Revisiting Transcutaneous Cardiac Pacing

“Transcutaneous cardiac pacing is an effective procedure for patients experiencing unstable bradycardia.”

Or is it?

False Capture

False Capture

False Capture

If you’ve read Tom’s introduction to the subject of false capture you’re already ahead of the game.

We’ve shown case after case of unstable bradycardia patients receiving ineffective transcutaneous pacing due to a lack of capture. In each case, phantom pacing impulses are interpreted by the paramedic as electrical capture. Typically, this is confirmed by an improvement in other vital signs, such as mental status or blood pressure.

If I was being shocked 70 to 80 times a minute, you would likely notice an increase in my blood pressure too!

So why do we fail to recognize true electrical capture?

Are paramedics just that bad at ECG interpretation? Absolutely not.

This is a failure on the educational side.

We’ve conditioned paramedics to fail by showing them unrealistic ECG strips time and time again. We tell them to start at unrealistically low outputs and ask that they gingerly increase the output. We scare them that high outputs are painful. Check out the ACLS standard for “electrical capture”:

ACLS's idea of Electrical Capture

That looks pretty simple to me! 60 mA? Awesome. Another SAVE!

How about what a rhythm generator shows to a real live cardiac monitor during training?

Rhythm Generator Without Capture

One spike, no complex. Easy as pie, we need more milliamps. We’ve got this, right?

Rhythm Generator Obtains Capture

That is really, really easy to see.

Except that’s not what the progression of false capture to true capture looks like at all!

Check out this great progression, used by permission, from the amazing Float Nurse Mike blog:

Unstable bradycardia 04

Unstable bradycardia 05

Unstable bradycardia 06

Unstable bradycardia 07

Unstable bradycardia 08

Can you find all of the conducted and non-conducted complexes?

What about fusion of false capture and underlying beats?

This looks a lot harder than the ACLS strips or the rhythm generator! Why don’t these strips feature the same phantom complexes?

The phantom complexes are due to the interaction of the electrical stimulation applied during pacing and the recording electrodes. The energy being delivered polarizes the electrodes as they receive the “massive” stimulus in comparison to the electrical impulses of the heart.

It takes time for that polarization to bleed away. A great example of this is the exaggerated deflections after you defibrillate somebody, such as in the conclusion to our last case:

Uh Please Standby - Rhythm Defibrillation

It jumps off the screen before returning to the baseline, in fact, the cardiac monitor stopped recording for a full second and yet it still sees the effects of polarization.

In our pacing example we’re polarizing the recording electrodes 70 to 80 times a minute, which they must recover from. Because TCP uses much less energy than defibrillation (less than 1 J), the recovery time of the electrodes is much faster. However, it isn’t instantaneous!

Rhythm generators and textbook examples do not feature these phantom impulses because the recording electrodes do not see the electrical pacing stimulus and thus do not become polarized!

In order to succeed at TCP, we must expect all of the electrocardiographic findings of transcutaneous pacing:

  1. Phantom Impulses
  2. Pacemaker dissociation
  3. Pseudo-fusion
  4. True Capture

What do each of these look like?

Phantom Impulses are easy to spot once you know what they look like. Starting with the pacemaker impulse, you’ll see a sharp deflection that rapidly returns to the baseline without a true T-wave. There may be a pseudo-T-wave, but it won’t be real looking. Remember, when we’re pacing a patient we’re activating the ventricles without using the normal conduction system. The complex will be broad, slurred, and bizarre. It will not be sharp and pointy. Sharp and pointy means speedy conduction, which cell-to-cell ventricular depolarization is not.

Phantom Pacing Complexes

The Physio-Control clinical note on transcutaneous pacing artifact has a great example of phantom complexes (pdf), and they are the only manufacturer which acknowledges this problem in their literature! Kudos to Physio-Control.

False Capture

Pacemaker Dissociation is when the pacemaker impulses are dissociated from the underlying rhythm. With phantom impulses this will look like two competing rhythms. You’ll notice physiologically impossible R-R intervals as well, i.e. “beats during the absolutely refractory period.”

Unstable bradycardia 05

Pacemaker Dissociation

Pseudo-fusion of the pacemaker and underlying rhythm may be present, lending to the possibility that the impulse is real. However, do not be fooled by these imposters! They may look appropriately wide, with discordant T-waves, but they are not truly paced impulses.

TCP Pseudo Fusion

True capture looks like any other paced rhythm. Broad, slurred, QRS complex with a discordant T-wave. There should be no evidence of pacemaker dissociation, pseudo-fusion, or physiologically impossible complexes! Better yet, you should see a realistic capture threshold. If you’re using anterolateral pad positioning, which is common in EMS patients, be very suspicious of capture less than 90-100 mA.

True Capture

True Capture

You should also compare the ECG tracing in multiple leads to the pulse oximetry waveform, or better yet, confirm with increasing end-tidal CO2′s.

If you’ve got a strip of successful or unsuccessful transcutaneous cardiac pacing, we’d love to see it! Send it our way at ems12lead@gmail.com or post it to our Facebook page.

May the 4th Be With You Update: one of the crews who read this encountered an asystolic arrest, obtained ROSC, and paced the patient during transport. Great example of true capture here:

Post-Arrest True Capture

 

Vacunas, alimentos cocidos y condones: las recomendaciones del Minsal para quienes irán al Mundial

bisonlux (CC) 

 Publicado por Daniel Medina

Miles de chilenos ya están con la mirada fija en el este del continente, con aspiraciones de arribar a Brasil para presenciar la Copa del Mundo. El mundial se iniciará el 12 de junio, mientras que al día siguiente Chile debutará en la instancia ante Australia.
En este marco, la campaña “En el mundial campeones en prevención” que encabeza el Ministerio de Salud busca que los futuros viajeros tomen las precauciones antes de encaminarse a las tierras cariocas y enfrentarse a patologías que en nuestro país no son comunes.
El subsecretario de Salud Pública, Jaime Burrows, recordó en entrevista con Expreso Bío Bío que el sarampión es una enfermedad que en Chile se encuentra erradicada pero que en Brasil aún persiste. Por ello, sostuvo que en los consultorios la vacuna para esta infección se entrega de forma gratuita.
La fiebre amarilla también es un problema que podrían presentar algunos chilenos en ese país. Aclaró que la vacuna no es gratuita, por lo que los viajeros deberán dirigirse a los vacunatorios internacionales o privados para inmunizarse.
Junto a ello, subrayó la importancia de consumir alimentos cocidos de forma apropiada y en lugares habilitados para ello, evitando adquirirlos en la calle. Asimismo, afirmó que es mejor evitar los refrescos con hielo debido a las dudas que pueda genera la procedencia de este último, lo que podría incluso generar contagios por hepatitis o fiebre tifoidea.
Añadió además que en el sitio web del Ministerio, en las oficinas de Sernatur y en las agencias de turismo se podrá encontrar el detalle de las recomendaciones.
En la presentación de la campaña, Burrows manifestó también que la gente debe tener cuidado con las enfermedades de transmisión sexual, particularmente el sida y la hepatitis B, por lo que es necesario el uso del condón.
Tomado de Biobio .cl

Asymptomatic Hypertension

Asymptomatic hypertension is a frequent presenting complaint to the emergency department. Often, patients may be sent in by their primary care provider for work-up or evaluation. ACEP has developed a guideline in order to assist us with the management of this complaint, which can be varied depending on your training. A concise, practical summary of their recommendations for patient management is provided below.

Question 1: Should we screen for end-organ damage in patients who present with asymptomatic elevated blood pressure?

While there is no great evidence for this question, ACEP has two recommendations. In general, ACEP recommends that no screening is indicated for routine patients that present with asymptomatic hypertension. They state that physicians may screen for elevated creatinine in specific populations, such as patients that have poor or no follow-up. Based on three studies, there is a relatively high rate of incidental abnormal findings that may require addressing, and few true positives that altered management, although there were a few cases that did result in admission for renal insufficiency. They also recommend that screening for anything other creatinine does not appear useful, including obtaining an EKG.

Question 2: Should we intervene on patients with asymptomatic elevated blood pressure?

Again, no great evidence exists for this question, but ACEP has three Level C recommendations. They recommend no intervention based on the limited available data. There is evidence that the rapid lowering of blood pressure outside of a hypertensive emergency can worsen outcomes. A study done by Grassi et al (cited by the guidelines) found that of patients who presented with asymptomatic hypertension, 32% had a decrease in blood pressure within 30 minutes without intervention. This finding can lead to some questioning the utility of acting on our blood pressure readings in this patient population.

Consensus opinion recommends that for patients with poor follow-up, treatment can be started. They also recommend that all patients should be referred for outpatient follow-up. ACEP does suggest that for limited patient populations, such as those with no follow-up, treatment can be initiated, but they also report that many patients’ blood pressures will improve within 90 minutes without intervention, based on previous studies.

One should interpret their guidelines as evidence that we should only intervene in very limited circumstances in patients who present with asymptomatic blood pressure. If a patient has a primary care doctor, they can be referred to them for follow-up. In the case of extreme hypertension in a patient with no follow-up, we can consider screening for renal insufficiency and potentially even starting treatment, but the most important aspect is that we should ensure adequate follow-up for the patient.

Further Reading

Edited by Alex Koyfman

The post Asymptomatic Hypertension appeared first on emDocs.

ST elevation and QS-waves. ECG is equivocal. Use ED Echo!!

A male in his 50's with history of CAD, Diabetes, AAA with repair, and HTN presented for chest pain.  He complained of left-sided chest pain, onset while sitting, and described it as squeezing and radiating to left arm for the past hour.  He had similar pain with an MI 2 years ago.  The pain was worse with exertion but unchanged with Nitro.  Here is his ED ECG:
There is ST elevation in V1-V3.  The Computer Read: "Anterior ST Elevation  ***Acute MI***    
What do you think?









There is not just ST elevation, but there are QS-waves in V1-V3.  QS-waves can be due to old MI or to LVH, Cardiomyopathy, or COPD.  QS-waves with ST elevation should make one think of old anterior MI with persistent ST elevation (LV aneurysm morphology), or LVH.  The voltage is not enough for LVH, so (as with yesterday's post), LV aneurysm is high on the differential diagnosis

So we should use the LV aneurysm vs. anterior STEMI rule to help differentiate:

Rule 1: The lead in V1-V4 with the highest T-wave to QRS amplitude ratio.  This lead is V3 and we get:  4.5/14 = 0.32 (less than 0.36 suggests LV aneurysm, not STEMI)

Rule 2: (sum of T-wave amplitudes in V1-V4 divided by sum of QRS amplitudes in V1-V4).  This equals 13.5/56.5 = 0.24 (a value greater than 0.22 suggests STEMI, so this value suggests STEMI)

So we have discordant results from the 2 T-wave to QRS rules!  What to do?  

ED Echo!!

Here is the ED Echo:
This is the subxiphoid view, and it shows a bulging at the apex (an LV aneurysm).  There is an echo density at the apex that is frequently found with LV aneurysm.  This is a mural thrombus and puts the patient at great risk of stroke.

Here is the Apical 4-chamber view:
Again, this shows bulging of the apex, confirming LV aneurysm.



The patient was anticoagulated for the thrombus.  He ruled out for MI with serial troponins.  Records obtained confirmed previous diagnosis of LV aneurysm with thrombus.


Lessons:

The rules for differentiating LV aneurysm from acute STEMI are not perfect, but they can be greatly aided by bedside echo.

Button Battery Ingestion

Button Batteries

We all know that kids love to put odd objects in their mouths (and ears, and nostrils, and other interesting places).  We also know that this can cause significant problems and lead to true emergencies.  The location of the object (ie, airway) may lead to the emergency, but don’t forget that the object itself may lead to problems and severe tissue destruction!  Button batteries are one of these unique objects that warrant our specific concern and respect!  We have discussed previously the problems that a button battery in the nostril can cause, now let us turn our attention to a potentially even more devastating problem: Button Battery Ingestion.

Button Battery – Easy Access

  • With our ever increasing number small electronic devices, button batteries are becoming more prevalent.
    • Toys & Electronic Games
    • TV Remote Controls & Key Fobs
    • Flashlights & Calculators
    • Watches & Hearing Aids
  • They come in a variety of sizes, some that are rather large (>20mm).
    • A Button Battery that is smaller generally is able to pass uneventfully.
    • A Button Battery that is large (>20mm) is more likely to get stuck and lead to worse outcomes.

 

Button Battery – Scope of the Issue

  • During a 20 year period in the US, it was found that there was a significant increase in battery-related ED visits!
    • During this time, 65,788 patients <18 years visited EDs for battery-related issues equating to an average of 3,289 visits annually!
    • That works out to be 1 patient almost every 3 hours!
  • Unfortunately, in 2009, this number had increased (~6,000 children seen in US EDs for battery-related complaints).
  • Worse outcomes associated with larger Lithium button batteries and younger children (< 4 years).

 

Button Battery Ingestion – Presentation

  • Most often will present as other Foreign Bodies.
    • Cough & Gagging
    • Drooling & Dysphagia
    • Increased Work of Breathing & Stridor
  • But don’t forget kids can be tricky (and not tell you that they swallowed a FB).
    • Croup-like
      • Acute stridor without associated viral symptoms warrants concern.
      • Recurrent stridor warrants consideration for airway FB.
    • Wheeze
      • One great reason to check CXR in young child with first time episode of wheezing.
  • May have symptoms that initially don’t seem related to a FB ingestion, but are related to the evolution of tissue damage.
    • Vomiting
    • Fever
    • Irritability
    • Listless

 

Button Battery Ingestion – The Science

  • Tissue damage from Button Battery is due to alkaline caustic exposure.
    • Recall, aLkaLine caustics lead to Liquefaction necrosis.
    • When the battery is placed in a moist environment (ex, mucous membranes, saliva), an electrical charge is generated.
      • The Lithium Button Batteries have twice the capacitance of other button batteries (3 volts vs 1.5 volts).
      • Lithium Button Batteries can generate more current and have been associated with worse outcomes.
      • Even used (spent) Lithium Button Batteries can still generate enough current to damage tissue!
    • The discharged current hydrolyzes water, generating Hydoxide ions — leading to alkaline injury.
  • Negative-Narrow-Necrotic” Mneumonic
    • The current generates the hydroxide at the negative terminal of the battery.
    • The negative terminal is the more narrow side of the button battery when viewed laterally.
    • The anatomic orientation of the battery can predict where the necrosis will be and the subsequent injury.
  • The Esophagus (and nostril) are highly susceptible to this injury.
    • A button battery moving freely does not generate enough hydroxide ions in one location to produce focal damage.
    • The button battery lodged in the esophagus or nostril generates a focal collection of alkaline caustic material in a confined region that can cause tissue necrosis.
  • Serious damage can occur within 2 hours!
  • Damage can also occur from:
    • Leakage of alkaline material from the battery (usually, not the cause of the tissue damage that is seen to occur within 2 hours).
      • This is more of a problem with the non-lithium batteries.
    • Compression of local structures.

 

Button Battery Ingestion – Imaging

  • Fortunately, we are looking for a radio-opaque coin-like object!
    • Plain films should be sufficient.
  • Unfortunately, we can get fooled if we are not vigilant (common theme of the PedEM Morsels)!
    • 54% of fatalities due to a Button Battery FBs were misdiagnosed.
      • Most of these had non-specific presentations.
      • Additionally, a large, round, coin-like object in the esophagus, may be easily misinterpreted as a coin which would be appropriate to initially observe and repeat film to see if it passes…
      • If damage can occur within 2 hours, that period of observation can be very critical for your patient!!
    • Look carefully at the foreign body.
      • Viewed “en face,” a button battery will have a “halo rim” – ring of radiolucency just inside the outer edge of the object.
      • Viewed on edge, a button battery may have a central bulge or “step-off, although this can be difficult to appreciate if oblique or with newer, thinner Lithium batteries.

 

Button Battery Ingestion – The Problem

  • Any button battery ingestion should be treated promptly as if a emergent condition is developing before your eyes!
  • The button battery induced caustic tissue damage can lead to significant destruction of local structures:
    • Perforations
    • Fistulas
      • Tracheoesophageal Fistula
      • Fistulation of major blood vessels
    • Vocal cord damage and paralysis
    • Strictures
    • Spondylodiscitis
    • Massive Hemorrhage
    • Death
  • Removal can be difficult.
    • The local tissue damage can lead to friable structures that can be further damaged by instrumentation.
    • Should be removed under direct visualization.

 

Button Battery Ingestion – Management

  • Vigilance is required as the presentation may be non-specific and the outcomes severe!
  • Button Batteries that are in the Esophagus need to be removed promptly – within 2 hours!
  • Button Batteries that are in the stomach or beyond, in an asymptomatic patient, can be monitored and allowed to pass.
    • Repeat radiographs are reasonable.
      • Repeat in 4 days for < 6 years of age or for larger button batteries (> 15 mm).
      • Repeat in 10 – 14 days for older children if not large battery.
      • After that time, if battery still in stomach, endoscopic removal recommended.
    • Strict anticipatory guidance and return precautions should be given – emphasizing need to be evaluated for any abdominal pain, fever, or vomiting.
  • Co-ingestion of a magnet with the Button Battery necessitates removal.
  • After removal, some advocate for a delayed 2nd look endoscopy to ensure no damage occurred.
    • Perforations and fistulas may develop up to 18 days after removal.
    • Strictures can develop weeks and months after removal.
  • See nice algorithm.
  • Button Battery Task Force

 

References

Gohil R1, Culshaw J2, Jackson P3, Singh S3. Accidental button battery ingestion presenting as croup. J Laryngol Otol. 2014 Mar;128(3):292-5. PMID: 24555666. [PubMed] [Read by QxMD]

Jatana KR1, Litovitz T, Reilly JS, Koltai PJ, Rider G, Jacobs IN. Pediatric button battery injuries: 2013 task force update. Int J Pediatr Otorhinolaryngol. 2013 Sep;77(9):1392-9. PMID: 23896385. [PubMed] [Read by QxMD]

Jayachandra S1, Eslick GD. A systematic review of paediatric foreign body ingestion: presentation, complications, and management. Int J Pediatr Otorhinolaryngol. 2013 Mar;77(3):311-7. PMID: 23261258. [PubMed] [Read by QxMD]

Sharpe SJ1, Rochette LM, Smith GA. Pediatric battery-related emergency department visits in the United States, 1990-2009. Pediatrics. 2012 Jun;129(6):1111-7. PMID: 22585763. [PubMed] [Read by QxMD]

Centers for Disease Control and Prevention (CDC). Injuries from batteries among children aged <13 years–United States, 1995-2010. MMWR Morb Mortal Wkly Rep. 2012 Aug 31;61(34):661-6. PMID: 22932299. [PubMed] [Read by QxMD]

Litovitz T1, Whitaker N, Clark L, White NC, Marsolek M. Emerging battery-ingestion hazard: clinical implications. Pediatrics. 2010 Jun;125(6):1168-77. PMID: 20498173. [PubMed] [Read by QxMD]

Sharma A, Chauhan N, Alexander A, Campisi P, Forte V. The risks and the identification of ingested button batteries in the esophagus: a child safety issue. Pediatr Emerg Care. 2009 Mar;25(3):196-9. PMID: 19287282. [PubMed] [Read by QxMD]

The post Button Battery Ingestion appeared first on Pediatric EM Morsels.

Burn the ACC/AHA Low-Risk Chest Pain Guidelines

Management of low-risk chest pain is, by reasonable conjecture, one of the greatest failings of Emergency Medicine and the medical profession in general.  Whether driven by true altruism or by risk-management and zero-miss strategies based on the ACC/AHA guidelines, many, many, many patients are admitted and subjected to provocative testing.

And almost none of those patients are ultimately, correctly, diagnosed with the feared disease – acute coronary syndrome.

This is a prospective, observational evaluation of patients admitted for chest pain observation at a single academic center in Rhode Island.  Over the course of ~2 years, 3,543 patients were admitted for an initial evaluation of chest pain after initial negative cardiac biomarkers in the Emergency Department.  Approximately half of patients underwent stress testing.

Of 1,754 stress tests, there were 29 positives.  Of those, 9 were false positives.  Stratified by pretest probability, none of the patients with a "low probability" Diamond & Forrester Score had a true positive test.  Only 1% of patients admitted and stressed with "intermediate probability" D&F Score ultimately proved to have true positive tests.  Even with "high probability", 5% of all stress tests performed were true positives.

The author of this article means to specifically reduce stress testing in the "low probability" cohort.  this is a reasonable proposal to skim off a small percentage of tests.  However, he misses asking the better question – how do we reduce use in our "intermediate probability" cohort, which constituted 85% of admissions with just a 1.7% yield for ACS?  We need to seriously address the outdated and inefficient notion admission and testing for these patients is the ideal strategy – and that probably starts by tossing our current guidelines out the window.

“The Association Between Pretest Probability of Coronary Artery Disease and Stress Test Utilization and Outcomes in a Chest Pain Observation Unit”
http://www.ncbi.nlm.nih.gov/pubmed/24730402