its an easy looking but a difficult topic. I tried to cover it in this presentation. i hope it will help you somehow.

1. SICK SINUS SYNDROME
Ahsan Sajjad
RMU-43

2. Definition:
Sick sinus syndrome describes dysfunction of
the intrinsic pacemaker of the heart, the
sinoatrial node. As a result, the heart rhythm
becomes abnormal characterized by:
 Sinus bradycardia -- slow heart rates
 Tachycardias -- fast heart rates
 Bradycardia-tachycardia -- alternating slow
and fast heart rhythms

3. Mechanism:
 Normally, the sinus node produces a steady
pace of regular electrical impulses. In sick
sinus syndrome, these signals are
abnormally paced. A person with sick sinus
syndrome may have heart rhythms that are
too fast, too slow, punctuated by long pauses
— or an alternating combination of all of
these rhythm problems.

4. Types and Causes:
 Types of sick sinus syndrome and their causes
include:
 Sinoatrial block. Electrical signals move too slowly
through the sinus node, causing an abnormally slow
heart rate.
 Sinus arrest. The sinus node activity pauses.
 Tachycardia-bradycardia syndrome. The heart
rate alternates between abnormally fast and slow
rhythms, often with a long pause (asystole) between
heartbeats

5.  Sick sinus syndrome is relatively uncommon.
 It may be brought on by the use of certain drugs:
such as digitalis, calcium channel blockers, beta-
blockers, and anti-arrhythmics.
 Sick sinus syndrome usually occurs in people older
than 50, in whom the cause is often a nonspecific,
scar-like degeneration of the heart's conduction
system like amyloidosis, sarcoidosis, Chagas
disease and cardiomyopathies.
 In children, a common cause of sick sinus syndrome
is heart surgery, especially on the upper chambers.
 Coronary artery disease, high blood pressure, and
aortic and mitral valve diseases may be associated
with sick sinus syndrome.

6. Symptoms:
 Most people with sick sinus syndrome initially have few or no
symptoms. In some cases, symptoms may come and go.
 When they do occur, sick sinus syndrome symptoms may
include:
 Slower than normal pulse (bradycardia)
 Fatigue
 Dizziness or lightheadedness
 Fainting or near-fainting
 Shortness of breath
 Chest pains
 Trouble sleeping
 Confusion
 Palpitations
 Many of these signs and symptoms are caused by reduced blood
flow to the brain

7. ECG manifestations:
 Sick sinus syndrome can produce a variety of ECG
manifestations consisting of atrial bradyarrhythmias, atrial
tachyarrhythmias, and alternating bradyarrhythmias and
tachyarrhythmias.
 Supraventricular bradyarrhythmias may include sinus
bradycardia, sinus arrest with or without junctional escape,
ectopic atrial bradycardia, and atrial fibrillation with slow
ventricular response.
 The sino-atrial exit block that occurs in patients with sick sinus
syndrome may demonstrate a Mobitz type I block and a Mobitz
type II block. The ECG may reveal a long pause following
cardioversion of atrial tachyarrhythmias, and a greater-than
three-second pause following carotid massage. Sixty percent of
patients have tachyarrythmias.

8. Treatment:
 Treatment may not be necessary if you do
not have any symptoms.
 A permanent implanted pacemaker may be
needed if your symptoms are related to
bradycardia (slow heart rate).
 A fast heart rate (tachycardia) may be treated
with medications. Sometimes radiofrequency
ablation is used to cure tachycardia.

9. HEART BLOCKS
 Interference with the conduction process of
the heart causes the phenomena called
"heart block" or "AV block."
 Heart block is classified according to the level
of impairment — first-degree heart block,
second-degree heart block or third-degree
(complete) heart block.

10. FIRST DEGREE HEART BLOCK
 On an electrocardiogram (ECG), the PR interval is
defined as the time interval between the initial
deflection of the P wave to the start of the QRS
complex. Normally, this interval should be between
120 and 200 msec.
 First-degree heart block, or first-degree
atrioventricular (AV) block, is defined as
prolongation of the PR interval on the ECG to more
than 200 msec. First-degree heart block is
considered "marked" when the PR exceeds 300
msec. While the conduction is slowed, there are no
missed beats.

11. Causes:
 The following are the most common causes
of first-degree atrioventricular (AV) block:
 Intrinsic AV nodal disease
 Enhanced vagal tone
 Acute MI, particularly acute inferior wall
myocardial infarction (MI)
 Myocarditis
 Electrolyte disturbances (eg, hypokalemia,
hypomagnesemia)
 Drugs (especially those drugs that increase the
refractory time of the AV node, thereby slowing
conduction)

12.  Drugs that most commonly cause first-degree AV
block include the following:
 Class Ia antiarrhythmics (eg, quinidine, procainamide,
disopyramide)
 Class Ic antiarrhythmics (eg, flecainide, encainide,
propafenone)
 Class II antiarrhythmics (beta-blockers)
 Class III antiarrhythmics (eg, amiodarone, sotalol,
dofetilide, ibutilide)
 Class IV antiarrhythmics (calcium channel blockers)
 Digoxin or other cardiac glycosides
 Magnesium

13. Pathophysiology:
 With first-degree atrioventricular (AV) block, every
atrial impulse is transmitted to the ventricles,
resulting in a regular ventricular rate. This type of AV
block can arise from delays in the conduction
system in the AV node itself, the His-Purkinje
system, or a combination of both. Overall,
dysfunction at the AV node is much more common
than dysfunction at the His-Purkinje system.
 If the QRS complex is of normal width and
morphology on the ECG, then the conduction delay
is almost always at the level of the AV node.
 If, however, the QRS demonstrates a bundle-branch
morphology, then the level of the conduction delay
is often localized to the His-Purkinje system.

14. Diagnosis:
 It is usually an incidental finding on a routine
ECG.
 This is seen as a PR interval greater than
200 ms in length on the surface ECG.

15. Clinical Findings:
 History:
 Generally asymptomatic at rest
 Markedly prolonged PR interval may reduce
exercise tolerance in some patients.
 Syncope may result from transient high
degree AV block.
 Past history of heart disease including
myocarditis or MI
 Patients may be highly conditioned athletes
 History of infections such as lyme disease

16. Physical Findings:
 The intensity of the first heart sound is
decreased in patients with first degree AV
block.
 Patients may have a short, soft, blowing,
diastolic murmur heard at the cardiac apex

17. Treatment:
 No specific therapy is indicated for isolated
first degree A|V block. Management usually
includes identifying and correcting electrolyte
imbalances and withholding any offending
medications. Any associated condition should
be treated appropriately

18.  Thank You 