Impaired 6-min walk test, heart rate recovery and cardiac function post pulmonary embolism in long-term survivors

Abstract

Background: The functional capacity of long-term survivors of submassive pulmonary embolism (PE) is unreported. A six-minute walk distance (6MWD) <350 m and reduced heart rate recovery (HRR) indicate adverse prognosis in various chronic diseases.

Methods: Long-term survivors of acute PE (January 2000-June 2005) were invited to undergo prospectively planned six-minute walk test (6MWT), transthoracic echocardiogram (TTE), clinical and biochemical evaluation with cardiac biomarkers. HRR was calculated as the difference between heart rate at 6-min during and at 1-min post 6MWT.

Results: 120 patients (52 males; mean age [±standard deviation] - 65 ± 14 years) were identified 7.7 ± 1.4 years after PE. 6MWD was significantly lower than that predicted after adjustment for age, sex, and height (448 ± 114 m vs 475 ± 89 m, p = 0.005), and 16% (17/104) had 6MWD <350 m. Among patients with no baseline comorbidities at follow-up (Charlson comorbidity index = 0), 8% (4/52) had 6MWD <350 m. Resting TTE identified 29% of patients had raised right ventricular (RV) pulmonary pressure (pulmonary arterial systolic pressure [PASP] >36 mmHg) and 13% had impaired RV function. Patients with 6MWD <85% predicted had significantly greater impairment of RV longitudinal function (p < 0.001), higher PASP (p < 0.001) and pulmonary vascular resistance (p < 0.001), elevated NT-proBNP (p = 0.03) and high-sensitivity troponin-T (HsTropT, p = 0.03), but similar left ventricular systolic and diastolic function, to those with normal 6MWT.

Conclusions: Apparently well, long-term survivors of PE demonstrate impaired exercise capacity, heart rate recovery, mild pulmonary hypertension, raised PVR and right ventricular dysfunction associated with elevated NT-proBNP and HsTropT.

Keywords: Echocardiography; Functional assessment; Pulmonary embolism; Six minute walk test.