Causes of AF- pathophysiology and signs + symptoms

The principle of AFà any condition resulting in raised artrial pressure, increased atrial muscle mass, atrial fibrosis or inflammation and infiltration of the atrium may cause AF.
This includes systemic causes as well.

Cardiac and non-cardiac causes:-
Hypertension
Congestive heart failure
Coronary artery disease and myocardial infarction
Valvular heart disease
Cardiomyopathy: dilated, hypertrophic
Myocarditis and pericarditis
Wolff-Parkinson-White syndrome
Sick sinus syndrome
Cardiac tumours
Cardiac surgery
Familial tachyarrhythmia
(e.g. lone atrial fibrillation)
Thyrotoxicosis
Phaeochromocytoma
Acute and chronic pulmonary disease (pneumonia, chronic obstructive pulmonary disease)
Pulmonary vascular disease (pulmonary embolism)
Electrolyte disturbances (hypokalaemia)
Increased sympathetic tone (exercise, adrenergically mediated arrhythmia)
Increased parasympathetic tone (vagally induced and postprandial arrhythmia)
Alcohol abuse ('holiday heart' and long-term use)
Caffeine, smoking, recreational drug use

à Multiple re-entrant waveforms within the atria bombard the A V node, which becomes relatively refractive to conduction due to the frequency of upstream electrical activity. The AV node is continuously bombardedwith depolarization wavesof varying strength and depolarization spreads at irregular intervals down to the Bundle of His. (ALL OR NOTHING)How re-entrant waveforms occur? 3 mechanisms initiating and maintaining AF;àEnhanced automaticity in the left atrium extending to proximal portion of the pulmonary veins.à Electrical remodeling of the atria with resultant shortening of the atrial refractory period increases the duration and stability of AF. ‘AF begets AF’à In chronic AF, areas of functional conduction block further divide and maintain persistently chaotic electrical state.

AF occurs in 3 distinct clinical circumstances:àAs a primary arrhythmia in the absence of identifiable structural heart disease àAs a secondary arrhythmia in the absence of structural heart disease but in the presence of a systemic abnormality that predisposes the individual to the arrhythmia àAs a secondary arrhythmia associated with cardiac disease that affects the atria
3 Primary ways AF affects haemodynamic function include;- loss of atrial kick (synchronized atrial mechanical activity)- Irregularity of ventricular response- Inappropriate rapid heart rate.


Clinical Presentation
à Symptoms can be variable. About 30% patients are found to have AF incidentally with other findings.Usual complaintsà Palpitations, fatigue/ poor exercise tolerance, dyspnoea, chest pain, presyncope and generalized weakness.

àPhysical findingsà Pulse- Irregularly irregular rhythm.àHypotension and poor perfusionà caused by decrease in atrial filling pressures and decrease in stroke volumeà rate related or lack of normal atrial kick.à Congestive heart failure if presentà indicated by rales, jugular distension, peripheral oedema and a gallop due to rapid rate.à sign of embolization, including TIA, stroke and peripheral arterial embolization.