Electrical instability in a healthy 50 year old. How to manage?

Written by Magnus Nossen 

    (with 2 important comments by Smith at the bottom)

The patient in today’s case is a 50 year old man who presented due to "dizziness" and episodes of presyncope. 

• The patient's symptoms had started about 14 days prior to admission — but worsened significantly during the course of the last 24 hours. 
• Previously healthy, taking no medication and exercising regularly. 
• No anginal symptoms asymptomatic during physical exercise.  

Below in Figure-1 is this patient's admission ECG. How will you manage this patient?

Figure-1: Today's initial ECG (Cabrera layout, paper speed 25mm/sec.).

Interpretation: This 12-lead ECG shows sinus rhythm with a heart rate of 65 beats/minute with frequent unifocal PVCs. The sinus conducted beats have a normal PR interval and are narrow with slight ST elevation in V2. This ST-elevation is benign in appearance. The QTc is normal. Of note are the multiple premature ventricular contractions (PVCs). The ectopic beats can be seen isolated, coupled and in short salvos of 3 beats.

The PVCs have an LBBB-like morphology in the early precordial leads. The QRS axis is superior and towards the left shoulder. (ie, negative QRS complexes in the inferior leads — and positive in leads I and aVL). The axis and morphology of the PVCs are consistent with an origin of the premature ventricular beats somewhere near the apex of the right ventricle. The axis is not compatible with RVOT ectopic beats, which should have an inferior axis. Of note is the slight beat-to-beat variation in the PVC morphology (More on this later in the post).

PVCs originating in the right ventricle will have an LBBB-like QRS morphology in the precordial leads — whereas PVCs from the left ventricle will show RBBB-like morphology.

Whenever I see PVCs with the morphology and axis seen in todays case — I always look for signs of AC (Arrhythmogenic Cardiomyopathy). Arrhythmogenic cardiomyopathy often manifests with PVCs from the RV. The ECG in Figure-1 however, shows no signs of arrhythmogenic cardiomyopathy. See this case for an in-depth discussion of AC and an example of VT and ECG changes associated with this disorder. 

• During observation in the ED the patient had multiple self-terminating runs of Non-Sustained monomorphic Ventricular Tachycardia (NSVT). 
• IV metoprolol boluses were administered without any effect on the ventricular ectopy. Potassium and magnesium serum levels were normal.
• Bedside echo was challenging simply due the frequency of ectopic beats — but did not reveal any pathology. 
• A 150mg IV bolus of amiodarone was added to the IV metoprolol without any effect. Following this, an IV amiodarone infusion of 1200mg/24 hours was started.

Figure-2 below shows a consecutive recording of a single long lead II rhythm strip. There are 6 lines, each 30 seconds long. Each line is followed immediately by the one beneath it. The recording makes up a 3-minute rhythm strip. This tracing was obtained after initial treatment with an IV ß-blocker, amiodarone and magnesium sulfate.

Figure-2: Continuous 3-minute, long lead II rhythm strip — recorded after initial treatment. 

It is obvious from Figure-2 that treatment up to this point is not having the desired effect. On the contrary, the incidence and duration of VT was increasing (!) despite treatment. The patient was constantly dizzy, and the PVCs and runs of NSVT were associated with no more than faint pulses on the arterial line. 

How can you stabilize this patient? What will be your next measure?

You have given IV MgSO4 — a fast acting ß-blocker — and IV amiodarone bolus and infusion. 

• The possibility of an ischemic cause of the ventricular arrhythmia has to be considered! That said — there were no clinical symptoms or ECG findings suggestive of ongoing ischemia. Troponin T was negative on admission and on repeat blood draw. 

Therefore — A different approach is needed. There are 2 main options:

• Overdrive pacing could be considered — and in the right clinical situation, this is often effective for reducing ventricular arrhythmias (especially in the case of preventing pause induced or bradycardia-induced arrhythmias in association with QTc prolongation).
• Try a different kind of antiarrhythmic. This is what was done in today's case. The intricacies of the different classes of antiarrhythmics and their mechanism of action extend beyond the scope of this blog. I limit myself to the summarized overview in Figure-3 of antiarrhythmic agents and their principle site of action. 

Figure-3: Vaughan-Williams Classification of antiarrhythmic agents.

The CASE Continues:

It was decided to try a sodium channel blocker that acts primarily on the ventricular myocardium. Intravenous administration was sought for rapid onset of action. 

• IV lidocaine was given as a 100 mg bolus, followed by a continuous infusion. A few minutes after the bolus was administered, there was no more NSVT! In fact, after the bolus was completed — there were hardly any PVCs at all.

The patient was continued on IV lidocaine infusion until the next AM, at which point it was stopped. The plan was to try flecainide if symptoms recurred. If successful, this medication is much easier to give as an oral preparation. 

• The patient remained free of PVCs for several hours after the lidocaine was stopped. 
• Echocardiography was done and was completely normal. 

Approximately 10 hours after lidocaine infusion was stopped — multiple PVCs and runs of NSVT reappeared, increasing dramatically within a short time span.

• The patient was loaded with 100mg IV flecainide. 

Below in Figure-4 is the rhythm strip immediately recorded after initiation of the IV flecainide infusion. Again, there are 6 lines, each 30 seconds long. Each line is followed immediately by the one beneath it.

Figure-4: Long lead II 3-minute rhythm strip after initiation of IV flecainide. PVCs and short runs of NSVT are extremely frequent for the first half of the recording.

Following initiation of flecainide infusion — there was a nearly immediate and virtual complete cessation of PVCs and NSVT! 

• The patient was transitioned to oral flecainide. He has since been free of PVCs. 
• Below in Figure-5 — is a 10-minute continuous lead II recording on oral Flecainide, now showing sinus bradycardia without a single PVC! 

Figure-5: Long lead II recording on oral flecainide (10 minutes of continuous recording — each line being 1-minute long). No PVCs are seen.

A workup was undertaken in search of a cause of the patient's ventricular arrhythmia.

• As noted above — echocardiography was completely normal. 
• CT coronary angiogram showed a hypoplastic RCA and dominant LCx. There were no plaques or stenoses. 
• Once the arrhythmia was under control — cardiac MRi was performed. The MRi was completely normal without any early or late enhancement and without any signs of arrhythmogenic cardiomyopathy. 
• The patient has been scheduled for a PVC ablation procedure. This patient very likely has some form of idiopathic ventricular tachycardia. 

Idiopathic Ventricular Tachycardia: 

Idiopathic ventricular tachycardia occurs in patients with structurally normal hearts — in the absence of other identifiable cause such as channelopathy or cardiomyopathy. 

• There are many different types of idiopathic VTs with the outflow tract ventricular tachycardias (OT-VT) being most common. Of the ventricular outflow tract tachycardias — (RVOT-VT) makes up 80-90%. 
• Idiopathic VT is not limited to the outflow tract tachycardias however — as it can arise from other sites in the myocardium or conduction system. The list is extensive and includes but (but is not limited to) fascicular VT, annular VT, bundle branch VT and (what perhaps is the most likely diagnosis in todays case) — moderator band ventricular tachycardia.

Moderator Band VT: 

MB-VT exits near the apicolateral RV and therefore exhibits a LBBB morphology. The QRS morphology can have subtle variation (as seen in our case) — which may be a tip-off due to varying exits and fusion. 

• The axis is leftward and superior, with a predominantly positive QRS in lead I and negative QRS in the inferior leads. 
• Given early involvement of the specialized conduction system — the QRS may be relatively narrow with a sharp upstroke. However, this is dependent on the exit site — and the QRS could be wide if the exit is closer to the RV free wall. 
• Precordial transition is typically later than V4. 

A common feature of MB-VT is discordance between the inferior leads, with a dominant positive deflection in lead II and a negative deflection in lead III (because the VT is exiting closer to lead III). This was not seen in today's case.

• The differential diagnosis, especially in younger patients, includes atriofascicular tachycardia also known as "Mahaim" tachycardia.   

The idiopathic VTs are an interesting group of arrhythmias! See the September 14, 2018 post for a nice overview of this subject by Dr. Meyers. I list below links to other cases of idiopathic VT from Dr Smith's ECG blog.

Right Ventricular Outflow Tract (RVOT) Tachycardia

Fascicular Tachycardia

Bundle branch re-entry tachycardia

Discussion: 

The diagnosis and management of the idiopathic VTs are predicated on an understanding of the mechanism, relevant cardiac anatomy, and associated ECG signatures. Our patient was referred for EP study with a plan of PVC ablation if possible. Idiopathic ventricular arrhythmias generally have a favorable prognosis when compared to non-idiopathic VT. The various idiopathic VTs usually can be controlled well with medical treatment and/or catheter ablation therapy. Most patients can be managed without and implantable cardioverter defibrillator (ICD)

In patients with PVCs/VT and a presentation not typical for an idiopathic origin — cardiac magnetic resonance (CMR) should be considered, even if the Echo is normal. 

• Beta-blockers, non-dihydropyridine calcium channel blockers, or flecainide should be considered when catheter ablation is not available, not desired, or is particularly risky. 
• Catheter ablation or flecainide should be considered in symptomatic patients with idiopathic VT/PVCs from an origin other than the RVOT or the left fascicles. [1]

Considerations Regarding Use of Flecainide: 

A 12-lead ECG is mandatory before starting therapy. It is reasonable to perform an echocardiogram to evaluate LV function. Flecainide displays use-dependence, whereby it blocks voltage-gated sodium channels more at higher heart rates. This is why exercise stress testing is sometimes performed to ensure the drug does not cause significant QRS prolongation or precipitate Brugada ECG pattern at higher heart rates.

In general, it is strongly suggested to test the first dose under medical observation. The minimum effective plasma concentration of flecainide is about 200 ng/mL. The optimal range is between 200 ng/mL and 400 ng/mL. This plasma concentration leads to a QRS prolongation of about 10 msec. A prolongation of 40 msec or more is associated with and increased probability of cardiovascular adverse effects.

Smith comment-1: The primary side-effect of flecainide is sudden death. So you must be VERY careful before initiating a patient on this medication.  It is particularly dangerous in patients with low EF. In 2016, I doubled the number of night shifts and suddenly was having 10,000 PVCs per day, very distressingly symptomatic.  After a normal stress echo and normal MRI, my electrophysiologist put me on Flecainide. Within 1/2 hour of taking one tablet, all PVCs completely disappeared. He then insisted that I do another stress test, and I got my heart rate to 173 without any QRS widening. He then was satisfied that I would be safe on flecainide. Not too long after that, I stopped doing night shifts altogether and did not need the flecainide any more!!

----See the Cardiac Arrhythmia Suppression Trial (CAST) trial: patients with low EF and many chronic PVCs were trialed on anti-dysrhythmics.  Those whose PVC frequency decreased were randomized to Flecainide, Encainide, Moricizine, or Placebo.  The patients who received the anti-dysrhythmic (compared to placebo) had far more sudden death.

Smith comment-2: Another adverse effect from flecainide is atrial flutter with 1:1 conduction (if you happen to go into atrial flutter, the flecainide slows the flutter rate such that it is slow enough to conduct throught the AV node at 1:1 — and you can end up with a ventricular rate of 220!! ). Therefore, many cardiologists routinely add an AV nodal blocker when they start a patient on flecainide.  

See here: Narrow Complex Tachycardia at a Rate of 220

Below is a Practical Approach to Flecainide Dosing:

• Exclude contraindications such as structural heart disease; symptomatic bradycardia; 2nd-degree or high-degree AV block; QRS >120 msec.; and Brugada syndrome.
• Record an ECG and calculate the QRS duration.
• Administer a loading oral dose of 250 mg (200 mg if the weight is lower than 70 kg).
• At plasma concentration peak (after 90–120 min.) — record another ECG and calculate the QRS duration.

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1. If the QRS duration is increased by less than 20 msec. — prescribe 100mg twice daily or 200 mg once daily. Check ECG again after one week.
2. If the QRS duration is increased between 20 and 40 msec., or is wider than 120 msec — prescribe 50 mg twice daily or 100 mg once daily. Check again the ECG after 5 days.
3. If the QRS duration is increased more than 40 msec., or is wider than 130 msec., or a Brugada pattern is detected — consider flecainide as contraindicated in that patient.
4. An exercise stress test while taking the drug can be performed ensure that the QRS does not increase further at higher heart rates (ie, as a result of flecainide's use-dependence).

====================== 

References:

[1] 2022 ESC Guidelines for Ventricular Arrhythmias: Key Points - American College of Cardiology. (2022, September 2)

[2] Ward, R. C., Van Zyl, M., & DeSimone, C. V. (2023). Idiopathic ventricular tachycardia. Journal of Clinical Medicine, 12(3), 930. 

[3] Lavalle, C. et. al. (2021). Flecainide How and When: A Practical guide in supraventricular arrhythmias. Journal of Clinical Medicine, 10(7), 1456.

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MY Comment, by KEN GRAUER, MD (2/6/2025):

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I found today's case by Dr. Nossen intriguing, if not fascinating — because this previously healthy, middle-aged man with repetitive runs of NSVT proved resistant to multiple medications until finally responding to Flecainide. I thought this case raised a number of important clinical issues:

• What is idiopathic VT?
•     — Does this patient have idiopathic VT?
•             — Why should we care if this is idiopathic VT?

WHAT is Idiopathic VT?

We've periodically reviewed cases of idiopathic VT, in which otherwise healthy, younger adults without underlying heart disease present with VT (See my Audio Pearl and consolidated summary of this entity in Figure-7 of the ADDENDUM below — as well as comments in the February 14, 2022 post).

• As per Dr. Nossen — over 80% of idiopathic VT cases are the result of RVOT VT. Fascicular VTs make up many of the remaining cases — with both of these forms being readily recognizable based on QRS morphology — and with both often responding to specific medical treatment (as per Figure-7 below).
• But not all forms of idiopathic VT are predictable based on their ECG appearance. Was today's case one of those unpredictable forms?

Today's Initial ECG (that I've reproduced in Figure-6):

As per Dr. Nossen — sinus-conducted beats in today's initial ECG had a benign appearance (normal PR interval; narrow QRS, upright T waves with slight anterior ST elevation consistent with a repolarization variant). 

• Interesting features in this initial tracing included subtle underlying AV dissociation (PINK arrows highlighting the subtle deflections of partially-hidden on-time sinus P waves) — with periodic slight PR interval prolongation of some sinus-conducted beats due to "concealed" conduction following some PVCs (No evidence of AV block!).
• I thought QRS morphology of ventricular beats to be atypical for "idiopathic" VT in a patient ostensibly without underlying heart disease because: i) Ventricular beats are extremely wide (approaching 0.16 second in leads I,II,V5); and, ii) Although QRS morphology resembles LBBB conduction in the limb leads — the initial R wave in anterior chest leads is larger and wider than expected for LBBB conduction — and QRS morphology is bizarre in lateral chest leads V5,V6 (the vertical RED line highlighting onset of the QRS).

Figure-6: I've labeled the initial ECG in today's case.

Underlying Heart Disease?

As per Dr. Nossen — evaluation included:

• A normal Echo.
• CT angiogram — showing a "hypoplastic" RCA and dominant LCx (with distinction between what is a "smaller" RCA in a left-dominant circulation vs an RCA with a lumen that is "too small" sometimes being difficult).
• Cardiac MRI — completely normal.
• Upcoming EP study (hopefully allowing for ablative VT treatment).

Given more-than-expected QRS widening with unusual QRS morphology for ventricular ectopy on today's initial ECG, followed by resistance to multiple antiarrhythmic agents — I wondered if mention of an underdeveloped RCA on CT angiogram might reflect underlying heart abnormality in the form of HCAD (Hypoplastic Coronary Artery Disease)?

• Although rare — reduced lumen size of one or more coronary arteries has been reported as a cause of sudden death as its initial presentation in previously healthy young adults (See MacFarland et al — J Card Cases 4(3): E148-151, 2011 — and — Guo et al — JACC 17(18)- 2021).

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ADDENDUM: Summary on the usual forms of idiopathic VT.

• CLICK HERE — for my 8-minute Audio on Pearls for ECG Recognition of Idiopathic VT (with special attention to RVOT VT and Fascicular VT — which are the 2 most common forms).

Figure-2: Review of KEY features regarding Idiopathic VT.