Hypothermia and Right Bundle Branch Block, with ST Elevation?

This patient was found outside in the cold, unresponsive, hypotensive, and underwent brief chest compressions by EMS.

Here is his ED 12-lead ECG: 

What do you see?  Description/Answer below.

There is Atrial Fibrillation.  There is right bundle branch block (RBBB), but without the usual rSR', rather with a qR-wave in V1-V4 and aVL, highly suggestive of previous anterolateral MI.  The QRS is 160 ms, or is it longer?  There is a shoulder at the end of the QRS.  What is this?  Is this ST elevation?

The patient's temperature was 30 degrees C (86 deg F).  The "shoulder" is NOT ST elevation, but rather is an Osborn wave in the setting of RBBB.

He was resuscitated and warmed.  A bedside ultrasound showed global hypokinesis but wall motion was not well assessed.  

A repeat ECG was recorded:

The Osborn Waves are a bit more prominent now.  Or is this ST elevation?

Clinical Course: 

A head CT was negative.  The patient underwent coronary angiography, which showed a chronically occluded LAD.

He did well.  There was no acute MI.

Below are his previous ECG and a follow up after rewarming:

Previous

Sinus rhythm and RBBB with qR of old anterolateral MI.  No "shoulder" here.  There is a positive T-wave in the same direction as the R'-wave, which is slightly abnormal and may be due to the old MI.

After rewarming:

No significant difference from the previous.

The ECG in hypothermia 

Rhythm: The most common rhythms in hypothermia are sinus bradycardia, junctional bradycardia, and atrial fibrillation.  Shivering artifact is common.  Atrial flutter is seen in case 1.  At temperatures below 30 C, the patient is at risk for ventricular fibrillation.   In thisstudy of 29 humans cooled to 28-30 C for cardiac surgery, 19 developed atrial fibrillation and 2 ventricular fibrillation.

QRS: Osborn waves are thought to be pathognomonic of hypothermia, but can also be seen in normothermic patients.  "J-waves" or "J-point notching" is very common in early repolarization.   Very narrow Osborn waves were reported in severe hypercalcemia (level 16.3).  Sometimes a short ST segment of hyperCa can be misinterpreted as an Osborn wave (see image below); that is not the case in the aforementioned case report.   J-wave syndromes are proposed to give a unifying pathophysiology to Osborn waves of hypothermia and early repolarization, as well as Brugada syndrome.

Very large and wide J-waves, as in case 1, are almost exclusively due to hypothermia.  The etiology is beyond the scope of this blog, but may be read here.  

Hypothermia and pseudoinfarction patterns: MI or ischemia (either ST elevation or depression) may be mimicked either by 1)repolarization abnormalities (As in Case 2, with ST elevation) or by 2) confusing the J-wave with the ST segment, as in this case in JACC (full text) and this case in Archives of Internal Medicine (no full text).  This latter case also has ST segment depression as a repolarization abnormality.

Other blog cases of Osborn waves


Here is an example of RBBB with anterior STEMI (there are many others if you look at the RBBB "label" down the right side)

Interesting Left Main Occlusion....

Many believe that left main occlusion results in diffuse ST depression with ST elevation in aVR.  This is not true, as I write about in this post: The difference between left main occlusion and left main insufficiency.

A 38 year old male presented with 6 hours of chest pain, and recent chest pain with exertion.  He had no significant past medical history and was on no medications.  He is a non-smoker.  The initial troponin was 1.62 ng/mL.

Here is the initial ECG:

There is diffuse ST depression, with ST elevation in aVR.
This is consistent with coronary insufficiency, but not coronary occlusion.
It could be a tight left main, or a tight LAD, especially with 3-vessel disease.
There is ST elevation in lead III, with an ST axis directly to the left.  Is there inferior STEMI also? 

Such patients have about a 50% chance of needing CABG, as shown in an article referenced and described in this post.  Therefore, Plavix (clopidogrel) should be avoided.



The patient was taken for emergent angiogram:

This is an angiogram of the left main, and it is totally occluded.

How is that possible?  Why is the patient alive?  And why is there ST depression of subendocardial ischemia rather than ST elevation of anterior, lateral, and posterior walls?

Why is this not a STEMI?

The answer lies in the RCA angiogram:

The distal RCA is seen on the left side of the image (we do not see the catheter or the injection at the ostium of the RCA.
There are right to left collaterals which supply the left system with enough flow to keep the patient alive and to prevent subepicardial ischemia (STEMI).  All of the flow seen on the right side of the image is flow in the LAD and circumflex that is supplied by the RCA collaterals.

The apparent inferior STEMI may be due to "Coronary Steal Syndrome": Right to left flow is stealing blood supply from the inferior wall.

The left main was opened and the patient did well.

Most left main occlusions to not make it to the ED alive.

See this previous post for an extensive discussion (same link as above).

How are these cases related?

I saw these two cases on the same day.


This patient had a GI bleed and a massive transfusion:

What is it?

This patient had a history of "frozen shoulders," and had been treated for this elsewhere for quite a while.  He had been seen in the ED 6 days prior for increased shoulder pain, and was referred back to his orthopedic clinic.  He had this ECG recorded because shoulder pain can be a symptom of ACS:

What do you notice?

The first case has a very long ST segment and thus long QT.  This is classic for hypocalcemia; the ionized calcium was 3.0 mEq/L.  This is a common complication of massive transfusion.  One must be vigilant for hypocalcemia.

The second case shows a very short QT with short ST segment.  The computer measured it at 354 ms.   This was a tipoff to hypercalcemia and so we suspected that this patient had cancer as the etiology of his pain.  A chest x-ray (which we were going to get anyway) confirmed a chest mass.  A chest CT confirmed this and also showed otherwise occult spread to the shoulders.  The ionized calcium was 7.32 mg/dL and the total calcium was 15 mg/dL.

Here was the ECG after normalization of Ca in the second (hypercalcemia) case:

The QTc is now 384 ms

Wide Complex Tachycardia in a 20 something.

This was sent by a former resident.  He will remain anonymous because his identity could compromise patient confidentiality.

Case

A 20-something female presented with palpitations and lightheadedness.  She had no previous medical history except for some "in utero tachycardia" which was treated until a very early age.  She has had no problems since and takes no medications.  She has no specific conduction abnormality diagnosis.

Her mother states she is not thinking clearly ("acting as if she is intoxicated").  The patient reports exertional syncope and was syncopal on the way to the triage desk.

Exam: Very large, at 5' 10" (178 cm) tall and 346 lbs. (156 kg).
Pulse: 235
BP: 121/67
SpO2: 98% on room air

Otherwise unremarkable.

EKG:

There is a regular wide complex tachycardia at a rate of 231. 
There is no recognizable morphology, such as RBBB or LBBB.
The complexes are very wide
The initial portion of the QRS represents prolonged depolarization, arguing strongly against SVT.
So it must be VT or antidromic AV reciprocating tachycardia (AVRT)
There are small waves in lead II across the bottom.  Are these retrograde P-waves?

The rhythm strips, which unfortunately were not recorded, reportedly showed irregularity, with a rate varying from 180-250.

Because of this irregularity, the treating physician was worried about Atrial fibrillation and WPW, and therefore was reluctant to give adenosine.

See here for a discussion of Atrial fib and WPW, and the danger of adenosine and of other AV nodal blockers, and of the safety of these medications if it is NOT atrial fibrillation.

What would cause this rhythm but have some irregularity on the rhythm strip?  Could this be atrial fibrillation?  Is adenosine really contraindicated?

It is very important that you recognized that the ECG shown CANNOT be Atrial fibrillation with WPW.  
1) it is perfectly regular (I even used calipers)
2) When you have atrial fibrillation with WPW, there are multiform QRS complexes.



Clinical Course:

Procainamide was administered.  There was no response.

Labs were normal.  K was 3.5 mEq/L.

Electrical Cardioversion was the next step.  As the BP was stable after some fluids, low dose propofol  (60 mg) was used for sedation.

Synchronization was turned on; here it is:

Are the sync arrows pointing to a T-wave?  Or QRS?  If the point to the T-wave, synchronized cardioversion could result in ventricular fibrillation.
See this post demonstrating dangerous and erroneous identification of the QRS.

Cardioversion was done at 200J biphasic.

Here is the result:

The cardioversion occurs almost halfway through the strip. There is conversion to Polymorphic VT or Ventricular Fibrillation.

There was a pulse, so it must be Polymorphic VT.  The BP was 70 systolic.  She was given 2 g of Mg, and defibrillated at 200 J biphasic.  Here is the result:

Polymorphic VT has deteriorated into Ventricular Fibrillation

After a couple defibrillations, there was conversion back to a wide complex tachycardia:

Color and BP were improving and she was awakening.

Consultant recommends amiodarone and repeat cardioversion.

This was done without success.

She reverted to V Fib again:

Chest compressions were started.  She was given an Esmolol bolus and infusion and then defibrillated again, all during chest compressions:

She is defibrillated into an organized wide complex rhythm, which then becomes a narrow complex tachycardia with occasional wide complexes.

Continued monitor strips:

Finally stabilizes in sinus rhythm

12-lead:

Sinus rhythm.  There is no good indication of underlying pathology.

She remained on the esmolol drip and had no more dysrhythmias.  Cardiac MRI was normal.  Echo was normal.  EP study was done.  See below.




What happened?

Was there an irregular rhythm?  We must take the word of the physician.

Was it atrial fibrillation?  On the initial ECG, it certainly is not atrial fibrillation.   Therefore, if the irregular rhythm was atrial fib, then the patient was flipping back and forth between a rapid atrial fib and a regular wide complex tachycardia.  This is very improbable.  

What else could it be?

It could be what it was proven to be on EP testing: Dual AV nodal pathways and WPW (there is no delta wave, and thus there is 'concealed conduction'.  Read this to understand concealed conduction.

In this scenario, the dysrhythmia is antidromic AV reciprocating tachycardia (AVRT) that goes down the accessory pathway and up either one of two AV node pathways.  The resulting rate depends on which pathway is used.

Here are some schematics that were nicely drawn by the physician:

Dual AV nodal pathways:
Fast pathway: conducts quickly, longer refractory period
Slow pathway: shorter refractory period

Add an Accessory pathway to the mix:

Ablation of the Bypass tract (Accessory Pathway) was completed.


How would I have managed this?

I would have attempted adenosine.  It is not atrial fib with WPW.  If it is VT, adenosine will be safe.   It might work.  If adenosine does not work, then cardiovert.

I believe adenosine would have worked here.

I have talked with Ken Grauer about his comments below.

We are now agreed that this was indeed a wide complex tachycardia due to antidromic WPW.

 

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

MY Comment by KEN GRAUER, MD (5/30/2018):

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

Fascinating case — that was first published back in February, 2015 — and which Dr. Smith is reposting today because of its “timeless nature”. I find it always interesting to review tracings previously interpreted — since sometimes what we said earlier might not be what we think now. There are 2 reasons for this: i) Intra-observer variability (in which the same interpreter when given the same tracing at a later time says something different …). The literature suggests this occurs ~10-20% of the time in expert interpreters; and, ii) We may have learned something since the time that we first interpreted the tracing! So it is humbling for me to see how my interpretation today ( = May 30, 2018) differs from what I said in my 2 February, 2015 comments ...

• In 2018 — I see a regular tachycardia at ~240/minute that on first glance looks to be wide — but which I suspect is actually not wide. Leads V4,V5,V6 in particular suggest a narrow QRS complex. The vertical RED line I’ve drawn in Figure-1 shows where I think the limits of the QRS complex lie in the long lead II rhythm strip about the bottom. Looking at this precise point in the long lead II in leads I, II, III; and aVR; aVL, aVF — the vertical GREEN line suggests where I think the limits of the QRS complex may lie. Could this really be a narrow QRS with marked ST-T wave abnormality secondary to the marked tachycardia? What do YOU think? There may be some aberration — but perhaps the QRS is not nearly as wide as it first appears to be ...

Figure-1: Combining the initial tachycardia tracing with the post-conversion 12-lead ECG (See text for discussion).

• Even if the QRS complex was wide — my interpretation in an otherwise presumably healthy 20-year old woman who presents hemodynamically stable in a regular wide tachycardia at this fast a rate (~240/minute) — would be that this may well be AVRT conducting anterograde (ie, first down an AP). In either case (ie, whether the QRS was narrow or wide) — I completely agree with Dr. Smith that Adenosine would seem the clear drug of choice! (ie, low chance of significant lasting adverse effect — and excellent likelihood of converting AVRT with either anterograde or orthodromic conduction).
• The final clinical point I’d make relates to how to rapidly and accurately estimate the rate when the rhythm is regular and fast. I use either the “every-other-beat” or “every-third-beat” Method. I used the “every-third-beat” Method in this case. Find a part of a QRS complex that begins or ends on a heavy line. Count the number of large boxes that it takes to record 3 beats. This allows you to calculate 1/3 of the rate. In this case — it takes just under 4 large boxes (BLACK numbers) to record 3 beats (RED letters). Therefore 1/3 the rate ~80/minute X 3 = ~240/minute for the heart rate in this case. This is VERY helpful, because while AVNRT may record at this rapid a rate — one begins to think more of AVRT at a rate this fast ...
• Note that I’ve attached the post-conversion 12-lead ECG to the bottom of Figure-1. Doesn’t the narrow QRS in the post conversion tracing resemble  what I suggested above might reflect a narrow QRS during the tachycardia (vertical RED and GREEN lines)?
• We are told that EP testing revealed, “Dual AV nodal pathways and an Accessory Pathway, but no Delta wave” — therefore AVRT in which conduction is orthodromic (ie, first going down the normal AV nodal pathway [which is why the QRS may be narrow] — and then coming back up the AP). Given that delta waves are not seen in either the tachycardia or post-conversion tracing — isn’t my theory plausible (if not probable) that the QRS in the initial tracing (TOP in Figure-1) is actually narrow because this is orthodromic AVRT with marked ST-T wave changes?
•  

 

 

New Left Bundle Branch Block (LBBB) and Dyspnea

It is important to remember that the latest (2013) ACC/AHA STEMI guidelines removed New Left Bundle Branch Block (LBBB) as an indication for emergent reperfusion because there are too many false positives.

A reader sent this:

An elderly female presented with dyspnea, nausea, diaphoresis, and indigestion at 2am.  She had a history of CAD with stents, and no history left bundle branch block.

There is sinus rhythm and Left Bundle Branch Block.  There is not a lot of ST elevation, nowhere near 5 mm.  Lead V5 possibly has some concordant STE, but there is a wandering baseline and it certainly does not come to 1 mm.
However, the ST/S ratio in V2 is high in spite of only 3 mm of STE, and it thus meets the Smith-modified Sgarbossa criteria. 

The physician wrote to me that he was suspicious of LAD occlusion, based on the modified Sgarbossa criteria, and called the interventionalist, who said, “It doesn’t meet Sgarbossa criteria.”

The emergency physician continued: "I didn’t mention your study directly but expressed my concern that this was a STEMI. We activated the cath lab.  She had a totally occluded LAD with thrombus."

Here is a suggested algorithm by Cai and Sgarbossa, using the Modified Criteria (full text and algorithm copied below).

See two figures below:

A Relatively Narrow Complex Tachycardia at a Rate of 180.

I received a text message with this image: "Cardioversion didn't work.  Any thoughts?"

What do you think?  The heart rate is 180.

I was viewing this on my phone, but I saw what I thought were P-waves.  I could barely see them in lead II:

There are probable P-waves at the arrows, but I wasn't certain

I texted back: "Could be very fast sinus."

There is also a wide QRS at 113 ms and a large R-wave in aVR, so sodium channel blockade is likely.   Common culprits in this situation are tricyclic overdose and cocaine toxicity (remember cocaine not only increases dopamine in central synapses, but is also a local anesthetic (-caine!) due to Na channel blockade.  Both of these also cause seizures.


Here is the history:

Male in 40's who had seizures and was unconscious.  BP 200/100.  Pupils dilated.  They had already given adenosine 6 mg and 12 mg without effect.  They had already cardioverted at 120 J, then 200 J, which resulted in the following:

Ventricular Tachycardia

They then cardioverted at 200 J which resulted in the same narrow complex rhythm shown above, at 185 beats per minute.

I suggested esmolol if the heart rate did not improve.  This would treat both SVT or sinus tachycardia.

However, the heart rate gradually fell to 120 with fluids and was proven to be sinus tachycardia.

Later, he was found to have used cocaine.  There was a good outcome.



Comment:

Don't forget that sinus tachycardia can be very tricky!  I have seen it fool clinicians many times. In relatively young patients with syndromes of elevated catecholamines, it can be very fast. Dilated pupils and hypertension are a strong clue to sympathetic overload,  but don't forget anticholinergic syndromes, including tricyclics!

I also believe that we physicians and medics are eager to treat dysrhythmias, and we want to see them even when they are not there.  We want to do something, like give adenosine or cardiovert, and so we are not as eager to diagnose sinus tach.  I know this is true for me, and I have to always be aware of it in order to avoid it!

Suggestions on management:

First, examine the ECG very closely for P-waves.  The little "blips" that you think are artifacts are NOT artifacts if they happen every beat and at a fixed interval.

Try Lewis Leads!!   P-waves can be much more easily seen with Lewis leads than without.

Place the Right Arm electrode on the patient’s manubrium.

Place the Left Arm electrode on the 5th intercostal space, right sternal border.

Place the Left Leg electrode on the right lower costal margin.

Monitor Lead I.

Second, if the patient is hemodynamically stable, without pulmonary edema, it may be wise to try some fluids and and benzodiazepines and/or propofol for this post-seizure patient with likely high catecholamine levels.   Give it a little tincture of time to see if the rate floats down.

Third, if there is evidence of sympathetic overload, as in this case, with dilated pupils and hypertension, and you unequivocally need to decrease the heart rate, and fluids and sedatives and time are not working, then consider esmolol: it is likely to successfully treat SVT and sinus tach.  The short half life means you can turn it off if there are adverse effects.   Be ready to give nitroprusside if the blood pressure does go unacceptably high [unopposed alpha in possible cocaine overdose is an overblown concern: see discussion below]

Fourth, if it is AV nodal re-entrant tachycardia, sometimes a dose of 18 mg of adenosine is necessary.

Fifth, although it seems bad form to cardiovert sinus tach, it usually will turn out ok.  In this case, it resulted in VT, which could be cardioverted.






The prohibition against beta blockade in cocaine toxicity, causing "unopposed alpha" stimulation, needs to be re-examined.

I have treated several patients with severe hypertension and tachycardia due to cocaine and/or methamphetamine with a combination of esmolol + nitroprusside or phentolamine.



1. This is in this month's Journal of Emergency Medicine: http://www.jem-journal.com/article/S0736-4679(14)01085-3/abstract

Here is a quote from this editorial:  "It is time for all physicians to actively question the  dogma of “unopposed alpha-stimulation” with beta-blocker use that has persisted in medical textbooks and literature for three decades as an absolute contraindication despite scant evidence.  We believe this represents a form of “toxicomythology” given the millions of doses of beta-blockers administered in the past to patients with hyperadrenergic states, and a paucity of evidence of adverse outcomes (12). We believe more research is needed in this area, as amphetamine derivatives are one of the most widely abused drugs worldwide, and we expect this problem to worsen in the future."





2. This is a letter to the Editor I wrote in 2010 that was not accepted for publication:

It Is Not Surprising that Beta Blockade is not Dangerous in the Setting of Cocaine.

The data in the paper by Rangel et al. is intuitive, and not surprising.¹  (This paper showed no harmful effects of beta blockade on cocaine chest pain.)  Metoprolol and atenolol are overwhelmingly beta-1 cardioselective.  Beta-1 blockade decreases inotropy and chronotropy and has no vasoconstrictive effects.  Only beta-2 blockade (e.g., propranolol, labetalol) results in vasoconstriction because beta-2 activation relaxes bronchial and vascular smooth muscle.  The supposition that beta blockade in the presence of cocaine intoxication would lead to unopposed alpha constriction is not based in accurate pharmacology, and the study that showed this effect with human intracoronary administration was done, as mentioned in the article, with propranolol, a nonselective beta blocker.²  Indeed, major articles advising against the use of beta blockers in cocaine toxicity reference only this article and do not discuss cardioselectivity.  The one exception³ referenced only 2 case series/reports with a total of 8 patients treated with esmolol, with variable outcomes.^{4, 5}  There is indeed good reason to believe that beta-2 blockade in the context of cocaine intoxication would be deleterious, but there is no reason to believe that beta-1 blockade would be.  Thus, theoretically, metoprolol, esmolol, and atenolol should not lead to unopposed alpha effect, and there is no evidence that they do.  The long-standing recommendation against the use of all beta blockers in the context of cocaine has no basis in data or rationale.  Finally, there is evidence of danger with labetalol, and this is in accord with its prominent beta-2 blocking effects.³

1.         Rangel C, Shu RG, Lazar LD, Vittinghoff E, Hsue PY, Marcus GM. Beta-blockers for chest pain associated with recent cocaine use. Arch Intern Med;170(10):874-9.

2.         Lange RA, Cigarroa RG, Flores ED, et al. Potentiation of cocaine-induced coronary vasoconstriction by beta-adrenergic blockade. Ann Int Med 1990;112(12):897-903.

3.         McCord J, Jneid H, Hollander JE, et al. Management of cocaine-associated chest pain and myocardial infarction: a scientific statement from the American Heart Association Acute Cardiac Care Committee of the Council on Clinical Cardiology. Circulation 2008;117(14):1897-907.

4.         Pollan S, Tadjziechy M. Esmolol in the management of epinephrine- and cocaine-induced cardiovascular toxicity. Anesthesia and analgesia 1989;69(5):663-4.

5.         Sand IC, Brody SL, Wrenn KD, Slovis CM. Experience with esmolol for the treatment of cocaine-associated cardiovascular complications. Am J Emerg Med 1991;9(2):161-3.

ED Case of Catecholaminergic Polymorphic Ventricular Tachycardia

This case was provided by a reader; there are missing details, but I believe it is still instructive.

Case Presentation

First ED presentation

A male in his 40s had onset of pre-syncope during moderate exercise.  On arrival in the ED he was cyanotic and drowsy.  The monitor showed a wide complex tachycardia.  Electrical cardioversion at 120 J had no response, but then he spontaneously converted to sinus rhythm.  After being given a bolus of amiodarone, he was admitted.

Further review of past history revealed a remote episode of Polymorphic VT due to a presumptive diagnosis of Catecholaminergic Polymorphic VT due to an abnormal ryanodine receptor.

He had been managed with Nadolol and an AICD.  There was no relevant family history.   The patient had always been otherwise healthy, and had always enjoyed exercise.

In the more recent past, he had also had an internal shock once during exercise.  When the AICD was interrogated, it turned out to be due to sinus tachycardia, and so the acceptable heart rate limit was increased from 150 bpm to 188 bpm.

The hospital course was benign.  He remained stable and was discharged on flecainide, with a follow up stress planned.

This was in the plan: "The ICD therapy zone will not be lowered at this time because of concerns that ICD shocks in someone with CPVT could lead to high adrenergic response and trigger VT storm."

Second ED Presentation

The patient presented to the ED again 5 days later:

After moderate exercise, he presented in acute distress at a heart rate of 180, but with fewer perfused beats.

Here are his ECGs:

Wide complex tachycardia.  This is mostly monomorphic VT, but because V5 shows 2 narrow beats (which could be mistaken for fusion beats), this is polymorphic VT due to short episodes of bidirectional ventricular tachycardia.  Notice these beats do not occur while V2 and V3 are being recorded, unlike the next ECG.

Second recording, shortly after the first:

Here again we see Bidirectional Tachycardia, and it is more obvious because it occurs during the recording of V2 and V3, which show it more clearly than any lead except V5 (across the bottom),  which is by far the most diagnostic.

ED Course

He underwent synchronized cardioversion twice at 120 and 200 J with no response.  He maintained a wide complex tachycardia with a heart rate on the monitor up to 180, but with fewer perfused beats. He remained alert.

He was given metoprolol 15 mg IV with no response.  (Comment: I would consider this a small dose, and would give esmolol which is short acting and can be dialed up and stopped if there are adverse events).

In order to diminish the catecholamine surge thought to be driving his tachycardia, the patient was intubated and sedated with propofol.  This failed.

Overdrive pacing was attempted via his implanted pacemaker, and this also failed.

The rhythm was then managed with amiodarone (this failed).

He was given esmolol (this also failed).

Finally, he was given verapamil.

Following verapamil, the patient became very hypotensive until he became ashen and pulseless.  Chest compressions were started and he was defibrillated again at 200J, resulting in restoration of sinus rhythm at 30-40 bpm, with inadequate perfusion.

Atropine and pacing were instituted.  The patient stabilized, and he was able to be transferred out of the ED.

After a week in the hospital, he was discharged on amiodarone and nadolol after a benign stress test. Flecainide was discontinued.  There was consideration of future sympathetic denervation of the heart.

Catecholaminergic Polymorphic Ventricular Tachycardia

CPVT is one of the types of VT that occurs in a structually normal heart.  It is due to rare mutations (either inherited or spontaneous) of either the ryanodine receptor gene or the calsequestrin 2 gene.  Both in turn affect diastolic calcium release from the sarcoplasmic reticulum, and thus increase intracellular calcium levels (just as digoxin does), leading to delayed afterdepolarizations and triggered activity.  Just as with Digoxin, one of the primary dysrhythmias is Bidirectional Tachycardia.  

PMVT is characterized by episodic syncope during strenuous exercise or acute emotion in people without structural cardiac abnormalities.  It produces polymorphic VT, often with bidirectional VT, and can be well tolerated.

As mentioned above, some CPV are linked to mutations in the cardiac ryanodine receptor, also called the cardiac sarcoplasmic calcium release channel (which mediates the release of calcium from the sarcoplasmic reticulum, required for myocardial contraction).  Catecholamines can cause these ryanodine related channels to "leak" calcium in diastole and can trigger life threatening arrhythmias.

Further discussion of mechanism is beyond this blog (and beyond me!)

The mean age of onset is 7-12 years, so this is initially a pediatric problem.  However, onset may be as late as 40 years.  The first manifestation may be cardiac arrest.

The baseline ECG is normal.  There are multiple mechanisms involved, including re-entry and delayed afterdepolarizations due to calcium overload or changes in autonomic tone.  It generally cannot be induced in the EP lab.

VT is of polymorphic morphology or of bidirectional morphology, such as one sees in digoxin or aconite toxicity, with alternating QRS axis, or alternating LBBB/RBBB.

Further discussion is beyond the scope of this blog, except for emergent, and a bit on chronic, management.


ACUTE MANAGEMENT of Catecholaminergic Polymorphic VT
(there is little in the literature that I could find; the ACC/AHA guidelines on dysrhythmias have not, apparently, been updated since last published in 2006):

If it is a child with his/her first presentation, you may be presented only with polymorphic VT of unknown etiology.  If you can record an ECG in sinus, and there is a long QT, then you will know that it is not PMVT.  If you do not have that opportunity to record it, you will not know, but long QT is far more common than PMVT.  By the time of adulthood, the patient will probably be aware of the condition.  This is important, because the management of the two entities is very different.

If you are able to record an episode of sinus rhythm:

1. If there is a long QT, then the polymorphic VT is Torsade.

2.  If there is ischemia or evidence of cardiomyopathy on the ECG, then it is polymorphic VT due to ischemia or a structurally abnormal heart.

Here is a post on the management of Polymorphic VT NOT due to CPVT.

3. If the QRST is normal when in sinus, then strongly consider CPVT.

Or perhaps, as in this case, the patient is known to have CPVT.

Here are some management steps to take:

1. Cardioversion or defibrillation (depending on presence of pulses), but with beta blocker pre-treatment (if possible), as the shock itself can cause catecholamine surge, further aggravating the situation and causing early recurrence of VT.

2. Intravenous beta blockers should be administered.  Esmolol is a great choice, as it has a very short half-life and can be turned off if there are complications.  Dose: Esmolol can be given in a bolus of 500 mcg/kg (0.50 mg/kg), followed by a drip of 50 mcg/kg/min (0.05 mg/kg/min).  It can be rebolused repeatedly, as needed, each time increasing the infusion by 50 mcg/kg/min.

3. For recurrent VT in the absence of prolonged QT, amiodarone should be administered by bolus and drip.  Amiodarone has beta-blocking effects.

4. Verapamil is recommended based on studies in which it prevents exercise-induced PMVT (3, 4).  However, I haven't found literature on its use in the acute situation.  Our electrophysiologist wrote that he would try it.  In this case, it appears to have made things worse, but that is the problem with isolated cases without control groups.

4.  Sedation, as in this case, to decrease sympathetic drive?  Or, class IIb in ACC/AHA guidelines for incessant VT is general anesthesia.

Avoid isoproterenol and overdrive pacing.  For polymorphic VT due to acquired long QT (Torsade de Pointe), isoproterenol is indicated to increase the sinus rate and prevent further torsade.  However, this makes CPVT worse.  Fortunately, Torsade is more common, but if you know the patient has CPVT, avoid isoproterenol.

Overdrive Pacing is listed as class IIb for incessant VT in the ACC/AHA guidelines, but this should not to be applied to CPVT. 

Overdrive pacing is used to prevent recurrence of pause-dependent PMVT (Torsade), which is worsened by bradycardia and improved by tachycardia).  The pathophysiology of CPVT is very different from Long QT syndrome.  CPVT, unlike Torsade, is worsened with tachycardia.   See this post for management of Torsade.


CHRONIC MANAGEMENT (these are a few therapies that the electrophysiologist may pursue)

1. Beta blockers
2. AICD consideration, especially if survivor of cardiac arrest.  ICD treatment without concomitant use of beta blockers is dangerous because of the risk of electrical storm induced by the adrenergic surge related to a shock.
3. Flecainide if refractory to above (it inhibits the cardiac ryanodine receptor)
4. Verapamil
5. Strictly avoid competitive sports
6. Sympathetic denervation if refractory to above

Missing just one dose of beta blocker can lead to a fatal or near fatal event

This is copied from the ACC/AHA guidelines (quote):

Supraventricular and ventricular arrhythmias are usually reproducibly induced by exercise stress when the heart rate reaches a threshold of 120 to 130 beats per minute. Isolated PVCs usually develop first and are followed shortly after by short runs of NSVT. If the patient continues to exercise, the duration of VT runs progressively increase and VT may become sustained. A beat-to-beat alternating QRS axis that rotates by 180°, “bidirectional VT,” is the typical pattern of CPVT-related arrhythmias. CPVT patients can also present with irregular polymorphic VT or VF.

Beta blockers prevent recurrences of syncope in the majority of patients, even if VT and SVT usually can still be elicited during exercise stress test. If syncope occurs in a patient taking a beta blocker, the implantation of an ICD is recommended. However, ICD therapy requires careful programming of the device to prevent needless therapy for nonsustained episodes of ventricular tachyarrhythmia.

References:

Zipes DP et al.  ACC/AHA Guidelines for management of patients with ventricular arrhythmias and sudden cardiac death.  JACC Vol. 48, No. 5, Sept. 2006:e247– e346

Pflaumer A.  Davis AM.  Guidelines for the diagnosis and management of Catecholaminergic Polymorphic Ventricular Tachycardia.  Heart, Lung, and Circulation 2012:21(2):96-100.

Rosso R, et al. Calcium channel blockers and beta-blockers versus beta-blockers alone for preventing exercise-induced arrhythmias in catecholaminergic polymorphic ventricular tachycardia. Heart Rhythm 2007;4:1149–1154.

Swan H, et al. Calcium channel antagonism reduces exercise-induced ventricular arrhythmias in catecholaminergic polymorphic ventricular tachycardia patients with RyR2 mutations. J Cardiovasc Electrophysiol 2005;16:162–166.  This article only comments on chronic management, not acute management.