| ID | 76 |
|---|---|
| Name | HEART BLOCK |
| Cause | Causes: A. Acquired.- 1. Coronary artery disease-specially myocardial ischaemia or infarction. 2. Focal fibrosis (idiopathic) 3. Rheumatic heart disease. 4. Infective endocarditis. 5. Syphilis. 6. Digitalis poisoning. 7. Atrial fibrillation. ‘ 8.’Diphtheria. 9. Sarcoidosis. 10.Chagas disease. 11. Cardiac surgery 12. Drugs- such as digoxin, b-blockers. B. Congenital- Maldevelopment of the bundle of his. |
| Signs Symptoms | |
| Diagnosis | |
| Investigations | |
| Management | |
| Introduction | It may be defined as either depression of cardiac impulse or impaired conduction of formed impulse. |
| History | |
| Etiology | |
| Clinical Features | Clinical features: 1. First degree heart block- a. Only diagnosed by ECG * b. P-R interval is prolonged beyond the upper limit of normal (> 0.20 see) 2. Second degree heart block-In this heart block, some inpulses from atria fail to reach ventricles. As a result ventricles can not always respond to atrial contraction. Two types - a Mobitz type-1: there is progressive lengthening of successive P-R intervals followed by a drop beat (known as Wenckebach’s phenomenon); its prognosis is good, b. Mobitz type-II: here the conducted beat has a normal P-R interval. The ratio between non-conducted atrial contractions may be as great as 5:1. So, it often progresses to complete heart block. Pulse is slow and reglar. 3. Complete heart block: In complete or third degree heart block AV conduction of cardiac impulse fails completely. As a result the atria and ventricles beat independently (known as AV dissociation). a. Presentations- - May be asymptomatic. - Stokes Adam’s syndrome. - Extreme fatiguability. - Breathlessness. - Heart failure. - Rapid loss of consciousness and patient may fall on the ground. b. Signs- i. Pulse- high volume, collapsing in character, regular rhythm, rate 30-40/min; don’t change after fever or exercise, ii. B.P - high systolic & low diastolic; high pulse pressure, iii Raised & cannon wave (as atria & ventricle contract simultaneously), iv. Changing intensity of first heart sound. Systolic and diastolic murmur may be heard, v. ECG findings- P-wave and QRS complexes are independent; but P-R interval & R-R interval regular. |
| Preventions | |
| Treatment | Treatment: Treatment should be given according to the type of heart block. 1. Prolonged heart block but no haemodynamic effect- no treatment. 2. First degree heart block: No treatment is required, but-i. monitoring of the underlying heart diseases & ii. warning of drug toxicity etc. are needed. 3. Second degree heart block: a. Asymptomatic case does not require treatment, but should be observed in case it progresses to complete heart block. 24-hour ECG monitoring may be helpful, b. In symptomatic case- Inj. Atropine 0.3 mg i.v and repeated to a maximum of 1.2mg; if it does not respond- a temporary pacemaker may be needed, c. In chronic symptomatic case- A permanent artificial pacemaker is indicated. 4. Complete heart block: a. Rest in bed. b. O2 supplementation. c. Initially, Inj. atropine or isoprenaline 5mg in 500ml of 5% dextrose in aqua in i.v infusion may be given slowly (10-30 drops/min) until the ventricular rate is above 60 beats/min. d. To prevent recurrence-Long acting isoprenaline 30mg 4 times daily orally. Or, manage the patient with pacemaker. e. Correction of acidosis by 7.5% NaHCO3 preparation. 5. Complete heart block after myocardial infarction: a. Inj. atropine 0.6mg i.v to increase heart rate, b. Temporary pacemaker or i.v corticosteroid at bed side for 2 weeks. Or, if not available isoprenaline 5mg in 500ml of 5% dextrose in aqua may be given as i.v infusion, c. Insulin and glucose to improve cardiac function. |
| Complications | |
| Prognosis | |
| Types | |
| Classification | Classification: 1. Sinoatrial (SA) block. 2. Atrioventricular (AV) block. a. First degree block (delayed AV conduction), b. Second degree block (partial heart block), c. Third degree block (complete heart block). 3. Bundle branch block and Hemiblock. a. Right bundle branch block, b. Left bundle branch block. i. Left anterior hemiblock. ii. Left posterior hemiblock. 4. Purkinjee block. |
| Observation | |
| Pathology |
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