Presentation on theme: "Cardiac arrhythmia. Anatomy and physiology of conduction system."— Presentation transcript:
Anatomy and physiology of conduction system
ECG (Electrocardiogram or Electrocardiograph)
INTERPRETING THE ECG P wave: Atrial depolarization. It is normally 2.5mm or less in height 0.11seconds or less in duration. QRS COMPLEX: Ventricular depolarization. Less than 0.04 seconds in duration Less than 0.12 seconds in duration. T wave : Ventricular repolarization. U wave: Repolarization of the Purkinje fibers.
continues….. PR interval: It is measured from the beginning of the P wave to the beginning of the QRS complex In adults, the PR interval ranges from 0.12 to 0.20 seconds. ST segment: Early ventricular repolarization, QT interval: Total time for ventricular depolarization and repolarization. The QT interval is usually 0.32 to 0.40 seconds TP interval: It is measured from the end of the T wave to the beginning of next P wave.
CARDIAC ARRHYTHMIA Cardiac arrhythmia is a conduction disorder that results in an abnormally slow or rapid heart rate or one that dose not proceed through the conduction system in the usual manner.
TYPES OF ARRHYTHMIAS 1. Sinus Node Arrhythmia: a) Sinus Bradycardia: An impulse at a slower than normal rate. Etiology: Vagal stimulation Drugs like calcium channel blockers, amiodaron, beta blockers. Altered metabolic states, such as hypothyroidism. Increased intracranial pressure (ICP). The process of ageing, Certain cardiac diseases, such as Myocardial Infarction.
ECG interpretation Rate: 55 Rhythm: R-R interval is regular. P wave: present for each QRS complex, normal configuration, and each P wave is identical. P-R interval: falls between seconds. QRS complex: normal in appearance, one follows each P wave. QRS interval: seconds. T wave: follows each QRS and is positively conducted.
Management : Atropine 0.5mg IV push blocks vagal stimulation to the SA node. If the bradycardia persists, a pacemaker may be required.
Sinus Tachycardia: Sinus tachycardia occurs when the sinus node creates an impulse at a faster than normal rate. Etiology: Physiological and psychological stress Medications that stimulate the sympathetic response
Continues….. Clinical Manifestation: Tachycardia, heart rate increases, Syncope Low blood pressure ECG interpretation: Rate: 130 P wave: normal configuration P-R interval: between 0.12 and 02.0 or 0.16 seconds. QRS complex: normal in appearance, QRS interval: 0.06 seconds. T wave: is positively conducted.
Continues…. Management: Treatment is directed towards elimination of the cause. Beta blockers and calcium channel blockers, although rarely used, may be administered to reduce the heart rate quickly.
Atrial Arrhythmia: a) Premature Atrial Contraction: A premature atrial complex (PAC) is a single ECG complex that occurs when an electrical impulse starts in the atrium before the next normal impulse of the sinus node. Etiology: Stretched atrial myocardium( for example in hypervolemia) Caffine, alcohol, nicotine, Anxiety Hyperkalemia(low potassium level) Hypermetabolic states( for example with pregnancy) Atrial ischemia, injury or infarction. Clinical Manifestation: Irregular heart rate.
Continues… ECG interpretation: Rate & Rhythm: may be slow or fast & will be irregular. P wave: the P wave of the premature contraction will be distorted in shape. P-R interval: may be normal but can also be shortened. QRS complex: with in normal limits T wave: normally conducted. Management: PACs should be monitored for increasing frequency.
Atrial Flutter It is caused by conduction defect in the atrium & causes a rapid regular atrial rate usually between times per minute. Etiology: Patients with chronic obstructive pulmonary disease, valvular diseases, thyrotoxicosis, following open heart surgery & repair of congenital defects. Clinical Manifestation: Chest pain Shortness of breath Low blood pressure
Continues…. ECG interpretation: Rate: 250 and 400 bpm Rhythm: regular or irregular P wave:not present; instead, it is replaced by a saw-toothed pattern. These waves are also reffered toas F waves. QRS complex: normal T wave: present but may be obscured by flutter waves. Management: calcium channel blocker Digitalis and quinidine beta-adrenergic blocking drug cardioversion.
Atrial fibrillation Its an uncoordinated atrial electrical activation, causes a rapid, disorganized and uncoordinated twitching of atrial musculature. Etiology: advanced age with structural heart diseases Inflammatory or infiltrative diseases &Coronary artery diseases. Hypertension, congenital disorder & heart failure. Diabetes, obesity, hyperthyroidism. Heavy ingestion of alcohol. Clinical Manifestation: Irregular palpitation Symptoms of heart failure Hypotension, chest pain, pulmonary edema & altered LOC
Continues…. ECG interpretation: Rate: immeasurable Rhythm: irregular irregularity. P wave: replaced by fibrillatory waves, called little f waves. P-R interval: not measurable. QRS complex: normal T wave: normal Management: depends on the causes. Electrical cardioversion The beta-adrenergic blocking drugs or calcium ion Adenosine ( Adenocard)
Ventricular Tachycardia It is defined as three or more premature ventricular complexes (PVC) in a row, occurring at a rate exceeding 100 bpm. Etiology Acute MI Syndrome of accelerated rhythm that deteriorate Metabolic acidosis Electrolyte disturbance. Toxicity to certain drugs Intake of caffine, nicotine or alcohol.
Continues…. ECG interpretation: Rate & Rhythm : 140 and 220 bpm, regular /irregular. P wave: not present. P-R interval: not measurable. QRS complex: broad, bizarre in configuration, widened greater than 0.12 second. T wave: deflected opposite to the QRS complex. Management: need antiarrhythmic medications: IV procainamide lidocain used for immediate. Cardioversion
Ventricular fibrillation Its a rapid, disorganized ventricular rhythm causes ineffective quivering of the ventricles. Etiology: Coronary artery diseases, acute MI. Untreated or unsuccessfully treated ventricular tachycardia, cardiomyopathy, valvular heart diseases. Acid-base and electrolyte abnormalities & electric shock. Clinical Manifestation: Absence of audible heart beat, palpable pulse, respiration.
Continues…. ECG interpretation: Rate: not measurable because of well-formed QRS complex. Rhythm: Chaotic. P wave: not present. QRS complex: bizarre, chaotic, no definite contour. T wave: not apparent. Management: immediate defibrillation. If third shock is unsuccessful, begin CPR and administer epinephrine(Adrenalin)
Ventricular Asystole: Ventricular Asystole is commonly called flat line. Etiology: - Hypoxia - Acidosis - Severe electrolyte imbalance - Drug overdose - Hypovolemia - Cardiac tamponade - Coronary or pulmonary thrombosis - Trauma - Hypothermia. Clinical Manifestation: Absence of heart beat. No palpable pulse No respiration
Continues…. ECG interpretation: Absent QRS complexes, confirmed in two different leads, although P wave may be apparent for a short duration. Management: The immediate treatment is CPR. After 2 or 5 cycle CPR, a bolus of IV epinephrine is administered and repeated at 3-5 minute intervals. One dose of vasopressin may be administered for the first or second dose of epinephrine. A bolus of IV atropine may also be administered as soon as possible after the rhythm check.
Continues…. Maze Procedure: This is an open heart surgical procedure for refractory atrial fibrillation. Small transmural incision are made through out the atria. The resulting formation of scar tissue prevents reentry conduction of the electrical impulse. Catheter Ablation Therapy: Catheter Ablation destroy specific cells that are the cause or central conduction route of a tachydysrrhythmia. Ablation is by using radiofrequency, which involves placing a special catheter at or near the origin of the dysrrhythmia. High frequency, low energy sounds waves are passed through the catheter, causing thermal injury and cellular changes that result in localized destruction and scarring.
CARDIOVERSION & DEFIBRILLATION Principle: an electrical current that depolarize a critical mass of myocardial cells. When the cell repolarize, the sinus node is usually able to recapture its role as the hearts pacemaker.
CARDIOVERSION - delivery of a timed electrical current to terminate a tachyarrhythmia. - the defibrillator is set to synchronize with the ECG on cardiac monitor. - The amount of voltage used varies from J, depending on the defibrillators technology, the type and duration of arrhythmia.
DEFIBRILLATION - Defibrillation is not used for patients who are conscious or have a pulse. - Defibrillation depolarizes a critical mass of myocardial cells all at once; when they depolarize, the sinus node usually recaptures its role as the pacemaker. - The electrical voltage required to defibrillate the heart is usually greater than that required for cardio version.
DIFFERENCE IN CARDIOVERSION & DEFIBRILLATION In Cardioversion, the delivery of the electrical current is synchronized with the patients electrical events; in defibrillation, the delivery of the current is immediate and unsynchronized.
PACEMAKER THERAPY A pacemaker is an electronic device that provides electrical stimuli to the heart muscle. Types: Pacemakers can be permanent or temporary. - Temporary pacemakers are used to support patients until they improve or receive a permanent pacemaker. - Temporary pacemakers are used only in hospital setting.
Complications of Pacemaker Local infection at the entry site of leads for temporary pacing or at the subcutaneous site for permanent generator placement. Pneumothorax. Bleeding & hematoma Hemothorax pericardial effusion & rarely, cardiac temponade.
Nursing management of patient with an implantable cardiac device: The patients heart rate and rhythm are monitored by ECG. The incision site is observed for bleeding, hematoma formation or infection, which may be evidenced by swelling, unusual tenderness, drainage & increased warmth. A chest x-ray is usually taken after procedure. Patient is also assessed for anxiety, depression or anger In the perioperative & postoperative phases the nurse carefully observes the patient & family with further teaching as needed.
NURSES RESPONSIBILITIES: When using pads or paddles, we must observe two safety measure. First, good contact must be maintained between the pads or paddles and the patients skin (with a conductive medium between them) to prevent electrical current from leaking through the air(arcing) when the defibrillator is discharged. Second, no one is to be in contact with the patient or with anything that is touching the patient when the defibrillator is discharged, to minimize the chance that electrical current is conducted to anyone other than the patient.
Other nursing care include:- Preventing Infection: Promoting effective coping: Promoting home and community based care: