click below
click below
Normal Size Small Size show me how
EKG PASS 573
Question | Answer |
---|---|
What are the 3 layers of the heart wall? | Epicardium, Myocardium, and Endocardium |
What are the two basic cell types of the heart? | Myocardial and Conducting cells |
Myocardial cells are surrounded by what kind of membrane? | Sarcolemma |
What is the name of the special contact points where myocardial cells connect? | Intercalated disks |
What holds the myocardial cells together during contraction? | Desmosomes |
How do myocardial cells contract when stimulated? | As a single unit |
What is the name of the contraction phase of the cardiac cycle? | Systole |
What is the name of the relaxation phase of the cardiac cycle? | Diastole |
Where are the 4 locations in which receptors that monitor cardiac output are found? | Blood vessels, kidneys, brain, heart |
What 4 methods regulate the heart? | Brain, hormones, heart tissue, and receptors monitoring cardiac output |
What is the name and locations of receptors that detect changes in pressure in the heart and main arteries? | Baroreceptors- found in the aorta and carotid arteries |
What is the name for the receptors that detect changes in chemical composition of the blood? | Chemoreceptors |
Which 2 neurotransmitters are released by the sympathetic nervous system, and what are their effects on the heart when released? | Norepinephrine and epinephrine; they increase heart rate, increase force of contraction, increase conduction through the heart, and cause coronary vasodilation |
What is the mechanism of action, neurotransmitter, and effects on the heart of the parasympathetic nervous system? | The vagus nerve releases acetylcholine, which slows the heart rate (via SA node) and electrical conduction |
What are 4 key properties of myocardial cells? | Automaticity, excitability, conductivity, and contractility |
The ability of certain cells to produce an electrical impulse without outside nerve stimulation is the definition of what key property of myocardial cells? | Automaticity |
The ability to respond to an electrical stimulus is the definition of what key property of myocardial cells? | Excitability |
The ability to transmit an electrical stimulus from cell to cell is the definition of what key property of myocardial cells? | Conductivity |
The ability to contract when electrically stimulated is the definition of what key property of myocardial cells? | Contractility |
What 2 types of cells are specialized to generate and transmit electrical impulses throughout the myocardium? | Pacemaker and Electrical conducting cells |
Which cell type in the conductive pathway has the ability to spontaneously generate an impulse at a certain rate? | Pacemaker cells |
What cell type in the conductive pathway carries the electrical impulses to the appropriate regions of the heart? | Electrical conducting cells |
Which bundle of cells act as the heart's primary pacemaker? | Sinoatrial node |
What is the intrinsic rate/normal sinus rhythm of the sinoatrial node? | 60-100 bpm |
Which bundle of cells in the heart act as the pathway for impulses to reach the ventricles? | Atrioventricular node |
Where in the heart is the sinoatrial node located? | High in the posterior right atrium |
Where in the heart is the atrioventricular node located? | Low right atrium |
What is the intrinsic rate of the atrioventricular node? | 40-60 bpm |
Which bundle of cells in the heart act as a gatekeeper? | The atrioventricular node |
What is the flow of electrical activity through the heart? | SA node -> AV node -> Bundle of His -> R&L Bundle branches (L. bundle branch branches into anterior and posterior fascicles) -> Purkinje fibers |
What is the intrinsic rate of the purkinje fibers? | 20-40 bpm |
In a polarized/resting state, negatively charged ions are found where in reference to the myocardial cell? | Inside the cell |
In a polarized/resting state, positively charged ions are found where in reference to the myocardial cell? | Outside the cell |
What happens during depolarization of myocardial cells? | Positive Na ions enter the cell |
What happens during repolarization of myocardial cells? | Positive Na, Ca, and K ions leave the cell |
What is the name for the time after depolarization when the cell becomes resistant to further depolarization? | Absolute refractory period |
What is the name for the late phase of repolarization in which a very strong electrical stimulus causes depolarization? | Relative refractory period |
How are bipolar limb leads numbered? | I, II, III, etc. |
How are unipolar limb leads numbered? | V1-V6 for chest/precordial leads; aVR, aVL, or aVF for augmented limb leads |
Electrical impulses moving in what direction cause an upright wave/tracing on the EKG? | Toward a positive electrode |
Electrical impulses moving in what direction cause a negative deflection/below baseline on the EKG? | Toward a negative electrode |
Many small electrical currents in various directions is the definition of what? | Vectors |
The overall direction of the sum of the currents (vectors) is the definition of what? | Axis |
Which leads are in the frontal plane? | Limb leads I, II, and III, and aVR, aVF |
Which leads are in the horizontal plane? | Precordial chest leads V1-V6 |
The P wave represents what electrical activity in the heart? | Atrial depolarization |
The QRS complex represents what electrical activity in the heart? | Ventricular depolarization |
The T wave represents what electrical activity in the heart? | Ventricular repolarization |
Which electrical activity in the heart is hidden and by what wave? | Atrial repolarization is hidden by the QRS complex |
What length of time does each small square on an EKG paper represent? | 0.04 seconds |
What length of time does 5 small squares on EKG paper represent? | 0.20 seconds |
What is the name of the flat line that occurs either when no electrical activity is occurring, or when electrical impulses are too weak to be detected? | Isoelectric line |
What is the normal duration of the P wave? | 0.06-0.10 seconds |
What is the starting and ending point for measuring the PR interval? | Start measuring at the beginning of the P wave, end measuring at the end of the QRS complex |
What is the normal duration of the PR Interval? | 0.12-0.20 seconds |
What is the starting and ending point for measuring the PR segment? | The PR segment is the isoelectric line between the end of the P wave and the beginning of the QRS complex |
What is the normal duration of the QRS complex? | 0.06-0.11 seconds |
What is the starting and ending point of the ST segment? | The ST segment is the isoelectric line that begins at the end of the QRS complex, and ends at the beginning of the T wave |
What is the name given for the point where the QRS complex meets the ST segment? | The J point |
What is the starting and ending point of the QT Interval? | The QT Interval begins at the beginning of the QRS complex and ends at the end of the T wave |
What electrical activity of the heart is represented by the QT Interval? | The time of ventricular depolarization and repolarization |
What is the normal duration of the QT Interval? | 0.36-0.44 seconds |
What is the term given for markings on an EKG that are not a product of the heart's electrical activity? | Artifact |
Where are the positive and negative electrode placings in the bipolar lead I? | Positive on the left arm, negative on the right arm |
Where are the positive and negative electrode placings in the bipolar lead II? | Positive on the left leg, negative on the right arm |
Where are the positive and negative electrode placings in the bipolar lead III? | Positive on the left leg, negative on the left arm |
Which limb has two negative bipolar electrodes? | The right arm |
Which limb has two positive bipolar electrodes? | The left leg |
Which limb does the positive electrode of aVR attach to? | The right arm |
Which view of the heart does the aVR lead represent? | The base of the heart: the atria and great vessels |
Which lead gives a base view of the heart: the atria and great vessels? | aVR |
Which limb does the positive electrode of aVL attach to? | Left arm |
Which view of the heart does the aVL lead represent? | The lateral wall of the left ventricle |
Which lead gives a view of the lateral wall of the left ventricle? | aVL |
Which limb does the positive electrode of aVF attach to? | Left leg |
Which view of the heart does the aVF lead represent? | The inferior wall of the left ventricle |
Which lead gives a view of the inferior wall of the left ventricle? | aVF |
Where is the precordial V1 lead placed on the chest? | In the 4th ICS on the right of the sternum |
Where is the precordial V2 lead placed on the chest? | In the 4th ICS on the left of the sternum |
Where is the precordial V3 lead placed on the chest? | Halfway between V2 and V4 |
Where is the precordial V4 lead placed on the chest? | In the 5th ICS in Mid-clavicular line |
Where is the precordial V5 lead placed on the chest? | At the anterior axillary line |
Where is the precordial V6 lead placed on the chest? | Mid-axillary line |
Which leads provide anterior and lateral views of the heart? | Precordial leads V1-V6 |
Which leads provide information about the anterior surface of the heart? | V1-V4 |
Which leads provide information about the lateral surface of the heart? | I, aVL, and V5-V6 |
Which leads provide information about the inferior surface of the heart? | II, III, and aVF |
What characteristics of a P wave constitute normal sinus rhythm? | P waves are upright, round, and one is present before each QRS complex |
What characteristics of a QRS complex constitute a normal sinus rhythm? | QRS complexes are narrow, and are 0.06-0.11 seconds in duration |
What are the 3 methods available for determining heart rate? | Multiply the number of QRS complexes in a 6-second interval by 10; start 300 150 100 75 60 50 large boxes between R waves; 1500/the number of small squares between 2 consecutive R waves |
When is a person considered to have bradycardia? | Heart rate <60 bpm |
When is a person considered to have tachycardia? | Heart rate >100 bpm |
What constitutes a regular rhythm? | The distance between RR-intervals is the same, and the distance between P-P intervals is the same |
What 7 types of irregular rhythm are there? | Occasionally irregular, very irregular, slightly irregular, sudden heart rate acceleration, patterned irregularity, total irregularity (irregularly irregular), and variable conduction ratio |
What is an explanation of occasionally irregular heart rhythm? | Rhythm is mostly regular, but can be irregular from time to time |
What is an explanation of very irregular heart rhythm? | There are many areas of irregularity |
What is an explanation of a slightly irregular heart rhythm? | Pacemaker changes locations = wandering atrial pacemaker. P waves look different (some are smaller, some are inverted, etc.) |
What rhythm is seen with a wandering atrial pacemaker? | Slightly irregular rhythm |
What is an explanation of a sudden heart rate acceleration rhythm irregularity? | A normal heart rate suddenly accelerates to tachycardia = paroxysmal tachycardia |
What rhythm irregularity is seen with paroxysmal tachycardia? | Sudden heart rate acceleration |
What is an explanation of a patterned irregularity heart rhythm? | Irregularity is repeated in a cyclic fashion |
Which rhythm irregularity is seen with sinus dysrhythmia, breathing, or 2nd degree A-V heart block? | Patterned irregularity |
What is an explanation of a totally irregular/irregularly irregular rhythm? | No pattern to the irregularity |
Which rhythm irregularity is seen with atrial fibrillation? | Irregularly irregular |
What is the normal duration and amplitude of a P wave? | Duration 0.06-0.10 seconds, Amplitude 0.5-2.5 mm/small boxes |
What is the name for a tall P wave (greater than 2.5 mm/small boxes high), and what might it indicate? | P pulmonale suggests RAE |
What 2 possible heart conditions might be represented by a notched, wide, or biphasic P wave? | Increased left atrial pressure or left atrial dilation |
What is the name for a wide P wave (greater than 0.10 seconds), and what condition might it indicate? | P mitrale suggests LAE |
What might the P wave look like in atial tachycardia? | It might be buried in the T wave |
A saw-toothed pattern between QRS complexes could indicate what condition? | Atrial flutter- an ectopic site in the atria fires at 250-300 times per minute |
When does atrial fibrillation occur? | When ectopic sites in the atria fire faster than 350 times per minute |
What is the physiological explanation behind an inverted P wave? | Results when a P wave arises from the lower right atrium near the AV node, in the left atrium, or the AV junction |
What condition is associated with inverted P waves? | Dysrrhythmias originating from the AV junction |
What is the explanation for the presence of more P waves than QRS complexes? | The pulse was initiated in the SA node or atria, but was blocked before reaching the ventricles |
Tall QRS complexes indicate what 3 possible heart conditions? | Ventricle(s) hypertrophy, abnormal pacemaker, or aberrant conduction |
Short/Low-voltage QRS complexes indicate what 3 possible conditions? | Obesity, hypothyroidism, pericardial effusion |
Wide, bizarre QRS complexes may be explained by what condition? | Right or left bundle branch block resulting from a defect in ventricular conduction |
What is the explanation for the wide QRS complex seen in aberrant conduction? | An electrical impulse reaches the bundle branch while it is still in a refractory period after a previous impulse. The new impulse travels down |
When does atrial fibrillation occur? | When ectopic sites in the atria fire faster than 350 times per minute |
What is the physiological explanation behind an inverted P wave? | Results when a P wave arises from the lower right atrium near the AV node, in the left atrium, or the AV junction |
What condition is associated with inverted P waves? | Dysrrhythmias originating from the AV junction |
What is the explanation for the presence of more P waves than QRS complexes? | The pulse was initiated in the SA node or atria, but was blocked before reaching the ventricles |
Tall QRS complexes indicate what 3 possible heart conditions? | Ventricle(s) hypertrophy, abnormal pacemaker, or aberrant conduction |
Short/Low-voltage QRS complexes indicate what 3 possible conditions? | Obesity, hypothyroidism, pericardial effusion |
Wide, bizarre QRS complexes may be explained by what condition? | Right or left bundle branch block resulting from a defect in ventricular conduction |
What is the explanation for the wide QRS complex seen in aberrant conduction? | An electrical impulse reaches the bundle branch while it is still in a refractory period after a previous impulse. The new impulse travels down the non-refractory bundle branch, and then down the other bundle branch. Separate impulses = wide QRS complex |
What 4 conditions would label the PR interval as abnormal? | Shorter than 0.12 seconds, longer than 0.20 seconds, absent interval, or interval duration varies |
What is the explanation for a short PR Interval? | Electrical impulses start from a supraventricular site, but travels to the ventricles via abnormal accessory pathways and causes premature ventricular depolarization = preexcitation |
What is the explanation for a long PR interval? | Conduction of electrical impulse through the AV node is delayed = 1st degree AV heart block |
What 2 conditions may cause varying PR intervals? | Wandering atrial pacemaker or 2nd degree AV heart block |
What is the varying PR interval pattern seen with 2nd degree AV heart block? | PR intervals are progressively longer until a QRS complex is dropped. Repeat. |
In what 4 conditions are PR intervals absent? | Atrial flutter, atrial fibrillation, 3rd degree AV heart block, and ventricular dysrhythmias |
What is the explanation for absent PR intervals in 3rd degree AV heart block? | Atria and ventricles are beating independently of each other |
What is the characteristic of sinus bradycardia? | Normal sinus rhythm with heart rate <60 bpm |
What is the characteristic of sinus tachycardia? | Normal sinus rhythm with heart rate >100 bpm |
What problem with oxygen is associated with tachycardia? | Tachycardia can increase oxygen requirements = worsen ischemia, induce infarction |
Describe the pattern seen with sinus dysrhythmia. | Dysrhythmia is cyclic: slows down, then speeds up with breathing |
What 3 conditions might sinus dysrhythmia be normal in? | Athletes, children, or older adults |
Describe the pattern seen with sinus arrest. | A pause in EKG rhythm occurs (isoelectric), normal rhythm resumes |
What 3 mechanisms can cause atrial dysrhythmias? | Automaticity, triggered activity, and reentry |
What key characteristics are seen with atrial dysrhythmias? | Abnormal P waves that differ in appearance with each beat, varying PR intervals, narrow-normal QRS complexes |
What pattern is seen with premature atrial contraction? | Abnormal P-waves, followed by a non-compensatory pause, and wide QRS complexes |
What characteristics are seen with atrial tachycardia? | Abnormal, consistent P waves with a heart rate of 150-250 bpm |
What is the term for short bursts of atrial tachycardia? | Paroxysmal atrial tachycardia |
What characteristics are seen with multifocal atrial tachycardia? | Changing P wave morphology, irregular rhythm, and a heart rate of 120-150 bpm |
What characteristics are seen with supraventricular tachycardia? | Tachycardia with no P waves |
What is the heart rate seen with atrial flutter? | 250-350 bpm |
What are 2 potential side effects of atrial fibrillation? | Decreased cardiac output by 25%, clots form in the atria due to blood stagnating from inefficient atrial contraction... predispose pt. to a systemic emboli |
What characteristics are seen with junctional dysrhythmias? | Inverted or absent P waves, short PR interval if P waves present, P wave after QRS complex |
What characteristics are seen with premature junctional complex? | An early electrical impulse and an inverted P wave |
Where does the electrical impulse come from with premature junctional complex? | AV junction |
What characteristics are seen with junctional escape rhythm? | Inverted P wave before, during, or after QRS complexes, heart rate of 40-60 bpm, short PR interval |
What characteristics are seen with accelerated junctional rhythm? | Inverted P waves before, during, or after QRS complexes, short PR interval, heart rate of 60-100 bpm |
What characteristics are seen with junctional tachycardia? | Inverted P waves before, during, or after QRS complexes, short PR interval, heart rate of 100-180 bpm |