Thrombotic complications are rife among in-hospital patients with COVID-19, with patients in the ICU particularly at risk compared with those in the general wards, a study released at the ISTH 2020 Meeting has shown.

Nonetheless, adoption of more intensive anticoagulation strategies had led to fewer venous thromboembolism (VTE) diagnoses, as suggested by another study.

In the first study, 579 patients with COVID-19 in three Dutch hospitals were monitored for thrombotic complications during hospitalization. All patients were given pharmacological thromboprophylaxis. [ISTH 2020, abstract LB/CO01.4]

Out of the 71 thrombotic complications that occurred during admission, 50 developed in the ICU compared with 17 in a general ward. More than three-quarter of the complications were due to pulmonary embolism (76.1 percent).

At 30 days, the cumulative incidence of the composite of all thrombotic complications at the general ward was 5.3 percent (95 percent confidence interval [CI], 2.4–8.2). However, this cumulative rate quadrupled to 20.5 percent when those in the ICU were combined (95 percent CI, 15.6–25.4). 

Similarly, the cumulative incidence of VTE, specifically, was 3.8 percent (95 percent CI, 1.3–6.3) at the general ward and 18.7 percent (95 percent CI, 14.0–23.4) for both ward and ICU patients combined at 30 days.

The rates of VTE, both for all patients (18.7 percent) and when considering general ward alone (3.8 percent), were higher among patients with COVID-19 than those hospitalized for influenza (1.04, 95 percent CI, 0.92–1.16).

“The incidence of thrombotic complications in hospitalized COVID-19 patients was substantial, and considerably higher than that in hospitalized influenza patients, suggesting a possible SARS-COV-2 specific effect,” the researchers noted.

In addition, the 30-day incidence for arterial thromboembolism was 3.4 percent (95 percent CI, 1.2–5.6) for both ward and ICU combined — indicating that the composite outcome was mainly driven by VTE.

Also, while the cumulative VTE incidence continued to rise from 7.1 percent at 7 days to 18.7 percent at 30 days in all patients combined (ie, including ICU), those in the general ward alone stabilized at 3.8 percent from 11 days onward.

“COVID-19 may lead to thrombotic complications, aggravated by a stay at the ICU,” said the researchers.

As people became increasingly aware of VTE complications that could arise with COVID-19, thromboprophylaxis strategies also changed with the progression of the pandemic.

A separate retrospective study was conducted to look at how changes in thromboprophylaxis affected VTE incidence among 450 patients hospitalized with COVID-19 at the University Hospital of Lausanne, Switzerland. [ISTH 2020, abstract PB/CO18]

Among these patients, 41 were diagnosed with VTE, with pulmonary embolism being the most common VTE (n=27), followed by deep vein thrombosis (n=12) and one case of portal vein thrombosis and another with deep vein thrombosis plus pulmonary embolism. 

Of the patients with VTE, 18 (43.9 percent) developed the complication within 72 hours after admission, while 23 (56.1 percent) occurred later during the hospital stay after 72 hours.

Specifically, 22 patients who developed VTE were in the ICU, with 16 of the cases being late VTE. Of the late cases, fewer occurred while under intermediate intensity vs standard-of-care thromboprophylaxis (3 vs 13 cases; 4.9 vs 18.5 per 1,000 ICU-days; p=0.040).

“This reduction of VTE diagnoses could reflect the effect of more aggressive anticoagulation strategies implemented in ICU hospitalized patients,” the researchers concluded.