a lecture series by SWESEMJR

Transcription

1 Arrhythmias Automaticity- the ability to depolarize spontaneously. Pacemakers: Sinoatrial node: 70 bpm AV-nodal area: 40 bpm His-Purkinje: bpm it Mechanisms of arrhythmias 1. Increased automaticity Normal when doing physical activity. The resting membrane comes closer to the threshold of depolarization. Ischemia, hypokalemia, lung disease.

2 2. Reentry Credit to Anatomical reentry: Stable Atrial flutter, AVNRT, AVRT Functional reentry: Electrophysiological variations like refractory period or conduction Unstable Atrial and ventricular fibrillations

3 Atrial fibrillations Normally situated around pulmonary veins Irreversible causes: Hypertension, cardiac failure Reversible causes: Alcohol, hyperthyreosis ECG 1. Lack of typical p-waves, instead atrial fibrillation waves or isoelectric baseline. 2. Irregular ventricular rhythm. 3. Normal QRS-complexes. Irregular ventricular rhythm without clear p-waves? Suspect atrial fibrillations!

4 Atrial flutter Anatomical reentry around tricuspid valve. ECG 1. Regular flutter waves with saw-tooth pattern. Best seen in leads II, III, avf. 2. Regular atrial activity around 300 bpm. 3. Narrow QRS-complexes Narrow complex tachycardia at 150 bpm (range )? Suspect flutter! Atrial flutter with a 3:1 block Supraventricular tachycardias (SVT) Heart rate > 100 bpm Dyspnea, palpitations, vertigo.

5 AV-blocks Conduction in the AV-node is normally slow which gives time for the ventricles to be filled with blood. 1st degree AV-block Impulses passes slowly. ECG 1. Normal p-wave 2. PQ-time > 0,22 s 3. All P-waves are followed by QRS- complexes 2nd degree AV-block Mobitz 1 : Progressive prolongation of the PR-interval culminating in a nonconducted P-wave. Mobitz II: PR-interval remains constant but some p-waves are not conducted.

6 By Npatchett - Own work, CC BY-SA 4.0, 3rd degreeav-block - complete heart block No impulses are conducted from the atria to the ventricles. Perfusing rhythm by junctional or ventricular escape rhythm. ECG 1. Normal p-waves with regular rhythm. 2. QRS complexes without relation to the p-waves. 3. Slow ventricular rytm < 60 bpm.

7 AVNRT Extra conducting pathway in or next to the AV node. Sudden onset of rapid regular palpitations. Anterograde - to the ventricles. Retrograde - to the atria. ECG 1. Quick and regular ventricular rhythm bpm. 2. Normal QRS complexes. 3. P-waves are often hidden by the QRS complexes. 4. Pseudo R waves may be seen in V1 or V2. 5. Pseudo S waves may be seen in leads II, III or avf.

8 AVNRT Narrow complex tachycardia at 150 bpm. No visible P waves Pseudo R waves in V1-V2. Pseudo R waves in V1-V2.

9 Atrioventricular reentry tachycardia-avrt Pathway outside the AV-node to the ventricles. Wolff Parkinson White (WPW)- fast accessory pathway- ventricles are activated too early. ECG WPW 1. Short PQ-time < 0,12 s 2. Deltawave that leads to widened QRS complex 3. Secondary ST-T changes.

10 Atrioventricular reentry tachycardia - AVRT Orthodromic SVT > 90 %. Conduction through the AV-node and back to the atria through an accessory pathway.

11 Ventricular tachycardia (VT) ECG 1. Broad QRS-complex with deviant appearance. 2. Ventricular frequency > 100 bpm. 3. No p-waves or p-waves without connection to the ventricular complex. Ventricular tachycardia Torsade de pointes

12 Ventricular fibrillation (VF) No synchronous depolarization wave, ventricles cannot contract-no cardiac output. From coarse to fine VF to asystole. Cardioversion Coarse VF Fine VF Asystole By James Heilman, MD (Own work) [CC BY-SA 3.

13 Questions and practice What is automaticity? Mention one example of an anatomical reentry. When should you suspect atrial fibrillations on an ECG? Which are the symptoms of a SVT? What is the treatment for a SVT? How can you differ between AV-blocks? What is the principal anatomical difference between AVRT and AVNRT? What is antidromic conduction in AVRT and what is the the name of the opposite? What is the treatment for VF?

14 References EKG-tolkning, EKG-diagnostik, utredning, behandling och kardiologi - EKG.nu. [Accessed June 20, 2017a]. LITFL ECG Library and clinical cases in cardiology. [Accessed June 20, 2017b]. Jern, S., Jern, H. & Elander), Klinisk EKG-diagnostik 2.0, Ljungskile: Sverker Jern utbildning. Lind, Y. & Lind, L., EKG-boken, bok med elabb, Stockholm: Liber. Rang, H.P. & Dale, M.M., Rang and Dale s pharmacology 7. ed., Edinburgh [u.a.]