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SSS: Sick Sinus Syndrome

 

SSS is a condition of the Sinoatrial Node that develops over time such that the SA node is unable to perform its function as the pacemaker of the heart.  It most commonly affects the elderly and is often idiopathic. 

 

The syndrome has multiple manifestations on the ECG including sinus bradycardia, sinoatrial block and alternating tachycardia/ bradycardia.  Thus it is also known as Tachy/Brady Syndrome.  Sick Sinus Syndrome affects approximately 1 in 600 patients over the age of 65 years old.  It also accounts for nearly 50% of pacemaker implantations.

The treatment of choice for sick sinus syndrome is a dual chambered pacemaker. 

 

Causes of Sick Sinus Syndrome

 

The causes of SSS can either be intrinsic or extrinsic in nature.

 

Extrinsic causes include:  hyperkalemia, hypoxia, digitalis preparations, calcium channel blockers, beta blockers, sympatholytic agents, anti arrhythmics and toxins.

 

Intrinsic causes include:  cardiomyopathies, familial tendencies, leukemia, metastatic cancer, myocarditis, pericarditis, rheumatic heart disease and surgical injury

 

Coronary artery disease may co exist with SA node dysfunction, but is usually temporary when it follows an acute myocardial infarction.

 

Clinical manifestations of Sick Sinus Syndrome

 

Often SSS is asymptomatic or has only mild symptoms only.  The symptoms are related to a decease in cardiac output with brady or tachy dysrrhythmias.  By definition, SA node dysfunction is an atrial rate that is inappropriate for physiologic requirements.  Decreased cardiac outpur causes decreased cerebral perfusion and either syncope or pre syncope. 

 

The ECG findings include atrial bradydysrrhythmias including sinoatrial block, atrial fibrillation with slow response and second degree block, Mobitz I or II.  Tachy dysrrhythmias include paroxysmal supraventricular tachycardia, atrial flutter, atrial fibrillation with a rapid response and atrial tachycardia.  Atrial fibrillation is the most common tachydysrrhythmia that presents.

 

The most common method of diagnosing sick sinus syndrome is with a 24 hour Holter Monitor and a precise diary kept by the patient.  Once diagnosed, the patient is urged to seek medical attention for fainting, near syncope, palpitations, dizziness, chest pain, shortness of breath, fatigue or loss of memory.                                

 

EKG Characteristics. Rate: Any rate can occur with SSS. Rhythm: Can be regular regular or irregular. Normal P wave configuration. Normal PR Interval. QRS Complex: Normal configuration for intrinsic rhythm. Normal T Wave configuration.

Nursing Intervention: Notify the MD if SSS arrhythmia is new for the patient, or of the patient is becoming symptomatic. Administer oxygen. A pacemaker is usually used to treat SSS.

Source:  http://www.nlm.nih.gov/medlineplus/ency/article/000161.htm

 

1AVB: 1st Degree Atrial Ventricular Block

Definition: A 1AVB is a rhythm in which the electrical impulse which leaves the SA node and travels through the atria, AV node, Bundle of His to purkininjie fibers is slowed down and takes longer than normal to arrive at its destination. The normal PR interval is 0.12- 0.20 seconds. A 1AVBT is greater than 0.20 seconds. The cause ranges from coronary heart disease, inferior wall MI's, hyperkalemia, congenital abnormalities, and medications such as quinidine, digitalis, beta blockers, and calcium channel blockers.

EKG Characteristics: Rate: The atrial rate or P waves can vary to any rate. The ventricular rate can also vary. There must be a 1:1 conduction of the P waves to the QRS waves. Rhythm: Atrial and ventricular rates are usually regular, but they may also be irregular. P Wave: Usually normally shaped and occurring with a 1:1 ration with the QRS. PR interval: greater than0.20 seconds. QRS Complex: Within normal limits or may have a bundle branch block. ST Segment: Within normal limits for the intrinsic rhythm. T Wave: Within normal size and configuration. 

Nursing Interventions: If it is new, research the reasons or cause. Otherwise there are no nursing interventions.

http://www.lond.ambulance.freeuk.com/ecg/ECG2.htm

 

 

Wenckebach or Mobitz 1

Definition: Second degree AV block is also known as Second Degree Type I, Mobitz I, or Wenckelbach. This arrhythmia is characterized by a progressive delay of the conduction at the AV node, until the conduction is completely blocked. This occurs because the impulse arrives during the absolute refractory period, resulting in an absence of conduction, and no QRS. The next P wave occurs and the cycle begins again. Possible causes are acute inferior wall myocardial infraction, digitalis, beta blockers, calcium channel blockers, rheumatic fever, myocarditis, or excessive vagal tone.

EGK Characteristics: Rate is ususaly 60-100 beats per minute. Atrial rhythm is regular. Ventricular rhythm is irregular. P Wave configuration is normal. PR interval gets longer with each beat until QRS complex is dropped. QRS complex is normal, but is dropped periodically. ST Segment and T Wave are normal in configuration. 

Nursing Intervention: Observe patient status, obtain vital signs to see if the patient is tolerating the rhythm. Notify the MD if it is a new arrhythmia. Check medication for possible causes. The drug used to treat symptomatic Mobitz 1 is atropine.

The incidence of typical and atypical A-V Wenckebach periodicity. Denes P, Levy L, Pick A, Rosen KM.

The classic pattern of the typical WP's consists of (1) progressive lengthening of the P-R intervals with the largest increment occuring in the second conducted beat, (2) progressive decrease in P-R increment which accounts for the progressive shortening of successive R-R intervals, and (3) the pause produced by the nonconducted P-wave is less than two P-P intervals. In 45 patients with atrial pacing-induced Wendkebach periods of A-V conduction, the structure of these was studied with His bundle recordings. Of the 128 periods analyzed exceeding 3:2 A-V conduction ratios, 66 per cent were atypical. In 24 patients with spontaneous WP's of A-V conduction, the electrocardiographic records were studied. Of the 98 periods analyzed exceeding 3:2 A-V conduction ratios, 86 per cent were atypical. WP's with A-V conduction ratios greater than 6:5 were all atypical. Five categories of atypical WP's are described.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Abstract&list_uids=75070818
 

Mobitz II

Definition: Mobitz II is characterized by 2-4 P waves before each QRS. The PR pf the conducted P wave will be constant for each QRS. It is usually associated with acute anterior or anteroseptal myocardial infarction. Other causes are cardiomyopathy, rheumatic heart disease, coronary artery disease, digitalis, beta blockers, and calcium channel blockers. Mobitz II has the potential of progressing into a third degree heart block or ventricular standstill. This is a dangerous rhythm.

EKG Characteristics: Rate: Ventricular rate will depend on the number of impulses conducted through the AV node, and will be less than the atrial rate. Rhythm: Atrial and ventricular rate is irregular. P Wave: Present in two, three or four to one conduction with the QRS. PR Interval: Constant for each P wave proir to the QRS. QRS: May be within normal limits for the intrinsic rhythm. ST Segment: Normal in size and configuraration.

Nursing Intervention: Obtain vital signs, and notify the MD. Atropine can be used with symptomatic MobitzII. A transcutaneous or permanent pacemaker may be a solution for Mobitz II. Look for drugs that may cause the Morbitz II, such as digoxin, beta blockers, and calcium channel blockers. Be prepared for a code situation.

http://www.lond.ambulance.freeuk.com/ecg/ECG2.htm

 

Third Degree Atrial Ventricular Block

Definition: A third degree atrial ventricular block is also know as a complete heart block artrioventricular block of 3degree AV block. It is a problem with electrical conduction. All electrical conduction from the atria are blocked at the AV junction, therefore, the atria and the ventricles beat independently from each other. This arrhythmia is dangerous because it significantly decvreases cardiac output, and could lead to asystole. Possible causes: acute inferior and anterior myocardic infraction, coronary heart disease, excessive vagal tone, myocarditis, endocarditis, age, edema from heart surgery, and meditation toxitidy from digitalis, beta blockers, calcium channel blockers.

EKG Characteristics: Rate: Atrial rate faster than ventricular rate. Rhythm: Regular, but there is normal configuration. PR Interval: There is no relationship between P waves and QRS complexes. QRS Complex: Variates depending on the intrinsic rhythm. ST Segment and T Wave: Normal configurations.

Nursing Interventions: Oxygen administration, set up for temporary pacer, and notify the MD. The drug used to treat arrhythmia is atropine.

 

Tachy/Brady Syndrome.

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