This article appeared in the February 1989 issue of Jems Magazine.
Kate Dernocoeur has sometimes used the pseudonym Syd Canan
As she was getting ready for bed, a 52-year-old woman noticed a familiar squeezing or tightness in the middle of her chest. She had experienced cardiac problems in the past and felt this was a resurgence of her angina, so she took a sublingual nitroglycerin tablet. It burned underneath her tongue, yet provided no relief for her chest discomfort. In the next half hour, she took two more sublingual nitroglycerin tablets. The pain, rather than abating, started to radiate toward her back, which concerned her enough to call for help.
Paramedics arrived to find her alert and oriented to person, place and time. Her skin was warm, dry and normal in color. She didn't complain of shortness of breath, nausea, vomiting or dizziness — just substernal chest pressure that radiated into the middle of her back.
Her blood pressure was 106/50, respiratory rate was 18 and her pulse had a rapid, irregular rate of about 130 beats per minute. Blood pressure was equal in both upper extremities, and pulses felt equal in her dorsal pedal pulses as well. Her breath sounds were bilaterally clear and equal, and her abdomen was flat, soft and nontender.
In addition to her intermittent angina; the patient's medical history included a CVA two months before this episode and a myocardial infarction three or four years previously. She also said she couldn't remember exactly, but that there was 'something like 'supraventricular arrhythmias"' in her past history. Her known regular medications included magnesium, K-lite (a potassium supplement) and Cardizem. There were three other medicines for either her heart, her blood pressure or to thin her blood (she wasn't sure which).
Paramedics started an intravenous line of D5W with a 14-gauge angiocath and an extension tube, gave her oxygen at 3 liters per minute by nasal cannula and took the electrocardiogram shown in Figure 1. After reading her EKG, paramedics explained Valsalva's maneuver to the patient; despite good technique by the patient, the rhythm did not convert after four or five attempts. Then they changed her IV fluid to normal saline and gave her a fluid bolus of 200 cc with no rhythm conversion. They decided against carotid sinus massage because of her history of stroke.
After consulting with medical control, paramedics decided not to cardiovert the patient. During transport to the closest emergency department (about 5 minutes away by ambulance), oxygen delivery was changed to a non-rebreather mask at 12 liters per minute. There was no further ALS intervention and there were no major changes in her condition en route. Her mentation was good throughout.
At the emergency department, the patient received some intravenous Versed, which is a benzodiazepine similar to Valium but with a shorter half-life. (Versed is currently used in emergency departments for orthopedic procedures and to sedate patients for a short time.) She was restored to a normal sinus rhythm after synchronized cardioversion.
Case Discussion
The paramedics in this case had every reason to be concerned with the possibility of an aortic aneurysm in a patient with a history of vascular and cardiac disease. It was important to check (as they did) blood pressure in both arms, and pulses in both feet, and to do a thorough abdominal exam. Had their index of suspicion been supported by absent pulses in the feet or a pulsating mass in the abdomen, they would certainly have changed the priorities of treatment. They would then have rapidly transported the patient to the emergency department, with a second large-bore IV en route, setting up the hospital for an emergent major surgical case.
However, finding nothing to support this early premise, it was appropriate to stay and evaluate the EKG rather than do a rapid transport. They were smart to continue pursuing the potential of a cardiac event with the electrocardiogram.
On evaluating her electrocardiogram, they found a wide-beat tachycardia with a rate just over 200 beats per minute. The axis shows right axis deviation because of the negative QRS complexes in Leads I and II and the upright complex in Lead Ill. Since the patient had a suspected history of supraventricular tachyarrhythmias and was maintaining good mentation and adequate blood pressure, the paramedics chose to interpret the electrocardiogram and treat the arrhythmia as a supraventricular tachycardia with bundle branch block aberration.
When encountering a patient with a wide-beat tachycardia, how does one explore the differential diagnosis? The first place to look is in MCL1, which gives the best in a series of diagnostic clues for differentiating supraventricular from ventricular tachycardia. In Figure 1, MCL1 shows a notched, upright QRS complex with the left bump before the notch taller than the right, or as Henry Marriot, a noted expert in arrhythmias, would say, the "left rabbit ear taller than the right rabbit ear." Statistically, the left rabbit ear taller than the right in MCL1 (or VI) gives a 95 percent chance of ventricular tachycardia.(1)
After evaluating MCL1, looking at MCL6 allows you to gather more clues for differential diagnosis of wide-beat tachycardia. This is appropriate for this aspect of EKG analysis and should always be done to minimize the danger of making a diagnosis from just one lead. In this case, MCL6 shows a predominantly negative complex that can be described as a QS complex. In itself, this has a 95 percent correlation with ventricular tachycardia. And when the findings demonstrated here from both MCL1 and MCL6 are combined (a QS complex in MCL6 and a left rabbit ear taller than the right in MCL1), there is a 98 percent to 99 percent chance of a ventricular tachycardia.
There is a steadfast rule in medicine: Always treat the patient, not the electrocardiogram. That dictum holds true — for the most part. But patients in ventricular tachycardia deserve more, because the potential consequences are ventricular fibrillation and sudden death. Apparently this crew was led into a false sense of security by the patient's blood pressure and level of consciousness. They chose to believe that, despite the odds, this was probably not ventricular tachycardia. Also misleading was the patient's suspected history of supraventricular tachycardias and atrial arrhythmias.
“There is a steadfast rule in medicine: Always treat the patient, not the electrocardiogram. That dictum holds true—for the most part. But patients in ventricular tachycardia deserve more, because the potential consequences are ventricular fibrillation and sudden death.”
Pertinent Points
Cardioversion is obviously an option in treating any wide-beat tachycardia, whether ventricular or supraventricular. However, it is a procedure fraught with serious complications. One cardiologist is fond of pointing out that the only absolute he has noticed in his 55 years of practice is that, after you apply any sort of electricity to the heart, asystole appears 100 percent of the time. It may only last a few seconds, but you always see it. To him, as he was taught in medical school back in the 1920s, asystole was death, and it is inherently contrary to medical purpose to create death. Perhaps it would be better to try using nonelectrical means of converting wide-beat tachycardias prior to resorting to electricity.
Although the patient received one bolus of lidocaine in the emergency department before being cardioverted, she had no opportunity to convert her rhythm via pharmacologic means such as a maximum dose of lidocaine, or Bretylium or other available pharmacology. It would have been more appropriate for this patient to receive those treatment options in the pre-hospital phase instead of Valsalva's maneuver and fluid challenges. Once the correct EKG interpretation was defined, it was clear why their treatment choices were ineffective.
Another pertinent point would be that some people do tolerate wide-beat tachycardias for a long time without degenerating into ventricular fibrillation, sudden death, or both. The criteria for deciding whether or not a person can sustain an arrhythmia should include evaluation of age and past cardiovascular status. This patient's history and medications indicate that her heart is probably not in top shape. She probably could not sustain a tachycardia at a rate over 200 for very long. Consequently, some emergent intervention was warranted.
Be careful to guard against tunnel vision in a case like this — previous histories and diagnoses can be misleading. While they should certainly be considered, in this case, for example, the patient may have been misdiagnosed other times as well.
It is essential that we share our misdiagnoses and consequent mistreatments with other professionals so they can benefit from our mistakes instead of making the same errors on their own patients. Everyone, including the patients and the professionals there to help them, stands to benefit from an open forum and educational critique. Consequently, rather than chastising these paramedics, we want to compliment and congratulate them for their forthright openness and willingness to share this case with other EMS colleagues.
This case presents yet another example in which multiple leads are absolutely essential in making an accurate diagnosis. Paramedics in EMS systems that use only Lead II would have been unable to make an accurate differential diagnosis in this case. The use of both MCL1 and MCL6 for interpreting a wide-beat tachycardia is the best way to find the most clues. Use them to make adequate differential diagnoses and to provide appropriate treatment.
Reference:
(1) Wellen HJJ , et al: "The Value of the Electrocardiogram in the Differential Diagnosis of a Tachycardia with a Widened QRS Complex." American Journal of Medicine. 64:27, 1978.