Diagnosis and Treatment of Arrhythmia

Question 1

What is the definition of syncope?

What are the characteristics?

Answer 1

• Syncope is defined as TLOC (transient loss of consciousness) due to cerebral hypoperfusion.
• Characterised by:
  
  • Rapid onset
  • Short duration
  • Spontaneous complete recovery - reperfusion following falling to the ground (supine position increases venous return).

Question 2

What are the causes of syncope?

Answer 2

• Vasovagal / vasodepressor / neurally mediated
• Cardiac

Question 3

Describe vasovagal syncope.

Answer 3

• Fainting: caused by incorrect nerve control of your peripheral circulation.
• Vasovagal syncope isa temporary loss of consciousness caused by a neurological reflex that produces either sudden dilation of the blood vessels in the legs, or a bradycardia, or both.

Question 4

Describe cardiac syncope.

Answer 4

• Arrhythmia / heart failure.
• Very fast ventricular tachycardia - incorrect filling during diastole causing decreased cardiac output.
• Heart failure - has to be very bad to cause syncope, may arise from extensive use of medication causing hypotension.
• The presence of infection may further compromise cardiac output, causing syncope in a patient with heart failure.

Question 5

Which questions would you ask in Hx to rule out dangerous causes of syncope?

Answer 5

• Was the syncope associated with tachycardic palpitations?
  
  • May be an underlying sinister fast heart rhythm.
• Associated with exertion?
  
  • Asymmetric septal hypertrophy (also called hypertrophic cardiomyopathy).
• Is there FHx of sudden cardiac death?
  
  • May be due to channelopathy.
    
    • Brugada syndrome - a genetic disorder in which the electrical activity within the heart is abnormal; associated with mutations in the gene encoding the cardiac sodium channel.
• Is there complete heart block at an early age?

Question 6

What are the usual investigations for cardiac syncope?

Answer 6

• ECG
• 24 hour tape
• Echocardiogram
• Exercise tolerance test
• Cardiac MRI
• CT coronary angiogram

Question 7

Describe the use of echocardiogram.

Answer 7

• 2D real-time imaging of the heart with an ultrasound probe, allowing you to look for:
  
  • Left ventricular hypertrophy (cardiomyopathy)
  • Measure the septum thickness
  • Check valvular function
  • Look for left ventricular function
• Can help to detect:
  
  • Damage from a heart attack
  • Heart failure
  • Congenital heart disease - birth defects
  • Endocarditis - an infection of the heart valves

Question 8

Describe the use of an exercise tolerance test.

Answer 8

• The patient is on treadmill and simultaneously connected to an ECG.
• In women who are perimenopausal (menopause transition) the test is wrong as many times as it is right (positive predictive value 50%), therefore is not worth doing.

Question 9

Describe the use of CT coronary angiography.

Give an example of a problem it could identify.

Answer 9

• May identify coronary anomalies that underlie syncope.
  
  • A coronary artery may come off the wrong cusp, going right around the aorta. During systole, the aorta compresses the coronary artery, compromising blood to the left coronary artery.
  • This can cause chest pain and syncope.

Question 10

Describe the history of a patient with low risk syncope.

Answer 10

• Associated with prodrome typical reflex syncope: light-headedness, feeling of warmth, sweating, nausea and vomitting.
• After sudden unexpected sight, sound, smell or pain.
• After prolonged standing or in crowded, hot places.
• During a meal or post-prandial.
• Triggered by: cough, micturition or defecation.
• With head rotation OR pressure on the carotid sinus (tumour, shaving, tight collars).
• Standing from supine/sitting position.

Question 11

Describe the history of a patient with high risk syncope.

Answer 11

• New onset of chest discomfort, breathlessness, abdominal pain or headache.
• Syncope during exertion when supine.
• SUDDEN ONSET palpitation immediately followed by syncope.

Question 12

What syncopal symptoms are associated with minor risk, only if associated with structural heart disease or abnormal ECG?

Answer 12

• No warning of symptoms or short (10s) prodrone.
• FHx of sudden cardiac death at a young age.
• Syncope in sitting position.

Question 13

Describe a low-risk past medical history in a patient with syncope.

Answer 13

• Long history (years) or recurrent syncope with low-risk features with the SAME CHARACTERISTICS of the current episode.
• Absence of structural heart disease.

Question 14

Describe a high-risk past medical history in a patient with syncope.

Answer 14

Severe structural or coronary artery disease: heart failure, low left ventricular ejection fraction (e.g. 30%, when should be >50%) or previous MI.

Question 15

Explain what findings on physical examination of a patient with syncope would dennote high risk.

Answer 15

• Unexplained systolic BP in A&E of <90mmHg (hypotension and syncope is bad, usually caused in the elderly by sepsis and medication).
• Suggestion of GI bleed on rectal examination (PR bleed).
• Persistent bradycardia (<40BPM) in awake state and in absence of physical training.
• Undiagnosed systolic murmur - indicated aortic stenosis, or in a younger person may be a mitral murmur, presenting as a systolic murmur that is associated with hypertrophic cardiomyopathy.

Question 16

What ECG findings associated with a Hx of syncope are high risk (major) findings?

Answer 16

• ECG changes consistent with acute ischaemia.
• Mobitz II second- and third- degree AV block.
• Slow AF (<40bpm).
• Persistent sinus bradycardia (<40BPM), or repetitive SA block or sinus pauses >3 seconds in awake state and in absence of physical training.
• Bundle branch block, intraventricular conduction disturbance, ventricular hypertrophy or Q waves consistent with ischaemic heart disease or cardiomyopathy.
• Sustained and non-sustained VT.
• Dysfunction of an implantable cardiac device.
• Type 1 Brugada pattern.
• ST elevation with type 1 morphology in leads V1-V3 (Brugada pattern).
• QT interval >460ms in repeated 12-lead ECGs indicating LQTS (long QT syndrome).

Question 17

List the avoidance techniques for patients with vasovagal syncope.

Answer 17

• Attention to fluid balance - these syncopal patients do not tolerate dehydration.
• Educating a patient that frequently experiences pre-syncopal prodrome (light-headedness) in physical counterpressure manoeuvres, that act to increase venous return.
  
  • Crossing your legs
  • Clenching the muscles in your lower body
  • Squeezing your hands into a fist - increases vasopressor outflow, increasing venous return.
  • Tensing arm muscles.
  • Lying down with feet in the air.
  • Squatting.
• Fludrocortisone - corticosteroid that has a very high mineralocorticoid activity and increases sodium resorption and therefore boosts BP.
  
  • Clinical trial data hasn’t shown much better effects than placebo.
• Syncope is best managed in holistic syncope service.

Question 18

Which factors affect the risk of sudden death in HCM patients?

Answer 18

• FHx of sudden cardiac death during exercise.
• Syncope
• Non-sustained ventricular tachycardia
  
  • 4 ectopic beats in a row = VT
  • Thick, bulky heart does not fill properly during diastole

Question 19

Describe how symptoms can be managed in HCM.

Answer 19

• REFER TO HCM SPECIALIST!
• Drugs are used for symptom management
  
  • Anti-cardiac output drugs e.g. beta blockers and calcium antagonist to reduce cardiac output.
• Septal ablation - cath lab - inject alcohol down the septal arteries to destroy the tissue.
• Surgical myectomy - open the heart, pass through the aorta and remove several grams of ventricular tissue.

Question 20

Describe the use of ICDs in patients with HCM.

Answer 20

• ICD (implantable cardioverter defibrillator) may be implanted, and is used for survival instead of symptom management.
• Those with a FHx of sudden cardiac death, syncope upon exertion and with a very thick septum are indicated for an ICD.
• ICDs are used for primary and secondary prevention:
  
  • Primary - the patient has had a cardiac arrest or an aborted sudden cardiac death with HCM, and so they are at an increased risk of developing dangerous arrhythmias.
  • Secondary - ICDs are offered to patients with a history of dangeous sustained ventricular arrhythmias.

Question 21

What are the adverse factors of installing ICDs?

Answer 21

• ICDs only last ~5 years before needing to be changed.
  
  • Putting an ICD in a younger person commits them to a lifelong time of repeated surgical intervention - this must be discussed as part of ‘personalised medicine’.
• ICDs can occasionally become infected an give the patient endocarditis.
• Reserve ICD implantation for high-risk patients only.

Question 22

Describe the adaptations of the heart which can be caused by exercise.

Answer 22

• Athletic adaptation:
  
  • Ejection fraction measures below normal ~40-45% found during an echo at rest.
  • Atrial stretch; atria grow to cope with the increased cardiac output.
  • Left ventricular hypertrophy can be associated with athletic heart.
• It is difficult in the early stages of syncope presenting to determine if the patient has early dilated cardiomyopathy or just physiological adaptations of the heart to exercise.

Question 23

Describe pacemaker nomenclature.

Answer 23

• First letter is the chamber being paced.
• Second letter is the chamber being sensed.
• Third letter is the response to the intrinsic ‘beat’.
• Fourth letter is for special features:
  
  • ‘R’ = rate-responsive, meaning that it allows you some fluctuation in your heart rate.
• Note: the more intrinsic heart activity there is, the better. Becoming pace-dependent is not so good.

Question 24

Describe atrial fibrillation.

Answer 24

• AF is a common abnormal heart rhythm that happens when electrical impulses fire off from different places in the atria in a disorganised way.
• This causes the atria to twitch and is felt as an irregular pulse.
• AF is a major cause of stroke due to vegetations forming from stagnant blood in the atria, forming thrombi that can enter the brain via the internal carotid.

Question 25

Describe atrial flutter.

Answer 25

• The electrical impulses from the SA node form a smaller circuit in the atria, instead of travelling to the AV node.
• These impulses circulate very fast around the atria, causing ~300bpm instead of the usual 60-90bpm.
• The ventricles cannot pump that fast, causing the atria and ventricles to contract at different speeds, putting the heart under strain.
• Thrombi can form in the atria and cause a stroke.

Question 26

What is second-degree heart block?

Answer 26

• Second-degree AV heart block happens when one or more (but not all) of the atrial impulses fail to conduct to the ventricles due to impaired conduction.
• There are 2 types of second-degree heart block:
  
  • Mobitz II - the heart skips beats in a regular pattern; the body can usually cope well with this, so patients do not usually have symptoms.
  • Mobitz II - the heart skips beats in an irregular pattern; the body cannot compensate for this and this type of heart block can lead to presyncope, dizziness and syncope.
• Causes of second-degree heart block:
  
  • Underlying heart condition
    
    • Coronary heart disease
    • Cardiomyopathy
    • Congenital heart disease

Question 27

What is third-degree heart block?

Answer 27

• Referred to as ‘complete heart block’ - the most serious type of AV heart block.
• It occurs when the SA node electrical impulse does not pass to the AV node.
• A back-up system will take over (myocytes can intrinsically generate their own electrical rhythm), but the ventricles will beat too slowly to meet the oxygen demands of the body.
• Causes of complete heart block:
  
  • Most people with complete heart block have an underlying heart condition:
    
    • Coronary artery disease
    • Cardiomyopathy
    • Congenital heart disease

Question 28

What are the symptoms of complete heart block?

Answer 28

• Dizziness
• Syncope
• Tiredness
• Breathlessness
• Oedema

Question 29

What are the different types of heart block?

Answer 29

• Atrioventricular heart block
  
  • First degree
  • Second degree
  • Third degree
• Bundle branch block
  
  • Left
  • Right
• Tachybrady syndrome

Question 30

Describe the difference between first- second- and third- degree AV block.

Answer 30

• First-degree
  
  • Usually does not cause any symptoms or need treatment.
    
    • The PR interval is lengthened beyond 0.2 seconds.
• Second-degree
  
  • Some, but not all of the SA node electrical impulses fail to conduct to the ventricles.
• Third-degree
  
  • Complete heart block.

Question 31

Describe bundle branch blocks.

Answer 31

• A defect of the bundle branches of fascicles in the electrical conduction system of the heart.
• Left BBB - usually caused by an underlying condition, such as:
  
  • Congenital heart disease
  • Cardiomyopathy
  • Left ventricular hypertrophic cardiomyopathy
  • Ageing of the electrical pathway in the heart
• Right BBB - can be caused by congenital heart disease, or some lung conditions.
  
  • It can also happen naturally in people with a normal heart and no heart problems.

Question 32

Describe tachybrady syndrome.

Answer 32

• If the SA node does not work properly, it can cause the heartbeat to become too fast or too slow, or switch between fast and slow rhythms.
  
  • e.g. atrial flutter alternating with a slow heart rhythm.

Question 33

Describe the use of ILRs.

Answer 33

• ILRs (Implantable Look Recorders) are used if the patient has symptoms such as palpitations, dizzy spells or blackouts that may not happen very often, a small USB-sized stick is implanted and records the heart’s electrical activity.
• Battery lasts up to 3 years, and so is useful if an ECG has not been able to determine the cause of symptoms.
• Collects arrhythmic data.

Question 34

Describe the action of ICDs.

Answer 34

• ICDs are used to detect ventricular tachycardia or ventricular fibrillation.
• ICDs deliver shocks or ATP (anti-tachycardic pacing) when the heart is in VT - 30 joule shock is delivered, and keeps delivering a cycle of ATP, followed by a shock until the patient is successfully cardio-converted back to a normal sinus rhythm.
• CPR can be delivered to the patient during the ICD shock.

Question 35

Describe the use of CRTs.

Answer 35

• Cardiac resynchronisation therapy is offered if the patient has a broad QRS complex secondary to heart disease or an MI damaging the left ventricle.
• One way to resynchronise the QRS complex to make the heart ejection more physiologically normal is to PACE BOTH VENTRICLES.
  
  • Simultaneous pacing of both ventricles results in a more efficient ventricular contraction, thus improving the ventricle ejection.

Question 36

Describe the role of CRT in heart failure.

Answer 36

• When the heart becomes enlarged in heart failure, its electrical circuits can become stretched, leading to communication breakdown between different parts of the heart.
  
  • This disrupts the normal coordinated cotraction of the heart, making it inefficient.
• A CRT-P (also called a biventricular pacemaker) can be implanted that it sends small electrical impulses to both ventricles to help them to contract at the same time.