Cardiac Anatomy and Electrical Activity

• The following is an ECG workshop given by Dr Mathieu Nasarre from the Cardiology Department of CHU de Tours on March 4th, 2025

Anatomical Recall and Cardiac Electrical Activity

• Key anatomical structures include the superior vena cava, pulmonary valve, right atrium, tricuspid valve, right ventricle, and tricuspid pillars
• The aorta, left pulmonary artery, pulmonary veins, left atrium, aortic valve, mitral valve, interventricular septum, left ventricle, and apex are also important

Cardiac Electrical Activity (1/7)

• Cardiac electrical activity starts at the sinoatrial node (SA node)
• The SA node consists of cells that can spontaneously depolarize, called automatism
• The frequency of the SA node is modulated by the nervous system, hormones, temperature, medications, and other factors

Cardiac Electrical Activity (2/7)

• Depolarization from the SA node spreads through both atria
• It uses the myocardium and preferred conduction pathways, including the Bachmann's bundle to the left atrium
• These atrial cells do not possess automatism

Cardiac Electrical Activity (3/7)

• The ventricles are electrically isolated from the atria
• Depolarization must pass through the atrioventricular node (AV node), which has a decremental property functioning as a filter
• AV node cells have automatism at a slower frequency than the SA node, and can take over if the SA node fails

Cardiac Electrical Activity (4/7)

• The bundle of His, an extension of the AV node, propagates depolarization to the ventricles
• Conduction times in the AV node and the trunk of the bundle of His are long
• This allows time for the atrial systole to be hemodynamically effective before ventricular systole

Cardiac Electrical Activity (5/7)

• The bundle of His separates into two branches: a right and a left
• The left branch further divides into an anterior and posterior branch
• Propagation is rapid in the His branches

Cardiac Electrical Activity (6/7)

• The His bundle branches ramify into the Purkinje network, which lines the two ventricles
• Depolarization propagates very rapidly in the Purkinje network

Cardiac Electrical Activity (7/7)

• Depolarization reaches the entire myocardium of both ventricles
• If no other rhythm prevails, the ventricles can depolarize at a slow frequency in a process called the escape phenomenon

Escape Phenomenon

• The natural pacemaker rate is the sinoatrial (SA) node firing at 60 to 100 beats/minute
• The atria conduct impulses at 0.5 to 1 m/s
• The AV node fires at 40 to 60 beats/minute
• The His bundle intrinsic diffusion time is 30ms with a rate of 50 beats/minute
• The Purkinje Fibers fire at 40 beats/minute
• Ventricles diffuse Intrinsically at 1 m/s

ECG Waveforms

• P wave: Represents atrial activation/depolarization
• PR interval: Represents the conduction time between the atria and ventricles
• QRS complex: Represents ventricular activation/depolarization
• ST segment: Marks the beginning of ventricular repolarization
• T wave: Represents ventricular relaxation/repolarization

ECG Placement

• Limb leads are placed on the right arm, left arm, right leg, and left leg
• Chest leads V1-V6 are placed across the chest

Heart Axis

• The normal heart axis lies between 0° and 90°
• Left axis deviation lies between -30° and -90°
• Right axis deviation lies between 90° and 120°

Normal ECG

Normal Values for ECG Intervals

• Heart Rate (HR): 60-100 bpm
• P wave duration < 120 ms
• P wave axis 60° (D2)
• P wave amplitude < 2.5 mm (in D2)
• PR interval 120-200 ms
• QRS duration 80-100 ms, typically 80-120 ms
• QRS axis is: -45 to 110°, but in practise 30 to 90°
• Q wave amplitude is <1/3 of the QRS amplitude and < 40 ms

Bradycardia

• Bradycardia is a slow heart rate, with a frequency below 50 beats/min, and can be permanent or paroxysmal
• It is caused by a failure of the electrical command (sinus node dysfunction)
• Another cause may be conduction block between atria and ventricles (atrioventricular block)
• Symptoms include malaise, syncope, asthenia, and sudden death

Sinus Node Dysfunction

• Sinus node dysfunction includes; sinus bradycardia, sinoatrial block and sinus pause
• Sinus Bradycardia measures 35 / min
• A BSA paroxystique / pause sinusale has to measure 3.4 seconds

Atrioventricular Blocks

• Supra-Hisian block: Atrioventricular node
• Intra-Hisian block: Bundle of His
• Infra-Hisian block: Hisian branches
• Bloc Intra and Infra-Hisian dangerous

Degrees of AV Block

• First-degree: Prolonged PR interval and typically nodal origin, can be intra-nodal
• Second-degree: Intermittent blocked P waves
  • Mobitz Type I (Wenckebach/Luciani): P waves are blocked after progressive PR interval prolongation and the Block often lies within the AV node
  • Mobitz Type II: P waves are blocked without progressive PR interval prolongation and the Block often lies below the AV Node.
  • 2:1 AV block: Non-conducted P wave with every second beat

AV block Risks

• Third-degree blocks can be paroxysmal so may lead to; lipothymia/syncope
• Y causes if signes evocateurs de troubles conductifs atrio-ventriculaires sur l'ECG : BAV1, BBD, BBG, HBPG...

Branch Blocks

• Left bundle branch block (LBBB): Incomplete (BIG) or Complete (BBG), Fascicular, BFAG, BFPG, BFSG
• Right bundle branch block (RBBB): Incomplete (BID) or Complete (BBD)

Identifying RBBB and LBBB

• Leads to a right bundle branch block by deflexion of the mtrinsèque
• Wave T negative
• R aspect of the QRS is found in lead V6
• Q wave septal

RBBB and LBBB

• It illustrates the difference between a normal ventricular waveform compared to a branch block
• Normal QRS to branched block

Cardiac Stimulation

• Temporary cardiac pacing in emergency situations make use of patches Cutaneous
• A Sonde intracardiaque can also be used

Cardiac Stimulation Device

• Permanent cardiac stimulation can be given for unresolvable issues
• Can use Pacemaker leads which link a right atrium to the pacemaker through a Right ventricle

Cardiac device paths

• In bradycardia/asystole a syncope/mort subite occurs so a pacemaker(PM) is fitted
• In PM-VVI pathway one goes through: VD
• To go through: OD and VD we use PM-DDD

Permanent Pacemaker

• Defibrillateur cardiaque Automatique (DAI)
• In DAI-VVI it is: VD
• DAI-DDD the path way is via: OD and VD
• In Asynchronisme inter/intra ventriculaire (BBG) a FEVG of less than 30% causes Insuffisance cardiac
• So we get Resynchronisation which can be Biventriculaire by pathways through : OD, VD and VG
• To go through CRT-PM or CRT-DAI

Pacemaker Procedure

• Cardiac devices can be placed with:Bloc opératoire, AB prophylaxie, Anesthésie locale, Loge prépectorale and this all usually lasts less than 1H
• Veine sous clavière then goes with:Vcs, Od and Vci then finally reaches : Vd, Og,Vg

Cardiac Stimulation Complications

• Fixation de la sonde sur le myocarde may require Vis non retractable, Vis retractable or barbillions
• Or Stylets

Complicationes of Cardiac Devices

• Complications principales post-opératoires involve: Hématome, Pneumothorax, Tamponnade, Déplacement de sonde and Infection (loge/endocardite) are the: intérêt de la surveillance
• A Complication chronique: cassure de sonde(et dysfonction sonde) needs follow up and attention from staff

Living with a cardiac Device

• After l'Implantation follow guidelines especially regarding your health
• Things you can do include: Take Flight, Porter your ceinture de sécurité, Utiliser des appareils électroménagers , you can also utiliser your telephone portable.
• A IRM may require adjustment

More considerations when around ElectroMagnetic fields

• Things you cannot do include: Passez pas dans les champs magnétiques pour les portiques de sécurité, N'exposez pas la cicatrice directement et longtemps au soleil and be careful about sports.
• In this case you still need to see a doctor regarding: tel:02 47 47 46 50

Cardiac device alternatives

• One alternative to devices is a Stimulateur sans Sonde
• The Capsule Micra (Medtronic) measures: 26mm and 7mm

Tachycardia

• Tachycardia: heart rate above 100 beats/min (permanent or paroxysmal)
• Symptoms: palpitations, dyspnea, malaise, syncope, sudden death
• Atrial tachycardia examples: atrial fibrillation, atrial flutter, and atrial tachycardia,
• Junctional tachycardia: intra-nodal reentry and tachycardia through accessory pathways,
• Ventricular tachycardia: mono or polymorphic ventricular tachycardia / Torsade de pointe / Ventricular fibrillation (state of death).
• Tachycardias can be subdivided into QRS fins (supra-ventriculaires) and QRS larges

QRS complexes

• QRS complex pathway is critical in finding the course of action
• QRS fins = passage par la voie nœud-his = tachycardie supra-ventriculaire +++ (TSV)
• QRS larges: is a sign of cardio issue

Types of Arial Tachycardias

• Oreillettes types include :Fibrillation atriale, Flutter atrial and Tachycardie atriale are some other forms.
• These forms are considered types of:Jonction auriculo-ventriculaire and can become the disease known as Tachycardie jonctionnelle

Atrial/Electrical Issues

• Atrial/Electrical Issues can come form having: Voie lente and TJ sur réentrée intra-nodale or can Voie accessoire which can lead to: Kent: TJ orthodromique/ and or also: Kent: Antidromique

Tachy Mechanism example

Principles for Managing Atrial Tachycardias

• The guidelines take in: Anticoagulation selon risque embolique and (CHA2DS2VA)
• This can be helped with Antiarythmiques et/ou ablation si palpitations:Traitement de la cardiopathie sous-jacente.

Therapy

• Traitement des symptômes takes help in the direction of patients that are in danger
• This is also:Education thérapeutique

Fibrilation

• Ablation Flutter
• Ponction veineuse is done by: fémorale by Sous anticoagulants +++

Fibrilation Procedures

• Ablation Fibrillation requires: Ponction veineuse fémorale
• The doctor does need help by :Ponction trans-septale to assess problems
• Risk can occur during: L'ablation dans l'oreillette gauche to look for further Sous anticoagulants

Anatomy of the Triangle of Koch

• Looking at the Triangle of Koch will also greatly improve your chances
• It also helps see if issues are: Eustachian ridge Tendon Todaro which leads to issues near :Compact and AVN

ECG Measurements

• All measurements are taken from your respective graph

Procedure for treating tachias

• Ablation voie accessoire can assist with :Ponction veineuse and or fémorale
• If Kent G: helps with:ponction artérielle fémorale
• Proximité du NAV et risque de BAV is most likely if: kent septal

ECG types

• Ventricular rates vary across QRS and that provides the information of health
• • Bloc de branche pré-existant has to : Cardiopathie : CMI / CMD

Tachycardi Monomorphe

• Tachycardia ventricular(TV) in the ventricular

TV monorphe can be split into two camps they must take: + Pré-excitation and

• antiarrhytmiques

Polymorphe

• La TV polymorphe may require surgery depending.
• TV polymorphe, rapide (200-250/min)

Torsade Des Pointes

• There are many instances where to correct: Torsade de pointe puis fibrillation ventriculaire

Cardio procedure

• A:15 bpm+ Massage +++
• B:15 bpm+ Massage +++

Further Actions

• Once the 15 + are done continue with:Salves and V(13)
• A heartstart can be deployed at this location. Analysed to monitor key indicators

Acute Actions

• Acute Issues involve: ST which needs to be: fibrillation ventriculaire
• You do this through du SCA en urgence +++

Auto ECG System

• As an example see: Défibrillateur automatique implantable the automatic ecg may solve issues before they reach a critical state
• Technique implantation similaire stimulateur avec boitier et sonde spécifique

Devices

• • Some points to note: — Bradycardie Asystole — Syncope/Mort subite lead to :Pacemaker
• (PM ) — Resynchronisation

DAI

• The image shows what is a Deffibilateur cardiaque
• It makes a line via to the heart

ECG Actions

• As long as the heart keeps on
• Action takes place

Cardiac Complications

• Major heart complications are a concern.
• Major complications are a fracture, a sonde and a
• CHOC, so in other words, they can be very serious

Other Factors (DEffibilateur)

• The image shows us a few key factors of Defibrilateur
• They follow ECG lines

The differences with DAIS

• AVantages/ limites of 1. 2% of patients that are in: 1-2%

Life with a monitor

• Documents are presented as"informations" to show you an "implantantation"

Advice for using devices as this is key

• Patients most always be aware for:Signaux and tachyardia as these are the worst things.

Remote Monitoring Systems

• One such point comes from the use of a Télésurveillance des prothèses, and (DAI +++ et stimulateur).

Remote device process

• As such the key pathway consists of:
• .GSM Network
• (SMS) that is a key part also

A good device should have good integration

Good management is of the highest importance

Key Issues in all patients is having no Issues

• If no to very little then : ECG
• If too many then contact your doctor or surgeon for help

Cardiac Diagram

Diagram of a heart cycle helps show the current issues in your health

The cycle

• This refers to what we see through :BBGand then the:CRT

It also demonstrates pump cycles with great effect

Ischemia ECG

• Ischemia and then the :QT time helps show what the true values of your body are or would be

_Ischemia must be monitored if you do want to lead a healthy life ofc.