Weighing the consequences: body mass index trajectories after pediatric venous thromboembolism

Over the past 2 decades, the incidence of pediatric venous thromboembolism (VTE) has risen by an estimated 130% to 200% [1,2], prompting a concentrated research focus on identifying risk factors and optimizing prevention strategies through groups such as the Children’s Healthcare Advancements in Thrombosis (CHAT) [3,4] and the ongoing Catheter-Related Early Thromboprophylaxis with Enoxaparin (CRETE; NCT04924322) study [5]. Consequently, long-term outcomes have received comparatively less attention, with postthrombotic syndrome, a manifestation of chronic venous insufficiency, remaining the most well-studied sequela, affecting up to 25% of children following a VTE event [[6], [7], [8]]. In this issue of Research and Practice in Thrombosis and Haemostasis, Dang et al. [9] bring to light an important and underrecognized consequence of pediatric VTE: the increased prevalence of obesity in the months following VTE diagnosis. This study offers a novel perspective and underscores the need for expanded post-VTE surveillance in children that includes cardiometabolic health.

Dang et al. [9] present important findings on body mass index (BMI) trajectories following VTE diagnosis in children. The study evaluated 63 pediatric patients with a first episode of lower extremity deep vein thrombosis (DVT) and/or pulmonary embolism, enrolled in the Thrombosis Outcomes in Pediatric Venous Thromboembolism (TOP) study (NCT03068923). The TOP study, conducted at Children’s Medical Center Dallas, prospectively followed children for up to 24 months, with the broader aim of identifying biomarkers predictive of adverse outcomes after an initial VTE event. For this subanalysis, Dang et al. [9] examined changes in BMI over a 6-month period, using percent-of-BMI95, a measure that adjusts for age- and sex-specific growth and is calculated as ([BMI/BMI at the 95th percentile for age and sex] × 100).

The study found a mean increase in percent-of-BMI₉₅ of 1.5% (95% CI, −0.8 to 3.6) at 3 months and 2.2% (95% CI, −0.6 to 5.2) at 6 months following VTE diagnosis, with an even higher percentage mean increase of 3% and 4.5% at 3 and 6 months, respectively, for those without a stay in the intensive care unit. However, despite the overall trend toward weight gain, a decrease in BMI was observed in almost one-third of the total cohort, underscoring the need for further exploration into the factors driving these changes in patients who are critically ill and may lose lean muscle mass causing a decrease in BMI.

Rather than relying on raw BMI values, Dang et al. [9] utilized percent-of-BMI₉₅ as their primary outcome metric, a thoughtful and methodologically sound choice that accounts for age- and sex-related changes in BMI throughout childhood. This metric, which uses the US Centers for Disease Control and Prevention’s 95th percentile BMI cutoff as a reference point [10], offers a more precise assessment of obesity status during periods of expected growth and development. Identifying obesity as either a risk factor or a sequela of pediatric VTE has historically been complicated, particularly outside of adolescent and young adult populations, due to the natural increases in BMI associated with growth. Previous studies have often employed raw BMI (kilograms per square meter) [3,[11], [12], [13]] or BMI z-scores [14], which may not fully capture meaningful differences in adiposity, leading to mixed findings across patient groups, except in specific high-risk populations such as children with newly diagnosed acute lymphoblastic leukemia [15].

Percent-of-BMI₉₅ provides a dynamic and growth-adjusted measure of obesity, particularly well-suited for younger children who may not yet fall into conventional BMI classifications but may still be experiencing concerning upward shifts in weight. The application of this metric in the current study represents an important methodological advance and should be considered in future research investigating obesity as both a potential risk factor and a modifiable outcome in pediatric VTE. Moreover, its broader adoption could enhance the sensitivity of studies evaluating thrombotic risk in growing children, allowing for earlier intervention and more targeted prevention strategies.

These findings raise important considerations for clinical care, specifically the need for long-term follow-up even after VTE improvement or resolution. Given that obesity itself, like VTE, is increasing in incidence [16], the potential for further weight gain after a thrombotic event could contribute to a harmful cycle of recurrent thrombosis and compounding cardiovascular risk. Clinicians should counsel families on the importance of maintaining healthy activity levels and nutrition post-VTE, especially in the context of real or perceived limitations on exercise. Anecdotally, some healthcare providers advise patients to avoid physical activity acutely after a VTE out of theoretical fear of embolization, yet data suggest that early mobilization is both safe and beneficial to prevent increased weight gain and also postthrombotic syndrome [17].

Ideally, dedicated pediatric thrombosis care should integrate weight monitoring and early lifestyle interventions into the pediatric VTE recovery pathway (Table). Clinics should set up a multidisciplinary care model incorporating physicians, nurses, physical therapists, dieticians, and social workers or psychologists. Future research should aim to better understand the behavioral and psychosocial contributors to post-VTE weight changes in children. For example, assessing physical activity levels, screen time, gaming, dietary patterns, and psychosocial stressors before and after VTE could help identify modifiable targets for intervention.

Table.

Integrating weight management into post-VTE follow-up.

Timing	Opportunity	Rationale	Potential interventions
Initial VTE diagnosis	Screen for elevated BMI using percent-of-BMI95a	Early identification of overweight/obesity may signal future cardiometabolic risk	Routine BMI assessment; flag elevated percent-of-BMI95 for follow-up
Hospitalization or early outpatient visits	Educate families on physical activity and weight changes after VTE	Misconceptions about activity restrictions post-VTE may lead to reduced mobility and weight gain	Provide exercise guidance from thrombosis team; involve physical therapy
3–6 mo follow-up	Monitor BMI trajectory after VTE	Study shows average increase in BMI percent within 6 mo; critical window for intervention	Refer to dietitian or weight management services; reinforce healthy lifestyle counseling
Long-term follow-up (12+ mo)	Address persistent or worsening weight gain	Sustained obesity may compound long-term vascular and cardiometabolic risks	Consider integrating pediatric obesity specialists
Research and quality improvement	Embed weight management into VTE outcome studies	BMI change is an underrecognized but potentially modifiable outcome after VTE	Include BMI as a longitudinal outcome in VTE registries

BMI, body mass index; VTE, venous thromboembolism.

^aBMI₉₅ is a calculated measure adjusting for age- and sex-specific growth ([BMI/BMI at the 95th percentile for age and sex] × 100).

Moreover, expanding this research to include multisite or geographically diverse populations would allow for comparisons across different baseline rates of childhood obesity and social determinants of health. Given the disproportionately higher rates of obesity among Hispanic and non-Hispanic Black children in the United States, future studies should also strive for greater transparency in reporting race, ethnicity, and socioeconomic variables to fully understand disparities in outcomes [18].

Caution should be taken in terms of generalizing the results of this study to the broader population of children diagnosed with a VTE, specifically those who are chronically ill and underweight with complex medical conditions and those with upper extremity, typically central venous catheter–associated, DVT as both groups constitute a substantial portion of the pediatric VTE population [19,20]. This study’s cohort may be skewed toward children without underlying medical issues with lower extremity DVT or pulmonary embolism, presentations that may result in greater physical limitations or increased anxiety surrounding exertion. Future studies should consider evaluating physical activity patterns both before and after VTE or incorporating a control cohort without VTE to better isolate the effect of the thrombotic event on weight trajectory.

Ultimately, as the pediatric VTE population grows, there is a pressing need to shift our focus beyond acute management and toward the long-term sequelae of thrombosis, including its impact on metabolic health and quality of life.