Acute Myocardial Infarction (AMI) Short Term Mortality Risk

Patient selection:  Patients were enrolled in the GUSTO-I trial, receiving thrombolytic therapy after acute myocardial infarction.

 

Parameters used to calculate risk:

(1) age in years

(2) systolic blood pressure in mm Hg

(3) heart rate per minute (pulse)

(4) QRS duration

(5) sum of the absolute ST-segment deviations in the 12 leads of the ECG

(6) height

(7) history of diabetes

(8) history of prior coronary artery bypass graft (CABG)

(9) Killip class

(10) evidence of prior myocardial infarction on ECG

 

 

Age	Points
0	0
20	0
30	13
40	25
50	38
60	50
70	62
80	75
90	87
100	100

 

 

Height in cm	Points
0	NA
140	30
150	27
160	23
170	19
180	15
190	11
200	8
210	4
220	0

 

 

Systolic Blood Pressure	Points
0	NA
40	46
50	40
60	34
70	28
80	23
90	17
100	11
110	6
120	0
130	0
140	0
150	0
160	0

 

 

Heart Rate	Points
0	NA
40	0
60	0
80	6
100	11
120	17
140	23
160	28
180	34
200	40

 

 

QRS Duration	Anterior	Nonanterior
0	NA	NA
60	16	22
80	21	23
100	26	25
120	31	26
140	36	27
160	41	29
180	47	30
200	52	32

 

 

Sum of Absolute ST-Segment Deviations	Points
0	0
10	7
20	15
30	19
40	19
50	19
60	19
70	19
80	18

 

 

Parameter	Finding	Points
history of diabetes	yes	6
	no	0
history of prior CABG	yes	10
	no	0
Killip class	I	0
	II	8
	III	18
	IV	30
evidence of prior MI on ECG	yes	10
	no and now inferior MI	0
	no and now noninferior MI	10

 

where:

• Inferior infarction carries a lower risk of death than other infarct locations if there is no evidence of previous infarction on the ECG.

 

 

total points for all risk factors =

= (points for systolic blood pressure) + (points for ST-segment deviation)+ (points for QRS duration) + (points for age) + (points for height)+ (points for diabetes)+ (points for prior CABG) + (points for Killip class) + (points for ECG prior MI)

 

Interpretation:

• minimum score: 16

• maximum score (theoretical): 343

 

Total Points	Probability
0	< 0.001
61	0.001
87	0.005
98	0.01
110	0.02
117	0.03
122	0.04
125	0.05
129	0.06
131	0.07
134	0.08
136	0.09
138	0.1
151	0.2
167	0.4
180	0.6
196	0.8

 

Equations to Match Total Points to Probability

 

The point vs probability data was analyzed in JMP.

 

for 61 to 87 points

 

probability =

= (0.0001538 * (points)) - 0.008385

 

for 87 to 98 points

 

probability =

= (0.0004545 * (points)) - 0.034545

 

for 98 to 122 points

 

probability =

= (0.0000356 * ((points)^2)) - (0.006598 * (points)) + 0.31435

 

for 122 to 138 points

 

probability =

= (0.0000809 * ((points)^2)) - (0.017343 * (points)) + 0.9528117

 

for 138 to 196 points

 

probability =

= (0.0000523 * ((points)^2)) - (0.005022 * (points)) - 0.214169

 

Limitation:

• The assignment of points for parameters have a range of values is a little unclear. There are 2 options: (1) use discrete intervals (e.g., assign points for a value of 120 until 130 is reached, then assign the points for 130 until 140 is reached, etc.); (2) round the interval between values (e.g., the points for 120 are assigned from 115 to 124, the points for 130 from 125 to 134, etc.)