An elderly patient with shortness of breath and near syncope

 Written by Pendell Meyers

An elderly patient experienced a week of shortness of breath on exertion, with acute worsening including near syncope and severe fatigue. She called EMS, who recorded this ECG on the way to the hospital:

What do you think?

On arrival at the Emergency Department, she appeared critically ill, and had severe hypotension but was alert and oriented and able to follow commands.

There is sinus rhythm at around 100 bpm. The QRS morphology alternates between two morphologies. The P waves are regular, the PR intervals are similar, and the QRS duration is similar throughout. This is electrical alternans. 

Here is her initial ED ECG:

Here is a prior ECG available from months ago:

No alternans.

A bedside echo revealed the large pericardial effusion, with tamponade physiology confirmed clinically and ultrasonographically.

An emergent pericardiocentesis was performed in the cath lab, with 700 cc of fluid removed with immediate improvement in hemodynamics.

The effusion was felt to be related to the patient's known cancer. Ultimately she improved during the hospitalization and returned to her previous state of health.

See these other related cases:

Acute chest pain and ST Elevation. CT done to look for aortic dissection.....

A woman in her 20s with syncope

80-something year old with acute chest pain. 3 visits. Fascinating Ultrasound progression

A young woman in her early 20s with syncope

Dyspnea on Exertion in a Middle Aged Woman.

===================================

MY Comment, by KEN GRAUER, MD (3/21/2025):

===================================

Today’s case by Dr. Meyers is a “Must KNOW” entity for emergency care providers.

• The patient is an elderly woman, who contacted EMS because of a 1-week history of worsening dyspnea on exertion — severe fatigure — and near syncope.
• Although alert on arrival in the ED — she was markedly hypotensive and appeared critically ill.
• Notable in her past medical history is a known diagnosis of cancer.

KEY Point: Given the above information — recognition of the cause of this elderly patient’s acute critical illness should be suspected within 1 minute of seeing the patient and seeing the ECG.

• In Figure-1 — I’ve reproduced the initial ECG recorded in the ED. As per Dr. Meyers — the long lead II rhythm strip shows a rapid sinus rhythm at ~90-95/minute, with a narrow QRS complex and alternating QRS morphology every-other-beat. 
• P wave morphology and the PR interval do not change throughout this tracing (as would be expected if the reason for the alternating QRS morphology was the result of intermittent preexcitation or late-cycle premature junctional or ventricular beats).
• T wave morphology does not change from beat-to-beat (as would be expected if the alternating QRS morphology was the result of some form of intermittent bundle branch block).
• Instead — each even-numbered beat in the long lead II rhythm strip manifests decreased R wave amplitude with a prominent J-wave that is not present in odd-numbered beats (RED arrows highlighting J-waves in several leads).
• PEARL #1: If you “step back” a bit from the tracing — Isn’t there a pendulum-like movement from the peak of the QRS from one odd-numbered beat to the next? (ie, downsloping dotted RED lines alternating with upsloping dotted BLUE lines).
• PEARL #2: Did you notice the low voltage? (with this finding most marked for even-numbered beats in the limb leads).
• PEARL #3: Why is the known history of cancer relevant to today’s case? 

Figure-1: The initial ECG in the ED.

DISCUSSION:

As per Dr. Meyers — the alternating QRS morphology seen in Figure-1 represents electrical alternans.

• As noted in My Comment in the October 23, 2023 post — the various forms of electrical alternans are frequently misunderstood, if not all-too-often overlooked.
• PEARL #4: Electrical alternans is most commonly encountered by emergency providers in association with supraventricular tachycardias (especially for the reentry SVT rhythms of AVRT and AVNRT). Although other entities may produce various forms of alternans (as discussed in the Oct. 23, 2023 post) — the recognition of alternans in a regular SVT rhyhm without atrial activity provides a clue that the mechanism of the SVT rhythm is likely to be reentry (See Figure-3 below for an example of this).

The above said — the importance of recognizing electrical alternans in today's case relates to it association with the presence of a large pericardial effusion. 

• To Emphasize: The overall sensitivity of electrical alternans for smaller pericardial effusions is poor. Even with larger effusions — its sensitivity is limited.
• That said — the likelihood of a large pericardial effusion is increased in today's case by the additional ECG findings in Figure-1 of low voltage and the pendulum-like variation in the peak of the QRS from one odd-numbered beat to the next.
• Verification of a large pericardial effusion was immediately forthcoming in today's case by Echo at the bedside (as shown above by Dr. Meyers' with several still ultrasound images ). 
• More than just a large pericardial effusion — concern for cardiac tamponade was raised by this patient's critical clinical condition (severe dyspnea — near syncope — marked hypotension in the ED) — and as per Dr. Meyers, by signs of tamponade physiology on physical exam and Echo (the parameters to look for described in the November 28, 2022 post and in Jensen et al: ESC 15(17), 2017). Fortunately — emergent pericardiocentesis with removal of 700 cc of fluid relieved the patient's symptoms.
• The history of cancer in today's patient is relevant — because malignancy is by far the most common non-traumatic cause of cardiac tamponade.
• To better illustrate the "swinging heart" pathophysiology of a large pericardial effusion — I show in Figure-2 the ultrasound recording that I've excerpted from another case in Dr. Smith's ECG Blog. Looking at this swinging heart recording in Figure-2 helps to explain the pendulum-like movement from one odd-numbered beat to the next that I highlighted with dotted BLUE and RED lines in Figure-1.

Figure-2: Illustration of the "Swinging Heart" phenomenon (This parasternal long axis view is from the cardiac ultrasound in the November 28, 2022 post of Dr. Smith's ECG Blog).

==================================

Electrical Alternans with Reentry SVT:

Figure-3: I’ve enclosed within a RED rectangle the 3 leads in this tracing in which there is clear evidence of electrical alternans. (Figure reproduced from My Comment at the bottom of the page in the September 7, 2020 post in Dr. Smith's ECG Blog).