In a comparison of thrombotic events between the first wave and second wave of the COVID-19 virus, the risk of overall mortality was 47% lower among all patients in the second wave, according to study results published in Thrombosis Research. However, patients in the second wave of COVID-19 had incidences of thrombotic complications that were high and unchanged compared with patients in the first wave, despite the more advanced therapy and thromboprophylaxis given to patients in the second wave.

Although the risk of thrombotic complications was comparable between patients in the first and second waves, study researchers noted that there was an increased risk of thrombotic complications in patients admitted to the general ward and a decreased risk in patients admitted to the ICU. They determined this was likely due to a lower threshold of early diagnostic testing for thrombotic complications for patients in the ICU, although they also identified other potential explanations.

The study cohort included a total of 947 adult patients with COVID-19 admitted to the wards and ICUs of 4 university hospitals and 4 teaching hospitals in the Netherlands during the second wave of COVID-19 infections (September 1 to November 30, 2020). Of these patients, 860 were admitted to the general wards and 358 were admitted to the ICU (271 patients were admitted to both the general ward and ICU). Patients had an average age of 66 years, 603 patients (64%) were men, and 127 patients (13%) used anticoagulation therapeutics.

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Of the patients included in the study, 120 patients (13%) were diagnosed with thrombotic complications (4 patients were diagnosed with both a venous thromboembolism [VTE] and an arterial thromboembolism [ATE]). Of the ATEs, most were an ischemic stroke (60%). Acute pulmonary embolism (PE) was the most diagnosed thrombotic complication (78%). A total of 144 patients (15%) died.

Among the 860 patients admitted to the ward, 73 patients (8.5%) were diagnosed with thrombotic complications; 59 patients were diagnosed with VTE, of whom 58 had a PE, and 12 patients were diagnosed with an ATE. Out of the ATEs, 9 patients had ischemic strokes, 3 had a myocardial infarction, 1 had a peripheral arterial embolism, and 1 had a thrombosis in an endovascular aneurysm repair (EVAR). A total of 70 patients (8.1%) died.

Compared with the first wave of patients with COVID-19, the adjusted hazard ratio (HR) for overall mortality in all patients (ward and ICU combined) in the second wave was 0.53 (95% CI, 0.41-0.70). Compared to the first wave of patients with COVID-19, the HR for thrombotic complications in the second wave of patients was 0.89 (95% CI, 0.65-1.2).

“Careful attention to provision of adequate thromboprophylaxis remains invariably warranted,” the study authors wrote in their report. “It remains to be demonstrated by randomized trials whether full dose anticoagulation will lead to lower incidences of thrombotic complications and associated lower mortality, without inducing too much bleeding.”

Disclosures: Some authors have declared affiliations with or received funding from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.


Kaptein FHJ, Stals MAM, Grootenboers M, et al. Incidence of thrombotic complications and overall survival in hospitalized patients with COVID-19 in the second and first wave. Thrombosis Research. 2021;199:143-148. doi:10.1016/j.thromres.2020.12.019

This article originally appeared on The Cardiology Advisor