Case Author(s): Stephanie P.F. Yen, M.D. and Mark A. Mintun, M.D. , 10/24/97 . Rating: #D3, #Q4

Diagnosis: Massive bilateral pulmonary embolism

Brief history:

71-year-old female who presents with acute shortness of breath.


Perfusion scintigraphy.

View main image(vq) in a separate image viewer

View second image(vq). Ventilation scintigraphy.

View third image(xr). Portable AP chest radiograph.

Full history/Diagnosis is available below

Diagnosis: Massive bilateral pulmonary embolism

Full history:

71-year-old female with history of pulmonary embolism and myasthenia gravis who presents with acute shortenss of breath following a near syncopal episode. Recent transesophageal echocardiogram performed unexpectedly demonstrated intraluminal filling defect within the pulmonary artery, suggestive of pulmonary embolism. A ventilation-perfusion pulmonary scintigraphy study was requested for further evaluation.


16.4 mCi Xe-133 gas by inhalation and 4.4 mCi Tc-99m MAA, intravenously


The ventilation study shows a uniform distribution of activity on the single-breath and washin images. Minimal Xe-133 retention at the left lung base is demonstrated during the washout phase. Perfusion scintigraphy demonstrates perfusion defects in the apicoposterior segment of the left upper lobe as well as in the posterobasal segment of the right lower lobe. These were noted on a prior ventilation-perfusion study of 6/23/92 (not shown) and are unchanged. However, the current study also demonstrates lobar areas of relative hypoperfusion involving the entire left upper lobe, left lower lobe, and right lung. The lingula appears relatively hyperperfused. The portable chest radiograph demonstrates no pulmonary infiltrates or large pleural effusions. The scintigraphic findings are worrisome for massive partially occluding bilateral pulmonary emboli.


In the evaluation of acute pulmonary embolism, regional areas of decreased ventilation leading to hypoxia-induced regional pulmonary vasoconstriction typically occurs, resulting in regional hypoperfusion. This is thought to occur due to the release of serotonin, prostaglandins, and angiotensin II in response to hypoxia. In contrast, the underlying etiology and physiology responsible for the occasional appearance of focal zones of relative hyperperfusion ("hot spots") on perfusion scintigraphy is not clearly understood. The zones of apparent hyperperfusion may reflect true local vasodilatation or preserved perfusion in an area of normal lung adjacent to abnormal lung regions.

To investigate the frequency and significance of hot spots on perfusion scintigraphy, Meigan et al. (1989) reviewed 72 patients who underwent both ventilation-perfusion scintigraphy and pulmonary angiography. Hot spots were seen in 18% of the perfusion studies, the majority of which involved less than one pulmonary segment. Most of the focal zones of hyperperfusion corresponded to areas of atelectasis on chest radiograph. It is postulated that the failure of hypoxic vasoconstriction in poorly ventilated lung results in a relative increase of perfusion in the atelectatic lung. In 3 patients with massive bilateral pulmonary emboli demonstrated scintigraphically and documented by angiography, as illustrated in this case, the focal zones of hyperperfusion represented areas of preserved normal perfusion.

Reference: Meignan M, Palmer EL, Waltman AC, Strauss HW. Zones of increased perfusion (hot spots) on perfusion lung scans: Correlation with pulmonary arteriograms. Radiology 1989; 173:47-52.


The patient subsequently underwent a pulmonary arteriogram later the same day, 10/17/97, which revealed bilateral large lower lobe and smaller upper lobe pulmonary emboli.

View followup image(an). Selective images from pulmonary arteriogram: right pulmonary arterial injection (right) and left pulmonary arterial injection (left).

Major teaching point(s):

Focal zones of hyperperfusion or "hot spots" on perfusion scintigraphy may represent areas of atelectasis. More importantly, hot spots may signify a patient with a large embolic burden, with the hot spots representing regions of relatively normal perfusion adjacent to hypoperfused, embolized lung.

ACR Codes and Keywords:

References and General Discussion of Ventilation Perfusion Scintigraphy (Anatomic field:Lung, Mediastinum, and Pleura, Category:Other generalized systemic disorder)

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Case number: vq025

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