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Primary ventricular fibrillation is an unpredictable ^[1] and potentially fatal arrhythmia occurring during the acute phase of a myocardial infarction leading to immediate collapse and, if left untreated, leads to sudden cardiac death within the first minutes. In the developed countries primary ventricular fibrillation is a leading cause of death. [1] World wide the annual number of deaths caused by primary ventricular fibrillation might be comparable to the number of death caused by road traffic accidents.^[2] A substantial proportion of these deaths can be avoided by seeking immediate medial attendance during symptoms of acute myocardial infarction. [2] If treated promptly, most patients have a life expectancy comparable to that of other patients without this complication during myocardial infarction.

Contents 1 Definition 2 Incidence 3 Risk factors 4 Mechanisms 5 Survival 6 Prognosis 7 References 8 External links

[edit] Definition

It is traditionally defined as ventricular fibrillation during a clinically uncomplicated acute myocardial infarction. More specifically the term primary refers to the absence of clinical heart failure or shock preceding the onset of ventricular fibrillation. Consequently, the term secondary ventricular fibrillation refers to ventricular fibrillation complicating heart failure or shock during the acute phase of myocardial infarction.

[edit] Incidence

Approximately 10 % of all myocardial infarctions are complicated by primary ventricular fibrillation. [3] The incidence peaks between 20 and 50 minutes after the onset of the acute myocardial infarction. With the current delays in seeking medical attendance for acute myocardial infarction two thirds (2/3) of the primary ventricular fibrillations occur before medical attendance and of these medically unattended events 2/3 occur after more than 30 minutes of warning symptoms of acute myocardial infarction. [4]

[edit] Risk factors

The risk for ventricular fibrillation during acute myocardial infarction not complicated by heart failure or shock is related to the magnitude of ST elevation, the presence of (mild) hypopotassemia, the absence of pre-infarction angina, the size of the infarction and the presence of an occlusion in the left coronary artery. Other risk factors, with moderate evidence include: younger age, male gender, first degree relatives with sudden death and probably some specific forms of warning ventricular arrhythmias.^[1]

[edit] Mechanisms

The multiplicity of ischemia related factors is rather overwhelming^{[3][4][4][5][6]} including depletion of adenosine triphosphate, acidosis, extracellular accumulation of potassium ion, intracellular accumulation of calcium and sodium ions, cell-to-cell uncoupling, generation of free radicals, increased level of plasma free fatty acid concentrations, release of catecholamines, reduced excitability, abbreviation of action potential duration, and altered mechanical properties of the ischemic tissue. In humans it is currently not possible to target any of these experimental parameters in order to manage or prevent ventricular fibrillation during myocardial ischemia or infarction.

[edit] Survival

The survival of PVF largely depends on the immediate presence or absence of an external defibrillator and the promptness of the defibrillation. The success rate of prompt defibrillation during monitoring is currently higher than 95%.^[7] The success rate of defibrillation decreases dramatically for each minute of delay to defibrillation, estimated -10% per minute.

[edit] Prognosis

After return of spontaneous circulation the hospital course is further characterized by a moderately higher risk of death compared to patients without PVF (relative risk from 1.0 to 2.8.) Whether this still hold true with most recent treatment strategies (earlier hospital admission and immediate angioplasty with thrombus aspiration) is unknown. PVF does not affect the long-term prognosis. Among those who survived the hospital admission the reported one year mortality rates of patients with PVF (3%^[8] , 4.1% ^[9] and 8%^[10] are not higher than the mortality rates of those without PVF in the respectively reference groups. More recently, for 339 consecutive patients with PVF during AMI treated by defibrillation followed by primary angioplasty the survival rate after 30 days with a mean follow up of 3.7 years was 94% comparable to controls (with comparable age, gender and infarction size) of which 92 % survived. ^[11]

[edit] References

1. ^ ^{a b} Gheeraert PJ, De Buyzere ML, Taeymans YM, Gillebert TC, Henriques JP, De Backer G, De Bacquer D (2006). "Risk factors for primary ventricular fibrillation during acute myocardial infarction: a systematic review and meta-analysis". Eur Heart J 27 (21): 2499–510. PMID 16952926. 
2. ^ Mathers CD, Loncar D. (2006). "Projections of global mortality and burden of disease from 2002 to 2030". PLoS Med 3 (11): e442. PMID 17132052. 
3. ^ Yan GX, Joshi A, Guo D, Hlaing T, Martin J, Xu X, Kowey PR (2004). "Phase 2 reentry as a trigger to initiate ventricular fibrillation during early acute myocardial ischemia.". Circulation 110 (9): 1036–41. PMID 15302777. 
4. ^ ^{a b} Luqman N, Sung RJ, Wang CL, Kuo CT (2007). "Myocardial ischemia and ventricular fibrillation: pathophysiology and clinical implications". Int J Cardiol 119: 283–290. PMID 17166606. 
5. ^ Clements-Jewery H, Hearse DJ, Curtis MJ. (2005). "Phase 2 ventricular arrhythmias in acute myocardial infarction: a neglected target for therapeutic antiarrhythmic drug development and for safety pharmacology evaluation.". Br J Pharmacol 145 (5): 551–64. PMID 15852034. 
6. ^ Carmeliet E (1999). "Cardiac ionic currents and acute ischemia: from channels to arrhythmias.". Physiol Rev. 79 (3): 917–1017. PMID 10390520. 
7. ^ Volpi A, Cavalli A, Santoro L, Negri E (1998). "Incidence and prognosis of early primary ventricular fibrillation in acute myocardial infarction--results of the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI-2) database.". Am J Cardiol 82 (3): 265–71. 
8. ^ Behar S, Goldbourt U, Reicher-Reiss H, Kaplinsky E. (1990). "Prognosis of acute myocardial infarction complicated by primary ventricular fibrillation. Principal Investigators of the SPRINT Study.". Am J Cardiol 66 (17): 1208–11. PMID 2239724. 
9. ^ Volpi A, Cavalli A, Franzosi MG, Maggioni A, Mauri F, Santoro E, Tognoni G (1989). "One-year prognosis of primary ventricular fibrillation complicating acute myocardial infarction. The GISSI (Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto miocardico) investigators". Am J Cardiol 63 (17): 1174–8. 
10. ^ Nicod P, Gilpin E, Dittrich H, Wright M, Engler R, Rittlemeyer J, Henning H, Ross J (1988). ". Late clinical outcome in patients with early ventricular fibrillation after myocardial infarction". J Am Coll Cardiol 11 (3): 464–470. PMID 3343451. 
11. ^ de Jong JS, Wilde AA, Henriques JP, Dekker LR (2006). "Long Term Survival after First Myocardial Infarction is not Determined by the Occurrence of Ventricular Fibrillation in the Acute Phase but Family History for Sudden Death is Detrimental.". Circulation 114 II: Abstract. 

[edit] External links

• Research on Primary Ventricular Fibrillation during Acute Myocardial Infarction