When trying to decide on a subject for this blog post, I remembered an article I read a few months ago originally published in the Journal of Paramedic Practice, by Logarajah and Alinier titled ‘An Integrated ABCDE Approach To Managing Medical Emergencies Using CRM Principles’.

At the time I first read this article I was lucky enough to have the experience of undertaking a secondment on a Critical Care Paramedic unit and had attended a number of high acuity incidents, and felt the principles outlined assisted me in preparing when heading to these.

I feel using a structured approach can help break down the mental workload, especially when applied to incidents that involve a large degree of decision-making and prioritization. The principles described can be applied to all incidents you may attend as a Paramedic, however in keeping with the increasing focus on human factors and CRM in cardiac arrest management I have decided to tailor them to this area.

Its 17:00pm and nearing the end point of a tiring weekend day shift, just after arriving back on station for the first time since you left in the early hours of the morning you are called to a 51 year old male reported to be in cardiac arrest. Two local community responders and a Technician crew are also attending however you are the only Paramedic available. As you drive to the scene you start to mentally plan how you will approach this incident, what will you need to do, where will you transport the patient to…

ABCDE (alongside remembering how your crewmate likes their coffee) is a cornerstone of all levels of emergency medical care and the tried, tested and trusted tool we all use when we don’t know what to do next. Logarajah and Alinier (2014) proposed a modified version of this mnemonic, using CRM principles, as a tool ‘to remember the sequence in which to manage emergencies or difficult situations while ensuring effective and safe teamwork’ (pp.625).

These principles, in relation to thinking about cardiac arrest management, are as follows:

A: AWARENESS, ANTICIPATION & ALLOCATION OF ATTENTION

What details do you have? What are you anticipating you will find?

Awareness can be divided into two areas; self-awareness and situational awareness. Consideration of both these is vital to maintain control of complex situations and prevent the unanticipated development of additional problems. Anticipating what you will encounter on arrival at the scene is highly dependent on how much or little information you have received.

Try and think about what you would expect to find based upon factors such as the type of incident, the location, or the likely cause of cardiac arrest. This can help prepare you with making decisions such as what equipment to take in with you, treatment algorithms to use and logistical issues such as the locations of nearby hospitals and cath labs.

If you have received an update from resources already on scene you can start to plan how you are going to allocate your clinical attention once you arrive and discuss your plan of action.

B: ‘BE IN THE REQUIRED ROLE’ & BEHAVIOUR

What do you need to do for the team? How can you make the most of your skills? Are you required to be a leader or a follower?

Some of this is dependent on your clinical role however everybody needs to build and maintain a team effort. Does your service use a ‘pit-crew’ CPR approach? Knowing the role you need to assume beforehand can save vital time in decision-making and reduce disruption to already established and organized resuscitation attempts.

C: CALL FOR HELP, COMMUNICATION & COGNITIVE AIDS/CHECKLISTS

Are you going to be able to communicate effectively? What barriers will there be?

Factors such as noise, incidents involving multiple patients, a chaotic scene and poor lighting can all contribute to poor communication. Check your radio, do you know the correct channel to pass updates on? Use your awareness and anticipation to request extra assistance, such as enhanced care teams, early if you think it may be needed.

‘Medicine is not a memory game’

Ensure you have cognitive aids available. Cardiac arrest checklists, resuscitation algorithms and clinical guidelines all can save bandwidth and enable you and the team to focus on the task at hand without having to perform complex mental calculations such as drug doses or tube lengths.

D: DYNAMIC PRIORITISATION, DECISION MAKING & DELEGATION

Do you have enough help? Does everyone have a task?

Based on your awareness and anticipation of the resuscitation be decisive on your immediate priorities, make and execute a plan of action, but remember to also be prepared to change as required.

Ensure you have enough resources available for everybody to be able to concentrate on their task fully and not be overloaded. As the resuscitation progresses it is likely your priorities will change and require you to adapt to these and redistribute the workload accordingly.

E: ERROR WISDOM & ENVIRONMENT

What are the potential errors that could occur? Can you carry out effective resuscitation within the environment the patient is in? What needs to change?

‘Forewarned is forearmed’

Be aware of the potential for errors. During stressful events such as resuscitation attempts, with a number of interventions performed and drugs administered, it is easy for these to occur. Considering this risk beforehand and utilizing tools such as checklists and pocket books can help minimize the potential for mistakes and refresh things in your head that you may not encounter very often in practice.

If the patient you are attending is in an unusual environment, or a scene that may pose a danger, consider the options you have to minimize hazards and allow you and the team to carry out the resuscitation safely. Even in domestic locations, during the initial stages of resuscitation it is easy to forget about the environment you are working in. Ensure you have enough space to work in and if not, move something!

I hope you have found this interesting. It may all seem like common sense and I am sure we all give these factors consideration every day with every incident we attend, however personally I feel having a structured approach is worth thinking about to reduce mental overload in times when we all need a little bit of extra brain capacity!

Reference

Logarajah, S. and Alinier, G. (2014). An Integrated ABCDE Approach To Managing Medical Emergencies Using CRM Principles (PDF – Subscription Required). Journal of Paramedic Practice, 6(12), pp.620-625.

EMS is dispatched to a private residence for 70-year-old female who is believed to be unconscious.

On arrival, the patient is found lying in bed unresponsive to painful stimuli. The patient’s skin is pale and clammy. Her shirt is damp. Snoring respirations are noted and a slow carotid pulse is present.

A medical history is obtained from family members and includes heart failure, stroke, and hypertension.

Vital signs are assessed.

• RR: 8
• HR: Less than 30
• NIBP: 78/41
• SpO2: Not registering
• Temp: 96.1 F / 36.7 C
• BGL: 101 mg/dL

The cardiac monitor is attached.

The adult pads are placed and transcutaneous pacing is initiated.

The patient’s blood pressure improves slightly to 84/47 (confirmed by auscultation). However, paramedics are still concerned about the patient’s hypotension.

Additional treatments

• IO access is obtained in right proximal tibia.
• 0.5 mg of Atropine is administered x 3.
• 9% normal saline is run wide open with an additional IV line established in the left lower extremity.

The patient begins to move and reaches for the pacing pads. However, she is still non-verbal and does not follow commands.

• On arrival at the hospital the patient is transitioned to transvenous pacing.
• She is sent to the cardiac cath lab where a permanent pacemaker is placed.
• In the ICU the patient remains dangerously hypotensive in spite of dobutamine and levophed drips.

The patient eventually expires from multiple-system organ failure.

Discussion

Transcutaneous pacing (TCP) is a difficult skill that is often performed incorrectly. The problem of false capture (also known as echo distortion) is under-recognized and under-reported in the medical literature.

There are many reasons why medical professionals often fail to achieve true electrical and mechanical capture. Consider this excerpt from the Journal of Emergency Medicine where Douglas Ettin, M.D. and Thomas Cook, M.D. describe the difficulty.^[1]

“Shortly after cardiac pacing was initiated, the patient’s systolic blood pressure dropped to 50 mmHg. The EKG monitor continued to demonstrate adequate ventricular capture by the pacer. The patient appeared to have palpable pulses; however, the rhythm contractions of the patient’s body from the pacer shocks made this assessment difficult. With the etiology of the patient’s hypotension unclear, the decision was made to use transthoracic ultrasonography to assess the adequacy of her ventricular contractions.”

“Initially, the ultrasound demonstrated ventricular contractions at a rate of 30-40 beats per minute. These heart contractions did not correspond with the surrounding thoracic muscle contractions generated by the pacer. The current was gradually increased to 110 mA, and the heart began to contract in unison with the pacer shocks. The patient’s blood pressure subsequently increased to 90 mmHg.”

You can see another example where an echo was used to verify capture here.

With false capture, you will generally see a near-vertical upstroke or down-stroke to the “phantom” QRS complex (which is actually electrical artifact created by the current passing between the pacing pads).

You will also note that the underlying rhythm can be seen in the absolute refractory period of one of the (presumed to be) paced QRS complexes (red circle). That is not scientifically possible!

In contrast, true electrical capture will show wide QRS complexes with tall, broad T-waves.

Tips for success

• Perform, but do not rely on a pulse check!
• Use an instrument (SpO2, Doppler, capnography, or echo) to help confirm mechanical capture whenever possible
• Do not be fooled by skeletal muscle contraction!
• Know that the patient may become more alert whether capture is achieved or not
• The most common reasons for “failure to capture” are insufficient milliamperes and poor pad placement!

More examples of transcutaneous pacing (TCP) with capture

Reference

1. Ettin DCook T. Using ultrasound to determine external pacer capture. The Journal of Emergency Medicine. 1999;17(6):1007-1009.

Further reading

Pacing Artifact May Masquerade As Capture

This case was submitted by Roger Hancock with edits by Tom Bouthillet. Some details have been changed to protect patient confidentiality.

A 50-year-old male with a history of hypertension (HTN) and atrial fibrillation (AF) presents to the Emergency Department with complaint of palpitations, which started while mowing the lawn.

He is alert and oriented with a Glasgow Coma Scale (GCS) of 15 and no signs of Hypoperfusion.

• Heart Rate: 165/min, strong and irregular
• Blood Pressure: 140/100 mmHg
• Ventilatory Rate: 22/min
• SpO2: 98% on room air

The patient is compliant with his medications and denies any allergies.

A 12 Lead ECG is recorded.

The patient was treated with 20 mg of diltiazem (Cardizem) over 2 min, followed by 10 mg over 1 hr, and 0.25 mg digoxin (Lanoxin).

A rhythm change was noted on the monitor and another 12-lead ECG was recorded.

The patient was now asymptomatic and admitted for observation without further incident.

Understanding Diltiazem (Cardizem)

Diltiazem (Cardizem) is a Class IV antiarrhythmic and one of the most common pharmacological agents used for treatment of AF with RVR.

Class IV antiarrhythmics are Calcium Channel Blockers (CCBs), which inhibit intracellular calcium influx via calcium channel antagonism. These particular pharmacological agents can be further divided into subdivisions based on their molecular composition:

Dihydropyridines (DHPs)

• These CCBs can be easily identified by the last four letters of the generic name ending with “pine”.

• DHP CCBs are more selective to peripheral vasculature than cardiac cells, leading to arterial smooth muscle relaxation and decreased Systemic Vascular Resistance (SVR), thus, decreasing afterload and Myocardial Oxygen Demand (MVO2).

• Because of this peripheral calcium channel selectivity, they are commonly used for treatment of Hypertension and angina.

• Their hemodynamic effects can be associated with adverse effects such as hypotension and reflex tachycardia secondary to sympathetic stimulation as a compensatory mechanism for the decreased cardiac output.

Examples include:

• Amlodipine (Norvasc)
• Nicardipine (Cardene)
• Nifedipine (Procardia)

Non-dihydropyridines (NDHPs)

• These CCBs are those which generic name does not end with “pine”.

• Can be further divided into benzothiazepines (not to be confused with benzodiazepines) and phenylalkylamines.

• Non-dihydropyridine CCBs are more selective to L-Type Calcium Channels in cardiac cells, such as the Sino Atrial Node (SAN) and Atrio Ventricular Node (AVN), although all CCBs cause peripheral vasodilation.

• This Calcium Channel antagonism leads to decreased SAN chronotropic effect and decreased AVN conduction, making it useful for treatment of atrial arrhythmias such as AF, Atrial Flutter and Supra-ventricular Tachycardias (SVTs).

Examples include:

• Benzothiazepines: Diltiazem
• Phenylalkylamines: Verapamil

Vaughan-Williams Anti-arrhythmic Classification

There are four specific classes of antiarrhythmics with specific physiological functions divided into classes based on their mechanism of action. The rest of the pharmacological agents used as antiarrhythmics fall under the fifth class with different mechanisms of action from the previous classes.

One important aspect to understand is that although they are all antiarrhythmics, each class works under different mechanisms and therefore may have different effects on cardiac cells. Some target atrial, AV nodal or ventricular cells, while some have the capacity to address both atrial and ventricular arrhythmias.

Pharmacological Use

Diltiazem has a COR I, LOE-b classification, used for rate control of atrial arrhythmias, predominantly Atrial Fibrillation, and COR IIa, LOE-b for treatment of SVT with a reentry pathway mechanism.

Mechanism Of Action

• Negative Chronotropic, Inotropic and Dromotropic effect by blocking L-Type Calcium Channels in cardiac tissue

• Decreased Calcium influx affects Phase 2 of cardiac depolarization, delaying atrial and AVN conduction

• This ultimately leads to decreased ventricular rate, with or without conversion to sinus rhythm

Caution

• Diltiazem should be avoided in the presence of pre-excited AF with RVR, that is, AF in the presence of accessory pathway, i.e. Wolff Parkinson White (WPW) syndrome, as AVN blockage can lead to increased conduction through the accessory pathway, leading to life-threatening rapid ventricular rates.

• Procainamide and Ibutilide are the preferred treatment of pre-excited AF with RVR and hemodynamically stable patients.

• Diltiazem can be used in patients with AF and Heart Failure (HF) but with caution in reduced Left Ventricular Ejection Fraction and hypotension.

Dose and Administration

Although dosages may vary based on physician orders, protocols and age, a standard initial dose is 0.25 mg/kg, ranging between 10-20 mg over 2 minutes, with a second dose of 0.35 mg/kg, ranging between 20-25 mg over 2 minutes, often followed by a 5-10 mg/hr infusion.

Treatment of hemodynamically unstable patients in narrow QRS complex AF with RVR requires synchronized cardioversion at 120-200 J initially, and should not be delayed for administration of an anti-arrhythmic agent.

Conclusion

• Diltiazem is a Class IV, non-dihydropyridine CCB anti-arrhythmic, serving as the most common pharmacological agent used for the treatment of AF and SVTs, for patients that are hemodynamically stable.

• Caution should be used with CCBs and HF with decreased EF and hypotension.

• Electrical Cardioversion should not be delayed for treatment with an anti-arrhythmic agent in the presence of Hypoperfusion and hemodynamically unstable patients.

Bag mask ventilation is the cornerstone of airway management.

It’s often considered a basic procedure, but there is nothing “basic” about BVM ventilation. Skill acquisition requires extensive training and experience. It’s not pretty, sexy, or glamorous. Most people perform it poorly even though it’s an essential part of good airway management.

We often relegate the skill to a new or junior provider, and when the saturation drops we attribute it to the patients’ acuity and not to failure to provide adequate oxygenation and ventilation.

The AHA recognizes that bag mask ventilation “is a challenging skill that requires considerable practice for competency.”

When performed in an emergency, respiratory failure or arrest is often imminent. Because it is a BLS skill we toss a BVM to our partner while we prepare our intubation equipment. The mask is placed on the patient’s face and ventilations are administered too aggressively or ineffectively.

When this is not recognized the airway may become flooded with gastric contents during the intubation attempt making more difficult if not impossible. Aspiration occurs, hypoxia worsens, and the patient is at higher risk of experiencing cardiac arrest.

It is not widely appreciated that BVM ventilation is often ineffective. One assumes that it works better than it actually does without appreciate education and training, which is often lacking.

Early in my career I would place the mask on the patient’s face and apply the CE technique without any objective measurement of how well it was working.

How do you Know When Ventilations are Effective?

Clinical detection of adequate ventilation is notoriously difficult. So what is the litmus test for gas exchange at the alveolar level? ETCO2 of course!

In Emergency Medicine we want the technique that is most likely to be successful the first time. The traditional CE method is not always the best technique. Some will be quick to contest that assertion, and a few years ago I would have agreed with you.

Then I watched a video on EmCrit made by Reuben Strayer.

There are three main factors that contribute to poor BVM ventilation.

• Poor mask seal
• Improper positioning
• Excessive rate and volume

Poor Mask Seal

When using the traditional CE technique, pressure is not distributed equally across the mask. This means that when using your left hand, there is a tendency for air to leak between the mask and the right side of the patient’s mouth, which often goes unrecognized.

Improper Positioning

Because of the inherit difficulty maintaining a quality seal, and because maintaining a seal is fatiguing, the tendency is to push the mask onto the face. The mouth is then closed shut, leaving the nares as the only route of ventilation. Obstructive soft tissues of the pharynx collapse, blocking the glottic opening.

A superior technique was introduced 11 years ago in the 2005 AHA Guidelines.

“Bag-mask ventilation is most effective when provided by 2 trained and experienced rescuers. One rescuer opens the airway and seals the mask to the face while the other squeezes the bag. Both rescuers watch for visible chest rise.”

The two handed technique is sometimes referred to as the thenar eminence (TE), or “two thumbs down” technique.

Gerstein (2013) compared the effectiveness of the CE and TE technique when performed by novice clinicians and found:

“The TE facemask ventilation grip results in improved ventilation over the EC grip in the hands of novice providers.”

A few weeks ago I attended a cadaver lab in Baltimore. The first skill we practiced was BVM ventilation. Our group leader has us try the CE technique first, then TE. The chest was open and lungs exposed so we could see the effectiveness of our ventilations.

Six people were in my group, and no one was able to inflate the lungs using the CE technique despite multiple attempts. However, the lungs were inflated every time, every attempt, for every person when using the TE technique!

Excessive Rate and Tidal Volume (Hyperventilation)

Even when trying to be cognizant of rate and tidal volume, there can be a huge difference in what you think you’re doing, and what you’re actually doing.

This was proven in the Milwaukee study, in which Paramedics were taught to ventilate at the appropriate rate during cardiac arrest. They retrospectively looked at the ventilation rates objectively and found the average rate was 30 breaths/min!

An excessive rate and tidal volume isn’t only deleterious for patients in cardiac arrest, but increases the likelihood of exceeding the pressure of the lower esophageal sphincter, delivering large tidal volumes of air to the stomach.

This also was mentioned back in the 2005 AHA Guidelines:

“Gastric inflation often develops when ventilation is provided without an advanced airway. It can cause regurgitation and aspiration, and by elevating the diaphragm, it can restrict lung movement and decrease respiratory compliance. Air delivered with each rescue breath can enter the stomach when pressure in the esophagus exceeds the lower esophageal sphincter opening pressure. Risk of gastric inflation is increased by high proximal airway pressure and the reduced opening pressure of the lower esophageal sphincter. High pressure can be created by a short inspiratory time, large tidal volume, high peak inspiratory pressure, incomplete airway opening, and decreased lung compliance.”

To prevent gastric inflation the airway must be kept open, and breaths delivered slowly…very slowly. Based on my observations no one delivers breaths slow enough. When your own heart rate is going 150 beats per minute, waiting 6 seconds to deliver a breath feels like forever! I often tell someone who is bagging to fast to deliver a breath every 10 seconds and even then they often ventilate too fast.

How do we slow down? Well, if the patient is intubated they could be placed on the ventilator. But since we’re talking about facemask ventilation, consider purchasing a timing light that goes on the end of the BVM, or use a metronome. You could also try counting, “one, one thousand…two, one thousand…three, one thousand…” and so on.

In addition to delivering breaths too fast, we deliver too much. The average volume of an adult BVM is 1600 milliliters! Squeezing the bag until opposite sides of the BVM touch isn’t necessary! It’s recommended that only 1/3 of the bag be compressed to give a large enough tidal volume. Any more and the pressure is too much for the rigid trachea to accommodate, and the esophagus is more than happy to accept the rest!

BVM Ventilation during Cardiac Arrest

If you’re doing 30:2 during BLS CPR you don’t have the luxury of providing breaths slowly. The goal should be to have compressions resumed within 3 seconds, and to do that the breaths can’t be given quickly or it will take 5 or 6 seconds!

The goal should be “little bag squeeze, little bag squeeze” with full release between squeezes. Intrathoracic pressure stays elevated without a full release, and we know that increased intrathoracic pressure impedes venous return.

Conclusion

• BVM ventilation is a difficult skill for providers at all levels and specialties.
• The traditional CE method is not very effective, and sometimes totally ineffective.
• Use ETCO2 as an objective measurement.
• Adopt the “two thumbs down” technique
• Deliver breaths slowly
• Only compress 1/3 of the bag
• Give breaths quickly during cardiac arrest, but allow full release of BVM

References
“Beginner Facemask Ventilation Techniques | Emsworld.Com”. EMSWorld.com. N.p., 2016. Web. 17 Mar. 2016.
Gerstein NS, et al. “Efficacy Of Facemask Ventilation Techniques In Novice Providers. – Pubmed – NCBI”. Ncbi.nlm.nih.gov. N.p., 2016. Web. 17 Mar. 2016.
“Part 4: Adult Basic Life Support”. Circulation 112.24_suppl (2005): IV-19-IV-34. Web. 17 Mar. 2016

EMS is called to the home of a 62-year-old female who complains of shortness of breath and epigastric discomfort.

On their arrival, they find the patient sitting on a chair in her living room, holding her hand to her chest while she talks with first responders. She is not pale, but appears diaphoretic, anxious, and has mildly laboured respirations.

A brief medical history is obtained while gathering a set of vitals and applying the ECG electrodes.

Onset:              “It woke me up from my sleep”
Provocation:   “Nothing makes it better or worse”
Quality:            “Like heartburn, but worse”
Radiation:        None
Severity:           Rated 8 out of 10
Time:                “About ninety minutes ago”

Pulse:              74/min, strong and regular at the wrist
RR:                  20/min, clear air entry on auscultation
NIBP:              152/88
SpO2:              92% on room air
BGL:                7.4mmol/L (133 mg/dl)
Temp:             36.2C (97.2F)
PMHx :           Hypertension, asthma, dyslipidemia

A 12-lead ECG is acquired.

At this point, the attending paramedic was highly suspicious that an acute coronary event was taking place, and proceeded to treat with Aspirin, SL Nitroglycerin, and serial 12-leads while initiating transport.

The following ECG was acquired with V4 moved to the position of V4R, and V5 & V6 moved to the position of V8 & V9, respectively.

The transporting paramedic recognized the posterior STEMI and transmitted the ECG to a consulting physician. Based on these findings, and considering the significant distance to a PCI-capable facility, the decision was made to administer Plavix and IV thrombolytics (TNK).

About 20 minutes post-TNK, it was noted that the patient’s heart rate had decreased to the low 40’s, while her chest discomfort simultaneously improved.

The following 12-lead was acquired.

Despite the precipitous drop in blood pressure and heart rate, the patient appeared healthier now than she had at any point previously during the encounter.

Does this ECG represent improvement, or a decline in clinical condition?

Posterior STEMI

The diagnosis of a truly isolated posterior STEMI appears to be a relatively uncommon occurrence, presenting in about 3% of myocardial infarctions ¹, however it’s highly likely that underdiagnosis has played a role in these underwhelming stats. This may be due to a misconception by many practitioners that ST Depression (STD) in leads V1-V3 represents anterior ischemia, despite the fact that myocardial ischemia does not localize on the 12-lead ECG.

This misinterpretation, combined with arbitrary millimeter criteria, often result in delayed cath lab activation, or a diagnosis of UA/NSTEMI in patients who are in fact suffering acute posterior STEMI.

There are several key criteria on the 12-lead ECG that, when observed in a patient suffering from a suspected acute coronary syndrome, should lead you to make the diagnosis of posterior STEMI. They include:

• Horizontal ST depression in V1-V3 with upright T-waves
• Early R-wave progression in the precordial leads
• ≥ 0.5mm ST Elevation (STE) in one or more posterior leads (V7-V9)*

* Due to the anatomical structures located between the posterior leads and the heart, there’s an increased amount of electrical impedance, which results in the appearance of much smaller QRS complexes in the posterior leads. This is why half of a millimeter of STE is significant in these leads!

However, these low-voltage leads can make ST-segment elevation difficult to appreciate, which has the potential to confuse the diagnosis. As a result, some experts suggest that the diagnosis of posterior STEMI can and should be made using the other two criteria alone.

Prehospital Thrombolytics

Over the last ten years, the use of thrombolytics in the prehospital arena has increased significantly around the world, especially in rural and remote communities.

While primary-PCI within 120 minutes of first-medical contact (FMC) remains the ideal pathway for patients with acute STEMI, a combined pharmaco-invasive approach has been suggested to be comparably effective in reducing morbidity/mortality in patients presenting with acute STEMI in regions that cannot provide primary-PCI.

In these cases, patients are treated with intravenous fibrinolytics, usually following ECG transmission, expert consultation, and careful screening processes. Following this, the patient is promptly arranged transport to a PCI center where rescue catheterization or follow-up angiogram can be completed.²

With the goal being to minimize infarction size and myocardial necrosis, many services have implemented protocols that allow for EMS administration of fibrinolytics. This has been shown to significantly reduce the time-to-treatment when compared to services which transport to the closest facility prior to the administration of fibrinolytics.³

When paramedics are given the appropriate level of training and equipment, prehospital fibrinolysis can be an effective and efficient means of reducing total ischemic time, and efforts should be made to lobby for this intervention in regions which cannot meet the 2-hour PCI window.

Reperfusion Arrhythmias

Between 80-90% of STEMI patients who receive either PCI or thrombolytics will experience some form of reperfusion-related arrhythmias within the first 48 hours of treatment.

With the expanding utilization of thrombolytics for acute STEMI, the occurrence of these “reperfusion rhythms” has become increasingly common in prehospital and ED settings alike. These rhythms most commonly occur when oxygenated blood begins flowing through previously occluded coronary arteries, and while it’s uncertain what degree of coronary artery patency they represent, it’s generally accepted that these arrhythmias represent some degree of myocardial reperfusion.⁴

Slower reperfusion arrhythmias such as sinus bradycardia and ventricular escape rhythms are thought to be resultant of increased vagal tone in the recently ischemic myocardial tissue; a phenomenon known as the Bezold-Jarisch Reflex, which is most commonly seen in inferior or posterior MI’s.⁵

These slow rhythms often occur alongside periods of frank hypotension, however these incidents are most often self-limiting and well tolerated, and may in fact occur at a time when the patient reports finally feeling better! Consequently, aggressive interventions to increase the heart rate are rarely required, and can usually be limited to postural changes or the administration of atropine, or very rarely transcutaneous pacing. ⁷

Faster reperfusion arrhythmias may include frequent premature ventricular complexes, accelerated idioventricular rhythm, or nonsustained runs of ventricular tachycardia. These “irritable” rhythms  are thought to originate from the zone of ischemia, which surrounds the zone of infarction, where “overactive” calcium channels are believed to play a significant role. The arrhythmia may be occurring as a result of an ectopic foci, or serving as an escape rhythm when the sinus node is depressed (perhaps due to the vagal response mentioned above).

Recent research suggests that the presence of these arrhythmias may predict a larger area of infarction, or possibly incomplete or poor reperfusion (TIMI flow grade <3). Management of these patients should be aimed primarily at continuous cardiac monitoring and hemodynamic support to maximize myocardial perfusion, with use of antiarrhythmic drugs to be considered further down the treatment algorithm.

References

1. Oraii S, Maleki M, Abbas Tavakolian A, et al. “Prevalence and outcome of ST-segment elevation in posterior electrocardiographic leads during acute myocardial infarction.” J Electrocardiol 1999;32: 275-8 http://www.ncbi.nlm.nih.gov/pubmed/10465571
2. Danchin N, Durand E, Blanchard D, “Pre-hospital thrombolysis in perspective.” European Heart Journal. DOI: http://dx.doi.org/10.1093/eurheartj/ehn462 2835-2842 First published online: 23 October 2008
3. McCaul M, Lourens A, Kredo. “Pre-hospital versus in-hospital thrombolysis for ST-elevation myocardial infarction.” Cochrane Database Syst Rev. 2014 Sep 10;9:CD010191. doi: 10.1002/14651858.CD010191.pub2 http://www.ncbi.nlm.nih.gov/pubmed/25208209
4. Ersan Tatli, Güray Alicik, Ali Buturak, Mustafa Yilmaztepe, and Meryem Aktoz, “Arrhythmias following Revascularization Procedures in the Course of Acute Myocardial Infarction: Are They Indicators of Reperfusion or Ongoing Ischemia?,” The Scientific World Journal, vol. 2013, Article ID 160380, 7 pages, 2013. doi:10.1155/2013/160380 http://www.hindawi.com/journals/tswj/2013/160380/cta/
5. Koren G, Weiss AT, Ben-David Y, Hasin Y, Luria MH, Gotsman MS. “Bradycardia and hypotension following reperfusion with streptokinase (Bezold-Jarisch reflex): a sign of coronary thrombolysis and myocardial salvage.” http://www.hindawi.com/journals/tswj/2013/160380/cta/
6. Gulumser Heper, Mehmet Emin Korkmaz, Ayhan Kilic, “Reperfusion Arrhythmias: Are They Only a Marker of Epicardial Reperfusion or Continuing Myocardial Ischemia After Acute Myocardial Infarction?” ANGIOLOGY 2008 vol. 58 no. 6 663-670  doi: 10.1177/0003319707308891  http://ang.sagepub.com/content/58/6/663
7. Esente P, Giambartolomei A, Gensini GG, Dator C. “Coronary reperfusion and Bezold-Jarisch reflex (bradycardia and hypotension)”, Am J Cardiol. 1983 Aug;52(3):221-4. http://www.ncbi.nlm.nih.gov/pubmed/6869265