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Patients with suspected myocardial infarction who present with ST depression
H S Lee1, S J Cross, J M Rawles
1Department of Cardiology, Aberdeen Royal Infirmary, UK.
Insights
Patients with ST depression during suspected myocardial infarction face high mortality, with electrocardiogram (ECG) findings aiding prognosis. Severe ST depression on ECG is specific for infarction diagnosis.
Area of Science:
- Cardiology
- Internal Medicine
Background:
- Patients with suspected myocardial infarction (MI) presenting with ST depression have high mortality.
- Thrombolytic therapy has not shown to reduce mortality in this patient group.
- Limited data exist on the characteristics and prognosis of these patients.
Purpose of the Study:
- To investigate the electrocardiographic and clinical features of patients with suspected MI and ST depression.
- To evaluate the diagnostic and prognostic value of the presenting electrocardiogram (ECG).
- To explore reasons for high mortality and the apparent lack of thrombolytic efficacy.
Main Methods:
- Retrospective study of 136 patients admitted in 1990 with suspected MI and ST depression.
- Analysis of presenting ECG characteristics, clinical data, and 1-year mortality.
- Comparison of ECG findings between patients with and without confirmed infarction.
Main Results:
- 54% of patients had confirmed infarction, and 54% had a history of previous infarction.
- 1-year mortality was 26% overall, 31% for confirmed MI, and 19% for excluded MI.
- Severe ST depression (≥4 mm or ≥7 leads) was highly specific for infarction diagnosis, though sensitivity was low (20-21%).
- Higher mortality was associated with ≥2 mm ST depression (39%) and ≥3 leads (30%).
Conclusions:
- Patients with suspected MI and ST depression are often older, have prior infarctions, and a poor prognosis.
- The presenting ECG, particularly the severity and extent of ST depression, is valuable for predicting prognosis.
- Specific ECG criteria (≥4 mm ST depression or ≥7 leads) are highly specific for diagnosing infarction in this cohort.
Abstract:
Patients with suspected myocardial infarction who present with ST depression have a high mortality which is not reduced by thrombolytic therapy. Despite this, there are few data on these patients. We studied the electrocardiographic and clinical characteristics of these patients, the diagnostic and prognostic value of the presenting electrocardiogram (ECG), and the reasons for the high mortality and apparent lack of thrombolytic efficacy. We studied all patients with suspected infarction admitted during 1990 with ST depression. Of the 136 patients (84 men, mean [SD] age 68 [11] years), 74 (54%) had confirmed infarction and 73 (54%) had previous infarction. 1-year mortality was 26% for all patients, 31% for those with confirmed infarcts, and 19% for those in whom infarction was subsequently excluded. Patients with infarction had more severe ST depression (mean 2.5 mm [SD 1.5]) and more ECG leads with ST depression (mean 4.7 leads [1.8]) compared with patients without infarction (1.4 mm [0.8], p < 0.001; 3.6 leads [1.7], p < 0.001). Sensitivity and specificity for the subsequent diagnosis of infarction with ST depression were 20% and 97%, respectively, for at least 4 mm; and 21% and 95%, respectively, for at least 7 leads. 1-year mortality was low in patients with 1 mm ST depression (14%) or no more than 2 leads (11%), but high in patients with at least 2 mm ST depression (39%, p < 0.001) and at least 3 leads (30%, p = 0.08). Patients with suspected infarction and ST depression had a high mean age, high incidence of previous infarction, and poor prognosis. The presenting ECG is helpful in predicting prognosis, and ST depression of at least 4 mm or involving at least 7 leads is highly specific for diagnosis of infarction.