Atypical Electrical Alternans Due to Large Left Pleural Effusion

P. Vijay Shekar1,*, A. Nagarajan2

1Department of Cardiology, Kauvery-Heart City, Trichy, India

2Department of Pulmonology, Kauvery Hospital, Cantonment, Trichy, India

*Correspondence: Tel: +91 96864 69004 Email:


Background: Electrical alternans – beat to beat variation in QRS amplitude has been classically described in pericardial tamponade.

Case presentation: We report a case of electrical alternans in a middle-aged female in the absence of pericardial effusion.

Conclusion: Electrical alternans can occur in the absence of pericardial effusion. Recognition of atypical pattern provides clue to the underlying diagnosis.

Keywords: Electrical alternans; Atypical electrical alternans; Pleural effusion


Electrical alternans refers to beat to beat alteration in amplitude, axis or duration of any of the components of the electrocardiogram. QRS alternans – beat to beat variation in QRS amplitude has been classically described in pericardial tamponade. We report a case of electrical alternans in a middle-aged female in the absence of pericardial effusion.

Case Report

A 46-year-old female presented with complaints of fever and dyspnoea of one week duration. Patient was tachypnoeic at rest. Blood pressure was 110/70 mm Hg with a heart rate of 110 beats per min at the time of admission. Jugular venous pulse was normal. On auscultation, breath sounds were decreased in left hemithorax. Electrocardiogram was done (Fig. 1).


Fig. 1. A 12-lead electrocardiogram showing sinus tachycardia with change in QRS amplitude and axis. No beat-to-beat variation is observed. Waxing and waning pattern of QRS amplitude is observed in rhythm strip.

Echocardiogram was done which showed normal chambers and cardiac function with no evidence of pericardial effusion. Chest X ray showed a large left sided pleural effusion (Fig. 2).


Fig. 2. Chest X ray PA view showing a homogenous opacity involving the left hemithorax due to a large left sided pleural effusion.

In view of respiratory distress, an intercostal drainage using pigtail was positioned in the left pleural cavity. After aspiration of 700 ml of pleural fluid, patient was relieved of respiratory distress. A repeat electrocardiogram after pleural fluid drainage showed normalization of the QRS alternans pattern (Figs. 3 and 4).


Fig. 3. Chest X ray after insertion of pigtail catheter for drainage shows partial resolution of the pleural effusion.


Fig. 4. A 12-lead ECG after pleural drainage shows normalisation of the alternans pattern.


Electrical alternans is described as a beat-to-beat variation of amplitude, axis or duration of any components of the ECG. QRS alternans is beat to beat variation in amplitude of the QRS and has been classically described in large pericardial effusions and cardiac tamponade. The QRS alternans is attributed to the swinging motion of the heart which results in varying QRS amplitude [1]. QRS alternans has also been described in other conditions like supraventricular tachycardia and ventricular tachycardia. Pseudolelectrical alternans has also been described, where QRS alternans is attributed to intermittent fasicular or bundle branch block [2].

In our patient, we observe a change in QRS amplitude and change in the precordial QRS axis. However, a beat to beat variation is not observed. A gradual waxing and waning of QRS amplitude over successive beats are observed. A change in precordial R wave transition is also observed. The ECG changes can be explained by the large left pleural effusion, presence of which changes the relative position of the heart to the surface electrodes during each respiratory cycle. As the alternans pattern is in sync with respiratory cycle, there is absence of beat-to-beat variation. The disappearance of the ECG changes after drainage of pleural fluid confirms the notion.

Atypical pattern of alternans due to lung pathology have been described previously. A gradual change in amplitude of QRS over 2-3 beat without alternate beat to beat variation has been described in a patient with acute severe asthma [3,4]. Electrical alternans in patients with large bilateral pleural effusion has been described as pulmonary alternans [5]. Hemodynamic changes mimicking tamponade physiology is reported to occur in patients with large pleural effusions in the absence of pericardial effusions [6]. However, in our patient, no hemodynamic or echocardiographic features of tamponade physiology were observed. The alternans pattern is purely attributed to the mechanical cause – relative change in position of the heart during respiration than due to hemodynamic changes.


Electrical alternans, though classically described in cardiac tamponade can occur in extra cardiac conditions, especially in patients with large pleural effusions. An atypical alternans pattern with gradual change in amplitude of QRS without beat-to-beat alternation should raise the suspicion of a respiratory pathology.


We thank Dr. Prabhaharan Renganathan, Technical Editor – Kauvery Hospitals who was involved in editing and revising the manuscript.

Author contributions

Dr. Vijay Shekar and Dr. Nagarajan were involved in management of the patient. Dr. Vijay Shekar was involved in preparation and editing the manuscript.

Competing interests

The authors have no competing interest to declare.


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