Ch 36: Care of Pts with Dysrhthmias Flashcards
12 lead ECG placement
See pic Tale 36-1
P wave
Represents atrial depolarization. They have a consistent shape if the electrical pulse is coming from the SA node.
60-100 bpm
PR segment
isoelectric line from end of P to beginning of QRS complex, when the impulse is traveling thru the AV node where it is delayed. Allows the atria to contract and the ventricles to fill
PR interval
Beginning of P wave to the end of the PR segment. Depolarization plus impulse delay and time to travel to the purkinje fibers. Normal is 0.12 to 0.2 seconds (5 small blocks)
QRS complex
ventricular depolarization. Shape depends on the lead selected.
Q wave: 1st negative deflection and is not seen in all leads. It is small and represents initial ventricular septal depolarization. If it is abnormally present it represents necrosis
R wave: 1st positive deflection (small large or absent, depending on lead)
S wave: negative deflection following the R wave and is not present in all leads
QRS duration
time required for depolarization of both ventricles. beginning of QRS complex to the J point (where QRS ends and ST segment begins). Normal is .04 -.10 (3 small blocks)
ST segment
Isoelectric line that represents early ventricular repolarization. It is from the J point to the beginning of the T wave. It varies with changes in the heart rate, medications, and electrolyte disturbances. It is normally not elevated more than 1mm or depressed less than 0.5mm. Elevation or depression can be caused by myocardial injury, ischemia or infarction, conduction abnormalities, or medications
T wave
Represents ventricular repolarization. Usually positive, rounded, and slightly asymmetric.
U wave
when present It may result from slow repolarization of the ventricular Purkinje fibers. Same polorization as the T-wave but usually smaller. It’s not seen in all leads. It is common in V3. An abnormality may suggest hypokalemia or other imbalance.
Possibly request a potassium level and be care not to mistake it for a P wave
QT interval
The total time required for ventricular depolarization and repolarization. From the beginning of the QRS complex to the end of the T-wave. It varies with age, gender, and changes with heart rate. Prolonged QT interval can lead to ventricular tachycardia called torsades de pointes
Up to .40 is nomal
Artifact
An interference seen on the rhythm strip or monitor which looks like a wandering or fuzzy baseline. It can be caused by movement, loose or defected electrodes, improper grounding, faulty equipment. It can mimic lethal dysrhythmias or ventricular fibrillation.
ECG components
see pic Fig 36-5
ECG rhythm analysis
- Determine the heart rate
300 / # big blocks between 2 R wave
Count backward 300, 150, 100, 75, 60, 50, 43, 37, 33, 30
#QRS complexes in 6 seconds x 10 (use if irregular) - Determine the heart rhythm
Regular, irregular, regularly irregular, occasionally irregular, irregular irregular
Atrial rhythm: Count P-Pwaves, regular if varies less than 3 small blocks
Ventricular rhythm: RR intervals - Analyze the P waves
Ask : are P waves present, occurring regular, one for each QRS complex, Smooth rounded and upright or inverted, do they all look same? - Measure the PR interval
beginning of P wave to end of PR interval; 0.12-0.2 sec is normal, constant throughout - Measure the QRS duration
beginning of QRS to the j point; 0.04-0.10 sec, constant - Interpret the rhythm
ECG graph paper
1 small block = .04 sec
5 small blocks = 1 large block = .20 sec
5 large blocks = 1 sec
30 large blocks = 6 sec
Time is horizontal
Amplitude is vertical
Normal Sinus Rhythm
originates from the SA node
Rate: 60-100
Rhythm: atrial and ventricular are regular
P waves: present, consistent, one before each QRS
PR interval 0.12 - 0.2 sec and constant
QRS duration: 0.04-0.10 sec and constant
Sinus arrhythmia
variant of NSR, from changes during breathing. HR increases slightly during inspiration and decreases slightly during exhalation. All same as normal NSR except that PP and RR intervals vary with the difference between the shortest and longest intervals >0.12 sec
Can be caused by digitalis or morphine.
Dysrhythmia/arrhythmia
Results from
- a disturbance in the relationship between the electrical conductivity in the mechanical response of the myocardium.
- A disturbance of impulse formation either from abnormal rate or from ectopic focus.
- A disturbance in impulse conduction such as delays and blocks.
- The combination of several mechanisms. They have no clinical manifestations but can have serious consequences
Key features of sustained tachy dysrhythmias and Brady dysrhythmias
Chest discomfort, pressure, pain which may radiate to the jaw back or arm.
Restlessness, anxiety, nervousness, confusion. Dizziness, syncope.
Palpitations with tachy.
Changes and pulse rate and rhythm. Pulse deficit.
Shortness of breath and dyspnea, tachypnea, pulmonary crackles, orthopnea
S3 s4 heart sounds
Jugular venous distention. Weakness, fatigue, pill cool skin, diaphoresis, nausea and vomiting, decreased urine output, delayed capillary refill, hypotension