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First published online on June 15, 2007
Chest, doi:10.1378/chest.07-0430
doi:10.1378/chest.07-0430
(Chest. 2007; 132:554-561)
© 2007 American College of Chest Physicians
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Double Trouble for 2,609 Hospitalized Medical Patients Who Developed Deep Vein Thrombosis*

Prophylaxis Omitted More Often and Pulmonary Embolism More Frequent

Gregory Piazza, MD; Ali Seddighzadeh, MD, MSc and Samuel Z. Goldhaber, MD, FCCP

* From the Cardiovascular Division (Dr. Piazza), Beth Israel Deaconess Medical Center, Boston, MA; and the Cardiovascular Division (Drs. Seddighzadeh and Goldhaber), Brigham and Women’s Hospital, Department of Medicine, Harvard Medical School, Boston, MA.

Correspondence to: Gregory Piazza, MD, Cardiovascular Division, Beth Israel Deaconess Medical Center, 1 Deaconess Rd, Baker 4, Boston, MA 02215; e-mail: gpiazza{at}bidmc.harvard.edu

Abstract

Background: Hospitalized patients with medical illness are especially susceptible to the development of venous thromboembolism (VTE).

Methods: To improve our understanding of the demographics, comorbidities, risk factors, clinical presentation, prophylaxis, and treatment of hospitalized medical patients with deep vein thrombosis (DVT), we evaluated hospitalized medical patients in a prospective registry of 5,451 consecutive ultrasound-confirmed DVT patients at 183 institutions in the United States.

Results: Of those patients who participated in the registry, 2,609 (48%) were hospitalized medical patients. Compared with 1,953 hospitalized nonmedical patients with DVT, medical patients with DVT experienced pulmonary embolism (PE) more often (22.2% vs 15.5%, respectively; p < 0.0001). However, medical patients in whom DVT developed had received VTE prophylaxis far less frequently than nonmedical patients (25.4% vs 53.8%, respectively; p < 0.0001). The underutilization of VTE prophylaxis among hospitalized medical patients extended to both pharmacologic and mechanical modalities. In a multivariable logistic regression analysis of all hospitalized VTE patients, status as a medical patient was negatively associated with receiving prophylaxis (adjusted odds ratio, 0.47; 95% confidence interval, 0.28 to 0.78).

Conclusions: Hospitalized medical patients face "double trouble." First, during hospitalization for a reason other than VTE, VTE prophylaxis is omitted in medical patients more often than in nonmedical patients. Second, when VTE develops as a complication of hospitalization, hospitalized medical patients experience PE more often. Further studies should focus on understanding why prophylaxis is often omitted in hospitalized medical patients and on improving its implementation in this vulnerable population.

Key Words: deep vein thrombosis • medical patients • prevention • prophylaxis • pulmonary embolism • risk factors • treatment • venous thromboembolism

Venous thromboembolism (VTE), which encompasses deep vein thrombosis (DVT) and pulmonary embolism (PE), represents a spectrum of disorders that afflict millions of individuals worldwide and accounts for a significant number of hospitalizations annually in the United States.1 Furthermore, the incidence of DVT among hospitalized patients has increased.2 Complications associated with DVT may range from postthrombotic syndrome to acute PE with a 3-month mortality rate that exceeds 15%.345 Death usually occurs because of right ventricular dysfunction and, ultimately, right ventricular failure.6 Common conditions among hospitalized medical patients such as COPD, congestive heart failure, acute infection, and atherosclerotic vascular disease are associated with an increased risk of the development of VTE.78910 In this study, we explored the demographics, comorbidities, risk factors, clinical presentation, prophylaxis, and initial treatment of 2,609 hospitalized medical patients who were enrolled in the 183-center US DVT Registry of 5,451 patients with ultrasound-confirmed DVT.11

Materials and Methods

Patient Population
DVT Registry enrollment occurred from October 2001 to March 2002. Data were ascertained based on baseline patient characteristics, prophylaxis prior to the diagnosis of DVT, and initial treatment strategies. The only inclusion criterion was confirmation of DVT by venous ultrasound. The registry had no exclusion criteria.

We defined medical patients as those patients who had not undergone surgery within the 3 months prior to diagnosis. We defined hospitalized patients as those who were inpatients at the time of the diagnosis of DVT or who were subsequently admitted to the hospital when the diagnosis of DVT was established. We excluded 549 patients who had been treated exclusively as outpatients and 340 patients who had uncertain hospitalization status. PE was diagnosed when confirmed by a high-probability ventilation-perfusion lung scan, positive contrast-enhanced chest CT scan, contrast-enhanced magnetic resonance pulmonary angiogram, or conventional contrast pulmonary angiogram.

Data Collection
Data on patients with ultrasound-confirmed DVT were extracted from medical records at each study site and were recorded on case report forms by designated study coordinators. Each site that enrolled three or more patients was monitored with at least one site visit by an independent auditor, who confirmed the ultrasound diagnosis of DVT and reviewed the medical records to ensure accuracy. A standardized method of venous ultrasound interpretation was used. All patients were required to meet a primary criterion of noncompressibility of the vein for the diagnosis of DVT by venous ultrasound.12131415 Investigational review board approval was obtained from all 183 study sites.

Statistical Analysis
The mean or median and frequency of distributions were calculated for continuous variables. We used the Student t test or the Wilcoxon rank sum test to assess differences in the means or medians, respectively. Categoric variables were compared using the {chi}2 test or Fisher exact test. All tests were two-tailed, and a p value of < 0.05 was considered to be statistically significant. Variables that differed significantly between hospitalized medical patients and hospitalized nonmedical patients in univariable analyses were entered into a multivariable logistic regression model and adjusted for age to identify confounders of prophylaxis utilization. All statistical analyses were performed using a statistical software package (STATA, version 9.2; STATA Corp; College Station, TX).

Results

Baseline Characteristics
Hospitalized medical and nonmedical patients were similar with regard to median age (Table 1 ). However, hospitalized medical patients were more likely to be < 50 years old (24.1% vs 20.7%, respectively; p = 0.01) and > 80 years old (18.7% vs 12.9%, respectively; p < 0.0001) compared with hospitalized nonmedical patients (Fig 1 ). Hospitalized medical patients were more likely to have a body mass index (BMI) of > 35 kg/m2 (16.3% vs 13.9%, respectively; p = 0.04) compared with hospitalized nonmedical patients (Fig 2 ). Among 568 patients admitted to an ICU, 207 (36.4%) were medical patients and 361 (63.6%) were nonmedical patients.


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  		Table 1.. Baseline Characteristics of Patients With DVT*

 

Figure 1
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  		Figure 1.. Distribution of patients with DVT by age.

 

Figure 2
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  		Figure 2.. Distribution of patients with DVT by BMI.

 
Comorbidities and Risk Factors
Medical patients were more likely to have comorbid conditions of neurologic disease including stroke (27.1% vs 23.3%, respectively; p = 0.005) and acute lung disease including pneumonia (21.5% vs 14.4%, respectively; p < 0.0001) [Table 2 ]. Compared with hospitalized nonmedical patients, medical patients were more likely to have VTE risk factors of COPD (16.9% vs 13.2%, respectively; p = 0.001), congestive heart failure (16.8% vs 13.7%, respectively; p = 0.008), family history of VTE (10.5% vs 5.9%, respectively; p = 0.0001), personal history of VTE (30.1% vs 24%, respectively; p < 0.0001), protracted travel (9.9% vs 1.5%, respectively; p < 0.0001), and a diagnosis of thrombophilia (6.4% vs 4.3%, respectively; p = 0.005) than nonmedical patients (Table 2). Hospitalized medical patients were also more likely to be current smokers (17% vs 11.9%, respectively; p < 0.0001). In addition, hospitalized medical patients had a higher frequency of hormonal contraceptive use, hormonal replacement therapy, and pregnancy (24.3% vs 20.3%, respectively; p = 0.03). In the intensive care setting, medical patients with DVT were more likely to have congestive heart failure (31% vs 19.9%, respectively; p = 0.005) and COPD (29.4% vs 18.5%, respectively; p = 0.005) compared with nonmedical patients.


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  		Table 2.. Comorbid Conditions and VTE Risk Factors in Patients With DVT*

 
Clinical Presentation of VTE
Compared with hospitalized nonmedical patients with DVT, medical patients more often experienced symptoms of VTE (Table 3 ). In addition, hospitalized medical patients experienced more anatomically extensive VTE than nonmedical patients, as follows: PE, 22.2% vs 15.5%, respectively (p < 0.0001); proximal lower extremity DVT, 40.8% vs 36.3%, respectively (p = 0.002); and proximal lower extremity DVT with calf extension (40.9% vs 30.4%, respectively (p < 0.0001) [Table 4 ]. In contrast, calf DVT (12.9% vs 20%, respectively; p < 0.0001) and upper extremity DVT (8.3% vs 16.9%, respectively; p < 0.0001) were less likely to develop in hospitalized medical patients compared with nonmedical patients.


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  		Table 3.. Clinical Presentation of VTE*

 

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  		Table 4.. Characteristics of VTE Among Hospitalized Medical and Nonmedical Patients With DVT*

 
Prophylaxis of VTE
Hospitalized medical patients in whom DVT was diagnosed were less than one half as likely to have received VTE prophylaxis compared with nonmedical patients prior to the development of DVT (25.4% vs 53.8%, respectively; p < 0.0001) [Table 5 ]. In a multivariable logistic regression analysis of all hospitalized patients, status as a medical patient was negatively associated with receiving VTE prophylaxis (adjusted odds ratio, 0.47; 95% confidence interval, 0.28 to 0.78). The frequency of prophylaxis was low among patients in whom idiopathic (unprovoked) VTE subsequently developed and among those in whom DVT in the setting of trauma or cancer subsequently developed (37.7% vs 25.6%, respectively; p < 0.0001). Furthermore, we observed low rates of VTE prophylaxis among medical patients who were inpatients at the time of diagnosis, as well as in those patients who were outpatients and were subsequently admitted for the treatment of VTE (38.1% vs 14.8%, respectively; p < 0.0001).


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  		Table 5.. Characteristics of VTE Prophylaxis in Hospitalized Medical and Nonmedical Patients With DVT*

 
We observed underutilization of VTE prophylaxis with both pharmacologic and mechanical modalities (Table 5). The frequency of prophylactic inferior vena cava filter placement was similar between hospitalized medical and nonmedical patients. Among patients admitted to the ICU in whom DVT subsequently developed, medical patients were much less likely to receive VTE prophylaxis compared with nonmedical patients (51.6% vs 76.7%, respectively; p < 0.0001).

Initial Treatment of VTE
Most hospitalized medical and nonmedical patients were initially treated with either low-molecular-weight heparin or IV unfractionated heparin as a "bridge" treatment to therapeutic oral anticoagulation with warfarin (Table 6 ). Hospitalized medical patients were less likely to undergo inferior vena cava filter placement as the initial therapy for VTE (13.6% vs 18.2%, respectively; p < 0.0001) compared with nonmedical patients.


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  		Table 6.. Characteristics of VTE Therapy in Hospitalized Medical and Nonmedical Patients With DVT*

 
Discussion

This large "real-world" registry highlights several important distinctions between hospitalized medical patients with DVT and their nonmedical counterparts. Hospitalized medical patients represent a vulnerable subgroup with higher clot burden and lower rates of VTE prophylaxis. Compared with nonmedical patients, hospitalized medical patients had an approximately 43% higher relative frequency of PE. Despite having many risk factors for VTE as well as comorbid conditions that may further magnify the risk, hospitalized medical patients received VTE prophylaxis less than one half as often as nonmedical patients. Even within the particularly high-risk setting of the ICUs, medical patients were prescribed VTE prophylaxis before the diagnosis of DVT only about two thirds as often as nonmedical patients.

Similar to another registry analysis,16 we observed a higher frequency of PE among hospitalized medical patients compared with nonmedical patients. In addition to having more frequent PE, hospitalized medical patients experienced proximal lower extremity DVT with and without calf extension more often and isolated calf DVT less often than nonmedical patients. Based on these findings, hospitalized medical patients may be at risk for a more extensive and ominous clot burden than nonmedical patients. Further studies to elucidate differences in the pathophysiology of VTE between medical and nonmedical patients are necessary to explain these findings. In our analysis, PE may have been more common in hospitalized medical patients because they reported dyspnea and chest pain more often than nonmedical patients, thus prompting further evaluation for PE more frequently. Although highly statistically significant, the clinical importance of the difference in frequency of PE among hospitalized medical and nonmedical patients remains debatable.

The use of VTE prophylaxis including pharmacologic or mechanical modalities is a critical component of the care of hospitalized patients.1718 A recent metaanalysis19 that included a large proportion of low-risk patients demonstrated significant reductions in PE with pharmacologic prophylaxis. Guidelines published by the American College of Chest Physicians5 and the International Union of Angiology20 have defined the appropriate use of VTE prophylaxis. In our registry, we found a low rate of VTE prophylaxis in both medical and nonmedical patients (25.4% vs 53.8%, respectively). Despite having a higher frequency of risk factors for VTE, medical patients received prophylaxis less than one half as often as nonmedical patients. Our finding of VTE prophylaxis underutilization in medical patients is consistent with those of prior studies.162122

We do not know why VTE prophylaxis is omitted in medical patients with such a high frequency. Many patients may have comorbid conditions such as recent bleeding, chronic kidney disease, thrombocytopenia, or abnormal coagulation study findings that may result in a reluctance to administer anticoagulants.23 Contraindications to anticoagulant use among medical patients can explain the withholding of pharmacologic prophylaxis. However, mechanical prophylaxis can reduce VTE rates without increasing the risk of bleeding.24252627 Of note, most studies that have demonstrated the efficacy of mechanical prophylaxis have been performed in surgical patients rather than medical patients. A recent metaanalysis28 of trials evaluating the use of mechanical prophylaxis among critically ill patients, including those with medical illnesses, was unable to make a strong recommendation. Because it is a low-risk intervention, the use of mechanical VTE prophylaxis in hospitalized medical patients is reasonable, especially when contraindications to pharmacologic modalities are present, despite the current lack of evidence.

Prophylaxis patterns may have varied due to patient hospitalization status at the time of the diagnosis of VTE. Current practice is to administer VTE prophylaxis while the patient is in the hospital. On hospital discharge, it is assumed that the risk of VTE abates, and, consequently, prophylaxis is discontinued. However, the risk of VTE often persists as many patients continue to have limited mobility as well as other ongoing risk factors resulting in the development of VTE. Recent data29 have shown that a substantial proportion of patients in whom VTE develops as outpatients had recently undergone surgery or had been hospitalized within the 3 months preceding the diagnosis. Based on these data, the distinction between medical patients who are inpatients at the time of diagnosis and those in whom VTE develops as outpatients may not be as clear as previously thought. Although outpatient status may partly explain underutilization for medical patients who were admitted to the hospital after the diagnosis, we still observed a low rate of prophylaxis (38.1%) among inpatients who were hospitalized for other medical illnesses and in whom DVT subsequently developed.

The clinician’s assessment of the individual patient’s risk of VTE may also impact the use of VTE prophylaxis. Medical patients with risk factors such as cancer or recent trauma may be expected to receive prophylaxis more often than those without conditions known to provoke VTE. However, we observed a low rate of prophylaxis in all VTE patients, regardless of whether the VTE was provoked or idiopathic. Counterintuitively, patients with idiopathic VTE received prophylaxis more often than those with provoked DVT or PE. Although the reasons for this finding are unclear, the underutilization of prophylaxis in patients with risk factors known to provoke VTE highlights important deficiencies in the VTE prophylaxis of hospitalized medical patients.

In addition to a lower frequency of VTE prophylaxis, we observed a high rate of risk factors and comorbid conditions that contribute to the development of VTE among hospitalized medical patients. Higher rates of current smoking, obesity, personal or family history of VTE, and neurologic disease, including stroke, COPD, congestive heart failure, thrombophilia, and protracted travel, identify hospitalized medical patients as a high-risk patient population. Although statistically significant, the clinical difference in the rates of some of these conditions between hospitalized medical and nonmedical patients may be debatable.

Further education is required to raise awareness among health-care providers serving the medical patient population in order to encourage consistent VTE prophylaxis. Computerized provider order entry alerts have been shown to be an effective technique for improving VTE prophylaxis utilization and decreasing symptomatic DVT and PE among hospitalized patients.30 A VTE prevention program utilizing clinician education, verbal reminders, computerized recordings of adherence, and public reporting of performance markedly improved the consistency of VTE prophylaxis in the intensive care setting.31

The current analysis is limited by the exclusion of patients for whom data regarding hospitalization status was unclear. Although the loss of data most likely occurred in a balanced proportion between medical and nonmedical patients, the introduction of bias cannot be excluded. Furthermore, unrecognized confounding may remain despite extensive assessment of patient characteristics. The overall rate of PE may have been underestimated because enrollment in the registry did not require evaluation for PE. Finally, the registry does not provide data on outcomes or survival.

The methodology used in our study is consistent with the published criteria for assessing the scientific value of a clinical data registry.32 Consecutive patients with ultrasound-confirmed DVT were enrolled in the registry from diverse clinical sites, including urban, suburban, and rural medical centers, throughout the United States. A steering committee was responsible for overseeing the study. Institutional review board approval was obtained at each site.11 The diagnosis of DVT was standardized using the well-recognized ultrasound criterion of venous noncompressibility.121314 Venous ultrasonography has been validated for use in the diagnosis of DVT in both symptomatic and asymptomatic patients.1314 In addition, an independent auditor confirmed the diagnosis of DVT and reviewed the medical records of patients at all sites that enrolled three or more participants.

In summary, a higher prevalence of PE and a lower rate of VTE prophylaxis utilization spell double trouble for hospitalized medical patients. These patients comprise a vulnerable patient population with multiple comorbidities and risk factors for VTE, a higher rate of concomitant PE, and an unacceptably low rate of prophylaxis when compared to nonmedical patients. Even among the sickest of hospitalized medical patients, those in the intensive care setting, VTE prophylaxis was prescribed with surprisingly low frequency. This study suggests deficiencies in our implementation of VTE prophylaxis among hospitalized medical patients, a group that is especially susceptible to the development of DVT and PE. Further studies are required to elucidate why hospitalized medical patients with DVT may experience PE more often compared with nonmedical patients. Our report should serve as a catalyst for further study to identify why VTE prophylaxis is omitted and how utilization can be improved among hospitalized medical patients.

Footnotes

Abbreviations: BMI = body mass index; DVT = deep vein thrombosis; PE = pulmonary embolism; VTE = venous thromboembolism

This study was supported, in part, by an unrestricted research grant from Sanofi-Aventis.

Dr. Goldhaber has recieved consulting fees and clinical research support from Sanofi-Aventis. Drs. Piazza and Seddighzadeh have no conflicts of interest to disclose.

Received for publication February 15, 2007. Accepted for publication April 27, 2007.

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