1. Field of the Invention
The present invention relates to a heart monitor and more particularly but not solely to a heart monitor for use as a non-invasive screening tool for identifying potential atrial fibrillation in patients.
2. Related Background Art
In a healthy person the heartbeat is tightly regulated by waves of electrical activity that cause the co-ordinated contraction of the heart muscles. Electrical impulses are generated in the sinu-atrial node in the right atrium of the heart and travel to the atrioventricular node. The pulses then travel through the Bundle of “His” and down the left and right Bundle branches, causing the ventricles to beat rhythmically.
In a person with atrial fibrillation the electrical impulses are no longer generated in the sinu-atrial node but have shifted to some other area of the heart and travel continuously around the left and right atria. This means that they arrive at the atrioventricular node unpredictably with the result that the ventricles beat but with beats which are irregularly irregular.
Chronic atrial fibrillation is the commonest arrhythmia (abnormal heart rhythm) seen in medical practice. It causes an increased morbidity and mortality and adds significantly to the burden of health care costs. The prevalence of atrial fibrillation increases with age (0.5% of those aged 50-59 years to 8.8% of those aged 80-89), as do the associated risks.
There is a six-fold increase of thromboembolic phenomena in those with atrial fibrillation. Atrial fibrillation also accounts for 33% of strokes in elderly people. In an ageing population there will be a greater incidence of stroke and, therefore, an increase in the associated social and health-care costs.
In General Practice, patients with atrial fibrillation show symptoms of breathlessness, palpitations and fatigue as a result of reduced cardiac output. Heart failure may develop. Reversal of the atrial fibrillation to sinus rhythm will alleviate the symptoms.
Once diagnosed, treatment for atrial fibrillation is low-cost and highly effective. For example, prescribing a particular kind of drug can reduce the risk of stroke in atrial fibrillation sufferers by 70%. However, atrial fibrillation cannot be diagnosed without the patient taking an electrocardiogram (ECG), which is expensive in both time and equipment. For this reason, electrocardiograms are not used for mass screening.
Patients also have complications of atrial fibrillation such as stroke or cardiac failure. In such circumstances, atrial fibrillation can be detected by pulse palpation (detecting the pulse by touch) and confirmed by electrocardiogram. It is recognised that electrocardiogram diagnosis is more accurate in terms of specificity and sensitivity than pulse palpation which is subjective.
Screening for atrial fibrillation is not practiced as a routine procedure in most countries. The obvious place to provide screening is in the community, and doctors' surgeries are well placed to carry out this role. However, electrocardiogram recordings are time-consuming and expensive and they require reporting by an appropriately trained doctor. The concept of screening for atrial fibrillation is therefore fraught with difficulties.
We have now devised a heart monitor which can be used as a non-invasive screening tool for atrial fibrillation.