acting betablockers are better to use.
• If intra-operative heat rate goes above 80 start IV administration.(Look for alternative causes of tachycardia)

For more information on perioperative betablocker therapy click here.

Statins

• Statins have protective effective on cardiac complications in non cardiac surgery, but the dosage and the target levels are unclear.
• Utilizing the perioperative period as an opportunity to impact long-term health, consideration should be given to starting statin therapy in

patients who meet National Cholesterol Education Program criteria.

ACC / AHA 2007 Guidelines:Recommendations for Perioperative Statin Therapy

• Shown below are the ACC/AHA recommendations for perioperative statin therapy.

Class I

" 1. For patients currently taking statins and scheduled for noncardiac surgery, statins should be continued.(Level of Evidence: B) "

Class IIa

"1. For patients undergoing vascular surgery with or without clinical risk factors, statin use is reasonable.(Level of Evidence: B) "

Class IIb

" 1. For patients with at least 1 clinical risk factor who are undergoing intermediate-risk procedures, statins may be considered. (Level of Evidence: C) "

Alpha 2 Agonists

• Strong evidence is lacking for the recommendation of clonidine for blood pressure control.
• Administration of clonidine had minimal effects on hemodynamics and post operative mortality.

ACC / AHA 2007 Guidelines

Recommendations for Perioperative Alpha 2 Agonist therapy

References

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