Country cardiograms case 5:Pulmonary embolism

Can J Rural Med vol 2 (2):147

This paper has been peer reviewed.

© 1997 Society of Rural Physicians of Canada


Findings

The electrocardiogram (ECG) presented on p. 135 shows old left anterior fascicular block, new sinus tachycardia and new nonspecific ST segment and T wave changes in V2 and V3.

Although the ST­T changes were nonspecific, the rural physician would be correct to suspect a new problem involving the heart. The differential diagnosis for these ECG findings is wide and would include ischemic heart disease, cardiomyopathy for reasons other than ischemia, metabolic disturbances, medication effects and pulmonary embolism. A ventilation­perfusion scan in this patient confirmed pulmonary embolism.

Figure 1 compares the right precordial T waves during the pulmonary embolism in October with tracings on the patient's ECGs obtained 4 months before the event (in June) and 2 months after (in December). In the June and December ECGs, the ST segments are isoelectric relative to the TP interval and PR segments, and the ST segment smoothly enters the symmetric T wave. In contrast to those normal images, the ECG obtained during the episode of pulmonary embolism exhibits upsloping ST elevation in lead V3 and a biphasic appearance of the T wave in leads V2 and V3.

Discussion

Pulmonary embolism remains a dangerous, frustrating entity for patients and clinicians in all settings, urban or rural. Assuming that the Canadian population is 10% that of the United States, there are roughly 65 000 cases of pulmonary embolism each year in Canada, resulting in 20 000 deaths.[1,2] It has been estimated that 70% of cases are not detected before death.[2] The signs, symptoms and common laboratory findings of pulmonary embolism overlap with those of many other entities and are rarely characteristic of this condition alone.

The nonspecific pattern of sinus tachycardia combined with nonspecific ST­T wave changes in the right precordial leads is relatively common in pulmonary embolism. It was observed in 13 of 49 patients in one study[3] and was considered "characteristic" in a review by Manganelli and associates.[4] However, a wide variety of other ECG findings can occur in pulmonary embolism, including normal ones.[2]

Nonspecific ST-T changes are common on ECGs taken in rural settings. They were present on 1 in 5 consecutive ECGs in one rural Canadian study.[5] Although the term "nonspecific" means that a particular diagnosis cannot be assigned with any certainty, the physician should always be more suspicious that cardiovascular disease affecting the heart is present when nonspecific ST­T changes are found. In a case such as this one, the clinical history of dyspnea and cough in a patient with breast cancer should raise the suspicion of pulmonary embolism.

The patient was transferred to an urban hospital as an out-patient for confirmation of the diagnosis by lung scanning, then readmitted to the rural hospital and treated with heparin. She recovered without complications.

References

  1. Thompson JM. Epidemiology of ischemic emergencies in rural Alberta [working paper]. Canadian Association of Emergency Physicians meeting; May 25, 1996; Edmonton.
  2. Feied CF. Pulmonary chest pain, cor pulmonale and pulmonary thromboembolism. In: Gibler WB, Aufderheide TP (editors). Emergency cardiac care. St Louis: Mosby Year Book; 1994. p. 255-301.
  3. Sreeram M, Cheriex EC, Smeets JL, Gorgels AP, Wellens HJ. Value of the 12-lead electrocardiogram at hospital admission in the diagnosis of pulmonary embolism. Am J Cardiol 1994;73(4):298-303.
  4. Manganelli D, Palla A, Donnamaria V, Giuntini C. Clinical features of pulmonary embolism. Doubts and certainties. Chest 1995;107(1 suppl):25S-32S.
  5. Thompson JM. Computer interpretations of ECGs in rural hospitals. Can Fam Physician 1992;38:1645-53.


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