Bradycardia-tachycardia syndrome

Bradycardia-tachycardia syndrome
By: Presented by Ri

Sick sinus syndrome

* Multiple manifestations on EKG
* Sinus bradycardia
* Sinus arrest
* Sinoatrial block
* Bradycardia –tachycardia syndrom

Bradycardia-tachycardia syndrome

* Alternating patterns of bradycardia and tachycardia
* Often there is a long pause (asystole) between heartbeats, especially after an episode of tachycardia
* Tachycardia: PSVT, atrial fibrillation, atrial flutter

causes

* Most cases are idiopathic
* Intrinsic causes
* Extrinsic causes
* Cardiac surgery, especially to the atria, is a common cause of sick sinus syndrome in children.

Clinical manifestations

* Many people with sick sinus syndrome have no symptoms
* Symptoms are related to the decresed cardiac output that occurs with the bradyarrythmias or tachyarrythmias
* Fainting , Fatigue , Shortness of breath, or dyspnea, Chest pains , Confusion , Palpitations
* Bradycardia-tachycardia syndrome: peripheral thromboembolism and stroke

Treatment

* If the disorder is asymptomatic (without symptoms), no treatment is necessary
* Bradycardia-tachycardia syndrome
* Associated tachycardia may be treated with medications after the person is protected from symptomatic bradycardia by a pacemaker.
* Warfarin has been shown to decrease the number of strokes and embolic events

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Arrhythmias and EKGs

Arrhythmias and EKGs

Outline
* Sinus Arrhythmia and Sick Sinus Syndrome
* Multifocal Atrial Tachycardia
* Bigeminal Rhythms
* Preexcitation and AVRT

Mechanisms of Arrhythmogenesis
Sinus Arrhythmia
EKG Characteristics: Presence of sinus P waves
Variation of the PP interval which cannot be q attributed to either SA nodal block or PACs

When the variations in PP interval occur in phase with respiration, this is considered to be a normal variant. When they are unrelated to respiration, they may be caused by the same etiologies leading to sinus bradycardia.

Sick Sinus Syndrome
* Characterized by a collection of symptoms and ECG findings due to chronic dysfunction of the sinoatrial (SA) node:
o Chronic and severe sinus bradycardia
o Sinus pauses
o Sinus arrhythmia
o Complete sinus arrest
o Progressive development of atrial arrhythmias (a-flutter, a-fib, atrial tachycardia)
* Patients are usually elderly and present with lightheadedness and/or syncope, but it can also manifest as angina, dyspnea, and palpitations.

* About 50% of people with SSS also display some degree of dysfunction of the AV node
Sinus bradycardia (rate of ~43 bpm) with a sinus pause

Etiologies of Sick Sinus Syndrome
Familial SSS (due to mutations in SCN5A)
Infiltrative diseases
Pericarditis
Lyme disease
Hypothyroidism
Rheumatic fever
Sinus node firbosis
Atherosclerosis of the SA artery
Congenital heart disease
Excessive vagal tone
Drugs
Tachycardia-Bradycardia Syndrome
* Common variant of sick sinus syndrome severe bradycardia alternates with paroxysmal tachycardias, most often atrial fibrillation.
* There is usually a prolonged pause in the cardiac rhythm following cessation of the tachyarrhythmia.
Tachycardia-Bradycardia Syndrome
Abrupt termination of atrial flutter with variable AV block, followed by sinus arrest with a junctional escape beat.

Multifocal Atrial Tachycardia
Bigeminal Rhythms
* Arrhythmias in which each normal sinus beat is followed by a premature contraction (PAC, PJC, or PVC).
* Results in a couplet rhythm which can be detected by pulse or auscultation.
* Generally benign
Atrial Bigeminy
Ventricular Bigeminy
Preexcitation
ECG Characteristics of WPW:
1. Short PR interval
2. QRS prolongation
3. Delta wave
Preexcitation is a condition characterized by an accessory pathway of conduction, which allows the heart to depolarize in an atypical sequence.
The most common form of preexcitation is called Wolfe-Parkinson-White (WPW) syndrome, in which a direct atrioventricular connection allows the ventricles to begin depolarization while the standard action potential is still traveling through the AV node.

AV Reentrant Tachycardia (AVRT)
In patients with WPW, a reentrant rhythm can be generated where the AV node serves as one arm of the reentrant circuit, and the accessory pathway as the other.

Types of AVRT
* Orthodromic AVRT (More common) – Narrow complex tachycardia in which the wave of depolarization travels down the AV node and retrograde up the accessory pathway.
* Antidromic AVRT (Less common) – Wide complex tachycardia in which the wave of depolarization travels down the accessory pathway and retrograde up the AV node.

Mechanism of orthodromic AVRT
Mechanism of antidromic AVRT
What is this arrhythmia?
Antidromic AVRT
Classification Scheme for Arrhythmias

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Joints of the Foot

Joints of the Foot

There are 26 bones in the foot; all but five are involved in at least two joints.
* Hind foot
* Midfoot
* Forefoot
* foot biomechanics1

Subtalar joint: where the talus rests on and articulates with the calcaneus. This is a synovial joint with a weak capsule supported by medial, lateral, posterior & interosseous talocalcaneal ligaments.

* The interosseous talocalcaneal ligament (very strong) lies in the tarsal sinus (separates the anterior & posterior talocalcaneal joints).
* Anatomical subtalar joint- functionally a single synovial joint between the slightly concave articular surface of the talus and the convex posterior articular surface of the calcaneus.

Important Intertarsal joints:
1. Subtalar (talocalcaneal) joint
2. Transverse tarsal joint (calcaneocuboid & talonavicular)

* The main movement at these joints are foot eversion & inversion, eversion is augmented by extension of the toes (especially the lateral toes), inversion is augmented by toe flexion especially the 1st &2nd toes.

Transverse tarsal joints – a compound joint
1. Talonavicular part of the talocalcanealnavicular joint

2. Calcaneocuboid joint

* These 2 separate joints are aligned transversely. At this joint the forefoot & midfoot rotate as a unit on the hind foot around an AP axis. This augments inversion/eversion of the foot.
* Anatomical amputations of the foot are made through this joint.


1. Intertarsal joints:
These bones are so tightly opposed by ligaments that little movement occurs between them

2. Tarsometatarsal joints:
Plane type synovial joints involved in gliding/sliding type movements

3. Metatarsophalangeal joints
Flexion/extension in the foot occurs at the metatarsalphalangeal joints & the interphalangeal joints

4. Interphalangeal joints
Each has plantar, medial & lateral collateral ligaments, dorsal extensor aponeuroses act as dorsal ligaments.

All the joints proximal to the metatarsalphalangeal joints are united by dorsal & plantar ligaments.

All the bones of the metatarsals and interphalangeal joints are united by lateral & medial collateral ligaments.

Major ligaments of the Plantar foot
Plantar calcaneonavicular (Spring) ligament

* Fills a wedge shaped gap between the talar shelf & inferior margin of the posterior articular surface of the navicular. This ligament supports the head of the talus and plays an important role in the transfer of weight from the talus & maintaining the longitudinal arch.

Long Plantar Ligament
* Traverses from the plantar surface of the calcaneus to the groove on the cuboid. Some fibers extend to the base of the metatarsals (forming a tunnel for the tendon of the fibularis longus. This ligament is important in maintaining the longitudinal arch.

Plantar calcaneocuboid (short plantar) ligament:
* Located deep to the long plantar ligament, it runs from the anterior part of the inferior surface calcaneus to the inferior surface of the cuboid. It is located on a plane between the plantar calcaneonavicular (spring) ligament and the long plantar ligament. It is also involved in maintenance of the longitudinal arch.

Arches of the Foot
* The ligamentous bony arrangement of the foot allows considerable flexibility/deformation with weight bearing contact. The arches distribute the weight of the foot (pedal platform) acting both as shock absorbers & spring boards during ambulation of all types.
* Weight distribution is between the calcaneus and sesamoid bones at the 1st metatarsal and head of the 2nd metatarsal; weight is shared laterally with the heads of metatarsals 3-5. Elastic arches between weight bearing points compress with loading and recoil with unloading.
* Lateral Longitudinal arch
* Medial Longitudinal arch
* Transverse Arch

All three work as a unit in weight bearing

* Medial Longitudinal Arch higher and more prominent than the lateral arch.
* Consists of the calcaneus, talus, navicular, 3 cuneiforms and 3 metatarsals
* Talar head is the keystone of the medial longitudinal arch
* The medial arch is supported by the Tibialis anterior ligament as it attaches to the 1st metatarsal and medial cuneiform. Also the tib posterior & FHL.
* The tendon of the fibularis longus passes from lateral to medial and also supports the medial longitudinal arch.
* Lateral Longitudinal Arch is much flatter and consists of the calcaneus, cuboid & lateral metatarsals.
* The medial arch is involved in weight bearing while the lateral arch is involved in balance
* Transverse arch: cuboid, cuneiforms and bases of the metatarsals. This forms the medial & lateral parts of the longitudinal arches which serve as pillars fro the transverse arch.
* The tendon of the fibularis longus & tibialis posterior crossing the sole of the foot obliquely help maintain the curve of the transverse arch.
* The Arches of the foot are maintained by both passive & dynamic supports.

Passive factors
1. Shape of the united bones (especially the transverse arch).

2. 4 layers of fibrous tissue
o 1. Plantar aponeurosis
o 2. Long plantar ligament
o 3. Short plantar ligament
o 4. Spring ligament

Dynamic Support
1. Active (reflexive) bracing action of the intrinsic muscles of the foot support the longitudinal arches.
2. Active & tonic contraction of muscles & tendons extending into the foot:
Longitudinal arch
flexor hallicus longus
flexor digitorum longus
Transverse arch
fibularis longus
tibialis posterior &anterior
3. Plantar ligaments & aponeurosis bear the greatest stress and are most important in maintaining the arches.

Pes Planis (flat feet)
Prior to 3 years of age it is normal to have flat feet due to a fat pad. After the age of 3 this fat pad disappears.

Pes planis can be classified as:

* Flexible: the arch is normal when unloaded however with loading the arch is lost. this is the most common type. It is due to inadequate passive arch support (weak, loose ligaments).
* Rigid type, the arch is absent regardless of loading, this may be due to a congenital deformity.

* Acquired “fallen arches” is due to a tibialis posterior dysfunction due to trauma, denervation and/or degeneration. The plantar calcaneal ligament fails allowing the head of the talus to rotate inferomedially creating a prominence on the medial aspect of the mid-hind foot junction. This is often referred to as over pronation.

Talipes equinovarus (Club foot)
* Club Foot
* A congenital deformity males/females 2/1 Foot inverted, ankle plantarflexed and forefoot abducted. The abnormality is related to short, tight muscles, tendons and ligaments.

* Orthopedic Subtalar joint: anatomical subtalar joint + talocalcaneal part of the talocalcaneonavicular joint (these straddle the interosseous talocalcaneal ligament
* The main movement at this subtalar joint is inversion/eversion.

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