It’s all in a P-Wave

You know, the more you learn about medicine, the more you will realize how much there is out there that you will never know. ECGs are no exception. My obsession with cardiology began in paramedic school and it was only natural for me to grow a similar love for ECG interpretation.

Unfortunately, the usual prehospital training for 12-lead ECGs is limited, and generally doesn’t cover much more than STEMI and bundle branch blocks. The traditional resistance to further education usually involves a phrase like “well how is that going to change your treatment?” Nothing irks me more than hearing that stupid question. As if gaining new treatment strategies was the only reason to learn something. In this collection of posts, we will discuss some of the other things that an ECG can be used for, and you may find that it just might change your treatment.

The p-wave
The p-wave is the graphical representation of atrial depolarization. With normal physiology, this is initiated by the sinoatrial, or SA node. The p-wave can tell us many different things. A normal p-wave, married to a normal QRS lets us know that the patient has normal conduction.

There are many abnormals that may clue us in to a few pathologies though. If a p-wave is too tall, or peaked, right atrial enlargement is likely. A p-wave with two humps might indicate left atrial enlargement. The absence of a p-wave lets us know that the pacemaker is somewhere else in the heart. A p-wave that follows the QRS is likely not being used, and indicates that the AV junction is probably controlling the heart rate.

Maybe you have a p-wave that is slowly gaining distance between itself and it’s QRS complex, until finally there is no QRS; which indicates a Wenkebach pattern. The p-wave could be completely divorced from the QRS complex, indicating atrioventricular disassociation, or a complete heart block. It’s funny how much that little deflection can tell us. We often take it for granted, but when it is absent, we want it back desperately.

P-wave in red

Above you can see a relatively normal location for a P-wave. 99% of your patients will probably have a similar variation to this.

Below is an example of p-pulmonale, which is an indication of right atrial enlargement.

P-pulmonale

Why is it called p-pulmonale?

Well, this is enlargement if the right atrium.  The right atrium pumps its contents into the right ventricle which eventually empties its contents into the pulmonary trunk, pulmonary arteries, and eventually the lungs.  When the pressure is backed up or increased in the lungs from chronic respiratory conditions like COPD, or asthma, or as a result of left ventricular failure, the right ventricle has to work harder.  When the right ventricle works harder, so does the right atrium.  Consisting of mostly muscle, when the heart works harder it gets bigger, just like your biceps.  Consequently, right-sided heart failure is known as cor pulmonale.  There are other causes, such as a right ventricular myocardial infarction, but the concept remains the same.

P-mitrale

Above, you will see a p-wave with two humps.  These p-waves are usually wider than normal, and are an example of p-mitrale, which is indicative of left atrial enlargement.

How does the left atrium enlarge?

The left atrium generally hypertrophies as a result of heart failure.  To be more specific, left-sided heart failure.  Left ventricular hypertrophy can be expected as well.  This doesn’t have to be the case though, anything problem that causes the left atrium to increase its workload may result in an increased size.

While biphasic p-waves may be a normal finding in V1 on a 12-lead ECG, if it is deeper than it is tall, it is likely representing left atrial enlargement as well.

Left Atrial Enlargement

You may find that many of your patients have both atria enlarged, and maybe even all four chambers.  This cardiomegaly is a very good indicator that your patient may be suffering from heart failure.  When you see left atrial enlargement on the 12-lead, don’t forget to look for LVH.  Remember that LVH can present with a left ventricular strain pattern, and this can mimic STEMI quite well.  Check out ems12lead.com for more about that STE-Mimic.

The p-wave and its relationship with the QRS complex can tell you about abnormal conduction from the atria to the ventricles.  More specifically, you can diagnose an atrioventricular block by closely examining the p-wave and pr-interval.

How to identify which AV block you are looking at:

Is the PR-Interval a constant length?

Yes > Are there any dropped beats?                                                                            No > P wave for every QRS?

- Yes = Mobitz 2                                                                                                                 – Yes = Mobitz 1/Wencheback

- No = 1st Degree AV Block                                                                                             – No = Complete Heart Block

(Also posted at My Variables Only Have 6 Letters)

Scenario
It’s a summer afternoon and you’re dispatched to a 9 year old male patient involved in an ATV accident. The nearest ALS engine company has been dispatched as well. Upon your arrival you find an ATV on its side, another ATV upright, and a crowd gathered on the porch of a nearby house. A paramedic from the engine is assessing a distraught young boy, sitting in his mother’s lap, holding an obviously deformed right forearm. The officer on the engine informs you that the boy and his father were riding alongside the road, traveling at 20-30 miles per hour, when the boy lost control and was thrown from the ATV (his father insists he was wearing his helmet).

You introduce yourself to the child, assuring him you’re here to help, and ask him what happened. The boy states that when he fell he put his arms out and he heard a loud pop when his right hand hit the ground. He denies passing out or any other injuries but says his arm, “really hurts”. He reluctantly allows you to assess his radial pulse in the affected arm, which is rapid but easily palpable. There appears to be distal involvement of both the radius and ulna, however he does not tolerate any further assessment of the arm and screams if there is any movement. The remainder of your physical exam reveals only minor abrasions to exposed skin. The engine company reports tachypnea, tachycardia, and a normal blood pressure.

Discussion
It appears the child has suffered a Colles’ Fracture of the right distal forearm. Appropriate treatment would include splinting, ice packs, and pharmacologic pain control. However, given the current state of the patient, it may not be possible to splint the extremity due to anxiety and pain. Traditional prehospital pain management would require intravenous access or intramuscular administration. Both of these routes are likely to cause increased anxiety in this patient, which is best avoided.

Pain management in the pre-hospital setting is fraught with problems. Most studies have found poor provider perception of pain, underutilization of analgesics, and a hesitance to treat pediatric pain (Thomas; Greenwald). Often times, studies find that even if patients are provided analgesia, they do not feel their pain was managed adequately at all (Thomas). For pediatric patients, this problem is compounded as pre-hospital providers are often wary to provide pain management or may be unable to obtain invasive IV access to provide pain management (Greenwald). Moreover, pre-hospital providers are often placed in situations where access to patients is limited to provide pain-management, often times resulting in painful patient movements.

The addition of a noninvasive means of pain management would be an invaluable aid to pre-hospital providers and would remove a potential barrier to care. In pediatric populations, the importance of noninvasive pain management procedures is easy to grasp, as this patient population is often unable to comprehend the benefits of initially painful procedures. Improvements in “time to analgesia” will likely lead to and have a direct, positive impact on patient care and satisfaction.

Efficacy and Safety of Intranasal Fentanyl
The efficacy and safety of intranasal fentanyl (INF) has been the focus of multiple studies, both in-hospital and pre-hospital. Finn et al conducted an in-hospital randomized double-blind placebo controlled trial and found INF to have the same efficacy as oral morphine during procedural wound care in adult burn patients (n=26, 35.5 ± 12.4 years). The concentration of INF used in this study was 50 µg/mL, initial dosages of 1.48 ± 0.57 µg/kg, and no difference in the number of adverse events. Finn et al concluded that while patients receiving INF were more satisfied with their level of pain relief (p = 0.009) that overall only half of the patients in the trial reported they were “satisfied” or “very satisfied”.

In a randomized, controlled, open-label study of pre-hospital INF versus IV morphine,Rickard et al found no significant difference in efficacy or safety (n=258, 42.3 ± 13.7 years). This study differs from Finn et al in that there were a multitude of chief complaints treated due to an “all-comers” design. Moreover, the doses used of INF was significantly higher at 180 µg divided evenly between the nares with up to two repeat dosages of 60 µg. Patients in the INF group received pain medication earlier than in the IV morphine group, likely owing to the simpler route of administration. Adverse effects were noted to occur more frequently in the INF group (relative risk 2.09, 95% CI 0.92-4.78, p = 0.07), however, the Rickard et alwas not powered to adequately detect any statistical difference. One incidence of a significant adverse effect required a termination of the INF protocol, but it was unclear from the study if this was related to the treatment or the patient’s condition. Rickard et alconcluded that given the safety and efficacy of INF, it is a valuable option in patients where intravenous access is “undesirable or impossible”.

Borland et al 2005 and Borland et al 2007 were inpatient randomized double-blind crossover studies evaluating the efficacy and safety of INF versus oral or IV morphine, respectively, in pediatric patients. Borland et al 2005 studied INF in pediatric burn patients requiring daily dressing changes and found no significant difference in outcomes (n=24, median 4.5 IQR 1.8-9.0 years). The INF dosage was calculated against the bioavailability of the IN route (listed as 70%) with 1.4 µg/kg fentanyl equating to an IV dosage of 1 µg/kg. There were no incidents of significant adverse events, although this was likely due to the study size. However, sedation scores recorded found that INF patients recovered earlier than their oral morphine counterparts. Overall, Borland et al 2005 found INF to be safe and efficacious, but more importantly well tolerated by pediatric patients.

Borland et al 2007 found INF to be comparable to intravenous morphine in pediatric patients presenting to the emergency department with acute long-bone fractures (n=67, 10.9 ± 2.4 years). The median total dose was 1.7 µg/kg fentanyl with repeat doses given PRN. The impetus of the study was to find alternative methods of analgesia to intravenous narcotics in the pediatric population. The study authors note that given the comparable efficacy, INF is invaluable as a means to decrease “time to analgesia” in the pediatric population with potential for pre-hospital adoption.

Mudd conducted a systematic review of the available literature for INF in the pediatric population and graded 12 studies with evidence qualities of four Level I/A, one II/A, two II/B, one III/A, and four at III/B. There was a wide variation in dosing of INF amongst the studies, with a common range of 1-2 µg/kg fentanyl. Differences in concentrations existed as well, owing to the fact that in the US fentanyl is commonly available at 50 µg/mL and is used IV/IM/IO/IN yet overseas it is often given IN with a more concentrated 100-150 µg/mL solution. No differences in significance in pain reduction were found between concentrations, only in the volume of medication delivered. While no studies found a significant difference in adverse effects, many studies had small sample sizes and no long-term studies have been completed on the action of fentanyl on the nasal mucosa. However, the evidence in the reviewed studies demonstrated three clear points: (1) that INF is as efficacious as IV/IM/PO morphine or IV fentanyl, (2) it has no difference in adverse effects, and (3) it decreases the time to analgesia administration and pain relief.

Intranasal Fentanyl Protocol
Based on the research available and the existing 2009 NC EMS protocols, an appropriate pain management protocol for the administration of intranasal fentanyl is given below:

• Adult patients with indications for narcotic analgesia for whom intravenous access is not feasible, not available, or at the discretion of the lead Paramedic, an initial dose of 50-75 µg fentanyl may be delivered intranasally. The total volume to be administered should be divided equally between the two nares (not to exceed 1mL per nare).
  • If intravenous access is not available, repeat with 25 µg fentanyl delivered intranasally every 20 minutes to a maximum total dose of 200 µg.
• Pediatric patients with indications for narcotic analgesia an initial dose of 1-2 µg/kg fentanyl up to a total dose of 50 µg may be delivered intranasally. The total volume to be administered should be divided equally between the two nares (not to exceed 0.5mL per nare).
  • In order to decrease the anxiety of pediatric patients requiring analgesia and invasive procedures (such as intravenous access), it may be prudent to begin with intranasal fentanyl.

References

• M. Borland, I. Jacobs and I. Rogers, Options in prehospital analgesia, Emerg Med (Freemantle) 14(2002), pp. 77–84.
• M. Borland, I. Jacobs and G. Geelhoed, Intranasal fentanyl reduces acute pain in children in the emergency department: a safety and efficacy study, Emerg Med (Freemantle) 14 (2002), pp. 275–280.
• J. Finn, J. Wright, J. Fong, E. Mackenzie, F. Wood, G. Leslie and A. Gelavis, A randomized crossover trial of patient controlled intranasal fentanyl and oral morphine for procedural wound care in adult patients with burns, Burns 30 (3) (2004), pp. 262–268.
• M. Borland, R. Bergesio and E.M. Pascoe et al., Intranasal fentanyl is an equivalent analgesic to oral morphine in paediatric burns patients for dressing changes: a randomised double blind crossover study, Burns 31 (2005), pp. 831–837.
• M. Borland, I. Jacob and B. King et al., A randomized controlled trial comparing intranasal fentanyl to intravenous morphine for managing acute pain in the emergency department, Ann Emerg Med 49(2007), pp. 335–340.
• C. Rickard, P. O’Meara, M. McGrail, et al., A randomized controlled trial of intranasal fentanyl vs intravenous morphine for analgesia in the prehospital setting, Amer J Emerg Med 25 (2007), pp. 911-917.
• S. Thomas, S. Shewakramani, Prehospital Trauma Analgesia, J Emerg Med 35 (2007), pp. 47-57.
• M. Greenwald, Analgesia for the Pediatric Trauma Patient: Primum Non Nocere? Clin Pedi Emerg Med 11 (2010), pp. 28-40.
• S. Mudd, Intranasal Fentanyl for Pain Management in Pediatrics: A Review of the Literature, J Pedi Health Care (2010), Article in Press. doi:10.1016/j.pedhc.2010.04.011.

So the new AHA guidelines have been released.  Go here to read them for yourself.

PDF - New Guidelines 2010

From A-B-C to C-A-B

Much research has been done to conclude that the best course of action for all unresponsive and apneic or barely breathing patients is to immediately begin chest compressions.  No wasting time checking for a pulse (less than 10 seconds).  No, “well I think they are breathing”.  If they are unresponsive, you don’t immediately feel a pulse, and there are very few or no respirations, then begin chest compressions.  No more Look, Listen, Feel.

From AHA:

• The vast majority of cardiac arrests occur in adults, and the highest survival rates from cardiac arrest are reported among patients of all ages with witnessed arrest and a rhythm of VF or pulseless ventricular tachycardia (VT). In these patients the critical initial elements of CPR are chest compressions and early defibrillation.90
• In the A-B-C sequence chest compressions are often delayed while the responder opens the airway to give mouth-to-mouth breaths or retrieves a barrier device or other ventilation equipment. By changing the sequence to C-A-B, chest compressions will be initiated sooner and ventilation only minimally delayed until completion of the first cycle of chest compressions (30 compressions should be accomplished in approximately 18 seconds).
• Fewer than 50% of persons in cardiac arrest receive bystander CPR. There are probably many reasons for this, but one impediment may be the A-B-C sequence, which starts with the procedures that rescuers find most difficult: opening the airway and delivering rescue breaths. Starting with chest compressions might ensure that more victims receive CPR and that rescuers who are unable or unwilling to provide ventilations will at least perform chest compressions.
• It is reasonable for healthcare providers to tailor the sequence of rescue actions to the most likely cause of arrest. For example, if a lone healthcare provider sees a victim suddenly collapse, the provider may assume that the victim has suffered a sudden VF cardiac arrest; once the provider has verified that the victim is unresponsive and not breathing or is only gasping, the provider should immediately activate the emergency response system, get and use an AED, and give CPR. But for a presumed victim of drowning or other likely asphyxial arrest the priority would be to provide about 5 cycles (about 2 minutes) of conventional CPR (including rescue breathing) before activating the emergency response system. Also, in newly born infants, arrest is more likely to be of a respiratory etiology, and resuscitation should be attempted with the A-B-C sequence unless there is a known cardiac etiology.

The changes this year are minute in comparison to the changes back in 2005.  One thing noted has been a decreased emphasis on ALS medications during treatment of cardiac arrest.  There is still almost no evidence of improved outcomes due to any drug given in cardiac arrest.  Post-arrest cardiac catheterization is being advocated.  This has shown to increase chances of neurological recovery more than induced hypothermia in some studies.  In conjunction with hypothermia, PCI is even more beneficial.

Thanks for stopping by,

Adam Thompson, EMT-P

Also posted at Star of Life Law.

Fellow Fire and EMS bloggers, if you have not heard of Righthaven, LLC, you might be soon. In the name of a federal copyright lawsuit. Here is what you need to know:

1. Righthaven, LLC is a Las Vegas company established to sue bloggers who clip news content. Most newspapers firmly request bloggers or aggregators take down infringing content and link back to the paper. By comparison, Righthaven goes directly to suing, without any request to take down.

2. Righthaven has issued more than 100 lawsuits since its inception. See Righthaven Victims. See also Righthaven Lawsuits.

3. Righthaven’s first client was Nevada-based Stephens Media. The Las Vegas Review Journal is Stephens’ flagship.

4. Righthaven has just struck a deal with Arkansas-based WEHCO Media to expand its copyright litigation campaign, in which bloggers and aggregators across the country are being sued on allegations of infringement. WEHCO controls 28 papers, including the Arkansas Democrat-Gazette in Little Rock, and 13 cable stations largely in the south.

5. Go here for a complete list of Righthaven-owned domains and newspapers.

6. Go here for a Firefox add-on that will prevent you from accessing Righthaven-owned content.

7. From Clayton Cramer, The Armed Citizen, a Righthaven lawsuit victim:

“For those who think that this could be settled out of court cheaply: think again. Other defendants who have approached Righthaven without a lawyer to settle this matter have been told variously, “$7500″ or “low five figures” for a single newspaper article infringement.”

8. Here is some guidance on how to properly cite news articles on your blog. Post the headline of the story and then the first paragraph with a link to the original story. Like this:

Jogger was listening to iPod when plane hit him, coroner says
The (Hilton Head) Island Packet
Tuesday, Mar. 16, 2010

A Georgia man was running and listening to his iPod on the beach on Hilton Head Island when he was killed by an airplane that made an emergency landing Monday near Palmetto Dunes, the Beaufort County Coroner’s Office said today.

The rest of the article can be viewed by clicking here.

Hat tip to Ryan Giles.

9. Police your site. Remove or update potentially infringing posts. Properly cite and link to news sources.

10. If you are a Fire/EMS blogger and get served with a Righthaven lawsuit, feel free to email me.

Welcome to EMSBlogs.com. This is your first post. Edit or delete it, then start blogging!

I’ve been giving a lot of thought lately to paramedic education and the problem of 12-lead ECG interpretation.

Specifically, the reasons why paramedics aren’t taught to actually read a 12-lead ECG and are instead given a crash course in “STEMI recognition” which does not prepare the student to differentiate between the ST-elevation of acute STEMI and other causes of ST-elevation.

This TED Talk by Dan Meyer about high school math education struck a chord with me. I highly recommend the entire talk, but the most relevant part for this discussion starts at 01:50.

Here’s the part that really resonated with me:

“David Milch, creator of Deadwood and other amazing TV shows [...] swore off creating contemporary drama — shows set in the present day — because he saw that when people filled their minds with 4 hours a day of, for example, 2 1/2 Men, it shapes the neuro-pathways in such a way that they expect simple problems. He called it an “impatience with irresolution”. You’re impatient with things that don’t resolve quickly. You expect sitcom-sized problems that wrap up in 22 minutes, 3 commercial breaks and a laugh track.

I’ll put it to all of you — what you already know. No problem worth solving is that simple.”

Doesn’t that exactly describe the paramedic approach to 12-lead ECG interpretation?

EKGs for Dummies, 12-Leads Made Easy, Rapid STEMI ID, etc. etc. etc.

Just the “need to know” information without all the difficulty of axis determination, bundle branch blocks, electrolyte derangements, differential diagnosis of tachycardias, primary and secondary ST-T wave abnormalities, identifying acute STEMI in the presence of STE-mimics, and other things that we have no patience for because we can’t learn it in 22 minutes.

As if we can jump straight to the finish line and enjoy the fruits of victory without ever preparing for the race.

The problem is compounded by policy makers who “don’t know what they don’t know” (thank you Don Rumsfeld). They consider it a foregone conclusion that comprehensive 12-lead ECG knowledge is not practical for paramedics.

I say that it’s indispensable.

The August edition of Grand Rounds is now up over at EMSResponder.com.  Click here to check it out.

As some of you may know, Crew Resource Management is an area of interest for me.