Atrial Fibrillation Case Study

(5) Atrial fibrillation

The rate of atrial fibrillation is 10-15% among patients who have AMIs. The presence of atrial fibrillation during an AMI is associated with an increased risk of mortality and stroke, particularly in patients who have anterior-wall MI (Ashok et al. 2011).

AF develops for many different reasons, including left ventricular dys-function with hemodynamic impairment (Kobayashi et al., 1992), atrial is-chemia or infarction (particularly in patients with early onset atrial fibrilla-tion in the course of acute myocardial infarction), right ventricular infarction (Rechavia et al., 1992), pericarditis, excessive release of catecholamines. Atrial fibrillation is usually abrupt in onset and can cause rapid hemody-namic instability through one of three mechanisms: loss of the atrial com-ponent of the cardiac output, increased ventricular response rate with de-creased diastolic filling time, or irregular ventricular filling (Cristal et al., 1976).

Flugelman et al, found that atrial fibrillation has been associated with advanced age, congestive heart failure, poor left ventricular function and ex-tensive myocardial infarction (Flugelman et al., 1986).

The occurrence of atrial fibrillation is not related to the site of the my-ocardial infarct the relation of atrial fibrillation to outcome has been exten-sively investigated, and it is commonly considered a marker of poor prog-nosis (Liberthson et al.,

1976).

- In-hospital outcomes of AF
In-hospital death, early and late clinical congestive heart failure, sus-tained ventricular tachycardia, and ventricular fibrillation all occurred more often in patients with atrial fibrillation than in those without (P < 0.001).No significant difference was observed in reinfarction rate. The to-tal hospital stay in patients discharged alive was significantly longer for those with atrial fibrillation than for those without (p < 0.0001) (Pizzetti et al., 2001).

- Independent predictors of atrial fibrillation
According to Pizzetti et al, The most important predictor of atrial fi-brillation was age > 70 years .Other significant factors (in decreasing or-der) were raised heart rate at entry (> 100 beats/min), Killip class above 1 and a history of hypertension (Pizzetti et al., 2001).

B- Ventricular Arrhythmias
Ventricular arrhythmia is a common complication of acute MI, occur-ring in almost all patients, even before monitoring is possible. It is related to the formation of re-entry circuits at the confluence of the necrotic and viable myocardium. Premature ventricular contractions (PVCs) occur in approxi-mately 90% of patients. The incidence of ventricular fibrillation is approx-imately 2% to 4% (Sorin and David, 2011).
Mortality in the immediate postinfarction period, as well as during the first year after myocardial infarction, is most often due to sudden death from ventricular fibrillation (Campbell et al., 1981).

(1) Premature ventricular contractions
In the past, frequent premature ventricular contractions (PVCs) were considered to represent warning arrhythmias and indicators of impending malignant ventricular arrhythmias. However, presumed warning arrhythmi-as are frequently observed in patients who have an acute myocardial infarc-tion (AMI) and who never develop ventricular fibrillation. On the converse, primary ventricular fibrillation often occurs without antecedent premature ventricular ectopy. For these reasons, prophylactic suppression of PVCs with antiarrhythmic drugs, such as lidocaine, is no longer recommended. Prophylaxis has been associated