What is the most appropriate initial diagnostic test for a patient presenting with chest pain, tachycardia, and tachypnea, with a suspected atypical Pulmonary Embolism (PE), after a negative D-Dimer (D-Dimer) test, and without signs of Deep Vein Thrombosis (DVT) or immobility?

From the Guidelines

For a patient presenting with chest pain, tachycardia, and tachypnea with suspicion of atypical pulmonary embolism (PE) and a negative D-Dimer test, the most appropriate initial diagnostic test would be to reassess the clinical probability using a validated clinical prediction rule, as recommended by the American College of Physicians 1. Given the patient's symptoms and the initial negative D-Dimer result, it is crucial to estimate the pretest probability of PE using a validated clinical prediction rule, such as the Wells score or the Geneva score. This approach helps in stratifying patients into low, intermediate, or high probability of PE, which then guides further diagnostic testing.

Key Considerations:

• The patient's presentation of chest pain, tachycardia, and tachypnea, although suggestive of PE, does not automatically warrant advanced imaging without first assessing the clinical probability.
• A negative D-Dimer test in a patient with low to intermediate clinical probability effectively rules out PE, but the clinical judgment should be used to determine if the initial D-Dimer was appropriately timed and if clinical suspicion remains high despite the negative result.
• The use of age-adjusted D-Dimer thresholds, as suggested by the American College of Physicians 1, may help in reducing unnecessary imaging in older patients, but this does not directly apply to the decision of which initial test to use after a negative D-Dimer.
• If the clinical probability is deemed high after reassessment, or if the patient's condition changes, imaging with CT pulmonary angiography (CTPA) would be the most appropriate next step, as it is the recommended diagnostic test for patients with a high pretest probability of PE 1.

Diagnostic Approach:

• Reassess clinical probability using a validated clinical prediction rule.
• If the probability remains low to intermediate and the patient is stable, consider repeating the D-Dimer or observing the patient, depending on the clinical context.
• If the clinical probability is high, or if the patient's condition deteriorates, proceed with CT pulmonary angiography (CTPA) as the diagnostic test of choice. This approach prioritizes the use of clinical judgment and validated prediction rules to guide diagnostic testing, minimizing unnecessary exposure to radiation and reducing healthcare costs, while ensuring that patients with a high likelihood of PE undergo appropriate diagnostic evaluation.

From the Research

Diagnostic Approach for Suspected Atypical Pulmonary Embolism

• The patient presents with chest pain, tachycardia, and tachypnea, and has a suspected atypical Pulmonary Embolism (PE) after a negative D-Dimer test and without signs of Deep Vein Thrombosis (DVT) or immobility 2.
• Given the negative D-Dimer test, the next step would be to assess the clinical probability of PE using a structured score or clinical gestalt 2.
• If the clinical probability of PE is low or intermediate, and the D-Dimer level is less than 500 ng/mL, PE can be excluded without chest imaging 2.
• However, if the clinical probability of PE is high, chest imaging should be performed, and D-Dimer testing is not necessary 2.
• Computed Tomography (CT) angiogram is the initial imaging study of choice for stable patients with suspected PE 3.

Importance of Clinical Suspicion and Risk Stratification

• Clinical suspicion of PE is a critical step in diagnosis, and risk stratification is essential to identify patients at high risk of PE 2, 3.
• The presentation of PE can be highly variable and non-specific, making diagnosis challenging 4.
• Knowledge of clinical features, risk factors, and electrocardiographic findings associated with PE can aid in diagnosis and treatment 4.

Role of Electrocardiogram (ECG) in Diagnosis

• An ECG can be useful in diagnosing PE, but it is not a definitive diagnostic tool 5, 6.
• PE can present with abnormal ECG findings, including ST-segment elevation, which can mimic acute myocardial infarction 5, 6.
• A bedside echocardiogram can be an invaluable diagnostic tool in suspected PE, especially in patients with abnormal ECG findings 6.

Next Steps in Diagnosis

• Given the patient's symptoms and negative D-Dimer test, a CT angiogram or other chest imaging study should be considered to rule out PE 2, 3.
• If the patient has a high clinical probability of PE, or if the CT angiogram is positive, further testing and treatment should be guided by clinical guidelines and patient-specific factors 2, 3.