Correspondence

Clinical Problem-Solving: Multiple Pulmonary Emboli

N Engl J Med 1995; 332:1792June 29, 1995

Article

To the Editor:

I found the case presented by Dr. Thibault (Feb. 2 issue)1 reassuring in that even the expert clinician encountered the usual degree of difficulty traversing the slippery slope toward the diagnosis of chronic recurrent pulmonary embolism. In this case there were two pieces of misleading diagnostic information that increased the complexity of the case and resulted in the circuitous route taken toward the correct diagnosis.

Among the reported findings on the initial physical examination were 1+ pedal edema and a normal jugular venous pressure. It is difficult to believe that with a pulmonary-artery pressure of 90/50 mm Hg, the patient would not have had evidence of central venous hypertension. If he had, this finding, coupled with the pedal edema, would have suggested right ventricular failure and directed the focus toward a pulmonary process. Carbon monoxide diffusion in the lungs, determined during the diagnostic workup, was reported to be normal. Since this variable is directly proportional to the surface area of the pulmonary blood–air interface, how can we interpret the fact that enough of the vascular bed was obliterated to produce a severe degree of pulmonary hypertension without affecting carbon monoxide diffusion in the lungs? There is no mention of factors that would have artifactually increased the diffusing capacity.

I agree emphatically with Dr. Thibault's suggestion that in medicine an arrow is a better weapon than a shotgun, but the implied prerequisite is that you know exactly what you are shooting at.

Paul C. Mendelowitz, M.D.
Holy Name Hospital, Teaneck, NJ 07666

1 References

1. 1

   Thibault GE. Diagnostic strategy -- the shotgun versus the arrow. N Engl J Med 1995;332:321-325
   Full Text | Web of Science | Medline

To the Editor:

Recurrent pulmonary embolism, defined as unresolved embolism of the large pulmonary arteries, is indeed rare. But multiple pulmonary-artery emboli of the small and middle vessels seem to be another disease, frequently overlooked. According to data from intensive autopsy and clinical studies in Basel, Switzerland, there are 62.8 cases of multiple pulmonary emboli per 100,000 population per year.1

F. Flachsbart, M.D.
Eisenacher Str. 6, 37085 Göttingen, Germany

1 References

1. 1

   Herzog H, Perruchoud A, Dalquen P, Tschan M. Chronisch rezidivierende Lungenembolie. Dtsch Med Wochenschr 1978;103:1473-1478
   CrossRef | Web of Science | Medline

Author/Editor Response

Dr. Thibault replies:

To the Editor: Dr. Mendelowitz makes an excellent point about potentially misleading diagnostic information. The clinical Problem-Solving cases are presented as they unfolded in real time, with no attempt to delete inconsistencies and misleading information, which are part of the reality of clinical life. Physical findings are sometimes missed or misinterpreted, and I suspect that was true with this patient. When the patient's right atrial pressure was measured at the time of right-heart catheterization, it was 12 mm Hg, so the report of “normal” jugular venous pressure on the initial physical examination was probably erroneous. If a patient has a thick neck or if the venous pressure is markedly elevated, the examiner may be unable to detect venous pulsations and to estimate venous pressure on physical examination. In such a case, the finding should be correctly recorded as “indeterminate” rather than “normal.” In real life one can go back and reexamine the patient to verify a discordant observation or to look for a finding that would help confirm a diagnostic hypothesis. Laboratory findings may also be misleading. Although carbon monoxide diffusion in the lungs should be decreased if there is an extensive loss of vascular bed from pulmonary emboli, this is not always the case. The discrepancy may be due to errors in measurement or, in some cases, to more proximal pulmonary emboli.

Dr. Flachsbart raises a question about the frequency of the phenomenon described in this case. The terms “chronic,” “recurrent,” and “multiple” pulmonary emboli are often used interchangeably but sometimes refer to different clinical entities. Fixed pulmonary hypertension due to previously undiagnosed multiple pulmonary emboli (as in this case) is, I believe, rarer than the rate of occurrence of multiple pulmonary emboli in the autopsy series that Dr. Flachsbart cites. Since this disorder is difficult to diagnose, however, it may be more common than the data from some series suggest.

George E. Thibault, M.D.
Veterans Affairs Medical Center, West Roxbury, MA 02132