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

Original Cardiac Risk 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.

ACC/AHA - Surgery specific risk

• 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)

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)

ACC / AHA 2007 Guidelines for Perioperative Cardiac Assessment

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.

References

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