DYSRHYTHMIAS /VALVE DISORDERS

1. DYSRHYTHMIAS /VALVE DISORDERS MR OGUNDELE

2. ECG ECG paper consists of horizontal and vertical lines forming a grid. A piece of ECG paper is called an ECG strip The horizontal axis of the ECG strip represents time. Each small block equals 0.04 second, and five small blocks form a large block, which equals 0.2 second.

4. ECG

5. The ECG strip’s vertical axis measures amplitude in millimeters (mm) or electrical voltage in millivolts (mV). Each small block represents 1 mm or 0.1 mV; each large block, 5 mm or 0.5 mV.

6. ECG

7. P wave The P wave is the first component of a normal ECG waveform. A normal P wave has the following characteristics: location—precedes the QRS complex Amplitude—2 to 3 mm high Duration—0.06 to 0.12 second Configuration—usually rounded and upright

8. PR interval A normal PR interval has the following characteristics (amplitude, configuration, and deflection aren’t measured): location—from the beginning of the P wave to the beginning of the QRS complete Duration—0.12 to 0.20 second.

9. QRS complex The QRS complex follows the P wave and represents depolarization of the ventricles. A normal complex has the following characteristics: • Location—follows the PR interval • Amplitude—5 to 30 mm high but differs for each lead used • Duration—0.06 to 0.10 second,

10. ST segment • The ST segment represents the end of ventricular conduction or depolarization and the beginning of ventricular recovery or repolarization. • A normal ST segment has the following characteristics (amplitude, duration, and configuration aren’t observed): • Location—extends from the S wave to the beginning of the T wave • Deflection—usually isoelectric (neither positive nor negative)

11. T wave The T wave represents ventricular recovery or repolarization. Normal T waves have the following characteristics • Location—follows the S wave • Amplitude—0.5 mm •Configuration—typically round and smooth

12. Characteristics of normal sinus rhythm • Regular rhythm • Normal rate • A P wave for every QRS complex; all P waves similar in size and shape • All QRS complexes similar in size and shape • Normal PR and QT intervals • Normal (upright and round) T waves

13. CARDIAC CONDUCTION DISORDERS Cardiac arrhythmias can be classified according to whether they are bradycardias (<60 bpm) or tachycardias (>100 bpm).

14. CONDUCTION DISORDERS • Bradycardias may be due to disorders of the sinus node or the atrioventricular (AV) node: • _ Sinus bradycardia and sinus node disease (also called sick sinus syndrome). • _ Atrioventricular block where the atria may be acting normally, but the AV node does not conduct the impulses normally to the ventricles.

15. CONDUCTION DISORDERS • Tachycardias are also subdivided according to their origin: • _ Sinus tachycardia. • _ Supraventricular tachycardia including atrial or junctional (AV nodal) tachycardias. • _Ventricular tachyarrhythmias such as ventricular tachycardia and ventricular fibrillation are often secondary to ischaemic myocardial damage

16. CONDUCTION DISORDERS • Sinus bradycardia occurs when the sinus node creates an impulse at a slower-than-normal rate. A sinus rate of less than 60 bpm. • Sinus Tachycardia is defined as a heart rate greater than 100 beats per minute. Sinus tachycardia has the same components as a normal sinus rhythm except the heart rate is faster. More impulses originating from the SA node than normal cause this.

17. CONDUCTION DISORDERS • Premature Atrial Complex. A premature atrial complex (PAC) is a single ECG complex that occurs when an electrical impulse starts in the atrium before the next normal impulse of the sinus node. The PAC may be caused by caffeine, alcohol, nicotine. • ATRIAL FIBRILLATION/FLUTTER: The atria quiver rather than contract many times a minute, with only some impulses being conducted to the ventricles. The P wave appears flutter saw-toothed pattern. Some of the impulses get through the AV node and reach the ventricles, resulting in normal QRS complexes.

18. CONDUCTION DISORDERS • Premature ventricular contractions (PVCs) originate in the ventricles from another site other than the SA node. The ventricles are irritable and fire prematurely, before the SA node • Ventricular Fibrillation. Ventricular fibrillation is a rapid but disorganized ventricular rhythm that causes ineffective quivering of the ventricles. • Asystole: Asystole (the silent heart) is the absenceof electrical activity in the cardiac muscle. It is referred to ascardiac arrest. A straight line appears on an ECG strip

19. Pacemakers Pacemakers can be external and temporary or internal and permanent. Temporary pacemakers are used for bradycardias or tachycardias that do not respond to medications or cardioversion.

20. Pacemakers • Permanent pacemaker insertion is a surgical procedure guided by fluoroscopy. The pacemaker generator is implanted subcutaneously and attached to one or two leads (insulated conducting wires) that are inserted via a vein into the heart. The lead can then deliver the impulse directly to the heart wall. Types of permanent pacemakers are • Single Chamber: One wire placed in either the atrium or ventricle • Dual Chamber: Wire placed on both atrium and ventricle • Biventricular: wire placed in both ventricles

21. Cardioversion and defibrillation Cardioversion and defibrillation are treatments for tachydysrhythmias. They are used to deliver an electrical current to depolarize a critical mass of myocardial cells. Electrical current may be delivered through paddles or conductor pads.

22. Defibrillation Defibrillation is a lifesaving procedure used for lethal dysrhythmias. It delivers an electrical shock to reset the heart’s rhythm. It is used to terminate pulseless ventricular tachycardia or ventricular fibrillation.. The electrical voltage required to defibrillate the heart is usually greater than that required for cardioversion.

23. Cardioversion • Cardioversioninvolves the delivery of a “timed” electrical current to terminate a tachydysrhythmia. In cardioversion, the defibrillator is set to synchronize with the ECG on a cardiac monitor so that the electrical impulse discharges during ventricular depolarization (QRS complex).

24. Valvular Disorder There are four valves in the heart: mitral, tricuspid, pulmonic, and aortic. The chordae tendineae and papillary muscles are attachment structures for both the mitral and tricuspid valves. They ensure that the valves close tightly. The pulmonic and aortic valves do not have these attachment structures.

25. VALVE DISORDER • Valve disorder are of two types: Stenosis or insufficiency. • In valvularstenosis, a narrowing of the valve opening occurs and causes an obstruction to the normal blood flow. • In valvular insufficiency (also called incompetence/regurgitation) the disease valve is unable to close properly and blood flows back into the chamber after contraction.

26. VALVE DISORDER • AORTIC INSUFFICIENCY: Leakage of the aortic valve causes blood to flow back into the left ventricle. This results in increased blood volume in the left ventricle, causing it to dilate and become hypertrophic, eventually leading to left ventricular failure. • AORTIC STENOSIS: The opening of the aortic valve may be narrowed/stenosed from thickening, scarring, calcification, or fusing of the valve’s flaps. This makes the left ventricle to contracts more forcefully.

27. VALVE DISORDER • Mitral INSUFFICIENCY : In mitral insufficiency blood flow back from the left ventricle into the left atrium. As a result, blood might flow back into the lungs. It is usually due to an incompetent valve, damaged from rheumatic fever, CAD, or endocarditis. • Mitral STENOSIS: In mitral stenosis, there is narrowing of the mitral valve, which puts more pressure on the left atrium to work harder to maintain blood flow to the left ventricle.

28. VALVE DISORDER Mitral valve prolapse: It is often congenital. The mitral valve bulges back into the left atrium, allowing blood to flow backwards from the left ventricle into the left atrium.