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ekg supraventrikuläre tachykardie – 8 sekunden elektrokardiographie papier – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

EKG Supraventrikuläre Tachykardie – 8 Sekunden. ..

kardiale arrhythmia – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Kardiale arrhythmia

aids-schleife – supraventricular tachycardia stock-fotos und bilder

AIDS-Schleife

atrioventricular knoten re-entrant tachykardie, arterieller blutdruck, pulsoximeter wellenform und vitalfunktionen auf einem medizinischen monitor – supraventricular tachycardia stock-fotos und bilder

Atrioventricular Knoten Re-Entrant Tachykardie, arterieller…

monitor mit einem schwarzen bildschirm mit supraventrikuläre tachykardie – supraventricular tachycardia stock-fotos und bilder

Monitor mit einem schwarzen Bildschirm mit Supraventrikuläre…

ekg supraventrikuläre tachykardie (svt) – 12 elektroden ekg common case – 6 sek./ableitung – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

EKG Supraventrikuläre Tachykardie (SVT) – 12 Elektroden EKG…

ekg- oder ekg-puls-herzschlag-symbol mit roter linie auf schwarzem hintergrund. fibrillation. ekg mit kurzen paroxysmen supraventrikulärer extrasystole und neon-vorhofflimmern. – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

EKG- oder EKG-Puls-Herzschlag-Symbol mit roter Linie auf…

herzrhythmusstörungen – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herzrhythmusstörungen

Herzrhythmusstörungen, auch bekannt als Arrhythmie, Rhythmusstörungen oder unregelmäßiger Herzschlag.

defibrillator – supraventricular tachycardia stock-fotos und bilder

Defibrillator

defibrillator – supraventricular tachycardia stock-fotos und bilder

Defibrillator

Manuelle externe Defibrillatoren werden in Verbindung mit Elektrokardiogramm-Lesegeräten verwendet, die zur Diagnose eines Herzzustands verwendet werden

diagnose von supraventrikuläre tachykardie. stethoskop, grüne feder und elektrokardiogramm liegen auf medizinische form mit diagnose von supraventrikuläre tachykardie auf dem schreibtisch im büro des kardiologen – supraventricular tachycardia stock-fotos und bilder

Diagnose von Supraventrikuläre Tachykardie. Stethoskop, grüne…

defibrillator-einheit – supraventricular tachycardia stock-fotos und bilder

Defibrillator-Einheit

eine Defibrillatoreinheit, die über einen weißen Hintergrund isoliert ist

herzschock. defibrillator elektroden symbol. medizinische und gesunde ikonen. arztwerkzeuge konzept. vektor-illustration – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herzschock. Defibrillator Elektroden Symbol. Medizinische und…

herz defibrillator flach icon mit langen schatten – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz Defibrillator flach icon mit langen Schatten

defibrillator übung auf eine wiederbelebung – supraventricular tachycardia stock-fotos und bilder

Defibrillator Übung auf eine Wiederbelebung

resuscitate geräten im krankenhaus – supraventricular tachycardia stock-fotos und bilder

Resuscitate Geräten im Krankenhaus

Defibrillator ist Wiederbelebungsgerät für die Sicherheit Leben in leicht zugänglichen Bereich platziert.

mobile herz defibrillator-einheit mit arzt- notfall-technologie – supraventricular tachycardia stock-fotos und bilder

Mobile Herz Defibrillator-Einheit mit Arzt- Notfall-Technologie

Mobile Herz-Defibrillator-Einheit mit Arzt-Notfall-Hochtechnologie

abkürzung psvt (paroxysmal supraventrikuläre tachykardie) text akronym auf holzwürfeln auf dunklen holzrücken. medizinkonzept. – supraventricular tachycardia stock-fotos und bilder

Abkürzung PSVT (paroxysmal supraventrikuläre Tachykardie) Text…

herz-defibrillator flache vektor-symbol. elektro-schock-maschine für lebensrettende, rettung. medizinische geräte symbol. – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz-Defibrillator flache Vektor-Symbol. Elektro-Schock-Maschine…

herz defibrillator flach icon mit langen schatten – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz Defibrillator flach icon mit langen Schatten

defibrillator-einheit – supraventricular tachycardia stock-fotos und bilder

Defibrillator-Einheit

kaffee oder koffein und herz arrhythmien (herzrhythmusstörungen). stethoskop und ekg band auf grund von kaffeebohnen. wirkung und risiko trinken kaffee oder koffein auf herzrhythmusstörungen entwicklung – supraventricular tachycardia stock-fotos und bilder

Kaffee oder Koffein und Herz Arrhythmien (Herzrhythmusstörungen).

tragbare defibrillator für hearth notfälle – supraventricular tachycardia stock-fotos und bilder

Tragbare defibrillator für hearth Notfälle

Tragbarer Defibrillator für Herdnotfälle.

supraventrikuläre tachykardie während der mäßigung – supraventricular tachycardia stock-fotos und bilder

Supraventrikuläre Tachykardie während der Mäßigung

Supraventrikuläre Tachykardie im EKG während der Moderation vor dem Hintergrund des Krankenwagens

ekg- oder ekg-puls-herzschlag-lila-liniensymbol auf schwarzem hintergrund. fibrillation. ekg mit kurzen paroxysmen supraventrikulärer extrasystole und neon-vorhofflimmern. – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

EKG- oder EKG-Puls-Herzschlag-lila-Liniensymbol auf schwarzem. ..

ekg- oder ekg-puls-herzschlag-symbol mit blauer linie auf schwarzem hintergrund. fibrillation. ekg mit kurzen paroxysmen supraventrikulärer extrasystole und neon-vorhofflimmern. – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

EKG- oder EKG-Puls-Herzschlag-Symbol mit blauer Linie auf…

ekg- oder ekg-puls-herzschlag-lila-liniensymbol auf schwarzem hintergrund. fibrillation. ekg mit kurzen paroxysmen supraventrikulärer extrasystole und neon-vorhofflimmern. – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

EKG- oder EKG-Puls-Herzschlag-lila-Liniensymbol auf schwarzem…

herz defibrillator flach icon mit langen schatten – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz Defibrillator flach icon mit langen Schatten

herz defibrillator flach icon mit langen schatten – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz Defibrillator flach icon mit langen Schatten

herz defibrillator flach icon mit langen schatten – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz Defibrillator flach icon mit langen Schatten

herz defibrillator flach icon mit langen schatten – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz Defibrillator flach icon mit langen Schatten

herz defibrillator flach icon mit langen schatten – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz Defibrillator flach icon mit langen Schatten

herz defibrillator flach icon mit langen schatten – supraventricular tachycardia stock-grafiken, -clipart, -cartoons und -symbole

Herz Defibrillator flach icon mit langen Schatten

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Supraventricular Tachycardia (SVT) • LITFL • ECG Library Diagnosis

Definition

The term supraventricular tachycardia (SVT) refers to any tachydysrhythmia arising from above the level of the Bundle of His, and encompasses regular atrial, irregular atrial, and regular atrioventricular tachycardias

• It is often used synonymously with AV nodal re-entry tachycardia (AVNRT), a form of SVT
• In the absence of aberrant conduction (e. g. bundle branch block), the ECG will demonstrate a narrow complex tachycardia
• Paroxysmal SVT (pSVT) describes an SVT with abrupt onset and offset – characteristically seen with re-entrant tachycardias involving the AV node such as AVNRT or atrioventricular re-entry tachycardia (AVRT)

Supraventricular tachycardia (SVT): Rhythm strip demonstrating a regular, narrow-complex tachycardia

Classification

• SVTs can be classified based on:
  • Site of origin (atria or AV node) or;
  • Regularity (regular or irregular)
• Classification based on QRS width is unhelpful as this is also influenced by the presence of pre-existing bundle branch block, rate-related aberrant conduction, or presence of accessory pathways.

Classification of SVT by site of origin and regularity

Regular Atrioventricular

• AVRT
• AVNRT
• Automatic junctional tachycardia

AV Nodal Re-entry Tachycardia (AVNRT)

• This is the commonest cause of palpitations in patients with structurally normal hearts
• AVNRT is typically paroxysmal and may occur spontaneously or upon provocation with exertion, caffeine, alcohol, beta-agonists (salbutamol) or sympathomimetics (amphetamines)
• It is more common in women than men (~ 75% of cases occurring in women) and may occur in young and healthy patients as well as those suffering chronic heart disease
• Patients will typically complain of the sudden onset of rapid, regular palpitations. Other associated symptoms may include:
  • Presyncope or syncope due to a transient fall in blood pressure
  • Chest pain, especially in the context of underlying coronary artery disease
  • Dyspnoea
  • Anxiety
  • Rarely, polyuria due to elevated atrial pressures causing release of atrial natriuretic peptide
• The tachycardia typically ranges between 140-280 bpm and is regular in nature. It may self-resolve or continue indefinitely until medical treatment is sought
• The condition is generally well tolerated and is rarely life threatening in patients with pre-existing heart disease

Pathophysiology

In comparison to AVRT, which involves an anatomical re-entry circuit (Bundle of Kent), in AVNRT there is a functional re-entry circuit within the AV node.

Alrternate re-entry loops: Functional circuit in AVNRT (left), anatomical circuit in AVRT (right)

Functional pathways within the AV node

There are two pathways within the AV node:

• The slow pathway (alpha): a slowly-conducting pathway with a short refractory period.
• The fast pathway (beta): a rapidly-conducting pathway with a long refractory period.

Mechanism of re-entry in “slow-fast” AVNRT:
1) A premature atrial contraction (PAC) arrives while the fast pathway is still refractory, and is directed down the slow pathway
2) The ERP in the fast pathway ends, and the PAC impulse travels retrogradely up the fast pathway
3) The impulse continually cycles around the two pathways

Initiation of re-entry

• During normal sinus rhythm, electrical impulses travel down both pathways simultaneously. The impulse transmitted down the fast pathway enters the distal end of the slow pathway and the two impulses cancel each other out
• However, if a premature atrial contraction (PAC) arrives while the fast pathway is still refractory, the electrical impulse will be directed solely down the slow pathway (1)
• By the time the premature impulse reaches the end of the slow pathway, the fast pathway is no longer refractory, and the impulse is permitted to recycle retrogradely up the fast pathway (2)
• This creates a circus movement whereby the impulse continually cycles around the two pathways, activating the Bundle of His anterogradely and the atria retrogradely (3)
• The short cycle length is responsible for the rapid heart rate
• This most common type of re-entrant circuit is termed Slow-Fast AVNRT
• Similar mechanisms exist for the other types of AVNRT

Electrocardiographic Features

ECG features of AVNRT

• Regular tachycardia ~140-280 bpm
• Narrow QRS complexes (< 120ms) unless there is co-existing bundle branch block, accessory pathway, or rate-related aberrant conduction
• P waves if visible exhibit retrograde conduction with P-wave inversion in leads II, III, aVF. They may be buried within, visible after, or very rarely visible before the QRS complex

Associated features include:

• Rate-related ST depression, which may be seen with or without underlying coronary artery disease
• QRS alternans – phasic variation in QRS amplitude associated with AVNRT and AVRT, distinguished from electrical alternans by a normal QRS amplitude

Subtypes of AVNRT

Different subtypes vary in terms of the dominant pathway, and the R-P interval, which is the time between anterograde ventricular activation (R wave) and retrograde atrial activation (P wave).

1. Slow-Fast AVNRT (80-90%)
2. Fast-Slow AVNRT (10%)
3. Slow-Slow AVNRT (1-5%)

1. Slow-Fast AVNRT (common type)

• Accounts for 80-90% of AVNRT
• Associated with slow AV nodal pathway for anterograde conduction and fast AV nodal pathway for retrograde conduction
• The retrograde P wave is obscured in the corresponding QRS or occurs at the end of the QRS complex as pseudo R’ or S waves

ECG features:

• P waves are often hidden – being embedded in the QRS complexes
• Pseudo R’ wave may be seen in V1 or V2
• Pseudo S waves may be seen in leads II, III or aVF
• In most cases this results in a ‘typical’ SVT appearance with absent P waves and tachycardia

Top strip: Normal sinus rhythm. Absence of pseudo-R waves
Bottom strip: Paroxysmal SVT. The P wave is seen as a pseudo-R wave (circled) in lead V1 during tachycardia. This very short ventriculo-atrial time is frequently seen in typical Slow-Fast AVNRT

2. Fast-Slow AVNRT (Uncommon AVNRT)

• Accounts for 10% of AVNRT
• Associated with Fast AV nodal pathway for anterograde conduction and Slow AV nodal pathway for retrograde conduction
• Due to the relatively long ventriculo-atrial interval, the retrograde P wave is more likely to be visible after the corresponding QRS

ECG features:

• QRS-P-T complexes
• Retrograde P waves are visible between the QRS and T wave

3. Slow-Slow AVNRT (Atypical AVNRT)

• 1-5% AVNRT
• Associated with Slow AV nodal pathway for anterograde conduction and Slow left atrial fibres as the pathway for retrograde conduction.

ECG features:

• Tachycardia with a P-wave seen in mid-diastole, effectively appearing “before” the QRS complex.
• May be misinterpreted as sinus tachycardia

Summary of AVNRT subtypes

• No visible P waves? –> Slow-Fast
• P waves visible after the QRS complexes? –> Fast-Slow
• P waves visible before the QRS complexes? –> Slow-Slow

Management of AVNRT

• May respond to vagal maneuvers with reversion to sinus rhythm.
• The mainstay of treatment is adenosine
• Other agents which may be used include calcium-channel blockers, beta-blockers and amiodarone
• DC cardioversion is rarely required
• Catheter ablation may be considered in recurrent episodes not amenable to medical treatment.

Other types of SVT

Most other types of SVT are discussed elsewhere (follow links in classification table). Two less common types include:

Inappropriate Sinus Tachycardia

• Typically seen in young healthy female adults
• Sinus rate persistently elevated above 100 bpm in absence of physiological stressor
• Exaggerated rate response to minimal exercise
• ECG indistinguishable from sinus tachycardia

Sinus Node Reentrant Tachycardia (SNRT)

• Caused by reentry circuit close to or within the sinus node
• Abrupt onset and termination
• P wave morphology is normal
• Rate usually 100 – 150 bpm
• May terminate with vagal manoeuvres

ECG Examples

Example 1a

Slow-Fast (Typical) AVNRT:

• Narrow complex tachycardia at ~ 150 bpm
• No visible P waves
• There are pseudo R’ waves in V1-2

Pseudo R’ waves in V1-2

Example 1b

The same patient following resolution of the AVNRT:

• Sinus rhythm
• The pseudo R’ waves have now disappeared

Pseudo R’ waves in V1-2 have resolved

Example 2a

Slow-Fast AVNRT:

• Narrow complex tachycardia ~ 220 bpm
• No visible P waves
• Subtle notching of the terminal QRS in V1 (= pseudo R’ wave)
• Widespread ST depression — this is a common electrocardiographic finding in AVNRT and does not necessarily indicate myocardial ischaemia, provided the changes resolve once the patient is in sinus rhythm

Example 2b

The same patient following resolution of the AVNRT:

• Sinus rhythm
• Pseudo R’ waves have disappeared
• There is residual ST depression in the inferior and lateral leads (most evident in V4-6), indicating that the patient did indeed have rate-related myocardial ischaemia (± NSTEMI)

Example 3

Patient with Slow-Fast AVNRT undergoing treatment with adenosine:

• The top rhythm strip shows AVNRT with absent P waves and pseudo R’ waves clearly visible
• The middle strip shows adenosine acting on the AV node to suppress AV conduction — there are several broad complex beats which may be aberrantly-conducted supraventricular impulses or ventricular escape beats (this is extremely common during administration of adenosine for AVNRT)
• The bottom section shows reversion to sinus rhythm; the pseudo R’ waves have resolved.

Example 4a

Fast-Slow (Uncommon) AVNRT:

• Narrow complex tachycardia ~ 120 bpm.
• Retrograde P waves are visible after each QRS complex — most evident in V2-3.

Retrograde P waves

Example 4b

The same patient following resolution of the AVNRT:

• Now in sinus rhythm.
• The retrograde P waves have disappeared.

Retrograde P waves

Example 5a

Fast-Slow AVNRT:

• Narrow complex tachycardia ~ 135 bpm.
• Retrograde P waves following each QRS complex — upright in aVR and V1; inverted in II, III and aVL.

Upright retrograde P waves in aVRInverted retrograde P waves lead II

Example 5b

The same patient following resolution of the AVNRT:

• Sinus rhythm
• The retrograde P waves have disappeared

Retrograde P waves in aVR resolvedRetrograde P waves in lead II resolved

Example 6a

Fast-Slow AVNRT:

• Narrow complex tachycardia at ~ 125 bpm
• Retrograde P waves follow each QRS complex: upright in V1-3; inverted in II, III and aVF

Inverted retrograde P waves in lead IIUpright retrograde P waves in V2

Example 6b

The same patient following resolution of the AVNRT:

• Sinus rhythm.
• Retrograde P waves have disappeared.

Retrograde P waves in lead II have resolvedRetrograde P waves in V2 have resolved

Example 7

SVT with QRS alternans:

• Narrow complex tachycardia ~ 215 bpm
• Retrograde P waves are visible preceding each QRS complex (upright in V1, inverted in lead II)
• There is a beat-to-beat variation in the QRS amplitude without evidence of low voltage (= QRS alternans)
• The PR interval is ~ 120 ms, so this could be either a low atrial tachycardia or possibly an AVNRT with a long RP interval (i.e. either Fast-Slow or Slow-Slow varieties)

• Sinus tachycardia
• Atrial tachycardia
• Atrioventricular re-entry tachycardia (AVRT)
• Atrial flutter
• Atrial fibrillation
• Multifocal atrial tachycardia
• VT versus SVT with aberrancy

References

• Jazayeri MR, Massumi A, Mihalick MJ, Hall RJ. Sinus node reentry: case report and review of electrocardiographic and electrophysiologic features. Tex Heart Inst J. 1985 Sep;12(3):249-52
• Fox DJ, Tischenko A, Krahn AD, Skanes AC, Gula LJ, Yee RK, Klein GJ. Supraventricular tachycardia: diagnosis and management. Mayo Clin Proc. 2008 Dec;83(12):1400-11

Advanced Reading

Online

• Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
• Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
• Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
• Rawshani A. Clinical ECG Interpretation ECG Waves
• Smith SW. Dr Smith’s ECG blog.

Textbooks

• Mattu A, Tabas JA, Brady WJ. Electrocardiography in Emergency, Acute, and Critical Care. 2e, 2019
• Brady WJ, Lipinski MJ et al. Electrocardiogram in Clinical Medicine. 1e, 2020
• Straus DG, Schocken DD. Marriott’s Practical Electrocardiography 13e, 2021
• Hampton J. The ECG Made Practical 7e, 2019
• Grauer K. ECG Pocket Brain (Expanded) 6e, 2014
• Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography 1e, 2009
• Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric 6e, 2008
• Mattu A, Brady W. ECG’s for the Emergency Physician Part I 1e, 2003 and Part II
• Chan TC. ECG in Emergency Medicine and Acute Care 1e, 2004
• Smith SW. The ECG in Acute MI. 2002 [PDF]

LITFL Further Reading

• ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
• ECG A to Z by diagnosis – ECG interpretation in clinical context
• ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
• 100 ECG Quiz – Self-assessment tool for examination practice
• ECG Reference SITES and BOOKS – the best of the rest

Cite this article as: Robert Buttner and Ed Burns, “Supraventricular Tachycardia (SVT),” In: LITFL – Life in the FastLane, Accessed on July 20, 2023, https://litfl. com/supraventricular-tachycardia-svt-ecg-library/.

Robert Buttner

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

Ed Burns

Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

Adaptive image loading is a new feature on Tilda

We have implemented image processing technology that scales them to the size of the container on the site and converts them to WebP, a new generation format.

Adaptive image loading already works on all sites on Tilda by default, it does not need to be enabled. We have been testing the function for several months and are ready to share the details.

Watch a video about the new feature

Let’s take a look at what technologies are now available to optimize the delivery of images to your site visitors on Tilda:

Lazy Load

Lazy Load or lazy loading of images has been working on Tilda for a long time. When a visitor enters the site, images are loaded sequentially as they move through the site, and not all at once.

The image is fully loaded because it is on the screen

The image starts loading 700px before it appears on the screen

The image has not yet started loading

1. The image is fully loaded because it is on the screen

2. The image starts loading 700px before it appears on the screen

3. The image has not yet started loading

A CDN or content delivery network is a geographically distributed network of servers around the world. It helps deliver images from the closest node to the user. For example, if a user is from Berlin, they will get an image from Germany, not Russia.

WebP support

Tilda automatically converts all images on the site to WebP, a format that allows you to compress images up to 35% more than JPEG without losing quality. You do not need to upload images to the site in a new format, the system will do everything for you.

JPEG — 1680х1120px, 166 Kb

WebP — 1680х1120px, 78.6 Kb

Open image in new tab

Open image in new tab

8.9 Mb 90 003

2.8 Mb

Comparison of image weight due to their optimization using the example of a template. The weight of site images without adaptive loading is 8.9 Mb. The weight of images with adaptive loading is 2.8 Mb

After optimization, the total weight of images on the site is 3 times less

Most modern browsers, such as Chrome, Opera, Firefox and others support WebP. When a user visits the site, the script will check the browser for format support and, if it is supported, request WebP images from the server. If not supported, it will return the original image in the format that was uploaded – JPEG or PNG. Over time, we will add image conversion to AVIF format, which will make image weighting even easier.

Adaptive image resizing

The technology determines the size of the browser and container on the site layout, then requests an image of the appropriate size from the server.

Imagine you have uploaded a 1680px wide photo into a multi-image tile block. On the site layout, the container size is 450×300px. Accordingly, the visitor will receive not the original photo, but a photo reduced to the required size.

JPEG — 1680x1119px, 252 Kb

WebP— 450x300px, 23.5 Kb

Open the image in a new tab

Open the image in a new tab

Or suppose a person accesses the site from a mobile phone. To load the site cover on the device, the script will request from the server an image cropped to fit the screen with the required resolution.

JPEG —1680x1120px, 372 Kb

Open image in new tab

WebP — 560x1120px, 103 Kb

Open image in new tab

The system constantly analyzes site traffic on Tilda. The script prepares images in advance for the devices and browsers from which users access the site most often. This principle is more flexible than on-the-fly resizing: sometimes the browser spends less time downloading the original image than resizing and downloading the optimized image.

Retina displays and slow internet

If a site visitor has a high DPI display, the script will recognize this and request a high resolution image from the server. Thus, images will be sharp on Retina display devices.

But if a person has a slow Internet connection, let’s say in a country house, the system will download a light version of the image. This will allow you to not reduce the speed of the site.

Adaptive image loading may not work in some cases. Several reasons why this might happen:

You have disabled Lazy Load in your site settings.

You have disabled Lazy Load on an element in Zero Block.

An adaptive image has not yet been prepared. For example, you just uploaded an image or you are logging in for the first time from this device or browser.

Your browser does not support WebP. A list of browsers that support the format can be found here.

The difference in weight between the original and the optimized image is negligible, so the system will not further compress and crop the image.

Responsive image loading is one of the rather significant optimizations that we have implemented in Tilda. We continue to work on speeding up the loading of sites created on the platform, stay tuned for updates on the blog in your personal account and on social networks.

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What is a CDN? – Content Delivery Network Description – AWS

What is a CDN?

A content delivery network (CDN) is a network of interconnected servers that speeds up the process of loading web pages of high-load applications. The abbreviation CDN stands for “content delivery network” (content delivery network) or “content distribution network” (content distribution network). When a user accesses a website, the data stored on that website’s server traverses the Internet before reaching the user’s computer. If the user is far from the server, large files such as videos or images may take a long time to load. Instead, website content is stored on CDN servers that are geographically closer to users and therefore can reach their computers much faster.

Why is CDN important?

The main function of a Content Delivery Network (CDN) is to reduce data transmission delays caused by network design features. Due to the global and complex nature of the Internet, data travels from websites (servers) to users (clients) over long physical distances. In addition, data transfer occurs on a two-way basis, that is, clients send requests to servers, from which they receive responses.

CDN improves efficiency by introducing intermediary servers between clients and website servers. These CDN servers manage some of the data transfers between clients and servers. They reduce network traffic on web servers, reduce bandwidth, and improve the usability of your applications.

What are the main benefits of a CDN?

Content Delivery Networks (CDNs) provide many features that improve website performance and support the core network infrastructure. For example, a CDN can perform the following tasks.

Reduced page loading time

Website traffic decreases when pages load slowly. With the help of CDN, you can reduce the bounce rate and increase the time spent by users on the site.

Reducing the cost of providing bandwidth

Covering the cost of network bandwidth costs a lot, because with each incoming request to the website, this bandwidth decreases. Through caching and other network optimization techniques, CDNs reduce the amount of data that the origin server has to provide, allowing website owners to reduce hosting costs.

Increase content availability

High traffic or network equipment failures can cause websites to break. CDN services can handle a large amount of network traffic and reduce the load on web servers. Also, when one or more CDN servers go down, other working servers can replace them, thus ensuring uninterrupted service.

Improving website security

Distributed denial of service (DDoS) attacks attempt to stop applications by sending large amounts of fake traffic to websites. CDNs deal with traffic spikes by spreading the load across multiple intermediate servers to reduce the impact on the origin server.

How has CDN technology evolved?

Content Delivery Network (CDN) technology emerged in the late 1990s to enable rapid delivery of content over the Internet.

First generation

First generation CDN services focused on intelligent network traffic management principles and data centers for replication.

Second generation

Second generation CDNs have emerged in response to the growth of audio and video streaming services, especially video-on-demand and news-on-demand. In addition, this technology has evolved to address the new challenges of delivering content to mobile devices. Companies used cloud computing methodologies and peer-to-peer networks to speed up content delivery.

Third generation

Third generation CDNs are under development. AWS innovates as one of the world’s leading CDN service providers. With most web services hosted in the cloud, the focus today is on edge computing, in particular managing bandwidth consumption with smart devices that interact intelligently. Autonomous and self-managed edge networks could be the next step in CDN technology.

What Internet content can CDNs deliver?

Content Delivery Network (CDN) can carry two types of content: static and dynamic.

Static content

Static content is website data that does not change from user to user. Header images, logos, and font styles on websites remain the same for all users because companies rarely change them. Static data does not need to be modified, processed, or generated, making it ideal for storing on CDN servers.

Dynamic content

Dynamic content such as social media feeds, weather forecast, login statuses and chat messages is different for each website user. This data changes based on location, authorization time, or user preferences, so the website generates data for each user and interaction.

How does a CDN work?

Content Delivery Networks (CDNs) work by opening Points of Presence (POPs) or a group of edge CDN servers in multiple geographic locations. The geographically distributed network operates on the principles of caching, dynamic acceleration, and edge logic computing.

Caching

Caching is the process of storing multiple copies of the same data for faster access. In computing, the principle of caching applies to any kind of memory and storage management. In the field of CDN technology, this term refers to the process of storing the static content of websites on various network servers. Caching in CDNs works as follows:

1. A visitor to a geographically dispersed website submits the first request for static web content.
2. The request then reaches the Internet application server or origin. The origin server sends a response to the remote visitor. In addition, it simultaneously sends a copy of the response to the point of presence (POP) of the CDN network located in close geographical proximity to the site visitor.
3. The CDN Point of Presence (POP) server saves a copy as a cached file.
4. The next time this or any other visitor from this location sends a similar request, the caching server will send them a response instead of the origin server.

Dynamic acceleration

Dynamic acceleration is the reduction of server response time to requests for dynamic web content by using intermediary CDN servers between Internet applications and clients. Caching does not work well with dynamic web content because it changes for every user request. CDN servers need to reconnect to the origin server for each request for dynamic content, but they speed up this process by optimizing the connection between themselves and the origin servers.

If a client sends a dynamic request directly to a web server over the Internet, it may get lost or arrive late due to network delay. Also, time can be spent opening and closing the connection for security checks. On the other hand, if a CDN server in close proximity sends a request to the origin server, a permanent reliable connection will already be established between them. For example, in the future, the connection between them can be optimized using the following features.

• Algorithms for intelligent routing
• Geographical proximity to the source
• Ability to process client requests to reduce their size

Peripheral Logic

The CDN Edge Server can be programmed to perform logic to facilitate data transfer between client and server. For example, this server can perform the following tasks:

• monitoring user requests and changing caching behavior;
• check and fix bad user requests;
• Modifying or optimizing content before sending a response.

Distributing application logic between web servers and the edge of the network allows developers to remove the computational requirements of origin servers and improve website performance.

What is CDN used for?

Content Delivery Network (CDN) helps improve familiar website features and improve customer satisfaction. Below are some usage examples.

High-Speed ​​Content Delivery

By linking the delivery of static and dynamic Internet content, CDNs enable your customers to enjoy the functionality of a global, high-performance site. For example, Reuters is the world’s largest wholesale provider of news bulletins for leading news channels such as the BBC, CNN, New York Times and Washington Post. The main task of Reuters as a news agency is the prompt delivery of news content to customers around the world. Reuters uses Amazon CloudFront CDN with Amazon Simple Storage Service (Amazon S3) to reduce reliance on satellite communications and create a cost-effective, highly available and reliable globally distributed network platform.

Real-time streaming

CDNs help deliver high-quality multimedia files reliably and cost-effectively. Audio and video streaming companies use CDNs to solve three problems: reduce the cost of providing bandwidth, increase scale, and reduce content delivery time. For example, Hulu is an online video streaming platform owned by The Walt Disney Company. The service uses Amazon CloudFront to continuously stream over 20Gbps of data to its growing customer base.

User scaling

CDNs allow you to support a large number of concurrent users. Website resources can only handle a limited number of concurrent client connections. With the help of CDN networks, you can quickly increase it by taking on the load from application servers. For example, King is a company that develops cross-platform social media games that can be played anytime, anywhere, and on any device. More than 350 million gamers play 10.6 billion King games daily on their platform.

King’s gaming apps record users’ game data in central data centers so they can play across devices without losing their progress. Datacenters aim to provide a unified experience for users, even if they are connecting to games from an old device with limited bandwidth.

King uses Amazon CloudFront to deliver hundreds of terabytes of content daily and handle traffic surges of half a petabyte or more during new game launches or large-scale marketing programs.

What is Amazon CloudFront?

Amazon CloudFront is a Content Delivery Network (CDN) service built for performance, security, and developer convenience. With Amazon CloudFront, you can perform the following tasks.

• Data delivery through over 275 globally distributed Points of Presence (PoPs) with automated network binding and intelligent routing.
• Enhance security with traffic encryption and access control, and use AWS Shield Standard for free to protect against distributed denial of service (DDoS) attacks.
• Customizing code that runs at the edge of an AWS network with serverless computing to balance cost, performance, and reliability.