Normal Sinus Rhythm•Heart rate: between 60 and 100 beats/min•PR interval: 0.12–0.20 s•QRS complex: <0.12 s•T wave: upright•ST segment: flat•R to R interval: regular (varying less than 0.12 s between QRS complexes)
Sinus Tachycardiaone abnormality—an elevated heart rate.•Heart rate: >100 beats/min•PR interval: 0.12–0.20 s•QRS complex: <0.12 s•T wave: upright•ST segment: flat•R to R interval: regular (varying less than 0.12 s between QRS complexes)
Sinus Bradycardiaone abnormality—a decreased heart rate.•Heart rate: < 60 beats/min•PR interval: 0.12–0.20 s•QRS complex: <0.12 s•T wave: upright•ST segment: flat•R to R interval: regular (varying less than 0.12 s between QRS complexes)
Sinus DysrhythmiaA sinus dysrhythmia has an irregular R to R interval. The heart is usually normal but may result in a sinus brady dysrhythmia (too slow) or sinus tachy dysrhythmia (too fast).•Heart rate: may be normal, slow, or fast•PR interval: 0.12–0.20 s•QRS com
Dysrhythmia – Sinus tachycardiaAnxiety, pain, fever, hypovolemia, hypoxemia; also side effect of bronchodilator medication
Dysrhythmia – Sinus bradycardiaHypothermia and abnormalities in SA node
Dysrhythmia – Sinus arrhythmiaVaries with breathing (increased rate during inspiration, decreased rate during expiration)—more pronounced with lung disease; associated with inferior wall myocardial infarction and increased intracranial pressure; also affected by medications.
In heart block, there is a problem with conduction between the SA node and the AV node. The width of the QRS complex provides information about the location of the ventricular pacemaker•A normal QRS interval (<0.12 s) indicates pacing from the AV junction—a junctional ectopic beat.•A wide QRS interval (>0.12 s) indicates pacing from cells in the ventricles—a ventricular ectopic beat; ventricular beats normally produce slower heart rate
First-Degree Heart Block•Heart rate: usually between 60 and 100 beats/min•PR interval: >0.20 s, but constant•QRS complex: <0.12 s•T wave: upright•ST segment: flat•R to R interval: regular (varying less than 0.12 s between QRS complexes
Second-Degree Heart Block Type I•Heart rate:irregular, usually between 60 and 100 beats/min•PR interval:the PR interval gradually gets longer after each beat until a P wave is not conducted to the ventricles (no QRS complex)•QRS complex:<0.12 s•T wave:upright•ST segment:flat•R2R:Irreg
Second-Degree Heart Block Type II•Heart rate: irregular and lower than normal•PR interval: normal or slightly prolonged•QRS complex: <0.12 s if block at bundle of His, wider complex if block below the bundle of His•T wave: upright•ST segment: flat•R to R interval: irregular
Third-Degree Block•Heart rate: irregular and lower than normal•PR interval: variable•QRS complex: <0.12 s if block at bundle of His, wider complex if block below the bundle of His•T wave: upright•ST segment: flat•R to R interval: regular
Causes of Heart Blocks – First-degreeInferior wall MI, complication of medications such as digoxin or beta-blockers
Causes of Heart Blocks – Second-degree type IAbnormality in AV junction, ischemia to right coronary artery
Causes of Heart Blocks – Second-degree type ILeft coronary artery ischemia or anterior wall MI
Causes of Heart Blocks – Third-degreeAcute MI (more common with inferior and posterior wall MI), drug toxicity (digitalis)


Egan’s Chapter 17 Practice Questions:


1. Atrial Fibrillation: -Atrial muscle quivers in an erratic pattern that does not result in a coordniation contraction., -No true P waves, -Ventricular rate may be abnormal resulting in an abnormal R-R interval.

2. Atrial Flutter: -Rapid depolarization of the atria resulting from ectopic focus that depolarizes at a rate of 250-350 times per minute., -P waves appear similar, -Sawtooth pattern, -Numerous p waves to each QRS complex, -R-R interval may be normal or vary, – causes may include: heart disease, stress, renal failure, and hypoxemia.

3. First-Degree Heart Block: -PR interval is longer than .20 seconds, -there is one p wave before each QRS complex, -Typically the QRS complex has a normal configuration, – R-R intervals are regular, -Common following an MI that damages the AV node, or may be a complication of certain medications such as digoxin or Beta blockers.

4. Normal Sinus Rhythm: – upright p wave that is identical from one complex to the next, -Consistent PR interval, – identical QRS complex no longer than .12seconds, – Flat ST segment, -R-R interval is regular and does not vary more than .12 seconds, -HR is between 60-100

5. Premature Ventricular Contractions: -cause a unique and bizarre QRS complex, which is wider than normal., -no p wave preceding and may occur as a single event, -PCV may occur at every other beat, every third beat, or as a run., – often occurs as a result of stress.

6. PR interval: the distance (time) between the start of atrial depolarization and the start of ventricular depolarization.

7. P wave: Wave of depolarization in the atria

8. QRS: Wave of depolarization over the ventricles

9. Second Degree Heart Block: Two types

10. Second Degree Heart Block Type II (Mobitz type II): -result of more serious problems such as MI or ischemia., -a series of nonconducted P waves followed by a P wave that is conducted to the ventricles., -PR interval for the conducted impulses is consistent.

11. Sinus Arrhythmia: -recognized by irregular spacing between the QRS complex., -R-R interval varies more than .12seconds, -may occur with the effects of breathing on the heart or as a side effect of medications such as digoxin., -Most times this doesn’t need treatment.

12. Sinus Bradycardia: -Heart rate is less than 60 but the rest of the tracing looks normal., -represents a significant clinical problem if it causes the patient’s blood pressure to drop significantly or causes symptoms such as fatigue, lightheadedness, or syncope., -Most often caused by hypothermia or abnormalities in the SA node.

13. Sinus Tachycardia: -Heart rate exceeds 100 but the rest of the ECG tracing looks normal, -Most often caused by anxiety, pain, fever, hypovolemia, or hypoxemia., -May also be caused from certain medications such as bronchodilators

14.Steps to reading an EKG: 1. Identify the atrial rate, 2. Measure the PR interval, 3. Evaluate the QRS complex, 4. Evaluate the T wave, 5. Evaluate the ST segment, 6. Identify the R-R interval, 7. Identify the mean QRS axis.

15. ST segment: the time from the end of ventricular depolarization to the start of repolarization.

16. Third Degree Heart Block: -most serious, – indicated the conduction system between the atria and ventricles is completely blocked, and impulses generated in the SA node are not conducted to the ventricles. , -no relationship between the P waves and the QRS complex. , -The P-P intervals and the R-R intervals regularly march out, but they have no correlation with eachother., -QRS complexes are normal if ventricles are paced by the AV node., -QRS complexes are not normal in configuration if the ventricles are paced by an ectopic site and are abnormally wide., -often caused by MI or drug toxicity.

17. T wave: Wave of repolarization over the ventricles

18. Type one second-degree heart block, (Wenckebach or Mobitz type I): -occurs when an abnormality in the AV junction delays or blocks conduction of some of the impulses through the AV node., -prolongged PR interval until one impulse does not pass on to the ventricles at all.(p wave that is not followed by a QRS complex).


Egan’s Chapter 17 Study Guide:


1. atrial fibrillation: P wave-NO TRUE, R-R ABNORMAL, STAGNATION OF BLOOD, atrial muscle quivers, no pattern, no coordination/contraction

2. ATRIAL FLUTTER: sawtooth baseline, numerous P-waves. Causes: heart disease, Renal failure, stress rapid depolarization of atrial from ectopic focus

3. First degree heart block: P wave-upright, PR interval- GREATER THAN 0.20 seconds, QRS – identical, R-R regular intervals, heart rate 60-100bpm, SA node delayed in passing thru AV node or bundle of his, COMMON AFTER MI, TREATMENT NOT NEEDED IF ABLE TO MAINTAIN BP

4. Normal sinus rhythm: P wave-upright, PR interval- consistent 0.12-0.20 seconds, QRS – identical, <.12, R-R regular intervals’ <.12, heart rate 60-100bpm

5. premature ventricular contractions (PVC): when part of the impulse conducting system or myocardium is diseased and triggers depolarization, causes pulse outside the SA-Node, WIDE QRS, NO P WAVE,
occurs with ectopic beats

6. second degree heart block, TYPE II, Mobitz: P wave-NON CONDUCTED more than QRS
PR interval- PROLONGED0.12-0.20 seconds
R-R regular intervals
heart rate 60-100bpm

7. second degree heart block, TYPE I WENCKEBACH: P wave-random MORE THAN QRS
R-R regular
heart rate 60-100bpm

8. sinus bradycardia: P wave-upright
PR interval- consistent 0.12-0.20 seconds
QRS – identical
R-R regular intervals

9. sinus bradycardia is treated with: atropine

10. Sinus Tachycardia: P wave-upright
PR interval- consistent 0.12-0.20 seconds
QRS – identical
R-R regular intervals

11. sinus tachycardia is treated with: Beta2 Adrenergic

12. THIRD degree heart block: P wave-upright NON CONDUCTED
PR interval- PROLONGED 0.12-0.20 seconds
R-R regular intervals
heart rate 60-100bpm
Total blockage,
atria/ventricles are independent with no relaionship

13. Ventricular Fibrillation: MOST LIFE THREATENING

14. Ventricular tachycardia: Most life threatening, zig-zag pattern
P wave-NONE
heart rate 60-100bpm

15. automaticity: ability for cells to contract, depolarize without stimulation

16. AV node: impulse over the ventricle allows for the ventricles to fill,
located at the intraventricular septum, the back up pacemaker

17. axis: the imaginary line that can be drawn between the positive and negative electrodes in leads I,II,II these axis deviations are seen in QRS complex

18. Axis evaluation: -determine the general direction of the flow during ventricular depolarization, -helps to ID hypertrophy of on of the ventricles

19. Bachmann bundle: wave of depolarization occurs over atria
produces the atrial contraction

20. bundle branches: moves the impulse to right and left ventricles

21. bundle of His: rapidly moves the electrical impulse to the bundle branches

22. cardiac cells: pacemaker,

23. conducting cells: cells that conduct the electrical impulse throughout the heart,
perkinje fibers

24. Cor Pulmonale: negative QRS complexes in lead I,
consistent with right axis deviation,
often seen in COPD

25. a defect in the impulse conducting system leads to: inadequate cardiac output

26. depolarization: contraction

27. Dubb: the sound heard at the close of the atrial valve

28. ECG: inexpensive
easy to use to evaluate pt
show electrical activity of the heart
has no predictive value

29. ECG paper speed: 25 mm/sec

30. Ectopic beat: any heart beat originating outside the SA node

31. Einthoven’s triangle: using leads I, II, III (bipolar leads) that are placed on Right arm, left arm and left leg

32.Elevated or depressed ST segment is common in: MI and is a life threatening arrhythmia

33. impulse conducting system has 3 types of cardiac cells: pacemaker cells
Purkinje cells
atrial and ventricular muscle cells

34. interpretation of ECG is completed by: a doctor

35. ischemia: horizontal ST segment that is above or below the baseline,
blood is not properly flowing to the heart

36. Leads V1 &V2: right ventricle,
placed on the right and left side of the sternum in the forth intercostal space

37. Leads V3 &V4: ventricular septum

38. Leads V5 &V6: left ventricle

39. Lubb: is the sound heard as the bicuspid and tricuspid valve close

40. Multifocal PCVs or the R on T phenomenon with PVCs: this serious condition shows a response to ischemia of the myocardium

41. Myocardial cells: cells that contract in response to electrical stimuli
pump blood,
atrial and ventricular muscle cells

42. pacemaker cells: specialized cells that have a high degree of automaticity
provide electrical power for the heart
SA node and AV node

43. parasympathetic nervous system: slows the heart rate and AV conduction

44. PR interval: 0.12-0.20 seconds,
total atrial electrical activity prior to activation of the bundle of His,
ventricular branches,
purkinje fibers,
shows heart block problem if interval is long

45. Pulseless electrical activity PEA: ECG does not generate a pulse, rare

46. Purkinje fibers: finger like projections penetrate the ventricles, stimulate contraction of the myocardium from apex to base,
coordinates contraction of ventricles

47. P wave: atrial depolarization,
0.08-0.11 seconds

48. QRS complex: ventricle depolarization,
<0.12 seconds,
shows problem in ventricles

49. QT interval: <0.38 seconds,
represents the total ventricular – QRS complex, ST segment & T wave

50. repolarization: relaxing

51. Resting membrane potential: the electrical difference between the electrolytes inside the cell membrane and outside of the cells membranes,
measured in millivolts,
electrolytes responsible are K+, Na+, Ca2+, myocardial cells are about -90mV

52. SA node: impulse is generated to right atrium,
this is also called the pacemaker of the heart, automatic,
located in the upper right part of the atrium,
this is where the heart beat starts.

53. sinus arrhythmia: P wave-upright
PR interval- consistent 0.12-0.20 seconds
heart rate 60-100bpm

54. Sinus bradycardia clinical problem if: causes the pt blood pressure to decrease significantly or if pt is symptomatic

55. ST segment: Refractory period,
<0.12 seconds,
normal is the isoelectric line,
abnormal shows(elevated or depressed) ischemia and MI
potentially life threatening

56. T wave: Ventricle repolarization, <0.20 seconds,

57. Where is atrial repolarization seen on an ECG?: it is obscured by the QRS complex

58. Why do RT need to understand ECG: able to recognize serious arrhythmia’s
able to respond quickly and appropriately