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Bradycardia, also called bradyarrhythmia, is a resting heart rate under 60 beats per minute (BPM). While bradycardia can result from various pathologic processes, it is commonly a physiologic response to cardiovascular conditioning or due to asymptomatic type 1 atrioventricular block.
Cardiac arrest, also known as sudden cardiac arrest, is when the heart suddenly and unexpectedly stops beating. As a result, blood cannot properly circulate around the body and there is diminished blood flow to the brain and other organs. When the brain does not receive enough blood, this can cause a person to lose consciousness. Coma and persistent vegetative state may result from cardiac arrest. Cardiac arrest is also identified by a lack of central pulses and abnormal or absent breathing.
Cardiopulmonary resuscitation (CPR) is an emergency procedure consisting of chest compressions often combined with artificial ventilation, or mouth to mouth in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person who is in cardiac arrest. It is recommended for those who are unresponsive with no breathing or abnormal breathing, for example, agonal respirations.
Cardioversion is a medical procedure by which an abnormally fast heart rate (tachycardia) or other cardiac arrhythmia is converted to a normal rhythm using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart at a specific moment in the cardiac cycle, restoring the activity of the electrical conduction system of the heart. Pharmacologic cardioversion, also called chemical cardioversion, uses antiarrhythmia medication instead of an electrical shock.
Advanced cardiac life support, advanced cardiovascular life support (ACLS) refers to a set of clinical guidelines established by the American Heart Association (AHA) for the urgent and emergent treatment of life-threatening cardiovascular conditions that will cause or have caused cardiac arrest, using advanced medical procedures, medications, and techniques. ACLS expands on Basic Life Support (BLS) by adding recommendations on additional medication and advanced procedure use to the CPR guidelines that are fundamental and efficacious in BLS. ACLS is practiced by advanced medical providers including physicians, some nurses and paramedics; these providers are usually required to hold certifications in ACLS care.
Defibrillation is a treatment for life-threatening cardiac arrhythmias, specifically ventricular fibrillation (V-Fib) and non-perfusing ventricular tachycardia (V-Tach). A defibrillator delivers a dose of electric current to the heart. Although not fully understood, this process depolarizes a large amount of the heart muscle, ending the arrhythmia. Subsequently, the body's natural pacemaker in the sinoatrial node of the heart is able to re-establish normal sinus rhythm. A heart which is in asystole (flatline) cannot be restarted by a defibrillator; it would be treated only by cardiopulmonary resuscitation (CPR) and medication, and then by cardioversion or defibrillation if it converts into a shockable rhythm.
Ventricular fibrillation is an abnormal heart rhythm in which the ventricles of the heart quiver. It is due to disorganized electrical activity. Ventricular fibrillation results in cardiac arrest with loss of consciousness and no pulse. This is followed by sudden cardiac death in the absence of treatment. Ventricular fibrillation is initially found in about 10% of people with cardiac arrest.
Asystole is the absence of ventricular contractions in the context of a lethal heart arrhythmia. Asystole is the most serious form of cardiac arrest and is usually irreversible. Also referred to as cardiac flatline, asystole is the state of total cessation of electrical activity from the heart, which means no tissue contraction from the heart muscle and therefore no blood flow to the rest of the body.
An automated external defibrillator or automatic electronic defibrillator (AED) is a portable electronic device that automatically diagnoses the life-threatening cardiac arrhythmias of ventricular fibrillation (VF) and pulseless ventricular tachycardia, and is able to treat them through defibrillation, the application of electricity which stops the arrhythmia, allowing the heart to re-establish an effective rhythm.
Third-degree atrioventricular block is a medical condition in which the electrical impulse generated in the sinoatrial node in the atrium of the heart can not propagate to the ventricles.
Ventricular tachycardia is a cardiovascular disorder in which fast heart rate occurs in the ventricles of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period of time are referred to as an electrical storm. Short periods may occur without symptoms, or present with lightheadedness, palpitations, shortness of breath, chest pain, and decreased level of consciousness. Ventricular tachycardia may lead to coma and persistent vegetative state due to lack of blood and oxygen to the brain. Ventricular tachycardia may result in ventricular fibrillation (VF) and turn into cardiac arrest. This conversion of the VT into VF is called the degeneration of the VT. It is found initially in about 7% of people in cardiac arrest.
Precordial thump is a medical procedure used in the treatment of ventricular fibrillation or pulseless ventricular tachycardia under certain conditions. The procedure has a very low success rate, but may be used in those with witnessed, monitored onset of one of the "shockable" cardiac rhythms if a defibrillator is not immediately available. It should not delay cardiopulmonary resuscitation (CPR) and defibrillation, nor should it be used in those with unwitnessed out-of-hospital cardiac arrest.
Pulseless electrical activity (PEA) is a form of cardiac arrest in which the electrocardiogram shows a heart rhythm that should produce a pulse, but does not. Pulseless electrical activity is found initially in about 20% of out-of-hospital cardiac arrests and about 50% of in-hospital cardiac arrests.
A flatline is an electrical time sequence measurement that shows no activity and therefore, when represented, shows a flat line instead of a moving one. It almost always refers to either a flatlined electrocardiogram, where the heart shows no electrical activity (asystole), or to a flat electroencephalogram, in which the brain shows no electrical activity. Both of these specific cases are involved in various definitions of death.
Transcutaneous pacing (TCP), also called external pacing, is a temporary means of pacing a patient's heart during a medical emergency. It should not be confused with defibrillation using a manual or automatic defibrillator, though some newer defibrillators can do both, and pads and an electrical stimulus to the heart are used in transcutaneous pacing and defibrillation. Transcutaneous pacing is accomplished by delivering pulses of electric current through the patient's chest, which stimulates the heart to contract.
Pediatric advanced life support (PALS) is a course offered by the American Heart Association (AHA) for health care providers who take care of children and infants in the emergency room, critical care and intensive care units in the hospital, and out of hospital. The course teaches healthcare providers how to assess injured and sick children and recognize and treat respiratory distress/failure, shock, cardiac arrest, and arrhythmias.
Return of spontaneous circulation (ROSC) is the resumption of a sustained heart rhythm that perfuses the body after cardiac arrest. It is commonly associated with significant respiratory effort. Signs of return of spontaneous circulation include breathing, coughing, or movement and a palpable pulse or a measurable blood pressure. Someone is considered to have sustained return of spontaneous circulation when circulation persists and cardiopulmonary resuscitation has ceased for at least 20 consecutive minutes.
Rearrest is a phenomenon that involves the resumption of a lethal cardiac dysrhythmia after successful return of spontaneous circulation (ROSC) has been achieved during the course of resuscitation. Survival to hospital discharge rates are as low as 7% for cardiac arrest in general and although treatable, rearrest may worsen these survival chances. Rearrest commonly occurs in the out-of-hospital setting under the treatment of health care providers.
Neurocardiology is the study of the neurophysiological, neurological and neuroanatomical aspects of cardiology, including especially the neurological origins of cardiac disorders. The effects of stress on the heart are studied in terms of the heart's interactions with both the peripheral nervous system and the central nervous system.
John Alexander MacWilliam, a physiologist at the University of Aberdeen in the late nineteenth and early twentieth centuries, was a pioneer in the field of cardiac electrophysiology. He spent many years studying ventricular fibrillation, and was the first person to propose that ventricular fibrillation was the most common cause of sudden death - and that fibrillation could be terminated by a series of induction shocks to the heart. He was the first to accurately describe the condition of arrhythmia, and he suggested transthoracic pacing to treat transient asystole . Although his work was recognised within his lifetime, it was not until many decades later that it laid the foundations for developments in the understanding and treatment of life-threatening heart conditions, such as in the artificial cardiac pacemaker. MacWilliam was appointed Regius Professor of the Institutes of Medicine at the University of Aberdeen at the age of 29 in 1886, and remained in that post for 41 years until his retirement in 1927.
References
- ↑ Garcia T, Miller B. Arrhythmia Recognition: The Art of Interpretation. Jones and Bartlett, Sudbury MA: 2004.
- ↑ "UK Resuscitation Council. Adult advanced life support algorithm. 2010" (PDF). Archived from the original (PDF) on 2015-02-26. Retrieved 2014-04-14.
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