Proximal DVT Associated with Worse Prognosis, Outcomes than Isolated Distal DVT

New research from a multinational team of investigators is providing clinicians with an overview of the similarities and differences in presentation and risk of adverse outcomes observed for patients with isolated distal deep vein thrombosis (DVT) and proximal DVT.

An analysis of data from the Registro Informatizado Enfermedad Tromboembólica (RIETE) registry, which provided data on more than 30,000 patients from 200 centers in Africa, North and South America, Asia, and Europe, offers insight into the clinical characteristics of these patients and differences in short- and long-term outcomes, including a lower risk of 90-day mortality and 1-year stroke risk among those with isolated distal DVT compared to proximal DVT.

“Results of this cohort study suggest that patients with IDDVT had a less ominous prognosis compared with patients with proximal DVT. Such differences were likely multifactorial, including the differences in demographics, risk factors, comorbidities, particularly for all-cause mortality, and a potential association of thrombus location with VTE deterioration and postthrombotic syndrome,” wrote investigators.

Citing a lack of large, long-term studies assessing risk factors and comorbidities in those isolated distal DVT and proximal DVT, investigators conducted the current study with an interest in addressing these gaps in knowledge to improve prognostication treatment of these patients. With this in mind, investigators designed their study as an analysis of data obtained from the ongoing RIETE registry.

A prospective, ongoing registry of patients with venous thromboembolism (VTE) and pulmonary embolism, the RIETE registry contains data related to more than 100,000 and is the largest database on patients with VTE. Enrolling consecutive patients with objectively confirmed VTE and a minimum follow-up of 3 months from more than 200 centers across multiple continents, the registry provided investigators with data related to 33,897 for inclusion in the current analysis.

For the purpose of analysis, investigators limited their study to patients with isolated distal DVT and those with proximal DVT enrolled in the registry from March 1, 2001-February 28, 2021. Investigators noted patients were excluded if they had a history of asymptomatic DVT, upper-extremity DVT, coexisting pulmonary embolism, or COVID-19 infection.

Of the 33,897 patients identified for inclusion, 5938 had isolated distal DVT and 27,959 had proximal DVT. The cohort with isolated distal DVT had a mean age of 61 (SD, 17) years, 50.1% were male, and the mean BMI was 27.6 (SD, 5.2) kg/m2. The cohort with proximal DVT had a mean age of 65 (SD, 18) years, 51.2% were male, and the mean BMI was 27.8 (SD, 5.2) kg/m2. Compared to their counterparts with proximal DVT, those with isolated distal DVT were less likely to have chronic lung disease (6.9% vs 8.7%), prior stroke (4.2% vs 5.9%), prior VTE (14.2% vs 18.8%), or cancer (12.2% vs 16.8%), but more likely to have had recent surgery (15.6% vs 9.2%) or estrogen/hormone therapy use (13.5% vs 9.7%)

The primary outcomes of interest for the study 90-day and 1-year mortality, 1-year major bleeding, and 1-year VTE deterioration, which was defined as subsequent development of proximal DVT or PE. Investigators pointed out Cox proportional hazards models were used to assess 1-year all-cause mortality and Fine-Gray models were used to assess for 1-year PE-related mortality, VTE deterioration, and major bleeding.

Upon analysis, results indicated patients with isolated distal DVT had a lower risk of 90-day mortality (OR, 0.47 [95% CI, 0.40-0.55]) than their counterparts with proximal DVT. Similar results were observed when assessing 1-year risk of mortality in unadjusted (HR, 0.52 [95% CI, 0.40-0.55]) and adjusted analyses (HR, 0.72 [95% CI, 0.64-0.82]). Additionally, results also indicated those with isolated distal DVT had a lower risk of VTE deterioration in the first year than those with proximal DVT (HR, 0.83 [95% CI, 0.69-0.99]).

In further analysis assessing 1-year risk among patients without an adverse event with the first 3 months, investigators found those with isolated distal DVT had a lower risk of VTE deterioration than those with proximal DVT. At the 1-year follow-up, symptoms or signs of postthrombotic syndrome were observed less frequently in those with isolated distal DVT compared to those with proximal DVT (47.6% vs 60.5%).

“We urge caution for appropriate interpretation of the study results. Patients with isolated distal DVT had a lower burden of comorbidities and were more likely to have postoperative DVT than those with proximal DVT,” investigators wrote. “Differences in outcomes for patients with IDDVT compared with proximal DVT may be related to inherent differences in the risk profile and characteristics in each group, or a true difference as a result of the location of the DVT.”

This study, “Clinical Presentation and Short- and Long-term Outcomes in Patients With Isolated Distal Deep Vein Thrombosis vs Proximal Deep Vein Thrombosis in the RIETE Registry,” was published in JAMA Cardiology.