Baseline Q waves as a prognostic modulator in patients with ST-segment elevation: insights from the PLATO trial

Abstract

Background: Baseline Q waves may provide additional value compared with time from the onset of symptoms in predicting outcomes for patients with ST-segment elevation. We evaluated whether baseline Q waves superseded time from symptom onset as a prognostic marker of one-year mortality in patients with ST-segment elevation acute coronary syndrome. Our study was derived from data from patients undergoing primary percutaneous coronary intervention within 24 hours in the PLATelet inhibition and patient Outcomes trial

Methods: Q waves on the baseline electrocardiogram were evaluated by a blinded core laboratory. We assessed the associations between baseline Q waves and time from symptom onset to percutaneous coronary intervention with peak biomarkers, ST-segment resolution on the discharge electrocardiogram, and one-year all-cause and vascular mortality.

Results: Of 4341 patients with ST-segment elevation, 46% had baseline Q waves. Compared to those without Q waves, those with baseline Q waves were older, more frequently male, had higher heart rates, more advanced Killip class and had a longer time between the onset of symptoms and percutaneous coronary intervention. They also had higher one-year all-cause mortality than patients without baseline Q waves (baseline Q waves: 4.9%; no baseline Q waves: 2.8%; hazard ratio [HR] 1.78, 95% confidence interval [CI] 1.29-2.45, p < 0.001). Complete ST-segment resolution was greatest and all-cause mortality lowest among those with symptom onset three hours or less before percutaneous coronary intervention and no baseline Q waves. After multivariable adjustment, baseline Q waves, but not time from symptom onset, were associated with a significant increase in all-cause mortality (adjusted HR 1.42, 95% CI 1.10-2.01, p = 0.046) and vascular mortality (adjusted HR 1.58, 95% CI 1.09-2.28, p = 0.02).

Interpretation: The presence of baseline Q waves provides useful additional prognostic insight into the clinical outcome of patients with ST-segment elevation. Clinical Trials.gov registration no. NCT00391872.

Figures

Figure 1:

Selection of patients for inclusion in the study cohort. ECG = electrocardiogram, LBBB = left bundle branch block, MI = myocardial infarction, PCI = percutaneous coronary intervention, STEMI = ST-segment elevation myocardial infarction.

Figure 2:

Kaplan–Meier survival analysis of all-cause mortality within one year of randomization, by the presence of Q waves. plogrank < 0.001.

Figure 3:

Kaplan–Meier survival analysis of all-cause mortality within one year, by time from the onset of symptoms to percutaneous coronary intervention (PCI). plogrank = 0.03.

Figure 4:

Associations among baseline Q waves, time from symptom onset and mortality. (A) Association between all-cause mortality within one year and baseline Q waves and time from symptom onset to percutaneous coronary intervention (PCI). *Adjusted for age, systolic blood pressure, heart rate, Killip class, myocardial infarction location, Q waves and time from symptom onset. (B) Association between vascular mortality within one year and baseline Q waves and time from the onset of symptoms to PCI. †Adjusted for age, systolic blood pressure, heart rate, Killip class, myocardial infarction location, presence of Q waves and time from symptom onset.