Heart 8

oelomar's version from 2017-12-18 01:42


Question Answer
What is meant by the term “heart block”?Heart block is a disease or inherited condition that causes a fault within the heart's natural pacemaker due to some kind of obstruction (or "block") in the electrical conduction system of the heart.
What is first-degree atrioventricular block and what are the associated ECG changes?A disease of the electrical conducting system of the heart in which the impulse conducting from atria to ventricles through the AV node is delayed and travels slower than normal, therefore resulting in a PR interval >0.22 seconds.
Mobitz I block (Wenckebach block) and Mobitz II block are both types of second-degree atrioventricular block. What is the difference between them?Mobitz I block is progressive PR interval prolongation until a P wave is blocked, i.e. a "dropped QRS complex". Mobitz II block occurs when the PR interval is constant but the P wave is often not followed by a QRS complex.
What is the difference in the management between Mobitz I and Mobitz II block?The risk of progression to complete heart block is greater and the reliability of the resultant escape rhythm is less with Mobitz block II. Therefore, pacing is usually indicated in Mobitz II block, whereas patients with Mobitz I block are usually monitored.
What is third degree (complete) atrioventricular block?Complete heart block occurs when all atrial activity fails to conduct to the ventricles.


Question Answer
What are the causes of right bundle branch block?Can occur in normal individuals. May result from COPD, valvular disease, chronic CAD, or may follow the surgical repair of a VSD.
What are the symptoms of right bundle branch block?Asymptomatic.
What are the ECG changes seen in a right bundle branch block?RBBB produces late activation of the right ventricle. This is seen as deep S waves in leads I and V6 and as a tall late R wave in lead V1 (late activation moving towards the right, and away from left-sided leads). QRS complex is ≥0.12s. RBBB is best seen in V1 where an rSR pattern is seen.
How is right bundle branch block treated?No treatment is necessary.
What are the causes of left bundle branch block?Usually a sign of organic heart disease (hypertension, valvular disease, cardiomyopathy, CAD).
What are the symptoms of a left bundle branch block?Often asymptomatic.
What are the ECG changes seen in a left bundle branch block?QRS complex is ≥0.12s. LBBB produces a deep S wave in lead V1 and a tall late R wave in leads I and V6. Q waves are also abnormal. LBBB is best seen in V6 where an rSR pattern is seen.
How is a left bundle branch block treated?Usually none is necessary. A ventricular pacemaker is the definitive therapy in post-MI LBBB patients with conduction defects.
What is a hemiblock and what are the associated ECG changes?Delay or block in the divisions of the left bundle branch produces a swing in the direction of depolarisation of the heart. Left anterior hemiblock produces left axis deviation. Left postero-inferior hemiblock produces right axis deviation.
What is a bifascicular block?This is a combination of a block of any two of the following: the right bundle branch, the left antero-superior division and the left postero-inferior division. Block of the remaining fascicle will result in complete AV block.
The coexistence of RBBB and left axis deviation is associated with what?Ostium primum ASD (also known as an endocardial cushion defect, this is a defect in the atrial septum at the level of the tricuspid and mitral valves).


Question Answer
What is supraventricular tachycardia?SVT is an abnormal heart rhythm arising from improper electrical activity of the heart. It is a type of rapid heart rhythm originating at or above the AV node. It can be contrasted with the potentially more dangerous ventricular tachycardias – rapid rhythms that originate within the ventricular tissue.
Give examples of supraventricular tachycardias.Sinus tachycardia, atrial fibrillation, atrial flutter, atrial tachycardia, AVNRT, AVRT.
What is atrioventricular nodal re-entry tachycardia (AVNRT) and what are its symptoms?AVNRT is a type of tachycardia. AVNRT occurs when a re-entry circuit forms within or next to the AV node. The main symptom is the sudden development of rapid regular palpitations. Often, no precipitant is present, but exertion, coffee, tea, and alcohol may aggravate or induce the arrhythmia.
What is an atrioventricular reciprocating tachycardia (AVRT) and what are its symptoms?AVRT is a supraventricular tachycardia associated with Wolff-Parkinson White syndrome, in which an accessory pathway allows electrical signals from the ventricles to enter the atria and cause premature contraction and repeat stimulation of the AV node. An episode of SVT may present with palpitations, dizziness, shortness of breath, or syncope.
How are atrioventricular nodal re-entry tachycardia/atrioventricular reciprocating tachycardia attacks managed acutely?Vagal manoeuvres, including the Valsalva manoeuvre, carotid massage, and facial immersion in cold water. IV adenosine can also be used (contraindicated in asthmatics – verapamil is preferable option).
How can episodes of AVNRT/AVRT be prevented?Beta-blockers can be given. Radio-frequency ablation is curative.
Adenosine is an anti-arrhythmic agent. What are its side-effects?Bronchospasm, flushing, chest pain, heaviness of the limbs, sense of impending doom.
What is given to counter digoxin toxicity?Mg2+.


Question Answer
What is Wolff-Parkinson White syndrome and what are its symptoms?A disorder of the electrical system of the heart caused by the presence of an abnormal accessory electrical conduction pathway between the atria and the ventricles. Electrical signals travelling down this abnormal pathway (known as the bundle of Kent) may stimulate the ventricles to contract prematurely, resulting in a unique type of supraventricular tachycardia referred to as atrioventricular reciprocating tachycardia. People with WPW are usually asymptomatic. However, the individual may experience palpitations, dizziness, shortness of breath, or syncope during episodes of supraventricular tachycardia.
What are the ECG changes associated with Wolff-Parkinson White syndrome?Characteristic delta waves, which are a slurred upstroke in the QRS complex that is associated with a short PR interval due to ventricles partially depolarising earlier.
What is the definitive treatment of Wolff-Parkinson White syndrome?Destruction of the abnormal electrical pathway by radiofrequency catheter ablation.
Verapamil and diltiazem are both calcium channel blockers and class IV anti-arrhythmic drugs. What are the side-effects of their toxicity?Constipation, flushing, oedema, and CV effects (CHF, AV block).


Question Answer
What is a ventricular tachycardia? It is dangerous?A type of tachycardia that arises from improper electrical activity of the heart starting from the ventricles. This is a potentially life-threatening arrhythmia because it can cause low blood pressure and may lead to ventricular fibrillation, asystole, and sudden death.
What is torsades de pointes?A type of ventricular tachycardia associated with a prolonged QT interval on ECG. Note that prolongation of the QT interval can increase a person’s risk of developing torsades de pointes.
How is torsades de pointes treated?Mg2+.
One of the ways in which ventricular tachycardias can be classified is by the duration of episodes. Three or more beats in a row on an ECG that originate from the ventricle at a rate of more than 100 beats per minute constitute a ventricular tachycardia. What is the difference between a sustained and a non-sustained ventricular tachycardia?If the fast rhythm self-terminates within 30 seconds, it is considered a non-sustained ventricular tachycardia. If the rhythm lasts more than 30 seconds, it is known as a sustained ventricular tachycardia (even if it terminates on its own after 30 seconds).
What are the clinical features of sustained ventricular tachycardia?Often results in pre-syncope, syncope, hypotension and cardiac arrest. Examination reveals a pulse rate typically between 120 and 220 bpm. The ECG shows a rapid ventricular rhythm with broad, abnormal QRS complexes. 80% of all broad complex tachycardias are due to ventricular tachycardia.
How is sustained ventricular tachycardia treated?If the patient is haemodynamically compromised (Systolic <90, BP >150, heart failure or chest pain), emergency DC cardioversion may be required. Otherwise first-line drug treatment consists of amiodarone. Lidocaine can also be used. DC cardioversion is necessary if medical therapy is unsuccessful.
Verapamil is used as first-line treatment in ventricular tachycardia. True or false?False. Verapamil should not be used in VT.
What can be used to treat a symptomatic bradycardia, or a bradycardia <40bpm?Atropine.

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