Moving Us Closer To Osler
A Miller Coulson Academy of Clinical Excellence Initiative

Zebras Are Out There

Three common zebras (Equus quagga), Kruger National Park, South Africa.


Looking at the big picture and verifying details will help you consider diagnoses that may be unlikely, but still possible.

We’ve all heard the sound of hoofbeats in real life or in the movies. Their sound typically means “horses nearby” and not “zebras are coming.” But zebras aren’t unicorns—zebras really do exist.


The patient

A 69-year-old man with a history of hypertension, GERD, prostate cancer, and severe kyphoscoliosis underwent shock wave lithotripsy. He received a large amount of intravenous fluid and developed acute CHF following the procedure. He was admitted to the hospital, diuresed, improved, and discharged. In the past, he’d undergone a myocardial perfusion study (with ejection fraction> 70% and no evidence of ischemia). An echocardiogram several years prior showed E to A reversal without evidence of overt diastolic dysfunction.


A new cardiologist was consulted and an echocardiogram revealed diastolic dysfunction. A cardiac catheterization was performed, which revealed a 99% D1 lesion (which wasn’t “stentable”), and only moderate non-obstructive disease in other vessels. He was treated with diuretic, ACE-inhibitor, and beta blocker. His symptoms were deemed to be his “anginal equivalent.”


His condition worsened, with refractory edema, and shortness of breath with exertion so bad that he could barely walk across a room. He returned to our office, desperate for answers. I reviewed his history and all of his past testing. Several years prior, because of neuropathic symptoms, he’d undergone serum protein studies, which were abnormal. And he’d seen a hematologist for MGUS, but he’d been loath to follow up because, “I have enough doctors already.” And so the diagnosis of amyloid cardiomyopathy was entertained.


A cardiac MRI was performed, which showed diffuse abnormal enhancement. A myocardial biopsy confirmed AL amyloidosis. He’s now started chemotherapy and is being evaluated for stem cell transplant.


Lessons learned: 


1. Look for the big picture.

Have you ever gazed out the window as your flight takes off? How initially you can see the cracks in the tarmac, but within a few minutes you can see a whole cityscape? And how, from up above, you can tell the difference between Manhattan and St. Louis? Taking in the wide-angle view changes your perspective, and allows you to reach a better conclusion.


2. Trust, but verify.

Don’t doubt the cardiologist, but be sure to see the facts with your own eyes and put them together yourself. If something doesn’t fit (minimal stenotic burden on angiography argues against ischemia), question the conclusion.


3. Avoid anchoring by proxy.

The cardiologist was convinced that his symptoms were ischemic and was holding onto that belief. For several visits, I was anchored to the cardiologist who was anchored to his original diagnosis. But, when I stepped back and looked at the big picture, I realized I had additional information that ultimately led to an accurate diagnosis.



The source of the sound of hoofbeats is heavily influenced by location. Hoofbeats heard on the plains of Montana are likely from a horse. But if you hear that same sound on the African plains, you reach a much different conclusion. Unicorns are fictitious. Zebras . . . they’re out there.