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Dr. Littmann's Monthly ECG Lessons

7/4/2020 0 Comments

June 2020 ECG Lesson: "Is It Right?"

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By: Andrew Yde, MD
Editors: Drs. Littmann and Gibbs


Case:
A 61-year old woman with coronary artery disease and interstitial lung disease, on home O2 therapy, presented with a 3-day history of constant right-sided chest pain radiating to the right neck. She also complained of worsening dyspnea and exertional lightheadedness. On physical examination, the patient was afebrile, had a heart rate in the 60s, was mildly hypertensive at 147/71 mmHg, and was maintaining normal oxygen saturations on 2L supplemental O2. The examiner did not note abnormalities on cardiopulmonary exam. Chest CT angiogram was negative for pulmonary embolism and high sensitivity troponin was <6. She was given morphine and Toradol with some relief in her chest pain.

The following electrocardiogram was obtained:

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Physician interpretation of the ECG was as follows:
Normal sinus rhythm with a rate of 67, right axis deviation, otherwise normal intervals. ST depression in the septal and lateral leads. No ST elevation. When compared to an ECG obtained two months before, the complex morphology is generally unchanged. The ST depression is a bit more pronounced.
What is your interpretation of this initial ECG? Do you agree with the physician interpretation?
Do not agree.
The ECG shows sinus rhythm with dextrocardia. The ST-T morphology cannot be reliably assessed. Repeat ECG with limb leads reversed, and place right-sided chest leads.
Summary of key ECG findings:
  • Negative QRS complexes and inverted P and T waves in lead I (everything negative in lead I).
  • Negative QRS in lead II.
  • Reversal of direction of the P, QRS and T in aVR and aVL, largely positive in aVR and largely negative in aVL.
  • Reversal of typical QRS progression (R wave progression) in the chest leads. The tallest R waves are in V1. This is followed by R-wave regression and a decrease in the amplitudes of the QRS complexes rather than R-wave progression and an increase in the amplitudes of the QRS complexes.
  • In patients with dextrocardia, reversal of the arm leads will “normalize” the directionality of the QRS and P waves. On the same note, placement of the precordial leads in a right sided fashion (V1R-V6R) will result in “normalized” R wave progression and septal depolarization.
In this patient with dextrocardia, the chest leads were reversed but the limb leads were not. See ECG below:
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Note that the limb leads remained unchanged, but the QRS progression in the chest leads has normalized. One can now diagnose probable left ventricular hypertrophy (LVH) with secondary repolarization abnormality vs. anterolateral ischemia. As the repolarization abnormality was identical to that seen two years before, LVH was the more likely diagnosis. Possible abnormalities in the limb leads may have remained obscure.
Proof of situs inversus totalis:
(1) ECG showing dextrocardia – see above.
(2) Chest X-ray demonstrating a right-sided heart with the ventricular apex pointing to the right – below left.
(3) Abdominal CT showing the liver on the left and the spleen on the right – below right. The abdominal CT was recorded during a prior admission.

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Hospital Course:

Two sets of high-sensitivity troponin measurements remained within normal limits. An echocardiogram showed new moderate biventricular dysfunction with left ventricular ejection fraction (LVEF) calculated at 35%, changed from echocardiogram three years prior in which biventricular function was normal and LVEF was 55%. Given a history that was concerning for ischemia and new biventricular dysfunction, the Cardiology service recommended cardiac catheterization which revealed calcification and minor luminal irregularities of all coronary vessels and a 50% stenosis of the mid left main coronary artery. No stents were placed, and medical management was recommended. The patient experienced several bouts of right sided chest pain reliably relieved by oral Tylenol. Her chest pain was felt to be musculoskeletal in nature. She was discharged in stable condition with follow-up appointments with both her primary care physician and Cardiology.

What is situs inversus, and what does it mean for our patient?
Situs solitus refers to the normal orientation/location of the thoracic and abdominal viscera. In situs solitus, we find a tri-lobed right lung, a bi-lobed left lung, and a heart on the left side with the apex facing left. The liver and gallbladder are on the right, the spleen is present on the left, the descending colon is on the right, the ascending colon on the left, and the inferior vena cava (IVC) runs to the right of the aorta in the abdomen, etc.

In 1 out of 10,000 people, the orientation of the thoracic and abdominal viscera is reversed - a heterotaxy syndrome called situs inversus. Of these patients, the vast majority have situs inversus totalis, in which the heart is in the right chest with the apex oriented toward the right (dextrocardia). The remainder of the thoracic and abdominal viscera are in positions exactly mirroring situs solitus. For example, the right lung is bi-lobed, the left lung is tri-lobed, the liver and gallbladder are on the left side, the spleen is on the right side, the ascending colon is on the left, the descending colon is on the right, the IVC runs to the left of aorta in the abdomen, etc. Approximately 2-5% of these patients will have congenital cardiac anomalies, but the vast majority will be asymptomatic with normal quality of life and life expectancy.

Approximately 1 in 22,000 people in the general population will have situs inversus with levocardia, meaning that, although the thoracic and abdominal viscera are in mirror/reverse position from situs solitus as in situs inversus totalis, the heart remains in levocardia (its normal orientation), located in the left chest with the apex oriented toward the left. Nearly 100% of these patients have congenital cardiac anomalies, usually of the cyanotic variety (i.e. transposition of the great vessels). These patients have a severely shortened life expectancy. In fact, only about 5-13% of patients with situs inversus with levocardia survive beyond 5 years of age.
Of patients with situs inversus totalis, 17-25% will have Kartagener syndrome characterized by chronic sinusitis, bronchiectasis and situs inversus. This syndrome is a result of dynein protein abnormalities causing impaired mucociliary clearance, known as primary ciliary dyskinesia. Interestingly, only 50% of patients with primary ciliary dyskinesia will have situs inversus, and thus only 50% will meet official criteria for Kartagener syndrome.

Based on radiographic, echocardiographic, and ECG evidence proving dextrocardia, CT angiography of the chest confirming a tri-lobed left lung and bi-lobed right lung, and CT abdomen obtained during previous hospital admission, our patient has situs inversus totalis without associated primary ciliary dyskinesia. She had no evidence of congenital cardiac abnormalities on her echocardiogram or catheterization. She had respiratory bronchiolitis associated interstitial lung disease and chronic obstructive pulmonary disease, both secondary to a greater than 25 pack-year history of cigarette smoking, rather than chronic sinusitis. This patient’s coronary disease did not seem to be related to her underlying situs inversus totalis, but rather due to the significant smoking history, diabetes, and hypertension.

Dr. Littmann’s comments:
If you order an ECG, please spend a couple of minutes to analyze it. The first steps include rate, regularity and rhythm. Then go left-to-right, starting with the P waves. The normal sinus P wave cannot be negative in lead I as the SA node is in the upper right atrium and therefore, atrial activation is right-to-left, going towards lead I. If the P wave is negative in lead I, follow the steps below:
  • The most common cause of a negative P wave in lead I is limb lead reversal. If you suspect limb lead reversal, please order a repeat ECG with special attention to correct electrode placement.
  • If both the P and QRS is negative in lead I, as in the current case, the differential diagnosis includes left-right arm lead reversal and dextrocardia: either the heart is on the wrong side or the arm leads are on the wrong side. It is easy to distinguish the two: in arm lead reversal, the QRS progression in the chest leads is normal (see ECG below) whereas in dextrocardia, it is reversed.
  • The conventional ECG of patients with dextrocardia cannot be read; one needs to reverse both the limb leads (R arm - L arm leads and R foot - L foot leads) and the chest leads (place right-sided chest leads). Once you have done that, all ECG abnormalities become real. Unfortunately, as it happened in this patient, the chest leads are frequently reversed, but the limb leads are not which makes it essentially impossible to recognize abnormalities that only show up in the limb leads such as inferior ischemia or infarct.
  • Once dextrocardia is diagnosed, some type of abdominal imaging is needed to confirm or exclude situs inversus totalis.
  • In patients with situs inversus totalis, explore the possibility of the Kartagener syndrome.
Below is an example of right arm – left arm lead reversal. Note that the limb leads look essentially identical to what was seen in dextrocardia (everything negative in lead I, upright P, QRS and T in aVR and negative P, QRS and T in aVL), but in the chest leads, there is normal R-wave progression.
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References:
  • Abdullah, N., MBBS, FRCR, Quek, S., MBBS, FRCPCH, Seto, K., MBBS, FRCR, & Teo, L., MBBS, FRCR. (2015, April). Clinics in diagnostic imaging (160). Levocardia with abdominal situs inversus. Retrieved June 27, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4415098/
  • Burns, E., MD. (2019, March 16). Right Ventricular Infarction • LITFL • ECG Library Diagnosis. Retrieved June 26, 2020, from https://litfl.com/right-ventricular-infarction-ecg-library/
  • Mozayan, C., MD, & Levis, J., MD, PhD, FACEP, FAAEM. (2019, August 15). ECG Diagnosis: Dextrocardia. Retrieved June 26, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6730946/
  • Paul J. Shogan, MC USA, Les Folio, USAF MC SFS (Ret.), Situs Inversus Totalis, Military Medicine, Volume 176, Issue 7, July 2011, Pages 840–843, retrieved June 26, 2020 from https://doi.org/10.7205/MILMED-D-11-00039
  • Roongruangchai J, Narongsak W, Plakornkul V, Viravud Y, Sripaoraya K, Roongruangchai K. Situs inversus totalis and ultrastructure of respiratory cilia: report of a cadaveric case. J Med Assoc Thai. 2012;95(1):132-138, retrieved June 26, 2020 from https://pubmed.ncbi.nlm.nih.gov/22379754
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1/14/2020 0 Comments

December 2019 ECG Lesson

This month’s EKG is brought to you by Dr. Clayton Long.
​Editors: Drs. Littmann and Gibbs
Clayton Long, MDClayton Long, MD
​Case 
A 67-year-old male with 6-12 month history of recurrent syncope presented to the ED with facial trauma following a syncopal event. The patient experienced multiple prodromal episodes of presyncope in short succession, ultimately culminating in true syncope causing a nasal fracture. He refused additional work-up at the time of injury given his history of extensive previously negative evaluations for syncope. He had received multiple ECGs, nuclear stress testing and echocardiography in the past. The results of his past evaluations were unrevealing, and he was referred to a specialist with no further clarity provided. 
 
Within weeks he returned for outpatient surgical repair of his nasal fractures. In the perioperative period he was noted to have AV block on telemetry which self-resolved. He was reportedly symptomatic at the time this rhythm was recognized and was referred for subspecialty Cardiology – Electrophysiology (EP) for evaluation where the following ECGs were obtained.

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What is your interpretation of the ECGs?
Correct interpretation of the ECGs
ECG #1
- NSR with normal PR, normal QRS axis and RBBB 
- Sinus rate of 85/min with 1:1 AV conduction
 
ECG #2
- Regular bradycardia, still normal PR intervals and normal QRS axis, unchanged RBBB pattern 
- The sinus rate is now 90/min with 2:1 AV block; hence, the ventricular rate is 45/min
- Blue arrows below demonstrate twice as many sinus P waves as QRS complexes
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Significance of these findings? 
​These ECG findings are consistent with right bundle-branch block and acceleration-dependent second-degree AV block where there is 1:1 AV conduction at slower sinus rates but 2:1 AV block at faster atrial rates. Acceleration- dependent AV block localizes the block to the His-Purkinje system, which is characterized by all-or-none conduction. At a critical sinus rate, only every other sinus impulse is able to conduct through the His-Purkinje system and every other P wave is blocked. On the conducted complexes, there is no change in the PR interval. The blocked P waves are almost never recognized by the interpretation software, which usually reads the rhythm as sinus bradycardia, a clinically trivial dysrhythmia. Therefore, the ECG must be carefully scrutinized in order to identify this ominous rhythm and the correct diagnosis.
 
- In this case, slowing down the sinus rate with carotid massage or IV beta-blocker can paradoxically improve AV conduction.
- Atropine, on the other hand, is contraindicated because it can worsen AV conduction by increasing the sinus rate.
- This finding is concerning for extensive distal conduction disease. Patients with bundle-branch block and acceleration-dependent AV block are at high risk of complete heart block at an anatomically distal level, which may result in asystole and cardiac arrest. 
- This finding requires urgent EP evaluation and is an absolute indication for dual-chamber (AV sequential) pacemaker implantation
Hospital Course
​The patient was admitted directly from the outpatient EP office visit to Cardiology for permanent pacemaker implantation. He received a dual-chamber pacemaker. He continued to experience syncopal symptoms following his initial procedure due to intermittent loss of lead capture requiring revision and a brief admission to the cardiac ICU. The remainder of his hospitalization was uncomplicated, and he was discharged shortly thereafter with no recurrence of symptoms. During his first outpatient EP follow-up he was noted to be asymptomatic with no recurrence of syncope and a fairly low pacing burden. EP noted that they anticipate his pacing burden will increase over time.
Summary 
​This patient had right bundle-branch block and an occult acceleration-dependent 2:1 AV block that was present but unrecognized on the ECGs during multiple prior ED visits for syncope. 
 
Bundle-branch block combined with acceleration dependent 2:1 AV block is indicative of extensive distal conduction system disease and requires urgent EP evaluation for pacemaker implantation to avoid degeneration to complete heart block and potentially, cardiac arrest. 
 
This rhythm is rarely detected by the interpretation software and will be missed on ECG review unless thoughtfully searched for. 
Dr. Littmann’s Comments
It is well known that patients with bifascicular block are at risk of developing complete heart block. This is especially true for patients with bifascicular block who experience syncope. It is less appreciated, but still well documented that patients with simple left or right bundle branch block and syncope too, as in the current case, are frequently found to have paroxysmal AV block and asystole.1 Based on these data it is recommended that patients with unexplained syncope who have any type of intraventricular block should undergo prolonged monitoring with an implanted loop recorder (class I recommendation).2 In this case, the patient had numerous previous workups by cardiologists and underwent a number of minimal value testing such as echocardiography and stress testing, but was never offered cardiac monitoring.
 
A second important lesson of the case is that 2:1 heart block is almost never recognized by interpretation softwares and is rarely recognized by providers. Most cases are interpreted as sinus bradycardia, which is usually a more benign dysrhythmia. Whenever a patient’s ECG appears to demonstrate regular sinus bradycardia, please carefully search for twice as many P waves than meets the eye by halving the interval between the conducted P waves. This “trick” only takes a few seconds to do. It is most important to search for 2:1 heart block in patients who have bundle-branch block and in patients who present with presyncope or syncope.
Key references
  1. Moya A, et al. Bradycardia detection in Bundle Branch Block (B4) study. Eur Heart J 2011;32(12):1535-41.
  2. Kusumoto FM, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2019;74:e51-156.
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    Author

    This blog represents important ECG lessons that the Emergency Medicine Residents from Carolinas Medical Center (Charlotte, NC) rotating through the Cardiology service encounter.  Test your knowledge with them! The esteemed educators Dr. Laszlo Littmann and Dr. Michael Gibbs serve as the primary content editors and course directors. 

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