Chapter 35 part 2 Cardiac Disorders 1

Electricity of the heart

Interpreting the Electrocardiogram (Figure 33-15) Interpreting the electrocardiogram (Table 33-10) Rate Rhythm P waves PR interval QRS complex T waves Normal Sinus Rhythm Sinus Bradycardia Sinus Tachycardia Sinus Dysrhythmia Dysrhythmia (arrhythmia) is a disturbance of the heart rhythm caused by a problem in the conduction system

Sinus Rhythm Rhythm of normally functioning electrical system Electrical tracing follows a normal pathway There is no interference.

How do you know it’s Sinus Rhythm Rhythm - interval between two P and two R waves occurs in the same pattern Rate - 60 - 100 P-wave look: The same Usually upright deflection (the bump goes up) There is a P-wave before every QRS complex.

How you know continued PR interval QRS duration Consistently between .12 and .20 seconds QRS duration Consistently between .06 and .10 seconds

How does the patient with Sinus Rhythm feel? Cardiac output is normal The patient is not symptomatic Alert Breathing normally No chest pain or pressure Stable blood pressure

Sinus Bradycardia Less than 60 beats per minute and all other rhythm characteristics are the same as Sinus Rhythm

Is it Sinus Bradycardia? P-wave Looks the same “Bump is usually up” There is one before every QRS Rate - 40 to 60 beats per minute Rhythm – space between 2 P’s and 2 R’s occurs in a regular pattern

Sinus Bradycardia – more facts PR interval Between .12 and .20 seconds QRS duration Between .06 and .10 seconds

SB - How does the patient feel? Patient may or may not exhibit signs of decreased cardiac output. If symptoms are present, inform the physician Rhythm may require drugs or pacemaker.

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What is Sinus Tachycardia? Rate more than 100 beats per minute. All other rhythm characteristics are the same as SR.

More info on Sinus Tachycardia Rate - 100 – 150 beats per minute The interval between two P’s and two R’s is consistent The P-wave: Looks the same “The bump is usually up” The P-wave appears before every QRS complex.

Sinus Tachycardia continued PR interval Between .12 and .20 seconds QRS duration Between .06 and .10 seconds

How does the patient with ST feel? Patients may complain of heart palpitations or a racing heart Sinus tachycardia may be a normal response to exercise It can also be a response to decreased cardiac output (there is less blood circulating with each beat so the heart beats faster) ST may be life threatening in clients who recently had an MI Medications may be necessary

Sinus Arrhythmia The rate is within normal limits. Rhythm is irregular Irregular sinus rhythm can be caused by pressure on the heart from the respiratory cycle or changes in vagal nerve stimulation.

Sinus Arrhythmia (SA) - Criteria Rhythm - irregular Rate - 60 – 100 P-wave Shaped the same Usually “The Bump is Up” P-wave appears proceeds every QRS complex.

Sinus arrhythmia cont. Patient usually shows no visible signs Severe cases may slow the heart rate into the 40’s, causing dizziness, lightheadedness or palpitations Place copy of rhythm strip in patient’s record and notify physician

Sinus Arrest Condition where SA node (pace maker) stops firing, causing pause in electrical activity. Atrial and ventricular contraction do not occur during the pause .

Sinus Arrest- Is it serious? The seriousness depends on length of pause Frequent pauses of two seconds will cause symptoms of decreased cardiac output Immediate treatment is required Notify the physician

Premature Atrial Contractions (PAC) The electrical impulses originate in the atria and start an early impulse which disrupts regular rhythm.

Premature Atrial Contractions (PAC) Rhythm – the overall regularity between P-P and R-R intervals is constant, with the exception of an occasional early complex Rate - 60 to 100 depending on frequency of PAC’s

PAC’s- How do they look? P-wave PR interval P-waves look the same, except for early beat The early beat may be flattened, notched, biphasic or otherwise unusual. The early P-wave may be hidden within the T-wave. PR interval Between .12 and .20 seconds The early beat will have different PR measurements but within normal limits.

How does the patient with PAC’s feel? The patient may experience symptoms of low cardiac output Notify the physician if these symptoms occur

Atrial Flutter (A Flutter) Occurs when a rapid impulse originates in the atrial tissue The impulse may originate from ischemic areas or from the reentry pathway. Reentry pathways provide faster routes for impulses. AF may lead to more serious conditions if not treated

Atrial Flutter (A Flutter)

Atrial Flutter (A Flutter) -Criteria Rhythm- R-R interval is usually irregular, but may, occasionally be regular in the pattern. flutter-to-flutter waves will be regular and stay constant throughout rhythm. Rate - 250 - 300 beats per minute

Atrial Flutter - continued P-wave configuration P-wave’s are not seen, only flutter waves are present. Flutter waves resemble saw-tooth or picket fence and are best seen in leads II and III PR interval – can not be identified QRS interval - .06 - .10 seconds

A Flutter – How does the patient feel? Loss of atrial kick reduces cardiac output by 10 - 30%. Patients with increased heart rate will demonstrate signs of low cardiac output because the heart chambers do not have time to refill with blood between each beat Notify the physician Treatment may include oxygen

Atrial Fibrillation (A Fib.) Occurs when electrical impulses come from areas of reentry pathways or multiple ectopic foci. Electrical impulse results in depolarization of small groups of cells, versus whole atria. Multiple atrial activity is recorded as chaotic activity

Atrial Fibrillation (A Fib.)

A Fib. – Cont’. Rhythm Rate P-P interval can not be determined R-R interval is irregular Rate Atrial rate 375 - 700 beats per minute Ventricular rate, prior to the administration of medication is 160 - 180

A Fib. - Criteria P-wave configuration Cannot be identified Chaotic electrical activity or fib. waves may be seen PR interval - cannot be identified QRS duration - .06 - .10 seconds and irregular

A Fib. – How does the patient feel? Patient exhibits signs of decreased cardiac output When the heart rate is controlled, the patient may be able to tolerate the loss of atrial kick Blood collecting in atria can clot or form thrombus which increases risk of embolism; therefore, patients are given anticoagulants Report complications or vital sign changes to the physician

Supraventricular Tachycardia (SVT) Rapid heart beat makes identification of origin difficult.

Supraventricular Dysrhythmias R-R usually regular If identifiable, P waves usually regular Rate Ventricular rate is 150 - 350 beats per minute. Atrial rate is difficult to determine.

SVT – How does the patient feel? Patient may be in stable or unstable condition Observe patient for low cardiac output Notify the physician

Heart Block Rhythms Occur when electrical activity has difficulty traveling along normal conduction pathway Ventricular depolarization is absent or delayed. 1st Degree Heart Block 2nd Degree AV Block Mobitz I (Wenckeback) 2nd Degree AV Block Mobitz II 3rd Degree Block

First Degree AV Block Delay in electrical conduction from SA node to AV node Electrical stimulus is prevented from traveling to ventricular conduction system.

First Degree AV Block - Criteria Rhythm - regularity between P-P interval and R-R interval is constant. Rate - normal, 60 - 100 beats per minute PR interval - greater than .20 seconds P wave Looks the same P wave occurs before each QRS complex.

1st Degree AV Block – How does the patient feel? Patient can maintain normal cardiac output. Monitor and report development of other heart blocks

2nd degree AV Block, Mobitz I (Wenckeback) Some electrical impulses are blocked from SA node to ventricles at AV junction region. AV node conducts an electrical impulse to the ventricular conduction pathway until it fails, then resets in a repeat pattern

Second Degree AV Block, Mobitz I (Wenckeback) - Criteria P wave Normal size, upright One P wave for every QRS, with additional P waves PR interval - varies, starts short, gets progressively longer until QRS wave is dropped, then cycle is restarted QRS duration - normal .06 - .10 seconds

Wenckeback – How the patient feels The patient may not exhibit signs of low cardiac output until rate decreases to 40 beats per minute, or lower This condition usually results from inflammation around AV node and is often temporary If patient exhibits signs of low cardiac output, the physician should be notified. If no low cardiac output signs are exhibited, monitor patient for progression to third degree heart block

Second Degree AV Block, Mobitz II Classical heart block The AV node selects which electrical impulses to block No pattern or reason for dropping QRS complex exists Frequently progresses to third degree AV block

Second Degree AV Block, Mobitz II P wave looks: Normal size and upright There is one P wave for every QRS complex, but additional P waves PR interval - constant, even after QRS drop occurs QRS duration - normal, .06 - .10 seconds

2nd Degree Mobitz II – How the patient feels Observe patient for signs of low cardiac output Condition can progress within seconds to third degree AV block or complete heart block

Third Degree AV BlockComplete heart block (CHB) All electrical impulses originating above the ventricles are blocked. No correlation exists between atria and ventricle depolarization.

3rd degree AV Block Rhythm Rate P-P interval is regular. R-R interval is regular, but different from P-P interval. Rate Atrial rate is 60 - 100 beats per minute. Ventricular is 20 - 40 beats per minute. P wave configuration .

3rd degree block- a look at the P’s P wave looks: Normal size, but may be buried in QRS complex Number of P waves will not correlate to number of QRS complexes P waves will outnumber QRS complexes PR interval will vary A long PR interval followed by a short PR interval indicates complete heart block

3rd Degree AV Block – How does the patient feel? Patient will show signs of low cardiac output and may be unconscious Immediate medical intervention may be required Initiate Code Blue when patient shows first signs of low cardiac output Rhythm strips should be mounted and identified in patient’s record

Rhythms Originating from the Ventricles Rate- 20 - 40 beats per minute. Electrical Current is initiated in the Purkinje fibers Rhythm is longer than normal depolarization of ventricles.

Premature Ventricular Contractions (PVC) Ectopic beat that occurs early in the cycle and originates from the ventricles

Premature Ventricular Contraction (PVC) Rhythm P-P and R-R intervals are regular with early QRS complexes The early complex has a full compensatory pause Rate Atrial and ventricular rates are the same for the underlying rhythm Early complexes make ventricular rhythm faster than normal rhythm

Premature Ventricular Contraction (PVC) –The P-wave The shape is that of the underlying rhythm P waves not identified on early ventricular complex PR interval Follows underlying rhythm The P wave not present in early complex

Premature Ventricular Contraction (PVC) – the QRS QRS duration Follows underlying rhythm Duration of early complex greater than .12 QRS shape is unusual, with T wave in opposite direction from QRS wave

Types of Premature Ventricular Contractions (PVC) Unifocal - early beat (has similar shape and size suggesting only one irritable focus present) Multifocal - varied shapes and forms of the PVCs Interpolated - PVC occurs during the normal R-R interval without interrupting the normal cycle. Occasional - more than one to four PVCs per minute Frequent - more than five to seven PVCs per minute minute

Types of Premature Ventricular Contractions (PVC) Bigeminy - every other beat is a PVC. Trigeminy - every third beat is a PVC. Quadgeminy -every fourth beat is a PVC. R on T PVC’s - PVC occurs on the T wave or the vulnerable period of the ventricle refractory period. Coupling - two PVCs occur back to back.

PVC – How does the patient feel? Frequency of PVCs determines their significance More complex PVCs indicate increased risk of developing more serious ventricular dysrhythmias Watch for symptoms of low cardiac output Notify licensed practitioner if they occur Treatment includes oxygen

Ventricular Tachycardia (Vtach) the picture Three or more PVCs occur in a row. Ventricles are in continuous state of contraction-relaxation.

Ventricular Tachycardia (Vtach) Rhythm P-P interval usually not identifiable. R-R interval usually regular, can be slightly irregular, at times Rate Atrial rate cannot be determined. Ventricular rate - 100 - 200 beats per minute P wave is usually absent PR interval cannot be determined QRS duration Greater than .12 seconds T wave in opposite direction (usually down) from QRS complex

Vtach – How does the patient feel? If patient is unresponsive, issue code blue, begin CPR, use emergency equipment and notify the physician Mount rhythm strips in patient’s medical record and record code proceedings

Ventricular Fibrillation (Vfib) Chaotic electrical activity within ventricular tissue results in no cardiac output.

Ventricular Fibrillation (Vfib) - Criteria P wave configurations - not identifiable PR interval - cannot be identified QRS duration - cannot be determined

Vfib – Call a code blue! The patient will be unresponsive Code blue situation is present Begin CPR and emergency measures immediately Advanced cardiac life support (ACLS) should begin immediately If patient is conscious and talking it is not Vfib, leads are loose or detached.

Asystole Straight line or flat line No electrical activity is present in the myocardium.

Asystole – Initiate CPR The situation is life-threatening The patient is in cardiac arrest; initiate emergency procedures immediately

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Electronic Pacemaker Rhythms Deliver electrical impulse to myocardium, causing cells to depolarize Can pace the atria, ventricles, or both If the SA nodefires…the pacemaker will not Approximately 115,000 permanent pacemakers are implanted each year

Is the pacemaker working? Pacing spike There is a thin spike on ECG tracing indicating electrical current from pacemaker After the spike, either a P wave or QRS complex will appear