PURPOSE: To examine the prognostic significance of low QRS voltage in a large contemporary cohort of patients with a broad spectrum of acute coronary syndromes (ACS).
METHODS: 12409 patients with STEMI or NSTE-ACS from the Global Registry of Acute Coronary Events (GRACE) and Canadian ACS I registries were stratified based on the presence of low QRS voltage (<0.5 mV in all limb leads and <1.0 mV in all precordial leads) on the admission ECG. We performed multivariable logistic regression to assess the independent association between low voltage and in-hospital and 6-month mortality, and tested for its interaction with ST-segment deviation for these outcomes.
RESULTS: Patients with low voltage (3.2%) had higher GRACE risk scores, rates of prior myocardial infarction, and pathological Q waves, with less prevalent ST-segment deviation and ST-segment depression. They had worse left ventricular function and higher unadjusted rates of in-hospital and 6-month mortality. After adjustment for established prognosticators in the GRACE risk models in multivariable analysis, low voltage was independently associated with higher in-hospital mortality (adjusted OR 1.77, 95% CI 1.13-2.78, P=0.013) and mortality/re-infarction (adjusted OR 1.42, 95% CI 1.05-1.93, P=0.023), but not 6-month mortality (adjusted OR 1.25, 95% CI 0.85-1.84, P=0.27). There was no significant interaction between low voltage and ST-segment deviation for any endpoint (interaction P>0.10 for all endpoints).
CONCLUSIONS: Low QRS voltage was associated with previous myocardial infarction and adverse hemodynamic variables at presentation. After adjusting for other prognosticators, low voltage independently predicted higher in-hospital mortality. This increased risk was not modulated by concomitant ST-segment deviation.