Research from recent issues of Blood Advances
How Common Is Venous Thromboembolism in Patients Hospitalized With COVID-19 ?
Reports have suggested that venous thromboembolism ( VTE ) is a frequent complication of COVID-19 infection , and patients are at an increased thrombotic risk even with prophylactic anticoagulation , but the reported incidence of VTE varies based on geographic area and disease severity . In a study published in Blood Advances , researchers reviewed electronic health record ( EHR ) data from a large academic health system to characterize the association between VTE and COVID-19 infection , finding an overall VTE incidence of 3.1 % among patients hospitalized with COVID-19 . Risk was higher for patients who received mechanical ventilation .
The authors , led by Jason Hill , MD , of the University of Queensland Ochsner Clinical School in New Orleans , also noted , “ Although our overall rate of VTE in hospitalized patients was low , half of our cases occurred in patients who were receiving effective VTE prophylaxis prior to their VTE .” Still , they concluded that a traditional primary VTE prevention approach is sufficient for patients with COVID-19 , at least until more widescale and longer-term investigations are performed .
For this study , Dr . Hill and coauthors performed a retrospective review of EHR data obtained from Ochsner Health , a large New Orleans-based academic health care system . The analysis included records from 6,153 patients with PCR-confirmed COVID-19 infection who were admitted to the hospital or treated and discharged from an emergency department ( ED ) between March 1 and May 1 , 2020 .
Of these patients , 2,748 were admitted to the hospital and 3,405 received care only through an ED . A total of 637 patients required mechanical ventilation and 206 required renal replacement therapy .
There were 86 total VTE events diagnosed during hospital stay and an additional 3 VTEs diagnosed in the ED , for an incidence rate of 3.1 %. Among the 86 patients who developed a VTE during hospital stay , 84 had received thromboprophylaxis . The 2 patients who did not receive thromboprophylaxis were considered at low risk for VTE , as determined by Padua prediction score . Pharmacologic prophylaxis included low-dose low-molecular-weight heparin or unfractionated heparin . Patients with a contraindication for medical anticoagulant therapy received mechanical prophylaxis with elastic compression stockings or sequential compression devices .
Most of the inpatient VTE events were deep vein thrombosis ( DVT ; 48 %), and 40.6 % were diagnosed as pulmonary embolism . The remaining VTE cases did not have confirmatory studies available and were deemed to have VTE based on clinical impression of the care team . Three patients experienced VTE after discharge ( 0.1 %), on or before May 21 .
Most of the patients who had a VTE had a “ high risk ” Padua score of ≥4 ( n = 77 ; 89 %); of this group , 74 experienced VTE during their hospital stay , and 4 experienced a post-discharge VTE .
One-half of the patients with new VTE during inpatient stay ( n = 43 ) met the criteria for “ prophylaxis failure ,” defined as any DVT or pulmonary embolism event diagnosed ≥3 days after the admission of a patient who had received ≥2 days of evidence-based mechanical or pharmacologic VTE prophylaxis immediately prior . This group included :
• 7 patients who received mechanical prophylaxis only
• 4 who received unfractionated heparin
• 5 who received only low-molecular-weight heparin
• 27 patients who received a combination of mechanical and pharmacologic prophylaxis
VTE incidence was substantially higher in the subgroup of patients with COVID-19 who needed mechanical ventilation during the hospital stay , at 7.1 % ( n = 45 / 637 ), the authors reported . However , “ our observation that VTE occurred in less than 10 % of patients requiring mechanical ventilation ( the vast majority of whom were probably receiving effective VTE prophylaxis ) suggests that the prophylaxis ‘ failure rate ’ among very sick patients with COVID-19 may not be dramatically different from what has been previously described in other critically ill populations ,” they noted .
In the hospitalized group , 2,075 patients survived to be discharged , for a mortality rate of 24.5 %. The mortality rate appeared to be slightly higher among patients diagnosed with a VTE , the researchers added , at 28 % ( n = 24 / 86 ).
Limitations of this study included its retrospective nature , particularly the EHR query strategy , which the researchers suggest may have missed some VTE cases . In addition , the study ’ s search strategy was not designed to capture VTE events beyond May 21 , especially those that were fatal or did not require medical attention . The researchers noted that many of the patients in this study are still at risk of VTE , and longer-term follow-up may be necessary to identify future VTE events .
“ Until additional prospective outcome data are reported , and underlying mechanisms are better understood ,” the researchers concluded , “ our findings support a traditional approach to VTE prophylaxis , both during and after hospitalization , for patients with COVID-19 .” However , the rate of prophylaxis failure indicates that traditional approach to VTE prophylaxis may be inadequate for some patients with COVID-19 .
The authors report no relevant conflicts of interest .
Reference Hill J , Garcia D , Crowther M , et al . Frequency of venous thromboembolism in 6,513 patients with COVID-19 : A retrospective study . Blood Adv . November 2020 . * Exact date of publication was not available at time of press .
52 ASH Clinical News November 2020