Clinical Features and Management of Pulmonary Embolism

Clinical Presentations

Dyspnea is the most frequent symptom, occurring in approximately 80% of patients with pulmonary embolism, often with sudden onset, according to the European Society of Cardiology 1
Chest pain is present in 39-56% of cases and can be pleuritic or substernal/angina-like, representing right ventricular ischemia, as noted by the European Heart Journal 2
Syncope or presyncope occurs in 19-26% of patients and is associated with more severe hemodynamic compromise, as reported by the European Heart Journal 1
Cough affects approximately 20% of patients, and hemoptysis is reported in 5-11% of cases, according to the European Heart Journal 2

High-risk pulmonary embolism is characterized by hemodynamic instability, obstructive shock, and cardiac arrest, as defined by the European Heart Journal 3, 4
Intermediate-risk pulmonary embolism is characterized by hemodynamic stability but with right ventricular dysfunction, and a higher risk of clinical deterioration, as noted by the European Heart Journal 1
Low-risk pulmonary embolism is characterized by hemodynamic stability without signs of right ventricular dysfunction, and a better prognosis, according to the European Heart Journal 1

Chest X-ray abnormalities are common but nonspecific, and may include atelectasis, infiltrates, pleural effusion, and pleural-based opacity, as reported by the European Heart Journal 2
Hypoxemia is frequent, but approximately 40% of patients have normal arterial oxygen saturation, according to the European Heart Journal 1
Electrocardiographic changes may include T-wave inversion, QR pattern, S1Q3T3 pattern, and right bundle branch block, as noted by the European Heart Journal 1

Recent immobilization, major surgery, lower limb trauma, and clinical deep vein thrombosis are risk factors for pulmonary embolism, as reported by the Thorax journal 5
Previous proven deep vein thrombosis or pulmonary embolism, pregnancy or post-partum period, major medical illness, cancer, and advanced age are also risk factors, according to the European Heart Journal and Thorax journal 2, 5

Pulmonary embolism may be asymptomatic or discovered incidentally during diagnostic workup for another disease, as noted by the European Heart Journal 1
In patients with pre-existing heart failure or pulmonary disease, worsening dyspnea may be the only symptom indicating pulmonary embolism, according to the European Heart Journal 1, 2
Multiple pulmonary emboli of different ages are found in 15-60% of cases at necropsy, suggesting that earlier diagnosis could have prevented death, as reported by the European Heart Journal 6

Respiratory symptoms in pulmonary embolism, including dyspnea, are predominantly consequences of hemodynamic disturbances rather than direct impairment of gas exchange, as noted by the European Heart Journal 7
Small distal emboli may create areas of alveolar hemorrhage resulting in pleuritis and mild pleural effusion with minimal effect on gas exchange, according to the European Heart Journal 8, 7
Ventilation-perfusion mismatch contributes to hypoxemia in many cases, but the degree varies based on the size and location of emboli, as reported by the European Heart Journal and European Respiratory Journal 7, 9
The absence of hypoxemia may be related to adequate compensatory mechanisms, particularly in patients without pre-existing cardiorespiratory disease, as stated by the European Heart Journal 8, 10

The severity of pulmonary embolism should be understood as an individual estimate of PE-related early mortality risk rather than solely based on oxygenation status, as recommended by the European Heart Journal 11
Risk stratification of pulmonary embolism should be based on hemodynamic stability and right ventricular function rather than solely on oxygenation, according to the European Heart Journal and European Respiratory Journal 8, 9

Right-to-left shunting through a patent foramen ovale can lead to severe hypoxemia when present, as noted by the European Heart Journal 8, 7
Pre-existing cardiorespiratory disease significantly impacts gas exchange when pulmonary embolism occurs, as reported by the European Heart Journal 8, 7

The absence of hypoxemia does not rule out pulmonary embolism, and clinicians should maintain a high index of suspicion when other symptoms like unexplained dyspnea are present, as stated by the European Heart Journal 7
Failing to consider pulmonary embolism in patients with sudden onset dyspnea despite normal oxygenation can lead to missed diagnoses, as warned by the European Heart Journal 7
Not recognizing that pulmonary embolism can present with various clinical pictures, from asymptomatic to severe hemodynamic compromise, regardless of oxygenation status, is a common pitfall, as noted by the European Heart Journal and European Respiratory Journal 7, 9

Respiratory alkalosis is the most common acid-base disturbance in acute pulmonary embolism, characterized by hypocapnia and increased pH, according to the European Respiratory Society 12
Ventilation-perfusion mismatch from obstructed pulmonary vessels combined with zones of overflow in non-obstructed vessels contributes to respiratory alkalosis in pulmonary embolism 12
Low cardiac output leading to desaturation of mixed venous blood contributes to hypoxemia in pulmonary embolism 12
Ventilation-perfusion mismatch and right-to-left shunting through a patent foramen ovale contribute to arterial hypoxemia in pulmonary embolism 12, 13

Respiratory acidosis is not a typical finding in uncomplicated pulmonary embolism and would suggest pre-existing pulmonary disease, severe respiratory failure, or terminal stages with cardiopulmonary collapse, as noted by the European Respiratory Society 12
Decreased PaCO2 (hypocapnia) is a common finding in pulmonary embolism, indicating respiratory alkalosis 12

The development of a base deficit in a patient with pulmonary embolism suggests more severe disease, longer diagnostic delay, and possible underlying conditions, and is associated with more pronounced hypocapnia and lower bicarbonate levels, although specific values are not provided 12

Respiratory acidosis in pulmonary embolism may indicate impending or actual cardiopulmonary arrest, which occurs when right ventricular failure becomes so severe that cardiac output collapses, leading to inadequate tissue perfusion and ventilatory failure 14, 15
Ventilation-perfusion mismatch occurs from zones of reduced flow in obstructed arteries combined with overflow in non-obstructed vessels, leading to hypoxemia and hypocapnia 14, 15
Right-to-left shunting through a patent foramen ovale can cause severe hypoxemia, despite the intact ventilatory response producing hyperventilation and alkalosis 14, 15