What are Cardiac Defibrillators and ICDs?

Cardiac or heart defibrillators are used to restore a normal heart rate in patients who have ventricular tachycardia or ventricular fibrillation.

In a normally functioning heart, the heart beat or rate is controlled by small group of cells called the 'sinus node' near the filling chambers of the heart, called the atria. The sinus nodes generates an electrical impulse that flows from the atria or filling chambers to the pumping chambers or ventricles.

When a person has damage to the heart muscles, from a heart attack, heart inflammation (cardiomyositis), enlarged heart (cardiac hypertrophy) or damaged heart valves, the ventricles can start to beat very fast (ventricular tachycardia) or quiver in an uncontrolled fashion (ventricular fibrillation).

In both ventricular tachycardia, (V Tach) and ventricular fibrillation (V Fib), the heart can not do it's job properly. The ventricles can't fill with fresh blood from the lungs or pump the fresh blood to the body. That is why these abnormal heart rhythms can be deadly.

A cardiac defibrillator "depolarizes'' the heart muscles by delivery a pulse of electrical energy. This allows the rhythm to be reset by the sinus node and restore normal sinus rhythm.

There are two main types of cardiac defibrillators:

1- An emergency external defibrillator that can be used in sudden life threatening situations, as when person experiences an unexpected cardiac event such as a heart attack. Emergency defibrillators are becoming increasing user-friendly and compact. Emergency defibrillators are often found on planes, airports and other public places, but are small enough so that they can be purchased by the public.

2- Implantable defibrillators are small devices inserted under the skin in high risk patients. These Implantable Cardioverter Defibrillators (ICD) are employed in patients at high risk for developing V Tach or V Fib. ICDs are capable of detecting the abnormal heart rate and delivery the electrical impulse to restore normal heart rhythm.

Featured Angina| Acute Coronary Syndrome and Heart Disease Interviews

Author Interview: Claes Held MD Associate professor at Uppsala Clinical Research Center and the Cardiology department at Uppsala University Hospital in Sweden Publication: Physical activity levels, ownership of goods promoting sedentary behaviour and risk of myocardial infarction: results of the INTERHEART study Eur Heart J first published online January 11, 2012 doi:10.1093/eurheartj/ehr432 2012 doi:10.1093/eurheartj/ehr432 Claes Held, Romaina Iqbal, Scott A. Lear, Annika Rosengren, Shofiqul Islam,James Mathew, and Salim Yusuf What are the main findings of the study? The main findings are he following: It is well known that physical inactivity is a risk factor for developing cardiovascular disease. Our study shows that being physically active reduces the risk of having a heart attack. Older studies have mostly studied people in the developed countries. This study which has a global perspective and includes 52 countries from all continents, shows that physical inactivity reduces the risk also in both low- middle-and high-income countries. We also found that ownership of a car and TV was associated with a more than doubled risk of being sedentary and that in low- and middle income the risk for a heart attack was increased with 27 %. We can however, not conclude from this study that there is a causal relationship but it is an interesting finding.     Were any of the findings unexpected? We looked at the relationship between physical activity both at work and during leisure time. A bit surprising was that people with heavy physical labor did not have a reduction in the risk of heart attacks, whereas people with both mild and moderate intensity did. What should clinicians and patients take away from this study? The main findings above and also that physical activity with duration below the recommended 30 minutes/day does seem to prevent from heart attacks as well although not as much as when you do it according to guidelines. This may be a comfort to those who are completely sedentary and feel that it would be a too big step to move to the 30 minutes/day right away. All PA does a good job for the heart as compared to not doing anything at all!   What recommendations do you have for cardiology health care providers as a result of your study? It would be interesting to follow up on the ownership of car and TV and do a prospective study to see if the theory holds true. More Author Interview from Angina.com More on Exercise and Heart Disease More on Heart Attack Studies   3M Littmann Master Classic II Stethoscope

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Philips HeartStart Home Defibrillator (AED)

Be prepared for the unexpected.
When sudden cardiac arrest (SCA) strikes, the electrical system of the heart short circuits, causing the heart to quiver rather than pump in a normal rhythm. It typically results in the abnormal heart rhythm know as ventricular fibrillation (VF). It usually happens without warning and the majority of people have no previously recognized symptoms of heart disease. And it most often happens at home. For the best chance of survival from SCA caused by VF, a defibrillator should be used within 5 minutes. Yet, less than 1 in 20 people survive largely because a defibrillator does not arrive in time.
Just as seat belts or airbags do not save every life in a traffic accident, a defibrillator will not save every person who suffers a sudden cardiac arrest. Yet many lives could be saved if more people could be reached more quickly.

Philips HeartStart Home Defibrillator (AED)