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Revised Instrument of Pozen et al for Predicting Probability of Acute Myocardial Infarction

Purpose: To evaluate a patient for probability of acute myocardial infarction using the revised predictive instrument of Pozen et al.

Description

Pozen et al revised an instrument for predicting the probability of acute myocardial infarction developed at Boston City Hospital. This can be used to reduce inappropriate admissions for patients with chest pain and for comparing performance between different hospitals. The authors are from Boston City Hospitals and Boston University.


Parameters:

(1) pain in chest or left arm

(2) chief complaint of pressure, pain or discomfort in chest

(3) history of previous heart attack

(4) history of nitroglycerine use for chest pain

(5) ST segment elevation or depression

(6) ST segment elevation, straightening or depression

(7) T wave peaking or inversion

 

Parameter

Finding

Points

pain in chest or left arm

no

2

 

yes

1

chief complaint is pressure, pain or discomfort in chest

no

2

 

yes

1

history of previous heart attack

no

2

 

yes

1

history of nitroglycerine use for chest pain

no

2

 

yes

1

ST segment elevation or depression by >= 1 mm

no

2

 

yes

1

ST segment elevation >= 1 mm, straightening, or depression >= 1 mm

no

2

 

yes

1

T wave peaking or inversion >= 1 mm

no

2

 

yes

1

 

where:

• Straightening of ST segment is an abnormal straightening ("barring") not depressed by more than 0.5 mm.

 

X =

= (0.9988 * (points for pain)) + (0.7145 * (points for chief complaint)) + (0.4187 * (points for previous MI)) + (0.5091 * (points for nitroglycerine use)) + (0.7682 * (points for ST segment change #1)) + (0.8321 * (points for ST segment change #2)) + (1.1278 * (points for T wave change)) – 7.5698

 

probability of acute myocardial infarction =

= (1 / (1 + EXP(X))

 

Performance:

• The use of the instrument reduced CCU admissions by 30% for patients finally diagnosed as not having acute myocardial ischemia. Admissions to the ICU for patients who did not have acute ischemia went from 44% to 33%.

• There was no increase in missed diagnoses of acute ischemia.


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Specialty

Objective

ICD-10