Cardiopulmonary Assessments - CMA 130
Terms in this set (64)
graphic representation of the electrical activity of the heart
Sinoatrial (SA) Node
Specialized cells located in the upper right atrial wall near the superior vena cava.
Initiates each heart beat and sets its pace (pacemaker).
Has an intrinsic rate of 60-100
impulses per minute.
Atrioventricular (AV) Node
Specialized cardiac cells located in the lower right atrial septum.
The impulse travels from the SA to the AV node at a reduced velocity to permit both atria to contract.
Should the SA node malfunction, the AV node has an intrinsic rate of 40-60 impulses per minute.
Bundle of His
Specialized cells located in the ventricular septum.
The impulse travels from the AV node to the bundle of His at an increased velocity.
Should the SA and AV node malfunction, the Bundle of His has an intrinsic rate of 20-40 impulses per minute.
Bundle Branches & Purkinje Fibers
Two branches, extending from the Bundle of His, conduct impulses down the ventricular septum.
Purkinje fibers: Extend from the right and left bundle branches to the ventricular walls causing them to contract.
Cardiac Nerve Supply
Cardiac plexus: Cluster of nerves located near the aortic arch comprising sympathetic and parasympathetic nerve fibers.
Fibers from the cardiac plexus enter
the heart by way of the coronary
Fibers end in the sinoatrial node,
atrioventricular node, and atrial wall.
Complete heart beat consisting of contraction (systole) and relaxation (diastole) of both atria and ventricles.
Contraction of the atria.
the ventricles are relaxed and filling with blood from the atria.
Contraction of the ventricles.
The atria are relaxed
The ability of cardiac cells to generate its own electrical stimulus.
The ability of cardiac cells to respond to an electrical stimulus.
The ability of cardiac cells to receive a stimulus from a neighboring cell and pass it to the next cell causing a wavelike motion to create a contraction.
The ability to respond to a stimulus by contracting.
Cardiac cells are in a resting, negatively charged state.
Cells are discharging a positively charged electrical impulse to create a contraction.
Transformation of cells from a depolarized (active) to polarized (resting) state for recharging.
Each beat comprises five major waves: P, Q, R, S, and T.
Reflects the impulse emanating from the atria.
The Q, R, and S wave, as a unit, reflects the impulse passing through the ventricles.
Reflects repolarization of the ventricles.
Isoelectric line (base line or zero-voltage line):
The point on the ECG wave where no (upward or downward) deflection is present indicating no detectable electrical activity (voltage).
Any upward or downward deflection from the isoelectric line.
Lines between or connecting waves; distance between selected wave marks, but not including them; e.g. the ST-segment begins at the end of the S-wave to the beginning of the T-wave
A wave in addition to a connecting line, e.g. the QT interval represents the beginning of the Q-wave to the end of the T-wave.
Groups of related, recorded waves, e.g.QRS complex.
The first upward deflection representing atrial depolarization (contraction).
First portion of P-wave denotes right atrial depolarization.
Last portion denotes the completion of left atrial depolarization.
AV node activation occurs in the
middle of the P-wave.
It represents conduction of the impulse through the atria from the SA to the AV node.
Represents electrical activity associated with contraction of ventricles, i.e. ventricular depolarization.
It represents transmission of the impulse from the AV node to the Purkinje fibers.
The ST segment is the isoelectric line between the S- and T-waves.
It represents the transition from ventricular depolarization to repolarization.
Represents electrical recovery (repolarization) of ventricles to allow cells to recharge in preparation for ventricular depolarization (contraction).
Represents the time from the onset of the Q wave to completion of the T-wave.
It demonstrates the impulse from the beginning of ventricular depolarization to end of ventricular repolarization.
Composed of a grid of 1 mm squares where every fifth line is darkened creating large blocks of five small blocks high and five wide.
Cardiac voltage is measured on the vertical scale and time on the horizontal.
Horizontally, each large block represents 0.2 seconds;
Vertically, it represent 0.5 millivolts of electricity.
Electrical flow in the heart is measured by externally applied electrodes relative to a direct line, called an axis, between two poles.
A lead comprises one negative pole, one positive pole, and one ground.
Leads create an electrical picture of the heart taken at different angles.
Sensors (electrodes): Uses ten sensors--four limb sensors and 6 chest to create 12 leads.
Bipolar Limb Leads
Measures cardiac electrical activity between two extremities; between a negative and positive electrode (pole).
Six of the 12 leads are called limb leads.
Measures electrical activity from the right arm to the left arm (RA - LA).
From right arm to left leg (RA -LL).
From left arm to left leg (LA - LL). The right-leg position is not displayed as part of the flow of current through the heart, as it is used for grounding the system—electrical reference point.
Unipolar (Augmented)Limb Leads (9 unipolar leads)
Measures electrical activity between the heart and one extremity.
Each lead measures activity from the posterior heart to the positive pole (the positive electrode) on the anterior chest.
aVR: Augmented vector right-side.
aVL: Augmented vector left-side.
aVF: Augmented vector foot (left).
Limb lead electrodes are applied to the patient's extremities.
aVR (augmented voltage—right arm)
Records heart's voltage between right arm electrode and a central point between left arm and left leg
Augmented voltage—left arm)
Records heart's voltage between Left arm electrode and a central point between right arm and left leg
Augmented voltage, left leg or foot
Records heart's voltage between left leg electrode and a central point between right arm and left arm
Precordial (chest) Leads
Six unipolar chest leads that require a combination of electrodes from the extremities to represent one pole (at the posterior heart).
The positive electrode is then attached to the anterior chest in six specified locations.
Record heart's voltage from front to back of heart
From a central point "inside" the heart to a point on the chest wall where each chest electrode is placed
The precordial leads provide points of reference across the chest wall.
Lead V1: Electrode is placed at the fourth intercostal space just to the right of the sternum.
Lead V2: Fourth intercostal space just to the left of the sternum.
Lead V4: Left midclavicular line in the fifth intercostal space.
Lead V3: Line midway between leads V2 and V4.
Lead V5: Anterior left axillary line at the same level as V4.
Lead V6: Left midaxillary line at the same level as lead V4.
Defects on the electrocardiogram not caused by the electrical activity of the heart.
Interferes with normal appearance of ECG cycles
Characterized by fuzzy, irregular baseline
Due to involuntary muscle movement (somatic tremor), or voluntary muscle movement
Wandering Baseline Artifact
Caused by loose electrodes
Interrupted Baseline Artifact
Caused by metal tip of lead wire becoming detached from alligator clip: Reattach lead to alligator clip
Broken patient cable: Replace patient cable
Myocardial Infarction (MI)
Elevation of the ST segment followed by T wave inversion, which in turn is followed by a large Q wave (wider than one small block, or larger than one-third the QRS complex height).
Heart rate is more than 100 (100-160).
Heart rate below 60 (30-60).
A beat is not transmitted out of the SA node.
No P, QRS, or T wave is present at the cycle interval for one or more beats.
Premature Atrial Contraction (PAC)
A beat initiated by an ectopic atrial focus appearing early in the cycle, before the next expected sinus beat, i.e. beat that comes before next normal beat is due.
P wave has a different shape from P wave of normal beat--P wave may be superimposed on the preceding T wave.
Paroxysmal Atrial Tachycardia (PAT):
An abrupt episode of tachycardia with the heart rate usually between 150 and 250 beats per minute, averaging about 170.
The impulses are coming so rapidly, the AV node cannot accept and conduct each one, and therefore some degree of blockage occurs at the node.
Heart rate: 250 to 350 bpm
A very fast atrial rate rising from many ectopic foci.
The total atrial configuration may resemble a wavy baseline or almost straight line.
Premature Ventricular Contraction (PVCs)
Occur in most myocardial infarction patients. They are also seen in normal persons, and may be caused by smoking, coffee, or alcohol.
Originate in the ventricles below the AV node, showing a bizarre QRS configuration.
Series of multiple (three or more), consecutive PVCs occurring at a rate usually between 150 and 250 beats per minute.
Numerous ectopic foci in the ventricles are firing erratically.
Most serious dysrhythmia.
The heart essentially quivers.
Unit that generates a pulse to stimulate the myocardium to produce a ventricular contraction when the sinus pacemaker activity malfunctions or the heart does not maintain a sufficiently rapid rate.
Alternating Current Artifact
Due to electrical interference
Appearance of AC artifact: Small straight spiked lines that are consistent
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