Idiopathic ventricular fibrillation is a potentially fatal disease whose incidence is now declining, as underlying primary arrhythmia syndromes like long and short QT syndrome, Brugada syndrome, early repolarization syndrome and catecholaminergic polymorphic ventricular tachycardia are actively diagnosed in the present days. This condition is diagnosed when all primary arrhythmias listed above are excluded.
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 , suggesting a possible relationship with the enhanced adrenergic tone during the morning . Nocturnal episodes are encountered in patients with early repolarization . Patients with recurrent arrhythmic incidents can be suspected of coronary spasms .
Affected individuals are usually male , 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.
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   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 , procainamide , disopyramide  or flecainide  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 , despite the fact that a minority of idiopathic ventricular fibrillation patients have a sudden death family history .
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 . The QT segment can be relatively short, but not short enough to meet the short QT syndrome criteria . The Tpeak-Tend interval, a marker of arrhythmic risk, is normal . 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 . 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 , usually located in the Purkinje network and rarely in the right ventricular outflow tract.
Idiopathic ventricular fibrillation patients should receive an implantable cardiac defibrillator because the arrhythmia is very likely to occur again (11-45 of cases) . The physician should, however, keep in mind that patients may experience inappropriate shocks and inform them . 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 . 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 . The most potent beta-blocker a physician can use while trying to suppress an electrical idiopathic ventricular fibrillation storm is propranolol . 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 .
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 . 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 . 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 . 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 . 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 . 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 , 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  . 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 .
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.