Clinical case: Pulmonary embolism

Past medical history

An obese 25-year-old man, recently diagnosed with diabetes, presented to the emergency department with acute onset of shortness of breath for several hours. Importantly, he had been seen at the ED two weeks earlier for left foot pain and was diagnosed at the time as having an abscess on the sole of his foot. He denied foot trauma, insect, or animal bites.

The abscess was incised and drained, and he received intravenous antibiotics. During that admission, he was given subcutaneous heparin for DVT (deep venous thrombosis) prophylaxis. Cultures taken at the time grew methicillin-resistant Staphylococcus aureus (MRSA); he was discharged five days later on oral antibiotics. Since the time of the foot abscess, he had been mostly sedentary; this was not however significantly different from his normal behavior.

Present illness, chief complaints and examination

Sometime afterward, the patient returned to the ED. While playing video games at home he became aware of acute onset shortness of breath with associated palpitations and sharp left-sided chest pain. Upon admission had no fever, leg swelling, or calf pain. The patient denied smoking or illicit drug use. 

When examined at the hospital, the patient was slightly tachypnoeic at 20 breaths per minute, but spoke in full sentences. He was tachycardiac at 135 beats per minute and afebrile at 97.1 degrees Fahrenheit. His blood pressure was 144/96 mmHg. A cardiac exam revealed normal heart sounds with regular rhythm and no murmurs, rubs, or gallops. Breath sounds were normal. Limbs were not edematous and the left foot wound was well-healed.

Laboratory results revealed significantly elevated D-dimer, and an electrocardiogram showed sinus tachycardia with S1 Q3 T3 pattern. Considering the suspicion for pulmonary embolism, the patient was presumptively started on heparin and a CT pulmonary angiogram was ordered (Figure 2). The consulting radiologist upon reviewing the CT images urgently called the following day to report that the patient had an extensive saddle pulmonary embolism.

Management

The intensive care team then accepted the patient to the IC unit, and then arranged for transfer to a tertiary care cardiothoracic center for possible surgical intervention. An echocardiogram done there revealed a separate whirling echogenic mass in the right atrium (Figure 3 and Figure 4).

Now let's see on Figure 4 what was found in the right atrium of this patient.

The patient was urgently taken to the operating room for a cardiopulmonary bypass through a median sternotomy. Following the clamping of the aorta, when the incision was made for cannulation of the inferior vena cava, the surgeons observed a large amount of clot material extruding through the incision site. The patient then had right atriotomy and pulmonary endarterectomy with a removal of a large amount of thrombotic material from superior vena cava, right atrium and pulmonary arteries (Figure 5).

He had what is known as a saddle pulmonary embolus because the clot that straddles the pulmonary trunk at its bifurcation into the right and left pulmonary arteries. During the procedure, the surgeons noted that the patient also had a patent foramen ovale and that the atrial thrombus had actually straddled the foramen.

The surgeons removed the clot material from the atrium and sutured the patent foramen ovale closed. The surgical procedures were performed smoothly and the patient tolerated the procedure well.

Foramen ovale in fetal life

In the fetal heart, the atria are initially closed-off from one another by the septum primum except for a small opening in the septum, the ostium primum. As the septum primum develops further, the ostium primum narrows and finally closes. However, prior to this closing, the ostium secundum develops in the septum primum. This opening allows communication between the atria after the ostium primum closes.

Subsequently, a second wall of tissue, the septum secundum, develops over the ostium secundum in the right atrium. Blood then only flows from the right to left atria via a small passageway in the septum secundum and then through the ostium secundum. This canal is the foramen ovale. You can learn more about the fetal blood circulation in our article.

Foramen ovale in adults

When the lungs become aerated at birth, the pulmonary pressure decreases and the left atrial pressure becomes higher than that of the right. This acts to force the septum primum against the septum secundum, functionally closing the foramen ovale. Later the septae fuse, but a remnant of the foramen ovale remains, the fossa ovalis. And, in about 25% of adults the foramen ovale is not closed completely, but remains as a small PFO.

This defect is usually asymptomatic because left atrial pressure is higher than right atrial pressure. Complications of PFO are rare and incidental discovery of PFO generally does not require any surgical or pharmacological intervention. PFO is associated with cryptogenic stroke, potentially due to paradoxical embolism. Patients undergoing coronary bypass surgery have a higher risk of postoperative atrial fibrillation and hypoxemia, if they also have PFO. Decompression sickness, air embolism and migraine with aura are also associated with PFO.