CARDIAC ARREST (2)

Middle aged man suddenly slumps, lies unconscious, cannot be roused, not breathing, not making any movements, not making any sounds, no pulse is felt......

Is cardiac arrest reversible?

The treatment of cardiac arrest is a race against time because the brain is very sensitive to hypoxia and brain damage occurs usually after about 5 minutes of not receiving oxygen. Thus, treatment must also occur within 4-6mins. Since ventricular fibrillations occur in the majority of cases, the best treatment of cardiac arrest is defibrillation i.e. delivering a therapeutic dose of electrical energy to the heart using a defibrillator. The aim is to depolarize most of the heart muscles at the same time and give the SA node fibres the opportunity to resume normal pacemaker function since they are the fastest and will be the first to recover from the jolt. Unfortunately, most cardiac arrests happen outside the hospital setting where a defibrillator may not be available. In these circumstances, prompt CPR in form of Chest compressions and assisted ventilation have been shown to save lives by maintaining circulation and ventilation until help arrives or until heart beat is spontaneously restored. Automated external defibrillators are now often found in public places like shopping malls and can be used by bystanders to reverse a cardiac arrest. The cardiac thump, though less effective is another technique which works by the same principle as a defibrillator and can be used by a trained personnel to achieve the same objective. Many attempts at resuscitation are however unsuccessful even in a hospital setting especially if there are ongoing underlying anomalies.

Is cardiac arrest preventable?

As mentioned earlier, most cases of cardiac arrest are due to ischemic heart disease (IHD) which can be prevented by minimising the modifiable risk factors. These include smoking, high cholesterol levels, diabetes, and hypertension. Also early detection and management of ischemic heart disease will arrest the progression to myocardial damage and possible cardiac arrest. Symptoms of IHD include chest pain on exertion, in cold weather or emotional situations (angina pectoris) which may progress to acute severe chest pain not relieved by rest due to heart muscle damage (myocardial infarction or heart attack). It is therefore important to report any severe or recurring chest paint to your physician to rule out the possibility of IHD. Difficulty in breathing or swelling of the extremities may also occur due to weakness of the heart muscle (Heart failure). Unfortunately, not all cases of IHD are symptomatic (silent ischemia). Thus the best prevention is the primary prevention of ischemic heart disease by engaging in regular physical exercises, eating a healthy balanced diet low in saturated fat, avoiding smoking, maintaining optimal body weight/body mass index (BMI),screening for hypertension and maintaining good blood pressure control, screening for diabetes and maintaining good blood sugar control, screening for and treating hypercholesterolemia. This is important for everyone but even more important in individuals with the unmodifiable risk factors for IHD such as male gender, age above 40 and family history of ischemic heart disease.

The outcome of resuscitation from cardiac arrest varies from one individual to another. It ranges from full recovery, to recovery with only partial function, to being in coma for weeks, to death. Screen yourself and learn CPR today; you may just be saving your life or your neighbour’s.

lub dub

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CARDIAC ARREST (1)

From the moment it starts beating in the 21 days embryo, to the day the individual dies, the heart never stops pumping. Well, this statement is not absolutely true; not with the invention of by-pass surgeries and definitely not in people who were fortunate to have survived an episode of cardiac arrest.

Ever heard “He just slumped and died!”? – This is most likely sudden cardiac arrest.

Cardiac arrest refers to a state in which the heart suddenly stops beating due to a lack of electrical activity in the heart muscles. When the heart is not pumping, blood is not being carried around the body to supply oxygen to tissues. Lack of oxygen to the brain almost immediately causes loss of consciousness and cessation of breathing. Within 4 to 6 minutes, permanent brain damage occurs and death quickly follows.

What causes the sudden black out?

The pumping activity of the heart is dependent on the electrical impulses generated by specialized fibers in the heart itself called the pacemaker or the SA node (sinoatrial node). The SA node is located in the wall of the right upper chamber of the heart called the right atrium. The muscle fibers of the heart are structurally different from muscle fibers in other parts of the body and are connected to each other in a special arrangement such that the impulses generated in that special spot in the right atrial wall are propagated and programmed to arrive at each of the other 3 heart chambers (left atrium, right ventricle and left ventricle) in perfect timing.

Electrical conduction pathway of the heart.
Original heart diagram illustrated by Patrick J. Lynch; illustrator; C. Carl Jaffe; MD; cardiologist Yale University Center for Advanced Instructional Media

The result is that the 2 atria receive electrical impulses at the same time and contract in unison, pushing blood out into the ventricles while the ventricles receive electrical impulses a bit later and are thus relaxed when the atria are contracting. By the time the ventricles finally begin to contract, the atria have emptied out, the building pressure in the ventricles cause the atrioventricular valves to close and blood is pushed out of both ventricles; from the right to the lungs and from the left to the aorta, the biggest artery in the body.

Many conditions including the following: low blood volume, hypoxia , acidosis, hyperkalaemia or hypokalaemia (High or low potassium), hypothermia (low body temperature), Low or high blood glucose, toxins, drugs, cardiac tamponade(compression of the heart by blood or other fluid building up around it e.g. following chest injury), tension pneumothorax (a collapsed lung), myocardial infarction (Heart attack), pulmonary embolism, electric shock and other forms of trauma, can ultimately disrupt the electrical activity of the heart muscles and lead to ineffective and  uncoordinated contractions (ventricular fibrillations) which cannot pump blood out of the heart. 

 Some people are also born with heart diseases such as Wolff Parkinson-White syndrome and Marfan syndrome which predispose them to cardiac arrest. However, the most common condition  underlying a cardiac arrest is ischemic heart disease,  which causes  heart muscle damage secondary to low oxygen supply.
lub dub

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THE HEART BEAT

The human heart starts to beat around the 21^st day of life at a rate similar to the mother’s heart rate of about 75beats per minute. This rate increases and then decreases slightly through the fetal period. By the time the baby is born, the heart rate is about 145beats per minute. The heart beat can be heard by listening with the ordinary ear or with the aid of a stethoscope over the chest.  It is loudest over a point marked by the intersection of an imaginary line running horizontally in the space between the 5^th and 6^th left ribs and an imaginary vertical line running down from a point just to the right of the midpoint of the left collar bone.  This point is called the apex; it is the lowermost and outermost part of the heart and it is the point of maximal cardiac impulse.

The normal heart sounds are the sounds produced by turbulence in the heart as a result of the closure of valves as the different heart chambers contract and relax to pump out and receive blood respectively. The sounds are designated with the letter S, with S1 being the first heart sound (also referred to as   lub) and S2 the second heart sound (also referred to as dub).  

lubdub lubdub lubdub lubdub lubdub lubdub lubdub lubdub lubdub…………………

Sometimes, extra sounds may be heard by a doctor with the aid of a stethoscope. There may be 3^rd and 4^th heart sounds (S3, S4) or Murmurs. A murmur may or may not be a sign of a heart disease; for instance, hyper dynamic states in which there’s more blood flowing through the heart can result in turbulence which is heard as a murmur. Such states may be caused by fever, anemia, hyperthyroidism and pregnancy. With the reversal of the condition, the murmur also disappears. However, a murmur may be caused by heart disease, most often a congenital defect such as holes in the septum or valvular abnormalities. Heart valves may also be damaged by certain infections or age related changes.

In an adult, the normal rate of the heart is between 60-100 beats per minute. A rate faster than 100bpm is generally referred to as tachycardia while one slower than 60bpm is called bradycardia. There are many conditions which may lead to tachycardia or bradycardia. Some of these are physiological i.e due to normal body adjustments e.g the heart rate of an athlete is expected to be slower than average. Sudden fright or anxiety can, on the other hand, cause tachycardia which is only temporary and resolves when the cause is taken away.  Substances such as caffein, nicotine (in cigarette), drugs of abuse, prescription drugs may also cause changes in the heart rate. However, low heart rate or high heart rate may sometimes be manifestations of heart disease or other diseases. 

The most common symptom of a change in the rate or rythm of the heartbeat is palpitation. This refers to a sense of awareness of the heart beat. It could be disturbing and quite distressful.

heartfailurematters.org

 

The heartbeat, normal or abnormal, can provide a large amount of information about what is going on in the heart as well as other parts of the body, therefore auscultation for the heart sounds is a vital part of the medical examination.

lub dub

edited on 28/11/11