Haemodynamically unstable pulmonary embolism in the RIETE Registry: systolic blood pressure or shock index?

Patients with acute pulmonary embolism (PE) presenting with haemodynamic instability have the worst prognosis. However, what is understood by haemodynamic instability has not been clearly defined. The Registro Informatizado de la Enfermedad Tromboembólica (RIETE) is an ongoing registry of consecutive patients with symptomatic, objectively confirmed, acute deep vein thrombosis or PE. The present authors compared the predictive value of a systolic blood pressure (SBP) value of <100 mmHg and <90 mmHg and the shock index (cardiac frequency divided by SBP) on 30-day mortality in consecutive patients with PE. As of May 2006, 6,599 patients with PE were enrolled in the study. Of these, 417 (6.3%) died within 30 days: 153 of the initial PE, 29 of recurrent PE and 235 due to other causes. Of the 417 individuals who died, 127 (30%) had a positive shock index, 60 (14%) had SBP <100 mmHg and 33 (7.9%) had SBP <90 mmHg. On multivariate analysis any of the three parameters were independently associated with an increased mortality. The shock index had a higher sensitivity (30.5 versus 14.4 and 7.9% for SBP <100 mmHg and <90 mmHg, respectively) but lower specificity (86.3 versus 93.0 and 96.6). All three measures of haemodynamic instability are independent predictors of 30-day mortality. However, while the shock index had the highest sensitivity, a systolic blood pressure value <90 mmHg had the highest specificity.