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SYNCOPE – March 2017

 

Case Presentation 

Paramedics are called to a grocery store where a 32 year-old female had a syncopal event. She is now sitting up, and is alert and oriented x3. She recalls having palpitations and a feeling of anxiety just prior to passing out.  Witnesses report loss of consciousness for 30 seconds, with no shaking or seizure-like movements. Her vital signs are HR 97, BP 134/83, RR 21, and O2 saturation 97% on room air.

1.

What are the possible etiologies of this patient's syncope?

While young healthy individuals often have syncope from benign causes, such as vasovagal syncope and transient hypotension, they can also have more dangerous underlying  conditions as a cause of their syncope. These include life-threatening dysrhythmias (i.e. ventricular tachycardia or ventricular fibrillation) resulting from cardiac ischemia, aortic stenosis (narrowing of aortic valve), prolonged QT syndrome, or other genetic abnormalities.  Some other reasons for syncope include aortic dissection, subarachnoid hemorrhage, hypertrophic cardiomyopathy, pulmonary embolus, hemorrhage from trauma, or ruptured ectopic pregnancy.  Hypoglycemia should also a consideration in patients that do not spontaneously return to baseline mental status

2.

What assessment should be performed in the filed?

A thorough cardiac, pulmonary and neurologic assessment are necessary, including taking an appropriate history and physical examination.

 

For HPI – obtain signs and symptoms and their duration before and after the syncopal event.  Was there any precipitating factors that could cause the patient to feel nauseated or upset.

 

For past medical history obtain information about other syncopal events in the past and what was the outcome; obtain information about family members ill with similar symptoms or if there has been a family member with sudden death or serious heart or pulmonary problem (e.g. hypertrophic cardiomyopathy, prolonged QT syndrome, Brugaga, or pulmonary emboslism); obtain information on pregnancy (e.g., ectopic pregnancy), and travel history (e.g., pulmonary embolism with long plane flights).

 

On physical exam listen for heart murmurs and check for equal pulses in the upper/lower extremities as well assess vital signs. The patient should be placed on the cardiac monitor. If a dysrhythmia is identified or there is a possible cardiac cause of syncope, a 12-lead ECG should be obtained. When reading the 12-lead ECG, look for signs of ischemia (ST-segment elevation or depression), dysrhythmias, and intervals that are prolonged or shortened (this includes the PR, QRS and, in particular, the QT interval).  A blood glucose is important if the patient has not returned to his or her baseline mental status or remains unconscious.

 

3.

Case Continuation

The cardiopulmonary exam is normal, with normal lung sounds and no cardiac murmur. Her blood sugar is 132 mg/dL. The cardiac monitor shows a normal sinus rhythm. The paramedics then perform a 12-lead ECG, which is shown below. 

Prehospital 12-lead ECG

4.

ECG Interpretation

Obtaining a high quality tracing is crucial to appropriate interpretation. In evaluating the ECG, the first step, after noting the rate, is to determine if it is a normal sinus rhythm: This ECG has a regular rate and rhythm, with a P wave before every QRS complex, a QRS after every P, and the P wave in lead II is upright, so the rhythm is sinus.  Next, the paramedic must evaluate for signs of ischemia:  There is no ST-segment elevation or depression, so STEMI criteria are not met.  The next step is to look at the intervals.  This is particularly important for patients presenting with syncope.  The PR and QRS intervals are normal at 0.12 msec and 0.10 msec respectively.  The QT interval is very prolonged.  Grossly, it appears to be over half of the R-R cycle, which is a quick sign that it is abnormally long.  Measuring the boxes, the QT is over 600 msec.  A normal QT is ≤ 440 msec in men and ≤ 460msec in women, with QT >500msec raising particular concern

Case presentation

Photo from: Life in the Fastlane. http://lifeinthefastlane.com/ecg-library/basics/qt_interval/

5.

What are the main causes of prolonged QT?

Congenital prolonged QT syndrome is a primary cause of a prolonged QT interval.  There are also acquired abnormalities that can affect the QT interval including hypokalemia, hypomagnesemia, hypocalcemia, hypothermia, ischemia, and several medications (e.g. antibiotics such as azithromycin or psychiatric medications such as haloperidol).

6.

What is the significance of prolonged QT on the ECG?

QT interval prolongation is indicative of prolonged cardiac membrane repolarization. Prolonged repolarization increases the risk of premature depolarization during this refractory period.  An impulse during the refractory period can trigger a dysrhythmia known as torsades de pointes, a French term that literally means "twisting of the points”.  Torsades is a type of polymorphic ventricular tachycardia that appears to twist around the isoelectric line.

 

7.

What treatment should be initiated on this patient?

Since the patient had a syncopal event with prolonged QT on her ECG, she is at high risk for ventricular tachycardia, specifically for torsades de pointes.  Paramedics should be prepared to manage a dysrhythmia should it occur during their period of management.  It is appropriate to place defibrillator pads on the patient’s chest given her high risk of dysrhythmia, so that she can be immediately defibrillated or cardioverted as appropriate should a ventricular dysrhythmia occur. An IV saline lock should be established.  IV fluids are appropriate if the patient appears hypovolemic, but there is no indication of dehydration or hypovolemia in this case.  In addition to electrical cardioversion, IV magnesium sulfate will be administered in the emergency department to decrease the QT interval length and prevent recurrence of the dysrhythmia. Patients with syncope and any vital sign, exam, or 12-lead ECG abnormalities should be strongly advised against signing out AMA from paramedic care. Any AMA decision by these patients should be referred to the base station for discussion and counseling.

8.

Case conclusion

The patient signed out AMA from paramedic care, because she had her 2 small children with her.  Later that week, she had another sudden loss of consciousness.  This time she was found pulseless and apneic; a witness started CPR. When paramedics arrived, she was in pulseless ventricular tachycardia. She was defibrillated and had return of spontaneous circulation (ROSC).  Thanks to early bystander CPR and rapid defibrillation to normal sinus rhythm, she recovered and is neurologically intact. She was diagnosed with congenital prolonged QT syndrome. She had an internal defibrillator placed and is doing well.

 

Take Home Points

  • Patients with prolonged QT (QT interval >440 msec or greater than  half the length of the R-R interval) are at risk for torsades de pointes, a polymorphic ventricular tachycardia.  
  • Have a low threshold to obtain a 12-lead ECG in a patient with syncope, particularly if the patient is refusing transport.
  • When reviewing a ECG rhythm strip and/or 12-lead ECG for a patient with syncope, in addition to evaluating for dysrhythmia, look for prolonged intervals, especially the QT interval.
  • Patients with syncope and/or abnormal ECG intervals require ALS monitoring en route to the emergency department.  Be prepared to treat the patient with defibrillator pads in place if ECG abnormalities are noted.

 

References

Moskovitz JB, Hayes BD, Martinez JP, Mattu A, Brady WJ. Electrocardiographic implications of the prolonged QT interval. Am J Emerg Med. 2013 May;31(5):866-71.

 

El-Sherif N, Caref EB, Yin H, Restivo M. The electrophysiological mechanism of ventricular tachyarrhythmias in the long QT syndrome: three-dimensional mapping of activation and recovery patterns. Circ Res79: 474-492, 1996.


 

Acknowledgements: The EMS Agency would like to thank Dr. Ashley Sanello for her contribution of the above case