EMT-B Course Module 4 Cardiac EmergenciesI. Normal Cardiac Structure A. Heart is located: 1. In the chest, behind and slightly to the left of the sternum. 2. Sits in front of the spine and rests on the diaphragm. B. Extremely efficient and durable pump. 1. At rest, the heart beats 60-80 times per minute (adult). 2. When exercising, the heart may beat up to 180-200 times per minute. 3. Each day the heart beats up to 100,000 times and pumps 4,000 gallons of blood. This works out to ~2.7375 x 109 beats/lifetime and ~1.095 x108 gallons of blood in a lifetime.II. Normal Cardiac Function A. Contraction of the heart is an automatic, involuntary process. B. Requires electrical stimulus to contract. C. Electrical stimulus must be organized. D. Electrical stimulus provided by the cardiac conduction system: 1. Cardiac control centers in the brain. a. Helps control the rate, rhythm and force of the heartbeat via electrical im- pulse sent to the electrical system of the heart and by the release of chemi- cals (e.g. epinephrine) into the blood. 2. Electrical system of the heart. a. The heart has the ability to generate and conduct electrical impulses on its own (automaticity). The heart beat (contraction) is controlled by these im- pulses. b. This electrical stimulus is performed by specialized groups of cells, called “pacemaker cells”, located throughout the heart. c. Each set of pacemaker cells has its own inherent firing frequency and if one center fails the heart can continue to beat based on the firing of the other pacemaking sites. d. The two primary pacemaker cell groups are the: i. Sino-Atrial (SA) Node - located near the top right atria. 1. Heart’s natural pacemaker.
2. Normally the SA-Node initiates an electrical impulse 60 - 100 times per minute. ii. Atrioventricular (AV) Node - located near the junction of the right atrium and right ventricle. 1. Normally the AC-Node initiates an electrical impulse 40 - 70 times per minute. 2. Ventricular branches have automaticity of 20 - 40 times per minute E. Normal pattern of electrical activity within the heart: 1. The SA node sends a tiny electrical signal to the atria. The impulse spreads throughout the atria via interatrial pathways, depolarizing the atrial muscle fibers. During depolarization the atrial muscle contracts, ejecting blood into the ventri- cles. 2. This same signal is received and delayed by the AV node allowing time for the ventricles to fill with blood from the atria. 3. The delayed electrical signal is then passed from the AV node to the Bundle of His and onto the ventricular conduction system. The impulse spreads down the right and left bundle branches and finally throughout the Purkinje fibers causing ventricular depolarization and ventricular contraction. F. After the muscle fibers contract, they cannot respond to an electrical impulse for a short time known as the refractory period. During this time the muscle fibers repo- larize and return to the rest state. G. During the time (~30 msec) the ventricles are repolarizing, they are especially vul- nerable to VF. H. When things go wrong: 1. Any of the pacemaking cells can fire and setup a contraction in the heart. If they fire prematurely, they can create an extra heart beat. 2. In a normally functioning heart, these extra beats are tolerated well and the SA node regains control. 3. In a diseased heart, these ectopic impulses, especially if they occur during the ventricular vulnerable period may provoke VF. Recovery of the ventricular mus- cle cells is not uniform or homogeneous during the repolarization phase. An ectopic impulse may fragment the ventricles recovery and electrical chaos may occur which in turn causes mechanical chaos. 4. VF will not self-correct. It will persist and the patient will die if defibrillation is not performed.III. Cardiac Compromise A. Angina Pectoris 1. Caused by a reduced blood supply to the heart during times of stress or exer- cise. Reduced blood flow due to narrowing of coronary arteries. No death of cardiac muscle. B. Acute Myocardial Infarction (AMI)
2. A part of the cardiac muscle dies due to oxygen starvation. Often the result of coronary heart disease. May result in sudden death. C. Congestive Heart Failure (CHF) 1. Condition of excessive fluid buildup in the lungs and/or other organs and body parts. 2. Termed congestive because the fluids congest, or clog, the organs. Termed heart failure because the congestion both results and aggravates the failure of the heart to function properly D. Cardiac ArrestIV. Cardiac Arrest A. Signs and Symptoms 1. Unresponsiveness 2. Respiratory arrest 3. Absence of a palpable carotid pulse B. Chain of Survival 1. Early Access a. Witnessed, recognized arrest b. Early call to 911 2. Early CPR a. Within 1-2 minutes of arrest 3. Early Defibrillation a. On scene within 3-5 minutes after arrest b. Within 90 seconds of arrival on scene 4. Early Advanced CareIV. Automated External Defibrillators (AED) A. How they work: 1. Electrodes placed on the patient’s chest pick up the electrical activity of the heart. 2. A computer within the AED uses an algorithm to analyze the heart rhythm and identify if it is a shockable rhythm. 3. If it detects a shockable rhythm, it advises a shock and delivers it at the com- mand of the operator.
B. Shockable Rhythms 1. Ventricular Fibrillation (VF) a. Primary electrical disturbance resulting in cardiac arrest. 50-60% of all car- diac arrest patients will be in VF if EMS personnel arrive in the first 8 min- utes. b. Electrical energy in the heart is totally disorganized. Chaotic electrical activ- ity originating from many sites in the heart prevents the heart from contract- ing normal and thus pumping blood. c. Patient signs & symptoms: respiratory arrest, no palpable pulse, no blood pressure, unresponsive 2. Ventricular tachycardia (V-Tach) a. Not common. Only ~10% of patients will be observed to be in V-Tach. b. Heart rhythm is organized, but very fast. Depending on the rate, the heart’s chambers may not have time to fill with blood before the next contraction; and therefore blood flow to the body will be insufficient. C. Nonshockable rhythms 1. Pulseless Electrical Activity (PEA) a. Occurs in 10-15% of cardiac arrests. b. Electrical activity is normal, but heart muscle has failed. Heart muscle is se- verely and almost always terminally sick. Can also occur due to loss of too much blood. 2. Asystole a. Occurs in 20-25% of cardiac arrests. b. Heart muscle has ceased generating electrical impulses altogether. c. Can be caused by untreated VF, a sick heart, a terminal illness or severe blood loss.V. General Principles of AED Use A. One EMT operates the defibrillator. B. Defibrillation comes first. Don’t hook up O2 or do anything that delays analysis of the rhythm or defibrillation. C. Be thoroughly familiar with the AED you will be using. D. All contact with the patient must be avoided during analysis of the rhythm. E. State “Clear” and be sure everyone is clear of the patient before delivering each shock. F. No defibrillator is capable of working without functioning batteries. Always carry an extra.
G. If you have delivered six shocks and you have no ALS backup, you should prepare the patient for transport. H. An AED cannot analyze in a moving vehicle. I. It is not safe to defibrillate in a moving ambulance. J. Pulse checks should not occur during rhythm analysis.VI. Contraindications A. Patient is spontaneously breathing. B. Patient has a palpable pulse. C. Patient weights < 90 lb. D. Patient is < 12. y/o. E. Cardiac arrest is the result of trauma.VII. Safety Considerations A. Do not apply a shock when anyone is in contact with the patient. B. Do not defibrillate a soaking wet patient. Remove patients from wet environment before defibrillating. C. Do not defibrillate around a O2 or any flammable gas. D. Do not defibrillate the patient if he is touching anything metallic that other people are touching (e.g. a metal deck or the metal on a stretcher). E. Remove nitroglycerin patches before defibrillating. They may explode or cause burns to the patient. Be sure to wear gloves when removing.VIII. Special Circumstances A. Patients with pacemakers. 1. May recognize by: a. History from a knowledgeable bystander or family. b. Presence of an incision just beneath one of the clavicles (usually the left). c. Presence of a small lump in the area of the incision. d. Medical alert tag. 2. Special precautions - place the electrodes at least five inches away from the pacemaker. Failure to do so may cause electrical burns or injury to the patient in the area of the pacemaker. 3. After placement of electrodes. Treat as you would any other cardiac arrest pa- tient.
B. Patients with Automatic Implantable Cardiovascular Defibrillators (AICDs). 1. These are placed in patients identified as being at high risk of going into VF. When the device identifies VF, it delivers a shock to the heart. 2. May recognize by: a. History from a knowledgeable bystander or family. b. Presence of an incision near the umbilicus, usually to the left of the midline. c. Seeing a large (7 X 11 cm) bulge at the site of the incision due to the promi- nence of the rather large (290 gm) pulse generator just beneath the skin. d. A medical alert tag. 3. Treat as you would any other cardiac arrest patient. AICDs are protected from damage by shocks from AEDs. 4. The ACID may discharge and deliver a shock while the rescuer is touching the patient’s chest. No significant danger to rescuer. May feel the shock as a slightly painful tingling sensation. Maximum internal output of ACID is 30 joules. Energy levels at the surface is a mere 2 joules.IX. Code Procedures/Management A. Successful handling of a code requires an organized team approach. B. The team leader and defibrillator operator should be determined beforehand. The team leaders job it to lead and coordinate the actions of all the members of the team. C. Each member of the team has certain roles and responsibilities. Each member of the team should be able to fill any of these roles. D. A successful defibrillation code moves through several stages from start to finish: 1. Anticipation and planning 2. Scene entry and defibrillator placement 3. Patient assessment and CPR initiation 4. Patient preparation and defibrillation 5. Family notification and spectators 6. Transport 7. Transfer of careX.Anticipation and Planning A. Analyze dispatch information. B. Decide on a team leader and defibrillator operator. C. Outline duties. Ideal crew consists of a minimum of five people:
1. Team leader and defibrillator operator (1 person). 2. CPR compression (1 person). 3. Airway Control (2 people) a. Administers airway adjuncts. b. Administers high flow O2 . c. Ventilates patient. 4. Recorder/Interviewer/Go-For (1 person)XI. Prepare and check equipment. A. Check audio tape B. Check for defib cables. C. Check printer tape. D. Check for spare battery. E. BVM, airway adjuncts, O2 , suction F. BSIXII. Scene Entry and Placement A. Pinpoint the exact location of patient at scene. B. Transport AED and all equipment needed to manage cardiac arrest to the patient’s side. C. Determine need to move patient based on environmental concerns or need to have room to work. Position patient as needed. D. Position team members and defibrillator based on assessment of available space, layout and work room.XIII. Patient Assessment A. If no CPR has been initiated, team leader performs a quick initial assessment (ABCs). If patient is in cardiac arrest, team leader directs the start CPR. B. If CPR is in progress, team leader stops CPR and assesses carotid pulse. If cardiac arrest is confirmed, team leader directs resumption of CPR. Airway team ventilates patient and prepares airway management tools. C. Team leader directs recorder to request ALS backup.XIV. Patient Preparation/Defib Sequence A. Team leader prepares defib and patient. 1. Power up AED.
2. Expose patient’s chest. Wipe dry if necessary. 3. Apply electrodes pads to electrode cables, remove adhesive backing from pads, and correctly place onto the patient. 4. When unit has finished self-check, make sure the tape unit is operating, direct cessation of CPR, ensure all rescuers are CLEAR (by yelling “clear” and visu- ally confirming same) and initiate rhythm analysis. 5. Throughout the procedures the team leader should initiate a narrative including the following information: a. Call out time (Device on at 4:00 p.m.). b. Identify himself/herself and the responding EMS unit. c. Briefly describe the history of the present episode and current clinical situa- tion (“60 y/o male patient witnessed collapsing 5 minutes prior to our arrival by spouse - currently pulseless and apneic...”) d. Report each shock as they are delivered with the energy levels. e. Explain all important actions, events at the scene, decisions, problems, time of transport, etc.B. Complete one set of three shocks. Ensure the all rescuers are CLEAR before each shock is administered.C. Reassess pulse. If no pulse, resume CPR for one minute.D. Perform second set of three shocks. Ensure the all rescuers are CLEAR before each shock is administered.E. Reassess pulse. If no pulse, prepare patient for transport and transport.