Myocardial infarction: a high risk group increased likelihood of complications.

Clinical bottom line (level 2c)

  1. Nearly a fifth of patients with a suspected myocardial infarction had one.
  2. Nearly a twentieth of patients with a myocardial infarction had a life-threatening complication in-hospital.
  3. Patients were at an increased risk of having a myocardial infarction in-hospital if they are in a high-risk group (positive ECG) (NNF = 2 for unknown) .
  4. Patients were at an increased risk of having a life-threatening complication in-hospital if they are in a high-risk group (NNF = 2 for unknown) .
Stark et al: Archives of Internal Medicine 1987; 147: 843-846
Expires March 2003

The study

Prospective cohort study with objective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: Air Force medical centre, USA

221 patients (aged ?, ?% male) presented with chest pain and admitted because of suspected myocardial infarction


Chi-squared analysis was performed to compare low and high-risk patients ECGs.

100% followed for in-hospital
Outcomes studied:
  • myocardial infarction
  • life-threatening complications of myocardial infarction death, ventricular fibrillation, sustained ventricular heart block or tachycardia

  • Patients were considered to be at high risk if they had one or more of: significant Q waves, elevated ST segments, depressed ST segments, T-wave inversion consistent with infarction or ischaemia, left ventricular hypertrophy, left bundle branch block or paced rhythm (positive ECG). Patients were considered low risk if they had a negative ECG: normal, unchanged from that of a prior admission or with only nonspecific ST segment or T-wave changes.

The evidence

outcome time to outcome number of patients/total number %
(95% CI)
myocardial infarction in-hospital 39/221 17.7%
(17.7% to 22.7%)
life-threatening complications of myocardial infarction in-hospital 9/221 4.07%
(1.47% to 6.68%)

prognostic factor for
myocardial infarction 		time to outcome unadjusted RR
(95% CI)		 NNF+
(95% CI)
high-risk group in-hospital 2.87
(1.98 to 4.17) 		2
(1 to 5)

prognostic factor outcome present outcome absent unadjusted RR
(95% CI)		 NNF+
(95% CI)
high-risk group 24 39 2.87
(1.98 to 4.17) 		2
(1 to 5)
no high-risk group 15 143

prognostic factor for
life-threatening complications of myocardial infarction 		time to outcome unadjusted RR
(95% CI)		 NNF+
(95% CI)
high-risk group in-hospital 2.94
(1.94 to 4.46) 		2
(1 to 4)

Comments

  1. Good study to judge the clinical importance of a simple, commonly-used test.

Citation

  1. Stark JL, Vacek JL, JL: The initial electrocardiogram during admission for myocardial infarction: Use as a predictor of clinical course and facility utilization. Archives of Internal Medicine 1987; 147: 843-846
Contributor: Clare Wotton and Bob Phillips, January 2000
Reviewer: Timo Strandberg

Clinical Question.
Patient suspected myocardial infarction
Intervention or Exposure high risk group
Comparison low risk group
Outcome life-threatening complications