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Sick Sinus Syndrome
1. An interesting case of syncope
Dr. Sunil Thomas George 2nd year PG
Prof Dr. C.Ramakrisnan’s Unit (M4)
2. History
17 year old female came with the complaints of 1 episode of loss of conciousness the previous
night.
The episode accoding to the patient lasted for 15 minutes.
There was no history of up rolling of eye balls , involuntary movements
She has no significant past medical illness
3. Examination
Vitals : BP:110/80mmHG , PR: 80/min
General examination & systemic examination was unremarkable
4. Work up
ECG was withinin normal limits
Neurology opinion was sought
EEG done was withinin normal limits
5. Work up
Having ruled out seizure disorder, patient was worked up for possible cause of syncope
A cardiologist opinion was sought
ECG repeated was within normal limits
2D echo was normal
A 24 hour Holter monitoring study was suggested.
10. Sick Sinus Syndrome
Sick sinus syndrome (SSS) is the term used to describe the inability of the SA node to generate a heart rate that
meets the physiologic needs of an individual.
Numerous electrocardiogram (ECG) abnormalities can result in SSS, including:
●Sinus bradycardia
●Sinus pauses
●Sinus arrest
●SA nodal exit block
●Inadequate heart rate response to physiological demands during activity (chronotropic incompetence)
SSS can also be accompanied by supraventricular tachycardias (atrial fibrillation, atrial flutter, and atrial tachycardia)
as part of the tachycardia-bradycardia syndrome.
11. Epidemiology
Patients with symptomatic SSS are generally older (ie, seventh or eighth decade of life) with
frequent comorbid diseases.
Men and women appear equally affected, and although less common, SSS can occur in younger
adults and children.
Anomalies of systemic venous drainage need to be kept in mind in young patients presenting
with sick sinus syndrome – Recent studies suggest
Reference:
Heart Views. 2015 Jul-Sep; 16(3): 107–110.
Beware of Venous Anomalies in Young Patients with Sick Sinus Syndrome: A Report of Two Cases of Sick Sinus Syndrome with Systemic Venous Anomalies
Shanmuga Sundaram Rathakrishnan, Tamilarasu Kaliappan, and Rajendiran Gopalan
12. Etiology
Sinoatrial (SA) node dysfunction occurs as a result of disorders in automaticity, conduction, or
both.
Local cardiac pathology, systemic diseases that involve the heart, and medications/toxins can all
be responsible for abnormal SA node function and result in SSS.
13. Sinus node fibrosis — The most common cause of sick sinus syndrome
Medications and toxins — most commonly used prescription medications which alter myocardial conduction and can
potentially result in SSS include:
●Beta blockers
●Non-dihydropyridine calcium channel blockers
●Digoxin
●Antiarrhythmic medications
●Acetylcholinesterase inhibitors such as donepezil (Aricept) and rivastigmine used in the treatment of Alzheimer's disease
14. Etiology
Childhood and familial disease — SSS is rare in children, but when present it is most often seen in
those with congenital and acquired heart disease, particularly after corrective cardiac surgery
15. Etiology
Other — Infiltrative diseases ,Inflammatory diseases ,SA nodal artery disease,
Trauma hypothyroidism, hypothermia, hypoxia, and muscular dystrophies.
Some infections (eg, leptospirosis, trichinosis) are associated with relative sinus bradycardia, but
permanent SSS has not followed these
16. Note
Patients with SSS, particularly those with alternating tachycardia and bradycardia, are at an
increased risk for thromboembolic events even after pacemaker implantation.
17. Clinical presentation
Most patients with SSS present with one or more of the following nonspecific symptoms: fatigue,
lightheadedness, palpitations, presyncope, syncope, dyspnea on exertion, or chest discomfort.
Prior to any testing beyond an ECG, a thorough evaluation should be performed for potentially
reversible causes, which include medication use (eg, beta blockers, calcium channel
blockers, digoxin, antiarrhythmics), myocardial ischemia, systemic illness (eg, hypothyroidism),
and autonomic imbalance.
18. ECG findings
SSS is defined by ECG abnormalities (eg, bradycardia, sinus pauses, sinus arrest) that occur in
association with clinical signs and symptoms.
Alternating bradycardia and atrial tachyarrhythmias in over 50 percent of cases. Atrial fibrillation
is most common, but atrial flutter and paroxysmal supraventricular tachycardias (ie, due to atrial
tachycardia) may also occur.
19.
20.
21.
22. Approach to diagnosis
There are no standardized criteria for establishing a diagnosis of sick sinus syndrome (SSS), and
the initial clues to the diagnosis of SSS are most often gleaned from the patient’s history.
23. Suspected SSS
H&P,ECG,review of
prior records, and ETT
Ambulatory
monitoring
Symptoms/rhythm
correlation
SSS
Reversible causes
Not SSS, Evaluate for
other causes of
symptomes
Referral for PPM
implantation
Correct reversible
causes
YES NO/UNCERTAIN DIAGNOSIS
YES
YES
UNCERTAIN/NO
YESNO
25. Differential Diagnosis
Carotid sinus hypersensitivity,
Neurocardiogenic syncope with a predominant cardioinhibitory component
Physiologically normal bradycardia especially among highly conditioned athletes.
29. Types of permanent pacemaker systems
All cardiac pacemakers consist of two components: a pulse generator, which provides the
electrical impulse for myocardial stimulation; and one or more electrodes (commonly referred to
as leads), which deliver the electrical impulse from the pulse generator to the myocardium.
31. Transvenous systems
Usually placed percutaneously or with a cephalic cutdown, without the need for intrathoracic
surgery and inherent associated morbidities
Associated with a non-trivial rate of long-term complications, including:
●Infection
●Venous thrombosis and resultant subclavian vein occlusion
●Lead malfunction
●Tricuspid valve injury (resulting in tricuspid regurgitation)
32. Epicardial systems
Utilize a pulse generator with leads that are surgically attached directly to the epicardial surface
of the heart.
Largely been replaced by transvenous systems for patients requiring long-term cardiac pacing
The major role for epicardial pacing systems in current practice is for temporary pacing following
cardiac surgery
33. Leadless systems
In response to the limitations of both transvenous and epicardial pacing systems, efforts have
been made to develop leadless cardiac pacing systems
Two leadless pacemaker systems are commercially available, with slightly different sizes and
implantation requirements [15]:
●Nanostim (St. Jude Medical), which measures 4.2 x 0.6 cm and requires an 18-French sheath
●Micra (Medtronic), which measures 2.6 x 0.7 cm and requires a 23-French introducer sheath
Conclusion:
Anomalies of systemic venous drainage need to be kept in mind in young patients presenting with sick sinus syndrome. Preprocedural ECHO may give us a clue regarding these abnormalities and help us to avoid on table surprises. In patients with persistent left SVC and absent right SVC requiring pacemaker implantation, we need to be prepared for difficult right ventricular lead positioning. In cases with interrupted IVC temporary pacemaker lead positioning through transfemoral access is difficult though it can be done. Transjugular access may be an option in this situation.
Abnormal automaticity, or sinus arrest, refers to a failure of sinus impulse generation. Abnormal conduction, or sinoatrial delay or block, is a failure of impulse transmission. In such cases, the sinus impulse is generated normally, but it is abnormally conducted to the neighboring atrial tissue. Both abnormal automaticity and abnormal conduction may result from one of several different mechanisms including fibrosis, atherosclerosis, and inflammatory/infiltrative myocardial processes.
Other medications associated with depression of sinus node function include parasympathomimetic agents, sympatholytic drugs (eg, methyldopa, clonidine), cimetidine, lithium, and ivabradine [35,36]. In addition, poisoning by grayanotoxin, produced by some plants (eg, Rhododendron sp.) and found in certain varieties of honey, has been associated with depressed sinus node function [37].
