Sudden cardiac arrest (SCA) is a condition in which the heart suddenly stops pumping blood effectively due to a malfunction of the heart’s electrical system. Often victims of SCA have no prior warning signs or symptoms. SCA also can occur in people with previously diagnosed heart conditions. Survival from SCA depends on immediate and effective cardiopulmonary resuscitation (CPR).
The use of an external defibrillator within the first few minutes of a collapse can greatly improve a patient’s chance of survival. Heart attack and SCA are not the same, though sometimes a heart attack can lead to an SCA. If you are experiencing symptoms of a heart attack (chest pain, pressure, shortness of breath, tight feeling in the chest or elsewhere in the body), immediately seek medical attention.
Sinus Rhythm and Ventricular Fibrillation
The normal heart rhythm, known as sinus rhythm, creates electrical activity resulting in coordinated contraction of the heart muscle. This generates normal blood flow around the body.
Ventricular fibrillation (V-fib or VF) is a condition in which there is uncoordinated contraction of the heart muscle, making it quiver rather than contract properly. Ventricular fibrillation is the most commonly identified arrhythmia in SCA patients. In victims of SCA it is possible to re-establish normal sinus rhythm by means of an electric shock across the heart. This treatment is called defibrillation.
Ventricular Tachycardia
Ventricular tachycardia (VT) is a type of tachycardia (rapid heartbeat) that arises from improper electrical activity of the heart. VT starts in the bottom chambers of the heart, called the ventricles. Although there are many different types of VT, this arrhythmia can be potentially life-threatening if the patient presents with no pulse and is unresponsive. If not treated with immediate defibrillation VT may lead to other arrhythmias.
Treatment by AED
It is a common misconception that CPR alone and calling emergency services is enough. CPR is a temporary measure that maintains blood flow and oxygen to the brain. CPR alone will not return a heart to a normal rhythm during VF or VT. The key to survival is defibrillation – and the sooner the better.
Defibrillation is a common treatment for life-threatening arrhythmias, mainly ventricular fibrillation. Defibrillation consists of delivering an electrical shock to the heart with a device called a defibrillator. This restores normal heart muscle contractions and allows normal sinus rhythm to be restored by the body’s natural pacemaker in the heart.
The HeartSine samaritan PAD uses the HeartSine samaritan ECG arrhythmia analysis algorithm. This algorithm will evaluate the patient’s ECG to ascertain if a therapeutic shock is appropriate. If a shock is required, the HeartSine samaritan PAD will charge and advise the user to press the shock button. If no shock is advised, the device will pause to allow the user to deliver CPR.
It is important to note that cardiac defibrillators, like the HeartSine samaritan PAD, will not administer a shock unless a lifesaving shock is required.
References
Mehra, R. (2007). Global public health problem of sudden cardiac death. Journal of Electrocardiology. 40 (6), S118-S122.
Go AS, Mozaffarian D, Roger VL, et al. Heart disease and stroke statistics–2014 update: A report from the American Heart Association. Circulation.
CDC National Vital Statistics Report, Vol. 60, No. 3, Dec. 29, 2011. CDC Fire Deaths and Injury Fact Sheet
39,520 deaths from breast cancer were projected for 2011. U.S. Breast Cancer Statistics, breastcancer.org,
Hein J.J. Wellens, MD; Anton P. Gorgels, MD; Hans de Munter, MD, Cardiac Arrest Outside of a Hospital, How Can We Improve Results of Resuscitation?, Circulation.2003; 107: 1948-1950