A 74-year-old man with a history ofatrial fibrillation presents to hisprimary care physician with dyspneaof 4 days’ duration. The dyspnea developedwhile he was walking as partof his recovery from back surgery forspinal stenosis 1 month earlier. Hebecame progressively short of breathand was unable to carry out his exerciseprogram.
74-year-old man with a history ofatrial fibrillation presents to hisprimary care physician with dyspneaof 4 days' duration. The dyspnea developedwhile he was walking as partof his recovery from back surgery forspinal stenosis 1 month earlier. Hebecame progressively short of breathand was unable to carry out his exerciseprogram.He has no dyspnea at rest buthas experienced relatively continuousupper retrosternal tightness over thepast 4 days. He has not had any palpitationsrecently. He reports no dizziness,syncope, pleuritic chest pain,fever, cough, sputum production, orhemoptysis. The patient states thathis legs are usually somewhatswollen, but he has noticed that hisright leg has become progressivelymore swollen than his left.His medical history includes pacemaker insertion forsick sinus syndrome; a coronary angiogram obtained atthe time showed no significant coronary artery disease.His history also includes deep venous thrombosis (DVT)of his right leg. He has long-standing hypertension, whichis treated with prazosin, 2 mg/d, and furosemide, 40mg/d. He also takes amiodarone, 200 mg/d, and digoxin,0.125 mg/d, for rate control of his atrial fibrillation.His mother died of myocardial infarction at age 53,and his father died of stomach cancer at age 80. The patientdoes not use tobacco or alcohol.Pulse oximetry reveals oxygen saturation of 96% onroom air. He is sent to the ED for further evaluation.
Examination in the ED.
This obese patient is in noacute distress. Blood pressure is 130/60 mm Hg; heartrate, 70 beats per minute; temperature, 37
F); respirationrate, 22 breaths per minute and unlabored. Oxygensaturation is 96% on room air and 99% with 2 L of oxygenadministered by nasal prongs.The patient's pharynx is clear. His neck is supple;there is no adenopathy, jugular venous distention, or thyromegaly.Carotid pulsations are full and equal; no bruitsare audible. Lungs are clear; chest wall is not tender.Heart rhythm is regular with a grade 2/6 early-peaking,short systolic ejection murmur at the upper right sternalborder; no diastolic murmur, S
, or rub is noted. Noabdominal tenderness or masses are present.The right leg exhibits brawny, 3+ pitting edema, andthe girth is greater than that of the left leg. Pulses are 2+at the femoral, dorsalis pedis, and posterior tibial sites.Homans sign is negative, and no cords are palpable.
Imaging and laboratory studies.
The ECG shows adual-chamber paced rhythm. The brain natriuretic peptidelevel is slightly elevated at 310 pg/mL (normal range, 0 to100 pg/mL). A chest film and a D-dimer assay are ordered.The differential diagnosis includes anginal equivalent, mildright-sided heart failure, and pulmonary embolism.
What does the chest film show, and what furtheraction would you take to arrive at a diagnosis?
A STEALTHY KILLER
Because pulmonary embolism usually presentssilently and often recurs, it is important to act definitivelyto rule out this entity whenever it is included in the differentialdiagnosis. In retrospect, especially in view of the patient'ssupporting study results, the diagnosis in this casewas quite evident. However, the patient's clinical presentationlacked many of the pathologic disturbances indicativeof pulmonary embolism, including pleuritic chest pain andtachycardia. In addition, his oxygen saturation was normal,his chest film was nearly normal, he did not seekmedical attention until 4 days after the symptoms began,and he had a relatively ambiguous history of progressiveright leg swelling superimposed on chronic bilateral lowerleg swelling. His presentation underscores the need tomaintain a high index of suspicion to identify pulmonaryembolism.
DIAGNOSIS OFPULMONARY EMBOLISM
Clinical risk stratification.
This is the best methodto determine how extensive a workup should be performedto rule out pulmonary embolism. In our institution,we use a scoring system that stratifies the risk of pulmonaryembolism based on clinical criteria.The Prospective Investigation of Pulmonary EmbolismDiagnosis (PIOPED) is the landmark study of thediagnosis of pulmonary embolism. According to thisstudy, the pretest likelihood of pulmonary embolism is9%, 30%, and 68% for low, moderate, and high pretest riskgroups, respectively.
One of the more thoroughly studied strategies is theWells criteria, which use historical factors to stratify riskprobability.
In this approach, key findings are assignedpoint values, and the total score is directly proportional tothe patient's risk of pulmonary embolism (
). Havingmore than one of the criteria increases a patient's clinicalpretest probability from low to intermediate; having severalpositive findings increases the probability to high. Patientswho have an intermediate risk profile present thegreatest diagnostic challenge.Identifying the pretest probability of pulmonary embolismenables you to guide the workup appropriately.Test results can then be interpreted in light of the clinicalprobability.
Interpretation of diagnostic study results.
The Ddimerassay is nonspecific but highly sensitive for the detectionof pulmonary embolism. Thus, a negative D-dimerassay in a patient at low risk may be sufficient to rule outpulmonary embolism.
The patient with a positive D-dimerassay and a low-risk profile may or may not undergo furthertesting, based on the assessment of the significanceof the source of D-dimer positivity. A patient at intermediaterisk, as determined by a score of 2 to 6 points usingthe Wells criteria, would undergo a chest CT scan usingthe pulmonary embolism protocol. At present, it appearsthat using a combination of tests--as demonstrated in thiscase--is the best way to increase the likelihood of rulingout or detecting pulmonary embolism, especially in a patientwho presents with a paucity of symptoms.
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The PIOPED Investigators. Value of the ventilation/perfusion scan in acutepulmonary embolism. Results of the Prospective Investigation of PulmonaryEmbolism Diagnosis (PIOPED).
Wells PS, Anderson DR, Rodger M, et al. Excluding pulmonary embolism atthe bedside without diagnostic imaging: management of patients with suspectedpulmonary embolism presenting to the emergency department by using a simpleclinical model and D-dimer.
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Brown MD, Rowe BH, Reeves MJ, et al. The accuracy of the enzyme-linkedimmunosorbent assay D-dimer test in the diagnosis of pulmonary embolism: ameta-analysis.
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