Cardiac Zebras

When studying the ECG of a patient who just doesn’t seem to fit the usual picture, look for horses, not zebras


Kelly Grayson is a featured speaker at EMS World Expo 2012, scheduled for October 29–November 2 in New Orleans, LA. For more information, visit EMSWorldExpo.com.

A wise man once said, “When you hear hoof beats look for horses, not zebras.”

That’s usually pretty good advice…unless you’re in the Serengeti. The same caveat applies when studying the ECG of a patient who just doesn’t seem to fit the usual picture.

Most EMS education programs do a good job getting students to the point where they can spot signs of myocardial infarctions on 12-lead ECGs that show the usual signs of ST segment elevation (STEMI). Time constraints often limit the opportunity to go further into conditions that are not as easy to spot and are relatively rare occurrences, but some of those conditions have significant morbidity and mortality, and knowledge of them can be helpful to the savvy medic. We will discuss two such conditions and demonstrate how they look on a 12-lead ECG.

The first such condition involves Wellens syndrome (or sign), a pattern of T-wave changes associated with left anterior descending (LAD) artery occlusion. This condition has only been described for approximately 30 years, and it is important because it signals a condition that can lead to a disastrous cardiac event.1

The patient may present with chest pain and unstable angina, but with an ECG that lacks Q waves, significant ST-elevation or abnormal R-wave progression in the precordial leads. In other words, it looks pretty normal unless you know what to look for—the characteristic T-wave changes that indicate a degree of coronary artery disease that can progress to a disastrous anterior wall MI. Proximal occlusion of the left coronary artery is often referred to as “the widow-maker” because it affects the circulation of such a large part of the myocardium.2

Wellens appears before infarction begins, and identifying it can make the difference in whether your patient progresses to an infarction. There are a number of causes associated with Wellens: the usual atherosclerosis and coronary artery disease, increased myocardial oxygen demand and other causes of stress on the heart. Cocaine use has also been associated with the syndrome.2

Your patient may complain of chest pain or pressure, tightness or heaviness, which may or may not be induced by activity. The usual associated signs and symptoms such as pain radiating to the jaw, shoulder, arm or neck; sweating; nausea; vomiting; and fatigue are often present.

One may be led astray because the usual treatment for angina—rest, oxygen and nitroglycerin—may stop the pain. Alleviation of the symptoms, however, does not mean you have averted the MI. Your patient is still at significant risk for LAD occlusion.

The ECG in Figure 1 is typical of the T-wave changes in Wellens syndrome. Notice the deeply inverted T waves in leads V3–V5, and the biphasic T waves in V2. This is the most common presentation; however, sometimes there is also a significant biphasic T wave in some of the other chest leads.

Figure 2 shows characteristic T wave inversion and “dip” in V3 and V4, and typical biphasic T waves in V1, V2 and V3.3 These findings may seem subtle at first, but after studying them they become more apparent.

Now, you may ask, “Why is this so important for me to know?” The answer depends on one critical fact: The signs typically show up only when the patient is pain-free.

Let’s say your patient presents with typical anginal pain. You run a 12-lead and see no signs of STEMI, so you give your patient oxygen and nitroglycerin and the pain goes away. Your patient has a history of angina and thanks you for your help, refusing further treatment and transport.

You’re content that you’ve done a great job and your patient is happy, so you return to service. Two days later you’re called to take care of the same patient, who’s now in cardiac arrest and ultimately does not survive. Autopsy shows 99% occlusion of her left coronary artery. You break out into a cold sweat when a friend who just finished an advanced cardiology course points out the obvious Wellens syndrome in the ECG you obtained during your first visit with this patient.

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