Overview :
A modified cardiac risk index can be used to
perform cardiac risk assessment prior to noncardiac surgery
and to estimate a likelihood ratio for the patient. If the
overall cardiac complication rate for the a noncardiac surgery
(pretest probabilities) is known at an institution, then the
likelihood ratio can be used
to calculate the cardiac risk for the patient
(post-test probability).
Finding |
Grouping |
Points |
myocardial infarction within 6
months |
coronary artery disease |
10 |
myocardial infarction more than 6
months ago |
coronary artery disease |
5 |
Class III Canadian Cardiovascular
Society angina |
coronary artery disease |
10 |
Class IV Canadian Cardiovascular
Society angina |
coronary artery disease |
20 |
unstable angina within 6 months |
coronary artery disease |
10 |
alveolar pulmonary edema within 1
week |
alveolar pulmonary edema |
10 |
alveolar pulmonary edema, ever |
alveolar pulmonary edema |
5 |
suspected critical aortic
stenosis |
valvular disease |
20 |
rhythm other than sinus or sinus plus
atrial premature beats on last preoperative ECG |
arrhythmias |
5 |
more than 5 premature ventricular
contractions at any time prior to surgery |
arrhythmias |
5 |
poor general medical status (pO2 <
60 mm Hg, pCO2 > 50 mm Hg, K < 3.0 mEq/L, HCO3
< 20 mEq/L, BUN > 50 mg/dL, creatinine > 3
mg/dL, abnormal SGOT, signs of chronic liver disease,
bedridden for non-cardiac causes) |
|
5 |
age over 70 |
|
5 |
emergency operation |
|
10 |
The score is the sum from the individual
points, up to a maximum score of 50. From the score, a
likelihood ratio for the patient can be estimated.
Score vs Likelihood Ratios (from nomogram
Figure 3, page 218)
Score |
Likelihood
Ratio |
0 |
0.0004 |
5 |
0.23 |
10 |
1.10 |
20 |
4.06 |
30 |
7.54 |
40 |
10.85 |
50 |
13.51 |
A line approximating this data can be given
as:
likelihood ratio =
= (-0.000138 * (score ^3)) + (0.0119553 *
(score ^2)) + (0.0175033 * (score)) - 0.06541
If the rate of cardiac complications for a
given procedure is known (pre-test probability), then Baye's
formula can be used to estimate the risk of cardiac
complications for the patient (post-test probability), as
post-test probability =
= ((pre-test probability) * (likelihood
ratio)) / (((pre-test probability) * (likelihood ratio)) + (1
- (pre-test probability)))
Likelihood Ratios for Modified Index (at
Toronto General Hospital)
Points |
Class |
Major
Surgery |
Minor
Surgery |
All
Surgery |
0 - 15 |
I |
0.42 |
0.39 |
0.43 |
15 - 30 |
II |
3.58 |
2.75 |
3.38 |
> 30 |
III |
14.93 |
12.20 |
10.60 |
|
Detsky AS,
Abrams HB, et al. Predicting Cardiac Complications in Patients
Undergoing Non-cardiac Surgery. J Gen Intern Med. 1986;
1:211-219.
Devereaux
PJ, Ghali WA, et al. Physician estimates of perioperative
cardiac risk in patients undergoing noncardiac surgery. Arch
Intern Med. 1999; 159: 713-717.
Reilly DF,
McNeely MJ, et al. Self-reported exercise tolerance and the
risk of serious perioperative complications. Arch Intern Med.
1999; 159: 2185-2192.
|