Symptom Variability in Pulmonary Embolism with Intermittent Dyspnea
Yes, symptoms in pulmonary embolism characteristically vary and can be intermittent, particularly shortness of breath, which is the most common presenting symptom and occurs in 78-81% of cases but may fluctuate in severity rather than remain constant. 1
Why Symptoms Vary in PE
The intermittent nature of dyspnea in your 23-year-old male patient is entirely consistent with PE and should not lower your clinical suspicion. Here's why:
Pathophysiologic Basis for Variability
Ventilation-perfusion mismatch fluctuates based on patient position, activity level, and compensatory mechanisms, causing dyspnea to wax and wane rather than remain constant 2
Tachypnea (respiratory rate >20/min) is present in most PE patients and represents the body's attempt to compensate for hypoxemia, which itself varies with exertion and position 2, 1
Isolated dyspnea without cough, sputum, or chest pain occurs frequently in PE and is a particularly dangerous presentation because it is easily missed—this matches your patient's intermittent breathlessness 2, 1
Clinical Patterns That Support Variable Symptoms
Young patients (age <40) without traditional risk factors can still develop PE, though it is less common, making the diagnosis more likely to be delayed 2
The pulmonary hemorrhage syndrome (pleuritic pain and/or hemoptysis) occurs in 39-56% of cases and may come and go 1
Tachycardia accompanying intermittent dyspnea in your patient suggests episodic right ventricular strain, which is characteristic of PE 2, 1
Critical Diagnostic Approach for This Patient
Do not be falsely reassured by the intermittent nature of symptoms. Instead, proceed systematically:
Step 1: Assess Pretest Probability
Use the Wells score or Geneva score to stratify risk—the presence of tachycardia and dyspnea already increases probability 2, 3, 4
Apply PERC criteria only if pretest probability is low: age <50 years, heart rate <100/min, oxygen saturation >94%, no recent surgery/trauma, no prior VTE, no hemoptysis, no unilateral leg swelling, no estrogen use 2, 4
If your patient fails even one PERC criterion (likely given tachycardia), proceed to D-dimer testing 2
Step 2: D-dimer Testing Strategy
Obtain high-sensitivity D-dimer as the initial test if pretest probability is low or intermediate 2, 3
For patients >50 years, use age-adjusted cutoff (age × 10 ng/mL) rather than generic 500 ng/mL to improve specificity 2, 3
Never obtain D-dimer in high-risk patients—proceed directly to imaging 2, 3
Step 3: Imaging Decision
CT pulmonary angiography (CTPA) is indicated if D-dimer is elevated or if pretest probability is high 2, 3
Do not delay anticoagulation while awaiting imaging if clinical probability is intermediate or high—start weight-based unfractionated heparin (80 units/kg bolus, then 18 units/kg/hour) immediately 1
Common Pitfalls to Avoid
Do not dismiss PE because symptoms are intermittent—this is a classic presentation that leads to missed diagnoses 2, 1
Do not attribute isolated dyspnea to anxiety in a young patient with tachycardia—this is how PE gets missed in younger populations 2, 1
Do not order CT without first assessing pretest probability and D-dimer (unless high-risk)—this leads to unnecessary radiation exposure and false-positive findings 2
Elderly patients and those with severe cardiorespiratory disease are at highest risk for missed PE because symptoms overlap with baseline conditions, but your 23-year-old patient should have a clearer clinical picture 1
Additional Considerations for Variable Symptoms
Arterial blood gas analysis may show hypoxemia, hypocapnia, and respiratory alkalosis that fluctuates with symptom severity 2
Echocardiography findings such as RV enlargement, McConnell sign (RV free wall hypokinesis with apical sparing), and elevated RV systolic pressure provide objective evidence of PE even when symptoms are intermittent 2
The presence of deep venous thrombosis on lower extremity ultrasound establishes need for anticoagulation even without CT confirmation of PE 2