Electrocardiographic findings in cardiogenic shock, risk prediction, and the effects of emergency revascularization: results from the SHOCK trial

Objectives

To evaluate electrocardiographic (ECG) parameters as predictors of 1-year mortality in patients developing cardiogenic shock after acute myocardial infarction (AMI), and to document associations between these ECG parameters and the survival benefit of emergency revascularization versus initial medical stabilization.

Background

Emergency revascularization reduces the risk of mortality in patients developing cardiogenic shock after AMI. The prognostic value of ECG parameters in such patients is unclear, and it is uncertain whether emergency revascularization reduces the mortality risk denoted by ECG parameters.

Methods

In a prospective substudy of 198 SHOCK (SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK) trial patients, ECGs recorded within 12 hours of shock were interpreted by personnel blinded to the patients' treatment assignment and outcome.

Results

The baseline heart rate was higher in non-survivors than in survivors (106 ± 20 versus 95 ± 24 beats/minute, P = .001). There was a significant association between the QRS duration and 1-year mortality in medically stabilized patients (115 ± 28 ms in non-survivors versus 99 ± 23 ms in survivors, P = .012), but not in emergently revascularized patients (110 ± 31 versus 116 ± 27 ms respectively, P = .343). The interaction between the QRS duration, mortality and treatment assignment was significant (P = .009). Among patients with inferior AMI, a greater sum of ST depression was associated with higher 1-year mortality in medically stabilized patients (P = .029), but not in emergently revascularized patients (P = .613, treatment interaction P = .025). On multivariate analysis, the independent mortality predictors were increasing age, elevated pulmonary capillary wedge pressure, heart rate, sum of ST depression in medically stabilized patients, and interaction (P = .016) between a prolonged QRS duration and treatment assignment. The adjusted hazard ratio for 1-year mortality per 20 ms increase in the QRS duration was 1.19 (95% CI 0.98-1.46) in medically stabilized patients and 0.81 (95% CI 0.63-1.03) in emergently revascularized patients.

Conclusion

ECG parameters identified patients with cardiogenic shock who were at high risk. Emergency revascularization eliminated the incremental mortality risk associated with cardiogenic shock in patients with a prolonged QRS duration, or inferior AMI accompanied by precordial ST depression. Prospective assessments of the magnitude of the treatment effect based on ECG parameters are required.