WK 2: Dysrhythmias Flashcards
What is Dysrhythmia?
- Abnormal cardiac rhythms are termed dysrhythmias.
- Prompt assessment of dysrhythmias and the patient’s response to the rhythm is critical.
What is ECG monitoring?
· Graphic tracing of electrical impulses produced by the heart
· Waveforms of ECG represent activity of charged ions across membranes of myocardial cells.
What is the significance of lead placement?
Limb leads I, II, and III: These bipolar leads are located on the extremities.
Limb leads aVR, aVL, and aVF: These unipolar leads use the centre of the heart as their negative electrode.
Placement for the unipolar chest leads: V1, fourth intercostal space at the right sternal border; V2, fourth intercostal space at the left sternal border; V3, halfway between V2 and V4; V4, fifth intercostal space at the left midclavicular line; V5, fifth intercostal space at the l
Cardiac action potential
P Wave: representing atrial depolarization
QRS complex: QRS complex representing ventricular depolarization
T wave: T wave representing ventricular repolarization
ST segment: represents the time period in which the ventricles are completely depolarized.
What is Sinus bradycardia
· Sinus node fires <60 bpm
· Normal rhythm in aerobically trained athletes and during sleep
What is Sinus tachycardia
· Discharge rate from the sinus node is increased as a result of vagal inhibition and is >100 bpm.
· HR: 140bpm = Tachycardia
· Regular Rhythm - Sinus
What is Premature atrial contraction
· Contraction originating from ectopic focus in atrium in location other than sinoatrial (SA) node
· Travels across atria by abnormal pathway, creating distorted P wave
· May be stopped, delayed, or conducted normally at the atrioventricular (AV) node
· Changes in the P wave
Premature atrial contraction ECG findings
HR: 120bpm
Irregular rhythm
QRS: are different
P wave: some are smaller and shorter
Causes of Premature atrial contraction
· Emotional stress, physical fatigue
· Use of caffeine, tobacco, alcohol
· Hypoxia
· Electrolyte imbalances
· Hyperthyroidism, chronic obstructive pulmonary disease (COPD), heart disease including coronary artery disease (CAD) and valvular disease
Clinical significance of Premature atrial contraction
· Isolated PACs are not significant in persons with healthy hearts.
· In persons with heart disease, may be warning of more serious dysrhythmia
What is Atrial flutter
· Atrial tachydysrhythmia identified by recurring, regular, sawtooth-shaped flutter waves
Originates from a single ectopic focus
ECG findings of Aflutter
- Flutter waves - between each QRS
- P wave: unclear
Clinical significance of Atrial flutter
- High ventricular rates (>100) and loss of the atrial “kick” can decrease CO and precipitate HF
- Risk for stroke due to risk of thrombus formation in the atria
Warfarin (Coumadin) is given to prevent stroke in patients with atrial flutter of longer than 48 hours duration.
Causes of Atrial flutter
§ CAD
§ Hypertension
§ Mitral valve disorders
§ Pulmonary embolus
§ Chronic lung disease
§ Cor pulmonale
§ Cardiomyopathy
§ Hyperthyroidism
Medications: digoxin, quinidine, epinephrine
What is Atrial Fibrillation
· Total disorganization of atrial electrical activity due to multiple ectopic foci, resulting in loss of effective atrial contraction
· Most common dysrhythmia
· Prevalence increases with age
· The dysrhythmia may be chronic or intermittent. Atrial fibrillation is the most common dysrhythmia in Canada. with 1 to 2% of the population living with atrial fibrillation.
ECG Findings of Atrial Fibrillation
§ Irregular rhythm
No p waves
Clinical Significance of Atrial Fibrillation
· Can result in decrease in CO due to ineffective atrial contractions (loss of atrial kick) and rapid ventricular response
· Thrombi may form in the atria as a result of blood stasis.
· An embolus may develop and travel to the brain, causing a stroke.
· Overall risk of stroke increases three to five times greater with atrial fibrillation.
Medications: blood thinners
Causes of Atrial Fibrillation
· Rheumatic heart disease
· CAD
· Cardiomyopathy
· Hypertension
· HF
Pericarditis
What is Ventricular tachycardia?
· Run of three or more PVCs
· Monomorphic, polymorphic, sustained, and nonsustained
Considered life-threatening because of decreased CO and the possibility of deterioration to ventricular fibrillation
Clinical significance of is Ventricular tachycardia
· VT can be stable (patient has a pulse) or unstable (patient is pulseless).
· Sustained VT: severe decrease in CO
§ Hypotension
§ Pulmonary edema
§ Decreased cerebral blood flow
§ Cardiopulmonary arrest
§ Treatment for VT must be rapid.
§ May recur if prophylactic treatment is not initiated
Ventricular fibrillation may develop.
Causes of is Ventricular tachycardia
· MI
· CAD
· Electrolyte imbalances
· Cardiomyopathy
· Mitral valve prolapse
· Long QT syndrome
· Digitalis toxicity
· Central nervous system disorders
This dysrhythmia can be seen in patients who have no evidence of cardiac disease.
What is Ventricular Fibrillation
· Severe derangement of the heart rhythm characterized on ECG by irregular undulations of varying contour and amplitude
No effective contraction or CO occurs.
ECG findings of Ventricular Fibrillation
· No clear definition in any waves.
Varied rhythm
Clinical significance for Ventricular Fibrillation
· Unresponsive, pulseless, and apneic state
If not treated rapidly, death will result.
Causes of Ventricular Fibrillation
· Acute MI, CAD, cardiomyopathy
· May occur during cardiac pacing or cardiac catheterization
· May occur with coronary reperfusion after fibrinolytic therapy
· Accidental electric shock
· Hyperkalemia
· Hypoxia
· Acidosis
Drug toxicity
Management of Ventricular Fibrillation
· Assessment of circulation, airway, and breathing (CAB)
· Immediate initiation of cardiopulmonary resuscitation (CPR) and advanced cardiac life support (ACLS) measures with the use of defibrillation and definitive medication therapy
ECG changes in Acute Coronary Syndrome
· Definitive ECG changes occur in response to ischemia, injury, or infarction of myocardial cells.
§ Changes seen in the leads that face the area of involvement
The leads facing opposite the area involved in ACS often demonstrate reciprocal (opposite) ECG changes. Additionally, the pattern of ECG changes among the 12 leads provides information on the coronary artery involved in ACS.
ST depression in Acute Coronary Syndrome
· ST segment depression is significant if it is at least 1 mm (one small box) below the isoelectric line.
· The isoelectric line is flat and represents those normal times in the cardiac cycle when the ECG is not recording any electrical activity in the heart. These times are as follows: (1) from the end of the P wave to the start of the QRS complex, (2) the entire ST segment, and (3) from the end of the T wave to the start of the next P wave.
· Changes occur in response to the electrical disturbance in myocardial cells due to inadequate supply of oxygen.
Once treated (adequate blood flow is restored), ECG changes resolve and ECG returns to baseline.
ST elevation in Acute Coronary Syndrome
· ST-segment elevation is significant if >1 mm above the isoelectric line.
§ If treatment is prompt and effective, may avoid infarction
§ If serum cardiac markers are present, an ST-segment–elevation myocardial infarction (STEMI) has occurred.
T wave changes in Acute Coronary Syndrome
· T-wave inversion related to infarction occurs within hours and may persist for months
Pathological Q wave in Acute Coronary Syndrome
- A pathological Q wave indicates that at least half the thickness of the heart wall is involved.
- Referred to as a Q-wave MI
- Pathological Q wave may be present indefinitely
