Electrical Alternans


Article Author:
David Ingram


Article Editor:
Margaret Strecker-McGraw


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Updated:
6/27/2019 1:12:25 PM

Introduction

Electrical alternans is defined as alternating QRS amplitude that is seen in any or all leads on an electrocardiogram (ECG) with no additional changes to the conduction pathways of the heart. This rhythm is typically associated with pericardial effusion via the “swinging heart” from the fluid surrounding the heart. However, electrical alternans is also associated with other pathologies including but not limited to ventricular tachycardia, Wolff-Parkinson-White (WPW), accelerated idioventricular rhythm, and supraventricular tachycardia.[1] Understanding the varied pathologies causing this ECG finding is key to evaluation and if necessary, treatment success.

Etiology

Electrical alternans is most commonly attributed to pericardial effusion and tamponade pathology. In this scenario, the classic ECG rhythm is due to the pendulum-like motion and rotation of the heart from beat to beat manifesting as varied amplitudes when detected by the ECG electrodes. Electrical alternans is also seen in conduction and refractory changes in various rhythms including those mentioned above resulting in varied QRS amplitudes as detected by the electrodes. The mechanism that leads to these ECG changes will be further discussed in pathophysiology.[2][3]

Epidemiology

Electrical alternans is usually associated with pericardial effusion which is associated with many disease states including infection, inflammatory syndromes, trauma, malignancy, and idiopathic to name a few. Although the majority of effusions have an underlying cause, as much as 20% are from unknown causes, making approach and eventual treatment challenging. Incidence of pericardial effusion overall is low in symptomatic patients presenting with ECG findings of alternans. Despite this, effusion should remain on the differential as this is a potentially fatal complication if it remains unrecognized.[4] As mentioned above, there are additional pathologies that can lead to alternans on ECG also includes various arrhythmias and conduction pathway abnormalities.  Each of these pathologies have various and unique pathologies and further discussion of these will not be included in this paper.

Pathophysiology

Electrical alternans is the alternating voltage noted in the QRS complexes seen on an ECG; refer to the image below. Electrical alternans can be diagnosed by the varying changes in the amplitude of the QRS complex. Of note, T-wave alternans can be present as well. This review focuses on the QRS complex alternans. These changes are thought to be caused by the anterior-posterior swinging of the heart with each contraction in the fluid-filled pericardial sac. As the heart swings, the electrical signals detected by the electrodes travel over a greater distance through the fluid resulting in reduced voltage at the electrodes. Alternans may also be seen in other physiology including myocardial disease, pneumothorax or emphysema wherein the electrical conductivity of the tissues between the heart and the electrodes are affected causing variations in the QRS amplitudes. Other causes of electrical alternans can include AV nodal reentrant tachycardia, bundle branch block, Wolff-Parkinson-White syndrome (WOW), late premature ventricular complexes where the underlying change in conduction pathway is responsible for the change in the QRS amplitude observed on the ECG. In some ventricular tachycardias, changes in ion concentrations around the myocardium can result in regional changes in potassium causing varied action potential instability creating an alternans type pattern as different regions of the heart depolarize at varied levels of excitation.[5] It has been shown that deep breathing may be a cause of alternans in the precordial leads caused by the additional distance the electrical signal travels at full inhalation where electrical signals are reduced at the electrodes.

History and Physical

When electrical alternans is found on an ECG, further evaluation is needed because treatment will vary based on the underlying pathophysiology. Therefore, a thorough history and examination of the patient are necessary to focus on the cardiovascular and pulmonary exam. In the case of pericardial effusion, patients are usually asymptomatic unless tamponade physiology is present. Signs of tamponade include Becks triad: hypotension, muffled heart sounds, and distended neck veins. Additional signs of tamponade may also include tachypnea and dyspnea in the form of Kussmaul breathing and Pulsus Paradoxus.[6] In the case of arrhythmias, as mentioned above, patients may present with tachycardia and associated symptoms of light-headedness, fatigue, chest pain, shortness of breath, syncope, among others along with a potential history of cardiac conduction abnormalities. Based on this, a further cardiac history, including family history, may need to be obtained.

Evaluation

When electrical alternans is present on an ECG, further evaluation is needed to find the underlying cause as mentioned above. When considering a pericardial effusion, a transthoracic echocardiogram (TTE) is the first-line imaging modality. In the unstable patient, bedside echocardiogram is even more important as TTE provides very high sensitivity (near 100%) in diagnosing pericardial effusion.[7]

Treatment / Management

Once diagnosed, to treat serious tamponade pathology; you must first address resuscitative measures including intravenous (IV) access, oxygen as needed and cardiac monitoring. Intravenous fluid boluses may be needed to promote right heart filling and function to temporize poor hemodynamics. For definitive treatment of tamponade, however, a pericardiocentesis is necessary. This is typically performed in a cardiac catheterization lab in a non-life-threatening situation. However, in urgent conditions, for example, in patients at risk of arrest or who may have arrested, percutaneous pericardiocentesis may be performed in the emergency department. Once a pericardiocentesis and removal of fluid have been performed, and the patient is stabilized, further investigation is required to determine what pathophysiological process lead to the effusion.

For other causes of alternans including WPW, ventricular arrhythmias, and bundle branch block, therapy must be directed toward the underlying cause, with the early emphasis on hemodynamic stability of the patient as the first step in treatment.

Pearls and Other Issues

Electrical alternans, although considered pathognomonic for pericardial effusion, is not a diagnostic factor for effusion and cardiac tamponade as other pathologies can result in this ECG finding. When present on an ECG, early evaluation of the patient’s vitals and overall presentation are imperative. If and when the patient is stable following resuscitation, further evaluation of the heart, including echocardiogram, is necessary to identify the underlying pathology and rule out tamponade. If tamponade physiology is present on imaging or hemodynamic instability from tachycardic rhythms is present further action needs to be taken with a focus on hemodynamic stability, then correction of the underlying pathophysiology.

Enhancing Healthcare Team Outcomes

Healthcare workers should be aware that Electrical alternans, although considered pathognomonic for pericardial effusion, is not a diagnostic factor for effusion and cardiac tamponade as other pathologies can result in this ECG finding. If the rhythm is noted on the ECG, the next step is to order an echocardiogram and consult with a cardiologist. If the patient is hemodynamically unstable, immediate drainage of the pericardial fluid is required. The most fact is that electrical alternans is not a benign event and one should always rule of tamponade first.

 

 


  • Image 6895 Not availableImage 6895 Not available
    Contributed by Brandon Barth, MD and Magaret Strecker-Mcgraw, MD
Attributed To: Contributed by Brandon Barth, MD and Magaret Strecker-Mcgraw, MD

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Electrical Alternans - Questions

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Electrical alternans is most likely to be seen in a patient with which of the following?



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When electrical alternans is present, what is the first line imaging modality used to evaluate cardiac function in an unstable patient?



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A 35-year-old male presents to the Emergency Department in respiratory distress. On exam, you note some venous distention on his neck and have difficulty with auscultating heart sounds. Vital signs at this time show hypotension at 62/30 mmHg, heart rate 53 bpm, respiratory rate 26 per minute, and SpO2 92%. While evaluating the patient, he suddenly becomes unresponsive, and no pulses are detected. An ECG performed in triage shows the differing amplitude of the QRS complex. Following CPR and airway management, what is the next appropriate step?



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Which of the following may result in electrical alternans on an ECG?



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A 34-year-old male presents to the emergency department with reported chest pain. Soon afterward, the patient decompensates. Repeat vitals show a heart rate of 111 beats per minute, respiratory rate of 20 breaths per minute, blood pressure 84/69mm/Hg, oxygen saturation 93%, temperature 98.7 Fahrenheit. Lungs are clear to auscultation though you have difficulty in auscultating heart sounds. Imaging is unavailable for immediate evaluation. An electrocardiogram is ordered. Which of the following is diagnostic of the presenting pathology on the electrocardiogram?



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A 39-year-old patient presents to the emergency department with shortness of breath. On further examination, it is revealed he is tachypneic with a respiratory rate of 28/min as well as tachycardic with a heart rate of 112/min. His remaining vital signs reveal a temperature of 98.4 F, blood pressure 90/78 mmHg, and SpO2 95%. His examination is remarkable for JVD, though lungs are clear on auscultation, and the patient appears to be in some mild distress. An ECG has been ordered. What is the best next course of action that will help determine the diagnosis?



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A 24-year-old patient presents to the clinic for an annual physical. Physical examination is unremarkable, and vitals reveal a heart rate 76/min, respiratory rate 18/min, temperature 98.6 F, blood pressure 122/82 mmHg, and SpO2 98% on room air. Documentary review reveals a previous ECG showing an alternating amplitude of the QRS and a PR interval of 102 ms. Which of the following is most likely to be found on questioning the patient?



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A 65-year-old female presents to his healthcare provider for the evaluation of fatigue and general malaise that has been present for the past few days. On further questioning, she reports a recent head cold with some sinus congestion that has since improved. She, however, claims that she is now having some mild chest discomfort and some increased work in breathing. Her vital signs show a temperature of 99.2 F, pulse 89/min, respiratory rate 20/min, SpO2 95%, and blood pressure 118/76 mmHg. Her ECG shows a peculiar pattern of varying levels of the height of her QRS complex. If left untreated, which of the following combination of symptoms is most likely to occur?



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Electrical Alternans - References

References

Goyal M,Woods KM,Atwood JE, Electrical alternans: a sign, not a diagnosis. Southern medical journal. 2013 Aug     [PubMed]
Blaivas M, Incidence of pericardial effusion in patients presenting to the emergency department with unexplained dyspnea. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine. 2001 Dec     [PubMed]
Kandel SM,Roth BJ, ELECTRICAL INSTABILITY DUE TO REGIONAL INCREASE IN EXTRACELLULAR POTASSIUM ION CONCENTRATION. Journal of nature and science. 2015 Aug     [PubMed]
Honasoge AP,Dubbs SB, Rapid Fire: Pericardial Effusion and Tamponade. Emergency medicine clinics of North America. 2018 Aug     [PubMed]
Xu B,Kwon DH,Klein AL, Imaging of the Pericardium: A Multimodality Cardiovascular Imaging Update. Cardiology clinics. 2017 Nov     [PubMed]
Hazim A,Belhamadia Y,Dubljevic S, Mechanical perturbation control of cardiac alternans. Physical review. E. 2018 May;     [PubMed]
Wilson LD,Jeyaraj D,Wan X,Hoeker GS,Said TH,Gittinger M,Laurita KR,Rosenbaum DS, Heart failure enhances susceptibility to arrhythmogenic cardiac alternans. Heart rhythm. 2009 Feb;     [PubMed]

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