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Transcript
1 Dysrhythmias of the AV Node and Ventricles John Miller Atrioventricular (A-V) junctional dysrhythmias: AV Heart Block First degree AV block o Etiology/risk factors CAD, vagal stimulation, digitalis toxicity Excessive calcium channel blockers, sodium channel blockers, beta blockers Hyper or hypokalemia Assessment ECG: NSR except for a prolonged P-R interval (greater than 0.20 seconds). No symptoms. 1st Degree Block ECG First Degree AV Block Interventions Withhold AV nodal medications. o Digoxin, calcium channel blockers, sodium channel blockers, beta blockers Treat hypo or hyperkalemia. Watch for more severe AV block. Oxygen Second Degree AV Heart Block: Mobitz Type I (Wenckebach) Etiology/risk factors o Vagal stimulation, digoxin o Excessive calcium channel blockers, sodium channel blockers, beta blockers o Hyper or hypokalemia o Mildest form of second degree AV block, usually located in the AV node. Assessment o ECG: P-R getting longer with each beat until a QRS is missing. o Does not usually decrease cardiac output. Second Degree Mobitz Type I ECG Second Degree Type I Interventions Withhold AV nodal medications. o Digoxin, calcium channel blockers, sodium channel blockers, beta blockers Treat hypo or hyperkalemia. Give anti-ischemia medications as needed. If symptomatic (low cardiac output) follow ACLS Bradycardia guidelines. o Atropine o Transcutaneous pacing Oxygen 2 Second Degree AV Heart Block: Mobitz Type II Etiology/risk factors o Level of block is below AV node in bundle. o Ischemia, MI, digoxin o Excessive calcium channel blockers, sodium channel blockers, beta blockers o Hyper or hypokalemia Assessment ECG: Constant P-R on beats, but some QRS’s are missing. Decreases cardiac output (hypotension, angina, CHF) Can quickly progress into third degree AV block. Second Degree Mobitz Type II ECG Second Degree Block Mobitz Type II Interventions Withhold AV nodal medications. o Digoxin, calcium channel blockers, sodium channel blockers, beta blockers Treat hypo or hyperkalemia. Give anti-ischemia medications as needed. If symptomatic (low cardiac output) follow ACLS Bradycardia guidelines. o Atropine o Transcutaneous pacing Oxygen Third Degree AV Heart Block (Complete Heart Block) Etiology/risk factors o AV node or bundle block, atria and ventricles beat separately. o MI, cardiac surgery, drug toxicity, cardiomyopathy o Excessive calcium channel blockers, sodium channel blockers, beta blockers o Hyper or hypokalemia Assessment o ECG: more P-waves than QRSs, regular P-P and R-R intervals, irregular P-R interval, normal appearing P-waves. o Normal width QRS, less than 0.12 second: Ventricular beat comes from AV node o Wide QRS, 0.12 or more second: Ventricular beat comes from the ventricles, similar to a premature ventricular contraction. o Causes sudden death. Third Degree Block ECG Third Degree Block Interventions Withhold AV nodal medications. o Digoxin, calcium channel blockers, sodium channel blockers, beta blockers Treat hypo or hyperkalemia. Give anti-ischemia medications as needed. If symptomatic (low cardiac output) follow ACLS Bradycardia guidelines. o Atropine o Transcutaneous pacing Oxygen Temporary transvenous pacemaker insertion until a permanent pacemaker can be placed. 3 Ventricular dysrhythmias: Premature Ventricular Contraction (PVC) Etiology/risk factors o Irritable ventricular foci o Myocardial hypoxia, hypokalemia, hypocalcemia, acidosis, CAD, CHF, digoxin toxicity, exercise Assessment o ECG o Long QRS duration or width, 0.12 seconds or more, premature but next beat waits to reestablish initial rate (compensatory pause). PVC ECG PVC Interventions Treat cause: hypoxia; magnesium, calcium or potassium abnormalities; MI; Digoxin toxicity Antidysrhythmics o Beta blockers o Sodium channel blockers, class 1B, lidocaine Treat dangerous PVCs that may lead to ventricular tachycardia and fibrillation. o 6 or more per minute o 2 or more in a row o Multifocal (different shapes) o PVC starting on a T wave Ablation Ventricular Tachycardia (VTach, VT) Etiology/risk factors o CAD, cardiomyopathy, MI with acidosis and hypoxia, CHF, digoxin toxicity, follow PVC on T wave o Magnesium, calcium or potassium abnormalities Assessment o ECG: 3 or more PVCs in a row, no P-waves, T is part of the QRS (short ST) o Cardiac output may be slightly low or extremely low (cardiogenic shock) o Causes sudden death. VT ECG VT Interventions Treat cause: hypoxia; magnesium, calcium or potassium abnormalities; MI; Digoxin toxicity Has pulse and is conscious o Antidysrhythmics: Sodium channel blockers, class IA or IB, procainamide or lidocaine; or Potassium channel blockers, class III, amiodarone o Cardioversion (synchronized electrical shock to stop rhythm) o Avoid beta blockers, calcium channel blockers, and digoxin. o Ablation Oxygen Pulseless and unconscious o Treat like Ventricular Fibrillation 4 Ventricular Fibrillation (VFib or VF) Etiology/risk factors o CAD, cardiomyopathy, MI with acidosis and hypoxia, CHF, follow PVC on T wave or Ventricular Tachycardia o Magnesium, calcium or potassium abnormalities Assessment o ECG: no P-waves, QRS complexes, or T waves; disorganized fibrillatory waves seen. o No cardiac output and shortly after breathing will stop. o Causes sudden death VF ECG VF Interventions Call code. CPR 5 cycles Defibrillate with AED or manual defibrillator: Stand clear, remove oxygen source Intubate as soon as possible CPR 5 cycles Epinephrine IV or intraosseous (IO-in bone) Defibrillate Potassium channel blocker, class III: Amiodarone Treat cause. Ablation or AICD for long term management. Ventricular Asystole (standstill, cardiac arrest) Etiology/risk factors o Hypoxia, hyper or hypokalemia, acidosis, drug overdose, hypothermia, follow ventricular fibrillation or 3rd degree AV block Assessment o ECG: no rhythm o No cardiac output and no breathing o Causes sudden death. Asystole ECG Asystole Interventions Verify rhythm in two leads. Check patient. CPR Intubate Epinephrine IV or IO Treat cause. Medications: Sympathomimetics Epinephrine Use: Cardiac arrest, severe hypotension Therapeutic effects: Increased heart rate, contractility, and rate of conduction Adverse effects o CV: Palpitations, tachycardia, ventricular fibrillation, pulmonary edema o Resp: Dyspnea 5 Medications: Parasympatholytics (Anticholinergics) Atropine Use: Symptomatic heart block and other bradycardia Therapeutic effects: Increase heart rate Adverse effects: o CV: Tachycardia, hypotension, ventricular fibrillation o Skin: Dry mouth o Neuro: Blurred vision o GU: Urinary retention o GI: Constipation Medications: Sodium Channel Blockers Class IA: Procainamide Use: Ventricular tachycardia, premature ventricular contractions, SVT Therapeutic effects: Decrease electrical conduction, automaticity, rate of repolarization Adverse effects o CV: Heart failure, hypotension, blocks, ventricular dysrhythmias o Musc: Joint or muscle pain o Resp: Flu symptoms o Hem: Neutropenia, thrombocytopenia Medications: Sodium Channel Blockers Class IB: Lidocaine Use: Ventricular tachycardia, premature ventricular contractions Therapeutic effects: Decrease electrical conduction and automaticity, increase rate of repolarization Adverse effects o Resp: Arrest o Neuro: Agitation, confusion, dizziness, nervousness, seizures Medications: Potassium Channel Blockers Class III: Amiodarone Use: Ventricular tachycardia and fibrillation, SVT Therapeutic effects: Increases repolarization time and refractory period Adverse effects o Resp: Dyspnea, cough o Neuro: Vision problems including photosensitivity o GI: Hepatitis, increased LFT Pacemakers Lead: wire that connects to heart Pulse generator o Battery o Senses natural heartbeat. o Provides electrical initiated heartbeat. What Is a Pacemaker and How Does It Work? https://youtu.be/Y5rvTeAYuIY 6 Pacemakers: Purpose Slow ventricular rates o Second degree or third degree heart block Fast ventricular rates o Atrial fibrillation, atrial flutter, SVT Temporary o Cardiac surgery o Used before a permanent pacemaker o Emergency, using transcutaneous method Getting a Pacemaker https://youtu.be/WNN4Fw2EWxI Pacemakers: Insertion Methods Most common o Transvenous approach attaching to the endocardium (inside) of right ventricle Local anesthesia, through a branch of the subclavian vein Less common o Transthoracic approach attaching to the epicardium of heart outside surface Emergency o Transcutaneous, where pads are attached to outside, similar to an AED attachment. Figure 30–10 A permanent epicardial pacemaker. The pulse generator may be placed in subcutaneous pockets in the subclavian or abdominal regions. Pacing Leads Types o Temporary with external box or pulse generator o Permanent with internal pulse generator Pacing leads can be placed in o Right ventricle o Right atrium Demand Pacing The pacemaker senses the client’s own heart beat and fires an impulse only when the heart needs it. This is the mode that pacemakers most commonly function in. Settings for pulse generator o Heart rate: set at normal total rate of paced beats plus normal beats o Sensitivity: senses own heart rate o Milliamps of electricity: battery used up more if firing more Pacing failure Failure to sense o Is not detecting a natural heart beat o Impulses can be sent out, competing with the heart Failure to pace o Not sending out electricity when needed Failure to capture (does not cause ventricular contraction) o Lead not in contact with heart or not enough electricity is sent to lead 7 Postoperative Care for Pacemakers Maintain lead contact by bed position and/or limiting arm movement. o Sling or immobilizer Observe EKG for proper function Observe the incision for infection signs. Permanent type o Two incisions to observe. Pacemaker interference Causes of electrical interference that may prevent device from working properly o Stay away from large electrical engines, welding, MRI, and diathermy (medical heat device). o 6-12 inch distance acceptable: hair dryer, corded shaver, motors, cell phones o Brief exposure acceptable: security scanners. Carry ID about with pacemaker info. Do not cause interference: microwave ovens, curling irons, kitchen appliances, battery powered shaver Electromagnetic Compatibility Guide http://www.medtronic.com/content/dam/medtronic-comm/mdt/documents/emc_guide.pdf Pacemaker followup Battery depletion or other failure o Detected weeks earlier with monitoring equipment o Home monitoring or office monitoring o Check for symptoms of low cardiac output A Pacemaker Patient Talks about her Experience with the MyCareLink Smart™ Patient Monitor https://youtu.be/8NUnzz0onrY Electrical shock to stop a dysrhythmia Electricity delivered which stops the dysrhythmia and causes a brief period of asystole, so that a better rhythm will take over the heart. AEDs, crash cart defibrillator, and automatic internal cardioverter-defibrillator (AICD) Defibrillation o Emergency procedure, no informed consent needed, uses more electricity than cardioversion. o Consists of delivering a shock to a dysrhythmia, where no QRS or T wave is present. Synch switch is off if using a manual defibrillator instead of an AED. ACLS training is required. Many machines on crash carts have both an AED and manual mode. o Dysrhythmias: VT no pulse, VF Cardioversion Elective procedure, need informed consent, analgesia, use less electricity than defibrillation. Use same machine as manual defibrillator but the synch switch is on, not off as in defibrillation. Deliver shock that avoids the T wave. The T wave is a very vulnerable period. If a shock is given then, it can cause ventricular fibrillation. For dysrhythmias: AFlutter, SVT, VT with pulse Cardioversion Orders FHS http://www.chifranciscan.org/uploadedFiles/For_Physicians/Provider_Orders/PHYORDER.032.pdf Atrial Fibrillation Cardioversion (A MUST SEE) https://youtu.be/KIEFXJ8QHxw 8 Automatic Implanted Defibrillator (AICD)/Pacemaker Combination Indicated for those that need defibrillation or cardioversion. Insertion is similar to pacemakers. Nursing care is similar to pacemakers. The pulse generator is slightly larger. Patient teaching includes observing for shocks that did not occur when needed or occurred when not indicated. Anxious due to ventricular fibrillation history. New S-ICD (subcutaneous) defibrillator a safety net for cardiac patients https://youtu.be/C89PYbaHtcU Code teams Members o Designated ACLS certified teams chosen daily, using include staff from ED and ICU MDs In charge of the code Other MDs RNs, usually 3 Medications IV, NG, foley insertion Charge of the code for nursing Nurse who called the code and cared for the patient Respiratory Therapy, Radiology, IV Therapy, Lab, Pharmacy, Security, Pastoral Care