Idiopathic ventricular fibrillation presentation is variable. The arrhythmic episode can initially cause symptoms like palpitations and light-headedness- due to insufficient cerebral blood flow. It can be triggered by fever, as high body temperature normally raises the heart rate and diminishes the QT interval. However, the presence of fever is not mandatory, episodes can occur at rest, during exercise or while driving. Most episodes occur during daytime, especially during the morning, from 7.00 to 11.00 AM [1], suggesting a possible relationship with the enhanced adrenergic tone during the morning [2]. Nocturnal episodes are encountered in patients with early repolarization [3]. Patients with recurrent arrhythmic incidents can be suspected of coronary spasms [4].

Affected individuals are usually male [5], younger than their peers with ventricular fibrillation attributed to other causes and have a normal left ventricular ejection fraction.

Idiopathic ventricular fibrillation is characterized by its early adulthood onset. Arrhythmic storms are frequent in these patients and ventricular fibrillation episodes tend to organize into clusters. Programmed ventricular stimulation effectively reproduces the episode and quinidine administration is followed by a prompt response.

• Fatigue

  […] traumatic brain injury, brain hypoxia (inadequate oxygen, possibly due to a brain infarction or cardiac arrest), severe poisoning with drugs that depress the activity of the central nervous system (e.g., alcohol and other hypnotic or sedative drugs), severe fatigue [en.wikipedia.org]

  Symptoms include palpitations, fatigue, dyspnea, dizziness and presyncope. Syncope and sudden death are very rare. Most of the episodes occur at rest, although can be triggered by exercise and emotional stress. [escardio.org]

• Tremor

  This pattern of electrical tremor generally evolves over time (over a period of a few seconds to several minutes) with, in the absence of treatment, progression from a tracing with high amplitude oscillations to a tracing with low amplitude signals which [cardiocases.com]

  GJB3 603324 Erythrokeratodermia variabilis GJB4 605425 Fabry, ziekte van GLA 300644 Familiair boezem fibrilleren KCNQ1 607542 Fenylketonurie (PKU) PAH 612349 Floating-Harbor Syndroom SRCAP 611421 Fragiele X syndroom FMR1 309550 Fragiele-X geassocieerd tremor [dnadiagnostiek.nl]

The key to establishing the idiopathic ventricular fibrillation diagnosis is excluding the possible causes of other types of ventricular fibrillation. To this aim, blood workup should include thyroid function assessment, electrolyte panel- sodium, potassium, calcium and magnesium and cardiac enzymes- the MB fraction of creatine kinase and troponin I, as well as toxicological screening.

Required imaging methods include an electrocardiogram, echocardiogram, Holter monitoring, stress tests, coronary angiography and magnetic resonance imaging, all especially useful when cardiac ischemia is suspected. Coronary computed tomography and magnetic resonance angiography are recommended when ischemia is less plausible [6] [7] because, in contrast to a classical coronary angiogram, they only provide diagnosis information and do not have curative potential.

Stress tests are based on physical exercise or on pharmacological stimulation using ergonovine or acetylcholine, that can trigger a coronary spasm. Brugada syndrome is excluded by ajmaline [8], procainamide [9], disopyramide [10] or flecainide [11] administration. Endomyocardial biopsy is needed when myocarditis, cardiac tumors, cardiomyopathies or right ventricular dysplasia are suspected and electrophysiological testing can detect accessory pathways.

Certain concealed primary arrhythmia syndromes have a genetic basis, therefore targeted genetic screening can be performed in selected individuals [12], despite the fact that a minority of idiopathic ventricular fibrillation patients have a sudden death family history [13].

Long QT syndrome can be diagnosed using epinephrine with adequate sensitivity and specificity, but false positive results are to be feared [14].

An electrophysiological study is more likely to reproduce the ventricular arrhythmia if shout coupling intervals are used. Stimuli should be applied on the upslope of the T wave, on the peak or on the early segment of the downslope. The sinus rhythm electrocardiogram is either normal in idiopathic ventricular fibrillation patients or J-point elevation in the inferior leads can be observed [15]. The QT segment can be relatively short, but not short enough to meet the short QT syndrome criteria [16]. The Tpeak-Tend interval, a marker of arrhythmic risk, is normal [16]. Premature ventricular contractions that are closely coupled with the previous QRS complex can occur.

Other electrophysiological parameters, such as the A-H and H-V intervals and ventricular refractory periods are normal [17]. When the study is successful in inducing a ventricular arrhythmia, it is always polymorphic tachycardia or fibrillation. Furthermore, this procedure coupled with endocardial recordings can pinpoint the site of origin of the ventricular arrhythmia [18], usually located in the Purkinje network and rarely in the right ventricular outflow tract.

• Wide QRS Complex

  Mont L. et al: A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 83:1649, 1991. ‎ [books.google.es]

  A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 1991;83:1649-59. 16.- Ohe T, Aihara N, Kamakura S, et al. [escardio.org]

• Right Bundle Branch Block

  Only three patients (8%, group II) showed (in)complete right bundle branch block and > or =2 mm ST-segment elevation. [ncbi.nlm.nih.gov]

  Ajmaline unmasks right bundle branch block-like and ST segment elevation in V1–V3 in patients with idiopathic ventricular fibrillation. PACE 19, 599 (1996). 11 Miyanuma, H., Sakurai, M. & Odaka, H. [nature.com]

  This condition can also represent an unrecognized Brugada syndrome, in cases where the electrocardiogram presents a right bundle branch block with persistent ST-segment elevation in the right precordial leads or congenital short QT syndrome. [symptoma.com]

  Radiofrequency catheter ablationof idiopathic recurrent ventricular tachycardia with right bundle branch block, left axis morphology. Pacing Clin Electrophysiol 1993;16:327-36. [escardio.org]

• Abnormal ECG

  However, in contrast to previous studies reporting categories of IVF patients with abnormal ECGs or with VF triggers, we included exclusively those rare patients with IVF in whom the 12-lead ECG continued to be normal over a long-term follow-up, without [academic.oup.com]

Idiopathic ventricular fibrillation patients should receive an implantable cardiac defibrillator because the arrhythmia is very likely to occur again (11-45 of cases) [19]. The physician should, however, keep in mind that patients may experience inappropriate shocks and inform them [20]. Inappropriate shocks usually occur in the presence of atrial fibrillation. The cardioverter-defibrillator may remain silent for long periods of time, making the decision to replace or remove it difficult at times. Still, a cardiac defibrillator is to this date considered the most effective therapy for preventing arrhythmic death in idiopathic ventricular fibrillation patients. Moreover, it does not entail the potentially severe adverse effects of antiarrhythmic drugs.

Pharmacological therapy may prove useful because a cardioverter-defibrillator terminates episodes of idiopathic ventricular fibrillation, but does not prevent arrhythmias. However, drug administration should not represent the only therapeutic measure because of the high recurrence rate of the arrhythmia in this instance. Amiodarone, beta-blockers, and verapamil do not decrease the recurrence rate [21]. On the other hand, quinidine has proven much more effective. Quinidine should not be recommended to non-inducible patients, as they require an implantable cardioverter.

Amiodarone is useful during the acute episode. When administered by intravenous route, it blocks fast sodium channels, L-type calcium channels and inhibits norepinephrine release. Oral administration is suited for the long term, being able to prevent recurrent implantable cardioverter- defibrillator shocks [22]. The most potent beta-blocker a physician can use while trying to suppress an electrical idiopathic ventricular fibrillation storm is propranolol [23]. It effectively decreases sympathetic outflow and blocks the central and pre-junctional receptors.

Finally, radiofrequency catheter ablation is another safe end effective therapeutic measure. The procedure allows detection of the site of origin of the premature ventricular contractions and its ablation. It is also suited for patients receiving multiple cardioverter-defibrillator shocks [24].

Idiopathic ventricular fibrillation patients that have a normal electrocardiogram pattern outside the acute episode have a good 7-year prognosis. However, their lifelong prognosis requires additional studies, therefore the physician should recommend a cardioverter- defibrillator implant, according to current guidelines. Patients that have a history of supraventricular arrhythmias, atrioventricular conduction disease or sinus node dysfunction should receive a dual chamber device. Prior to the implant, an electrophysiological study should be carried out in order to evaluate the inducibility of sustained ventricular tachycardia and/or supraventricular tachycardia. Drugs can alter the electrocardiogram pattern, thus modifying the prognosis. 39% of patients without a Brugada syndrome pattern have recurrent ventricular fibrillation during a 3 year follow up if left untreated [25]. The prognosis is considered to be worse if the electrocardiogram exhibits an early repolarization pattern.

Idiopathic ventricular fibrillation is considered to be initialized by ventricular premature contractions with R-on-T phenomenon, originating in the Purkinje network [26]. This condition can also represent an unrecognized Brugada syndrome, in cases where the electrocardiogram presents a right bundle branch block with persistent ST-segment elevation in the right precordial leads [27] or congenital short QT syndrome [28]. Short QT syndrome individuals have spontaneous and inducible ventricular fibrillation episodes, very similar to those of true idiopathic ventricular fibrillation patients.

From a genetic point of view, this disease may be monogenic, polygenic or multifactorial [29]. Electrolyte disturbances or ischemic myocytes can trigger the arrhythmia in genetically predisposed patients.

Different studies report very different figures regarding idiopathic ventricular fibrillation epidemiology. Numbers range from 1.2% to 9% of sudden cardiac death not related to acute coronary syndrome survivors. Appropriate diagnosis methods may not be available in certain centers, thus including some cases of primary congenital arrhythmia in the idiopathic ventricular fibrillation category.

Idiopathic ventricular fibrillation originates from a well-determined locus in the Purkinje network and is initiated by premature ectopic contractions that generate reentrant ventricular fibrillation. Some researchers took this idea further, stating that this condition represents a focal ventricular fibrillation [30]. It is yet unknown why these very premature ectopic beats occur, but it is possible to demonstrate their existence by intracardiac recordings and radiofrequency ablation can be attempted.

From a genetic point of view, several hypotheses exist. Different patients may suffer from different mutations, all leading to the same result. Idiopathic ventricular fibrillation may have a monogenic [31], a polygenic or a multifactorial origin. Factors that can contribute to the multifactorial process include electrolyte disturbances or localized ischemia. Genes that seem to be involved include IRX3, RyR2, CALM1, and DPP6 [32] [31]. Another possibility is that this condition is caused by the accumulation of several mutations to the cell’s deoxynucleic acid. The activity of the potassium channel in the myocyte membrane seems to be disturbed in idiopathic ventricular fibrillation, explaining the occurrence of short-coupled ventricular premature contractions [33].

Primary prevention is not applicable to idiopathic ventricular fibrillation, but once the diagnosis is established, subsequent arrhythmic events are effectively prevented by an implantable cardioverter- defibrillator. Antiarrhythmic therapy can also be used in order to decrease the number of arrhythmic episodes and therefore the discomfort associated with shocks. Still, the cardioverter-defibrillator is considered more effective than drugs in death prevention in these patients.

Idiopathic ventricular fibrillation represents a rare type of arrhythmia, occurring in young men in whom demonstration of other inborn types of arrhythmia has failed. Initial symptoms include light-headedness and palpitations that occur at rest or during exercise and can be followed by consciousness loss. Affected individuals may have underlying genetic mutations, but in some patients, they only become apparent when associated with other factors, such as fever or electrolyte disturbances. The electrocardiogram, echocardiogram, Holter monitoring, stress tests (with ergonovine, ajmaline or acetylcholine), coronary angiography and magnetic resonance imaging should be performed in order to exclude other arrhythmias and the presence of heart ischemia. An electrophysiological study can reproduce the arrhythmia and guide radiofrequency ablation, but the most effective proven therapy is represented by a cardioverter- defibrillator implant. Antiarrhythmic drugs may decrease the number of heart rhythm disturbances and inappropriate shocks. Quinidine has proven much more effective than amiodarone, beta-blockers, and verapamil.

Idiopathic ventricular fibrillation is a rare disease affecting men more often than women. Patients experience palpitations and light-headedness at rest or during exercise and then lose their consciousness and die if help is not promptly available. The diagnosis is established using many types of tests, including an electrocardiogram, 24-hour heart rhythm monitoring, and stress tests- that is, the heart of the individual suspected to suffer from idiopathic ventricular fibrillation is observed after certain kinds of substances that make it beat faster are injected. The physician will also perform an echocardiogram, allowing him or her to rule out morphological abnormalities and may also order an electrophysiological test. This method precisely detects which part of the heart triggers the arrhythmia.

Every patient suffering from this condition should receive an implantable cardioverter- defibrillator. This device is implanted under the skin and has an electrode that is implanted inside the heart. It detects when ulterior arrhythmia episodes occur and provides a shock to the myocardium, thus terminating the episode. Certain drugs, quinidine, in particular, are used in order to decrease the number of arrhythmic episodes.

1. Bagai A, McNally BF, Al-Khatib SM, et al. . Temporal differences in out-of-hospital cardiac arrest incidence and survival. Circulation 2013;128:2595–602.
2. Muller JE, Ludmer PL, Willich SN, et al. . Circadian variation in the frequency of sudden cardiac death. Circulation 1997;1:131–8.
3. Aizawa Y, Sato M, Ohno S, et al. . Circadian pattern of fibrillatory events in non-Brugada type idiopathic ventricular fibrillation with a focus on J waves. Heart Rhythm 2014;11:2261–6.
4. Chevalier P, Dacosta A, Defaye P, et al. . Arrhythmic cardiac arrest due to isolated coronary artery spasm: long-term outcome of seven resuscitated patients. J Am Coll Cardiol 1998;31:57–61.
5. Sekiguchi Y, Aonuma K, Takagi M, Aihara N, Yokoyama Y, Hiraoka M. New clinical and electrocardiographic classification in patients with idiopathic ventricular fibrillation. J Cardiovasc Electrophysiol 2013;24:902–8.
6. Miller JM, Rochitte CE, Dewey M, et al. Diagnostic performance of coronary angiography by 64-row CT. N Engl J Med. 2008;359:2324–36.
7. Meijboom WB, Meijs MF, Schuijf JD, et al. Diagnostic accuracy of 64-slice computed tomography coronary angiography: a prospective, multicenter, multivendor study. J Am Coll Cardiol. 2008;52:2135–2144.
8. Hong K, Brugada J, Oliva A, et al. Value of electrocardiographic parameters and ajmaline test in the diagnosis of Brugada syndrome caused by SCN5A mutations. See comment in PubMed Commons below Circulation 2004;110: 3023-7.
9. Sangwatanaroj S, Prechawat S, Sunsaneewitayakul B, et al. New electrocardiographic leads and the procainamide test for the detection of the Brugada sign in sudden unexplained death syndrome survivors and their relatives. See comment in PubMed Commons below Eur Heart J 2001;22: 2290-6.
10. Chinushi M, Aizawa Y, Ogawa Y, Shiba M, Takahashi K. Discrepant drug action of disopyramide on ECG abnormalities and induction of ventricular arrhythmias in a patient with Brugada syndrome. See comment in PubMed Commons below J Electrocardiol 1997;30: 133-6.
11. Meregalli PG, Ruijter JM, Hofman N, et al. Diagnostic value of flecainide testing in unmasking SCN5A-related Brugada syndrome. J Cardiovasc Electrophysiol 2006;17: 857-64.
12. Priori SG, Wilde AA, Horie M, HRS/EHRA/APHRS expert consensus statement on the diagnosis and management of patients with inherited primary arrhythmia syndromes: document endorsed by HRS, EHRA, and APHRS in May 2013 and by ACCF, AHA, PACES, and AEPC in June 2013. Heart Rhythm. 2013;10:1932–63.
13. Pasquie JL, Sanders P, Hocini M, et al. Fever as a precipitant of idiopathic ventricular fibrillation in patients with normal hearts. See comment in PubMed Commons below J Cardiovasc Electrophysiol 2004;15: 1271-6.
14. Magnano AR, Talathoti N, Hallur R, Bloomfield DM, Garan H. Sympathomimetic infusion and cardiac repolarization: the normative effects of epinephrine and isoproterenol in healthy subjects. J Cardiovasc Electrophysiol. 2006;17:983–9.
15. Takagi M, Aihara N, Takaki H, et al. Clinical characteristics of patients with spontaneous or inducible ventricular fibrillation without apparent heart disease presenting with J wave and ST segment elevation in inferior leads. See comment in PubMed Commons below J Cardiovasc Electrophysiol 2000;11: 844-8.
16. Viskin S, Zeltser D, Ish-Shalom M, et al. Is idiopathic ventricular fibrillation a short QT syndrome? Comparison of QT intervals of patients with idiopathic ventricular fibrillation and healthy controls. Heart Rhythm 2004;1: 587-91.
17. Belhassen B, Viskin S, Fish R, et al. Effects of electrophysiologic-guided therapy with Class IA antiarrhythmic drugs on the long-term outcome of patients with idiopathic ventricular fibrillation with or without the Brugada syndrome. See comment in PubMed Commons below J Cardiovasc Electrophysiol 1999;10: 1301-12.
18. Haissaguerre M, Shoda M, Jais P,et al. Mapping and ablation of idiopathic ventricular fibrillation. Circulation 2002;106: 962-7.
19. Ozaydin M, Moazzami K, Kalantarian S, Long-Term Outcome of Patients With Idiopathic Ventricular Fibrillation: A Meta-Analysis. J Cardiovasc Electrophysiol. 2015;26:1095–1104.
20. Herman AR, Cheung C, Gerull B, et al. Outcome of apparently unexplained cardiac arrest: results from investigation and follow-up of the prospective cardiac arrest survivors with preserved ejection fraction registry. Circ Arrhythm Electrophysiol. 2016;9:e003619.
21. Viskin S, Belhassen B. Idiopathic ventricular fibrillation. Am Heart J 1990;120: 661-71.
22. Vassallo P, Trohman RG. Prescribing amiodarone: an evidence-based review of clinical indications. JAMA 2007;298: 1312-22.
23. Tsagalou EP, Kanakakis J, Rokas S, Anastasiou-Nana MI. Suppression by propranolol and amiodarone of an electrical storm refractory to metoprolol and amiodarone. Int J Cardiol 2005;99: 341-2.
24. Mok NS, Chan NY, Chiu AC Successful use of quinidine in treatment of electrical storm in Brugada syndrome. Pacing Clin Electrophysiol 2004;27: 821-3.
25. Champagne J, Geelen P, Philippon F, Brugada P. Recurrent cardiac events in patients with idiopathic ventricular fibrillation, excluding patients with the Brugada syndrome. BMC Medicine 2005;3:1
26. Haissaguerre M, Extramiana F, Hocini M, et al. Mapping and ablation of ventricular fibrillation associated with long-QT and Brugada syndromes. Circulation 2003;108: 925-8.
27. Brugada P, Brugada J. Right bundle branch block, persistent ST segment elevation and sudden cardiac death: a distinct clinical and electrocardiographic syndrome. A multicenter report. J Am Coll Cardiol 1992;20: 1391-6.
28. Gaita F, Giustetto C, Bianchi F, et al. Short QT Syndrome: a familial cause of sudden death. Circulation 2003;108: 965-70.
29. Alders M, Koopmann TT, Christiaans I, et al. Haplotype-sharing analysis implicates chromosome 7q36 harboring DPP6 in familial idiopathic ventricular fibrillation. Am J Hum Genet. 2009;84:468–76.
30. Haissaguerre M, Shah DC, Jais P, et al. Role of Purkinje conducting system in triggering of idiopathic ventricular fibrillation. Lancet 2002;359: 677-8.
31. Cheung JW, Meli AC, Xie W, et al Short-coupled polymorphic ventricular tachycardia at rest linked to a novel ryanodine receptor (RyR2) mutation: leaky RyR2 channels under non-stress conditions. Int J Cardiol. 2015;180:228–36.
32. Alders M, Koopmann TT, Christiaans I, et al. Haplotype-sharing analysis implicates chromosome 7q36 harboring DPP6 in familial idiopathic ventricular fibrillation. Am J Hum Genet. 2009;84:468–76.
33. Xiao L, Koopmann TT, Ördög B, et al. Unique cardiac Purkinje fiber transient outward current β-subunit composition: a potential molecular link to idiopathic ventricular fibrillation. Circ Res. 2013;112:1310–22.