Atrial fibrillation

9 Atrial fibrillation



Instruction


Examine this patient’s pulse.



Salient features



History




• Palpitations


• Pre-syncope, dizziness


• Fatigue


• Dyspnoea


• Asymptomatic and atrial fibrillation (AF) is discovered incidentally


• History of ischaemic heart disease, hypertension, valvular heart disease, rheumatic heart disease, chronic obstructive airway disease (COPD), congenital heart disease (atrial septal defect, ventricular septal defect), thyrotoxicosis (p. 506)


• History of consumption of caffeine, digitalis, theophylline.



Examination




• Irregularly irregular pulse (patients are often digitalized and in slow AF)


• Look for:


• malar flush (mitral stenosis)

• mitral valvotomy scar

• warm hands, goitre, pretibial myxoedema (thyrotoxicosis).

• Elevated JVP without ‘a’ waves


• Varying intensity of first heart sound (the intensity is inversely related to the previous RR cycle length; a longer cycle length produces a softer first heart sound)


• Pulse deficit, which is the difference between the rate of the apex and the pulse rate (because of varying stroke volumes resulting from varying periods of diastolic filling, not all ventricular beats produce a palpable peripheral pulse). The pulse deficit is greater when the ventricular rate is high


• If you are not sure tell the examiner that you would like to differentiate from ventricular ectopics by asking the patient to exercise: after exercise, ventricular ectopics diminish in frequency whereas there is no change in the rhythm of AF


• Look for the underlying cause:


• Examine the heart for mitral valvular lesion

• Check the BP for hypertension

• Ask the patient for history of ischaemic heart disease

• Check the patient’s thyroid status for thyrotoxicosis.

• Calculate the CHAD2 score (see below) to determine the eligibility for anticoagulation.



Diagnosis


This patient has fast atrial fibrillation (lesion), which is commonly caused by ischaemic heart disease (aetiology). The patient is short of breath, indicating that he may be in cardiac failure (functional status).



Questions




What are the components of the CHADS2 score?


Annual risk of stroke (adjusted stroke rate per 100 patient-years) in patients with AF is stratified by a score based on:



C, recent congestive heart failure


H, hypertension


A, age ≥75 years


D, diabetes


S, history of stroke or transient ischaemic attack (TIA).


The CHADS2 score is calculated by adding one point for each of the first four risk factors and two points for a history of previous stroke or TIA (JAMA 2001;285:2864–70). Patients with a CHADS score ≥2 and patients with rheumatic mitral stenosis should be managed with adjusted-dose warfarin to achieve an international normalized ratio (INR) of 2 to 3. At this intensity of anticoagulation, the annual risk of intracerebral haemorrhage is low: between 0.1% and 0.6%. For patients with a CHADS score of 1, anticoagulation with either aspirin or warfarin is reasonable. Patients with AF and no risk factors do not need anticoagulation. Opinion is divided about anticoagulation for those at intermediate risk (CHADS2 score 2 where stroke rate is 3–5% per year). Adjusted-dose oral anticoagulation is highly efficacious for prevention of all stroke (both ischaemic and haemorrhagic), with a risk reduction of 61% (95% confidence interval (CI), 47–71) versus placebo in randomized clinical trials. Aspirin offers only modest protection against stroke, a stroke reduction of 19% (95% CI, 2–34) (Ann Intern Med 1999;131:492–501).



What are the components of the bleeding risk index?


Scoring system for estimating risk of major bleeding related to warfarin (the bleeding risk index; J Gen Intern Med 2005;20:1008–13) gives points for the risk factors:



• Age >65 years: 1 point


• History of stroke: 1 point


• History of GI bleeding: 1 point


• Any, or several combined, of the following: 1 point:


• Diabetes mellitus

• Recent myocardial infarction

• Packed cell volume <30%

• Serum creatinine >1.5 mg/l.

The annual risk of stroke (based on points accrued) is then:



• low (0 points): 0.8%


• intermediate (1–2 points): 2.5%


• high (3–4 points): 10.6%



What are the common causes of atrial fibrillation?




• Mitral valvular disease in the young and middle aged


• Ischaemic heart disease or hypertension in the elderly


• Thyrotoxicosis (AF may be the only clinical feature in the elderly)


• Constrictive pericarditis


• Chronic pulmonary disease.



Mention common sites of systemic embolization


Brain, leg, kidney, superior mesenteric artery, coronary artery and spleen.



At the bedside how would you differentiate atrial fibrillation from multiple ventricular ectopics?


If the patient is not in heart failure, exercise the patient: ventricular ectopics after exercise tend to diminish in frequency whereas there is no change in the rhythm of AF.



How would you investigate this patient?




• ECG shows absent P waves. Fibrillatory or ‘f’ waves are present at a rate that may vary between 350 and 600 beats/min and the ‘f’ waves vary in shape, amplitude and intervals. The RR interval is irregularly irregular. Narrow QRS complex with varying RR interval (irregular unless there is an underlying ventricular conduction defect). It should be differentiated from sinus arrhythmia (Figs 9.1 and 9.2).


• Echocardiogram (transthoracic and transoesophageal) is useful to determine left atrial size and left ventricular systolic function, and to exclude underlying valvular heart disease and intracardiac thromboemboli. Transoesophageal echocardiography prior to cardioversion.


• Test of thyroid function to exclude thyrotoxicosis.


• Exercise treadmill will identify AF precipitated by exercise.


• Holter monitor is useful in paroxysmal AF to determine whether it was triggered by another arrhythmia, such as when a premature atrial complex during a rapid paroxysmal atrial tachycardia may cause the immediate onset of AF.

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Dec 4, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Atrial fibrillation

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