DEEP VEIN THROMBOSIS



DEEP VEIN THROMBOSIS

Cary Gross, M.D.

WEEK 2: 01/10 – 01/14/05

Learning Objectives:

1. How to evaluate a patient with suspected DVT

2. How to incorporate D-dimers into the clinical decision making process

3. Which patients are candidates for outpatient therapy of DVT

CASE ONE:

Mrs. Z, a 44-year-old woman without significant PMH, presents for an urgent visit with left leg swelling of two days duration. She takes no medications and reports moderate leg pain but no chest pain, shortness of breath, or palpitations.

Questions:

1. What is the differential diagnosis of unilateral leg swelling?

The differential diagnosis for unilateral leg swelling includes both local and systemic processes. Local processes include superficial thrombophlebitis, ruptured popliteal (Baker’s) cyst, calf injury (with accompanying hematoma), asymmetric venous insufficiency, and other knee injuries. Systemic problems can include CHF, drug-related edema, or lymphedema – although all of these are usually symmetric.

2. What additional questions would you ask her, in order to help you to assess her probability of having a deep vein thrombosis (DVT)?

There are many risk factors for venous thromboembolism, including:

Inherited Coagulopathy – patients should be asked about family history of “blood clots,” multiple miscarriages, rheumatic disease, or prior DVT/PE.

Acquired Coagulopathy – patients should be asked about:

a. Cancer risk

i. Are they up to date on their screening tests?

ii. Family history of cancer?

iii. Any cancer “warning” signs/symptoms (i.e. change in

bowel habits, possible breast lump, bony pain, etc.)?

b. Pregnancy - could she be pregnant?

c. Chronic conditions that predispose to clots

i. CHF (i.e. inquire about CHF symptoms in this patient)

ii. Medication use (HRT, OCPs, Tamoxifen…)

iii. Obesity

iv. Stroke

Situations/Exposures

a. Recent Immobilization

b. Recent surgery

c. Trauma

CASE ONE CONTINUED:

She reports that she has no family history of blood clots to her knowledge and that she is not pregnant. She denies any “warning signs” of cancer, and she is up to date on her cancer screenings (mammogram and pap smear). She denies any family history of colorectal cancer so she is not yet due for her colorectal cancer screening. She denies recent immobilization or trauma.

Her exam is significant for a minimally swollen right calf, measuring 1cm wider in circumference than the left. There is no edema or skin changes; no masses/cords are palpable. The thighs are symmetric, and no superficial veins are noted.

3. What is the probability that this patient has a DVT?

Preceptors, have the residents estimate the (adapted) Wells score for this patient, using Table 1 from the Annals article (page 788):

|Attribute |Points | Mrs.Z’s Score|

|Active Cancer |1 | 0 |

|Paralysis/Recent Cast |1 | 0 |

|Major surgery/bedridden >3 days |1 | 0 |

|Tenderness localized to deep veins |1 | 0 |

|Calf and thigh swollen |1 | 0 |

|Calf swelling >3cm asymmetric |1 | 0 |

|Pitting edema in symptomatic leg |1 | 0 |

|Nonvaricose superficial veins |1 | 0 |

|Alternative diagnosis at least as likely |-2 | 0 |

| TOTAL | | 0 |

4. How do you interpret this score?

0 = low pretest probability

5. What other tests would you obtain?

None. A recent article by Bates, et al. in the Annals of Internal Medicine describes the strategy to incorporate D-dimer with clinical suspicion of DVT in order to determine whether people need further testing. In this study, the authors use an adaptation of the Wells criteria (as outlined in the table above) to identify which patients had low or moderate pre-test probability for DVT. All of these patients then had a D-dimer test, which is relatively sensitive but not specific for DVT. Patients who had a negative D-dimer test had no further testing or intervention. Of the 283 patients who were followed up for three months after their initial presentation, only one of them had an actual DVT. The authors concluded that in these low-risk patients a negative D-dimer test essentially rules out a DVT and no further testing is necessary.

Preceptors - please review Table 3 with the learners so they can understand how the D-dimer test can change their management. It is important to note that among patients with a low pre-test probability, positive D-dimer was associated with a 17% prevalence of DVT. In the same low probability group, a negative D-dimer was associated with a 0% prevalence of DVT (0 of 193). Hence, in our patient who has a low pre-test probability and a low D-dimer, no further follow-up is necessary. The patient should be informed of potential signs and symptoms of DVT or PE and instructed to return to the clinic should they occur.

CASE TWO:

Assume a different patient comes, with the exact same presenting complaint and past medical history. And let’s assume her name is Ms. W. The only difference in the presentation of Ms. W is that she reports that she had the “flu” about one week ago, and was in bed for 4-5 days.

Additionally, her exam is significant for a swollen and tender right calf, measuring 3cm wider in circumference than the left. There is pitting edema on the right lower extremity, extending to the interior calf. There is no change in the skin, and no masses/cords are palpable. The thighs are symmetric, and no superficial veins are noted.

6. What is the probability that this patient has a DVT?

Preceptors – have the residents estimate the (adapted) Wells score for this patient, using Table 1 from the Annals article (page 788):

|Attribute |Points | Mrs. Z’s |

| | |Score |

|Active Cancer |1 |0 |

|Paralysis/Recent Cast |1 |0 |

|Major surgery/bedridden >3 days |1 |1 |

|Tenderness localized to deep veins |1 |0 |

|Calf and thigh swollen |1 |0 |

|Calf swelling >3cm asymmetric |1 |1 |

|Pitting edema in symptomatic leg |1 |1 |

|Nonvaricose superficial veins |1 |0 |

|Alternative diagnosis at least as likely |-2 |0 |

| TOTAL | |3 |

7. How do you interpret this score?

>2: high pretest probability

8. You check a D-dimer, and it is negative. What other tests would you obtain?

A Doppler ultrasound of the lower extremity. Given the high index of suspicion, you need to further evaluate this patient in order to comfortably rule out a DVT. Some studies have suggested that the negative predictive value of D-dimer is only ~80% among patients with a high pretest likelihood of DVT.

9. You obtain a compression (Doppler) ultrasound and the results are:

a. Negative – does the patient require further workup?

Traditionally, a negative Doppler exam in an outpatient requires some additional evaluation. Patients are instructed to follow-up in 5-7 days for a repeat Doppler examination to ensure that a DVT was not missed or that a thrombosis in the calf, which is frequently undetected by Doppler ultrasound, has not extended proximally into the thigh.

However, now that D-dimers are available, some studies have suggested that repeat ultrasound may not be required. In one study, 148 patients with a moderate-to-high clinical probability of a DVT and normal D-dimers and negative ultrasound at baseline were followed for three months without a second ultrasound. None of these patients developed a DVT during the follow-up period. Hence, it is an acceptable strategy to withhold further testing and follow the patient closely at this point. However, if your index of suspicion remains high, one could still consider further evaluation (i.e. repeat ultrasound).

b. Positive, and the patient reports that she has two kids at home and really does not want to be admitted to the hospital. What do you tell her?

The question about whether patients with an acute DVT can be treated as an outpatient has been addressed by several large clinical trials. The take-home point is that outpatient treatment with low molecular weight heparin and warfarin is a safe and effective approach. However, patients with chronic illness or other risk factors for bleeding, such as severe systemic hypertension, recent strokes, spinal cord injury, endocarditis, or pericarditis, should probably be monitored as inpatients. See Table 3 in the accompanying review article (Yusen et al). Patients who have these risk factors for bleeding may benefit from inpatient observation during the initial treatment phase of anticoagulation. It is important to continue the LMWH until the INR in the therapeutic range (2-3). Patient should be started on 5 mg of warfarin daily, and the INRs can be checked every other day in the initial period.

References:

1. Bates, SM. et al., A diagnostic strategy involving a quantitative latex d-dimer assay reliably excludes deep venous thrombosis. Ann Internal Med. 2003: 138: 787-94.

2. Yusen, RW. and Gage B.F., Outpatient treatment of acute venous thromboembolic disease. Clinics in Chest Medicine. 2003: 24: 49-61.

Additional References:

1. Lee AY et al. Ann Intern Med. 1999: 131: 417-23.

2. Tick LW et al. Am J Med. 2002: 113:630-5.

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