This was written by Magnus Nossen.
Today’s case is a bit different from the usual case on Dr. Smith’s ECG blog. This case tells a patient history spanning many years.
The patient is a 20-something female with a diagnosis of childhood epilepsy. She’s had a twenty year history of recurrent seizures. She has been on a variety of anticonvulsants but her seizures were never fully controlled.
The below ECG was recorded during one of her many hospital visits. Do you see anything worrisome on this ECG?
ECG #1
ECG #1, on file recorded when the patient was in her early teens.
The ECG shows sinus rhythm at 68 bpm. QRS complexes are narrow. The PR interval = 130ms with a normal frontal plane axis and normal R-wave progression. Pediatric ECGs often show features that would be considered abnormal in adults, but are completely normal for children. For instance, prominent right ventricular forces and sinus tachycardia are common in neonates and young children. A short PR interval is common in young adults. By adolescense, the ECG should not be too different from that of an adult, although T wave inversions in the right precordial leads may persist.
Due to episodes of loss of consciousness and reported palpitations, HOLTER monitor recordings were done on several occations. The HOLTER recordings were described as below:
Normal sinus rhythm with occational premature ventricular complexes
On one occation however the ambulatory ECG recorded a regular tachycardia as shown below. The patient did not experience any loss of consciousness during this episode of tachycardia.
HOLTER # 1
The above excerpt shows a regular narrow complex tachycardia at 204bpm. Despite the poor image quality and the odd paper speed (12,5mm/s) one can be certain that this is some form of SVT. There was abrupt termination consistent with a PSVT — of which there are many types. The abrupt nature of the tachycardia rules out sinus tachycardia (which could attain heart rates in excess of 200bpm in the young adult population).
The patient had been admitted to the hospital on several occasions, usually to optimize medical seizure management. During one of these hospitalizations, the below ECG (ECG #2) and a telemetry recording (Telemetry #1) were obtained. What do you make of these recordings?
ECG # 2
Telemetry rhythm strip
Single lead from a telemetry rhythm strip. Paper speed 50mm/s.
ECG #2 and the single lead telemetry rhythm strip both show intermittent wide QRS complexes. These wide QRS complexes are not occasional PVCs. Distinguishing occasional premature ventricular complexes from intermittent pre-excitation on an ECG can be tricky because both produce wide QRS complexes. However, there are important differences:
PVCs are usually clearly premature — the QRS complex appears earlier than expected, resulting in a noticeably shorter RR interval. The R wave occurs ahead of schedule, and the QRS is typically wide and unusual in shape because the ventricles are activated outside the normal conduction system. After a PVC, there is often a compensatory pause before the next normal beat.
Intermittent pre-excitation involves early ventricular activation through an accessory pathway. This produces a wide QRS complex with a delta wave — a slurred upstroke at the start of the QRS due initial ventricular activation through the accessory pathway. Unlike PVCs, these beats are not truly premature; the peak of the R wave generally occurs at the expected time, since the rhythm is still controlled by the sinus node and there often is fusion of activation from accessory pathway and the native conduction system.
Below the intermittent delta waves are marked by arrows.
Excerpt of ECG # 2 with red arrows pointing to delta waves
Having another look at the first ECG in today’s case (ECG # 1) and applying the “retrospectoscope” we might suspect very subtle delta waves in leads V3-V5.
The finding of an SVT and pre-excitation on the ECG makes the diagnosis of WPW syndrome. If there is pre-excitation only, the term (simple) pre-excitation is used. Not all patients with pre-excitation will go on to develop re-entrant arrhythmias. The narrow QRS tachycardia showed previously (HOLTER #1) could be either orthodromic AVRT or AVNRT. In patients with WPW, orthodromic AVRT (in which case the QRS will be narrow) is far more common than AVNRT.
It was suspected that the patient’s symptoms were due to a re-entrant arrhythmia, and she had an EP study done where cryoablation of an accessory pathway was performed. Despite successful ablation of the accessory pathway — her symptoms of seizures and palpitations persisted. This led to a repeat EP study in which a typical AVNRT was induced and successfully ablated.
In my experience it is uncommon for a young patient to experience loss of consciousness from a PSVT like AVRT or AVNRT. If you have a structurally normal heart and normal systolic function, syncope from hemodynamic compromise secondary to PSVT is very unlikely. It may not surprise you then to learn that following two abation procedures the patient continued to have syncopal episodes. After another syncope with minor orthopedic injuries — the below HOLTER was done. This recording hints at the final diagnosis. What do you see?
HOLTER # 2
HOLTER #2: Top half shows the lowest recorded heart rate = sinus bradycardia, 39bpm. Bottom half shows the highest recorded heart rate = sinus tachycardia with couplets of multifocal PVCs, rate 148 bpm.
The HOLTER showed sinus rhythm throughout with a total of ~ 5000 PVCs during a 24 hour time period. This is definitely a pathologic amount, especially for a young adult.
The patient was asked to come in to the hospital for further evaluation. Her admission ECG is shown below and is clearly abnormal. How would you describe this ECG and what do you make of it?
ECG # 3
Soon after this ECG was recorded the patient’s heart rate and rhythm normalized. The patient was placed on telemetry. The telemetry revealed a pattern where PVCs would become increasingly more frequent during physical activity and completely disappear at night and during rest.
Discussion
As we have already noted, this patient had intermittent ventricular pre-excitation, and although she underwent ablation procedure — her symptoms persisted and she was admitted with a bizarre-looking ECG with frequent wide complexes with more than one single morphology. Does ECG #3 show intermittent pre-excitation? Perhaps the ablation procedure was not successful? Might there be something else going on?
The ECG recorded on admission (ECG #3) shows a wide complex tachycardia with an overall heart rate of 113 bpm. There are two distinct QRS morphologies that alternate (see the accompanying image below). One morphology (A) resembling right bundle branch block with left posterior fascicular block conduction (RBBB+LPFB) — and another (B) which resembles right bundle branch block with left anterior fascicular block conduction (RBBB+LAFB).
Excerpt of ECG # 3
All QRS complexes show RBBB-like morphology. There is alternating LPFB and LAFB morphology in leads I and II.
The ECG is consistent with a rather slow (120-130 bpm) bidirectional ventricular tachycardia. If you have a patient with syncope, bidirectional VT and increased PVCs during physical activity or emotional stess — you have very compelling evidence that the patient has Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT).
The patient could confirm that most of her seizures had happened during physical exercise and that she did experince palpitations during emotional stress. Contrary to simple PSVT, CPVT does cause hemodynamic compromise. Polymorphic VT seen in CPVT can be very rapid — and from a hemodynamic perspective it resembles VF. If persistent it will deteriorate into VF.
Some information on CPVT
CPVT is almost invariably caused by a mutation in the RyR2 gene, which encodes the ryanodine receptor. Gain-of-function mutations in this gene are found in the majority of cases. The mutation leads to increased diastolic calcium release from the sarcoplasmic reticulum and increased intracellular calcium levels. This increase in intracellular calcium can give rise to delayed afterdepolarizations and triggered activity in the form of PVCs. The intracellular calcium levels are futher amplified in adrenergic states — and this can lead to fatal ventricular arrhythmias (1).
Note! Digoxin increases intracellular calcium — and this is why bidirectional VT can be seen in Digoxin overdose.
Echocardiography and resting ECG are usually normal and do not help in diagnosing CPVT. A treadmill test may hint at the diagnosis by revealing PVCs or ventricular arrhythmia during exercise. The patient history is crucial, with symptoms of palpitations and syncope typically occurring during physical exercise or emotional stress. The average age of onset of symptoms (usually a syncopal episode) is between seven and 12 years of age, although onset in the fourth decade of life has been reported. If left untreated, CPVT is often fatal, with approximately 30% of people experiencing at least one cardiac arrest and up to 80% having one or more syncopal episodes. Sudden death may be the first manifestation of the disease (2)
Overall, Bidirectional VT is a rare ventricular arrhythmia — that in the past, was more often associated with digoxin overdose. It is also a hallmark arrhythmia in patients with CPVT, as today’s case illustrates. Bidirectional VT has also been described in patients with acute MI, severe hypokalemia from familial hypokalemic periodic paralysis, arrhythmogenic cardiomyopathy and myocarditis.
Even aconite poisoning, as in this case, can cause this dangerous arrhythmia.
Bidirectional VT due to subarachnoid hemorrhage.
Here is another case of Catecholaminergic VT:
A male in his 40s had onset of pre-syncope during moderate exercise……
https://drsmithsecgblog.com/ed-case-of-catecholaminergic/
Outcome
The patient underwent genetic testing, which revealed a mutation associated with CPVT in the RyR2 gene. She is now switched from metoprolol to nadolol (a non-selective beta-blocker) with improvement in her symptoms. She is being evaluated for an implantable cardioverter defibrillator (ICD). Implantation of ICD in patients with CPVT is controvertial as inappropriate ICD shock(s) may lead to arrhythmic storm.
Learning points
- A normal ECG does not rule out an accessory pathway — as preexcitation in the ECG can be intermittent.
- Multiple causes of tachycardia can co-exist in one patient. This patient was found to have WpW with intermittent pre-excitation, and proven AVRT, AVNRT and CPVT!
- A thorough medical history is vital and could have helped making the diagnosis earlier in today’s case.
- «Seizures» may be caused by arrhythmia. Be especially aware if the seizure disorder does not respond to antiepileptic treatment.
- AVNRT rarely produces syncope by itself if there is good LV function and no severe valvular disease.
References
- Burns, R. B. a. E. (2022, February 2).Pre-excitation syndromes. Life in the Fast Lane
- Napolitano, C., Mazzanti, A., Bloise, R., & Priori, S. G. (2022, June 23). Catecholaminergic polymorphic ventricular tachycardia
- Buttner, E. B. a. R. (2021, September 6). Bidirectional ventricular tachycardia (BVT). Life in the Fast Lane
- Wleklinski, M. J., Kannankeril, P. J. (2020). Molecular and tissue mechanisms of catecholaminergic polymorphic ventricular tachycardia. The Journal of Physiology, 598(14), 2817–2834
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MY Comment, by KEN GRAUER, MD (7/3/2025):
I found today’s case by Dr. Nossen to be truly fascinating! Fortunately — the correct diagnosis for this patient’s recurrent seizures was finally made after nearly 2 decades of uncertainty. I’ll highlight some of the lessons-to-be-learned brought out by Dr. Nossen’s discussion.
- Finding 1 diagnosis does not necessarily solve your patient’s problem(s). Despite finally (after a period of years) appreciating that this patient’s “seizures” were arrhythmia-related — neither detection of this patient’s elusive (only intermittently apparent) preexcitation with documented AVRT (that was successfully ablated) — nor subsequent detection after AVRT ablation, of documented AVNRT over the patient’s normal AV conduction pathway (that was also then successfully ablated) — was enough to resolve the cause of the frequent syncopal/seizure episodes.
- It wasn’t until runs of multiform PVCs were seen (ie, in Holter #2 and ECG #3) — which during hospital telemetry monitoring showed a clear relationship of increased frequency during physical activity, with complete cessation at rest — that the diagnosis of CPVT (Catecholaminergic Polymorphic VT) was made.
Hindsight is 100% in the “Retrospectoscope” …
- It’s easy to look back from the comfort of my office recliner chair — and comment on “what should have been done” (and when it should have been done). It is much more difficult to recognize this as it occurs (especially since finer details of today’s case are unknown to us).
- CPVT is a rare condition (estimated prevalence ~1:10,000, or less). I did not encounter a single case over the decades of my practice — and only now, in my volunteer role as an international ECG internet consultant do I encounter cases of CPVT as described to me by other clinicians. It’s easy not to think of CPVT — because most of us just do not see this condition. But as per Dr. Nossen — we need to be aware that this entity does exist — and that it should be thought of in younger individuals with a normal baseline ECG and no known heart disease, who report a distinct relationship between physical activity and/or emotional stress and their symptoms of palpitations or fainting.
- Today’s patient had multiple Holter monitors done over a period of years. As the one who read all Holter monitors for 35 providers over a period of 30 years (in my capacity as Attending at our Family Medicine Center) — the one “constant” in the numerous Holters I interpreted was the absence of a Patient Diary in over 90% of the Holters that I interpreted. It’s impossible to correlate symptoms with the occurrence of arrhythmias if no patient diary is filled out.
- Similarly, as a non-neurologist clinician — I was taught and routinely advised patients with seizures to keep a Seizure Diary. The reasons for doing so are that regular compliance with a seizure diary to include date, time, and duration of seizure activity — and especially what the patient was doing when the seizure occurred — is KEY to finding potential “triggers” of seizure activity, as well as providing feedback on whether treatment measures are effective.
- KEY Point: In today’s case, had an accurate seizure diary been kept — it might have prompted consideration of physical activity and/or emotional stress as the usual precipitant of seizure/syncopal episodes long before the 2 decades that this took to establish this relationship.
- NOTE: Distinction between seizure vs arrhythmia as the cause of episodes can be extremely difficult. That said — a Treadmill Stress Test in the office might have been diagnostic at a much earlier point in the course of today’s case once the role of physical activity as the primary precipitating factor was recognized.
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What then is BiDirectional VT?
As review — it’s good to be aware of the 4 basic types of VT (Ventricular Tachycardia) morphology: i) Monomorphic VT; ii) Polymorphic VT (PMVT) — which includes Torsades de Pointes; iii) Pleomorphic VT; and, iv) BiDirectional VT (BDVT). I review these terms in the June 1, 2020 post of Dr. Smith’s ECG Blog — and limit my comments here to BDVT:
- BiDirectional VT — was the KEY diagnostic feature of CPVT in today’s case. Of the above 4 morphologic forms of VT — BDVT is by far the least common. This rhythm is characterized by beat-to-beat alternation of the QRS axis. It distinguishes itself from PMVT and pleomorphic VT — because a consistent pattern (usually alternating long-short cycles) is seen throughout the VT episode. As implied in its name, there are 2 QRS morphologies in BiDirectional VT — and they typically alternate every-other-beat.
PEARL: It’s important to appreciate how difficult BiDirectional VT may be to recognize. This is because the rhythm is not common — the rate of this rhythm is usually rapid (so not easy to determine if P waves might be hiding within T waves or the wide QRS complexes) — and it is easy to mistake this rhythm for ventricular bigeminy or alternating bundle branch block. NOTE: When contemplating the diagnosis of BDVT — Consider one of the following conditions which are known to predispose to this arrhythmia:
- Digitalis toxicity
- Acute myocarditis
- Acute MI
- Hypokalemic periodic paralysis
- CPVT (Catecholaminergic PolyMorphic VT )
- Metastatic cardiac tumors
- Some types of Long QT Syndrome
- Herbal aconite poisoning
NOTE: In view of reduced use of Digoxin in recent years — CPVT is probably the most common cause of BiDirectional VT. As per Dr. Nossen — this familial cardiac arrhythmia is the result of gene mutation.
- The heart is structurally normal in patients with CPVT. As a result — the resting ECG tends to be normal.
- As per Dr. Nossen — Patients with CPVT are at high risk for malignant arrhythmias. Typically — these arrhythmias are induced by exercise or intense emotional states (ie, associated with increased catecholamine discharge).
- The mechanism for malignant arrhythmias with CPVT is a result of gene mutation. This leads to an increase in intracellular Ca++ concentration — which facilitates after-depolarizations and triggered arrhythmic activity — often beginning with multiple PVCs that evolve to BiDirectional VT. If this rhythm continues — BDVT has a disturbing tendency to deteriorate to VFib, which accounts for the high mortality of this condition if undiagnosed (Napolitano et al — Gene Reviews, 2022).
- Treatment of CPVT is aimed at suppressing excess adrenergic activity — which is why ß-blockers are the drug of choice for both acute and longterm treatment (Non-selective ß-blockers are preferred = nadolol, propranolol). If ß-blockers + the addition of flecainide fail to control episodes — an ICD is indicated.
- KEY Point: Competitive sports and/or other forms of strenuous exercise should be avoided!
- P.S.: As a result of its genetic inheritance — genetic counseling is advised!
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