Cardiology Flashcards
Supraventricular tachycardias
Sinus tachycardia
Atrial tachycardia
Atrial flutter
Atrial fibrillation
Atrioventricular nodal re-entrant tachycardia (AVNRT)
Atrioventricular re-entrant tachycardia (AVRT)
Ventricular tachycardias
Ventricular tachycardia
Polymorphic ventricular tachycardia
Accessory pathway
Accessory pathway = abnormal connection between the atria and ventricles away from the AVN that allows electrical activity to pass through
If electrical activity is conducted via accessory pathway, it will take an abnormal slow route -> can lead to a broad QRS
Sinus tachycardia
Sinus rhythm with a HR > 100 bpm
Normal physiological response when the body is put under stress
-Exercise
-Intercurrent illness
-Underlying pathology
Management is dependent on the underlying cause
Atrial tachycardia
Occurs due a abnormal focus of activity undergoing rapid depolarisation in the atria
Different types depending on the origin: single foci, multiple foci & small re-entrant circuit
Usually a regular tachyarrhythmia but multi-focal atrial tachycardia may present with an irregular rhythm
ECG: tachyarrhythmia, with a narrow QRS and abnormal P waves
-Typically there is an abnormal P wave axis with inverted P waves in the inferior leads (II, III, aVF)
Treatment - medications (beta-blockers, calcium channel blockers), ablation (treats certain areas of your heart to stop them improperly conducting electricity) - very helpful in stopping focal atrial tachycardia
Atrial flutter
Specific type of atrial tachycardia - that occurs due to a rapid macro-reentrant circuit within the atria
ECG: typically sawtooth pattern, which is best visualised in the inferior leads
Due to fast atrial rate, the AVN causes a ‘block’ (some atrial activity is not conducted to the ventricles)
-Physiological response to allow time for ventricular filling
-Classically seen as a 2:1 block (two flutter waves to one QRS complex)
Atrial fibrillation
Occurs due to multiple waves of spontaneous depolarisation leading to fragmentation of normal electrical activity
Causes muscle fibres to contract independently leading to ‘fibrillation’ of the atrial muscle
Multiple waves of electrical activity (varying in strength) reach the AVN -> intermittently conducts these to the ventricles -> irregular rhythm
-Irregularly irregular rhythm
-Absence of P waves
-Irregular, fibrillating baseline
AF rate control
Rate control - first-line to many patients
Beta -blocker first-line: atenolol, bisoprolol
Calcium-channel blocker: diltiazem/verapamil
Digoxin: only in sedentary people with persistent AF, requires monitoring & has a risk of toxicity
AF rhythm control
Rhythm control - offered to patients with reversible cause for their AF, new onset AF, heart failure caused by AF, symptoms despite being effectively rate controlled
-Cardioversion - immediate and delayed cardioversion
–Immediate - pharmacological or electrical
—Pharmacological - flecainide or amiodarone
—Electrical - aims to shock the heart back into sinus rhythm, involves using a cardiac defibrillator to deliver controlled shocks
-Long-term rhythm control using medications - beta blockers, dronedarone, amiodarone
AF anticoagulation
Anticoagulation to prevent strokes
DOACs are first line
Supraventricular tachycardia
Can refer to the origin of a tachyarrhythmia or a subset of abnormally fast heart rhythms that are due to reentrant circuits involving the AVN
Clinical practice -> the term SVT is reserved for these reentrant arrhythmias
1) Atrioventricular nodal reentrant tachycardia
2) Atrioventricular reentrant tachycardia
AVNRT
Most common SVT - typically occurs in patients with a structurally normal heart
Due to additional conduction pathways within the AVN, which allows initiation of a reentrant circuit
Usually a rapid, narrow-complex tachycardia with absent P waves
AVRT
Second most common SVT, usually presents at a younger age than AVNRT & can occur in children
Due to an accessory pathway away from the the AVN
May enable electrical impulses to pass antegrade (atria to ventricles) or retrograde (ventricles to atria)
Difficult to distinguish AVRT from AVNRT on an ECG
Wolff-parkinson-white syndrome
Preexcitation syndrome that is characterised by a congenital accessory pathway & episodic tachyarrhythmias
Accessory pathway = usually referred to as the ‘Bundle of Kent’ & can allow conduction antegrade or retrograde
ECG pattern in WPW is due to preexcitation of the ventricles via the accessory pathway
-Short PR interval
-Early slurred upstroke in the QRS complex = delta wave
-Remaining QRS complex is normal - usual conduction via the AVN
Main concern is development of AF -> can deteriorate into ventricular fibrillation
Ventricular tachycardia
Occurs due to a focus of electrical activity in the ventricles undergoing rapid depolarisation
Commonly due to scarring of the ventricles following MI
ECG: rapid, broad-complex tachycardia
Life-threatening arrhythmia -> loss of consciousness, loss of CO and cardiac arrest
VT without a pulse is one of the ‘shockable’ cardiac arrest rhythms
Polymorphic VT
Particular types of VT that is due to depolarisation of multiple foci within the ventricles leading to variable QRS complexes
Usually secondary to MI
Torsades de pointes - subtype of polymorphic VT
-Characterised by ventricular tachycardia that ‘twists’ around the isoelectric line
-Subtype occurs secondary to a prolonged QT interval
-Management is aimed at shortening the QT interval with IV magnesium sulphate
-If unstable, they should undergo immediate DC cardioversion as with any unstable tachyarrhythmia
Ventricular fibrillation
Ventricular muscle fibres contract independently
ECG: coordinated electrical activity with a chaotic, fibrillating baseline
VF is incompatible with life & patients who develop this rhythm will go into cardiac arrest
One of the ‘shockable’ cardiac arrest rhythms that requires immediate DC cardioversion
Escape rhythm
Escape rhythm = SAN fails to undergo spontaneous depolarisation so electrical activity is initiated lower down
Can occur as a single beat or a sustained rhythm
Sinus pause/arrest
Failure of the SAN to initiate electrical activity
Sinus pause = transient absence of P waves that lasts from 2 seconds to several minutes
Dysfunction of the SAN may manifest as failed initiation of conduction/failed transmission of electrical activity
Sinus node dysfunction (‘sick sinus syndrome’)
Collective term that refers to conduction abnormalities affecting the SAN and surrounding tissue
Manifests as a variety of ECG abnormalities: sinus bradycardia, sinus pause/arrest, sinoatrial exit block, chronotropic incompetence
Also associated with atrial tachyarrhythmias
-Tachy-brady syndrome: presents with alternating bradyarrhythmias and tachyarrhythmias
Occurs due to depression of the normal autorhythmicity of the SAN and surrounding tissue
Heart block
Interference of the normal transmission of conduction within the AVN can lead to varying degrees of ‘block’
First-degree heart block - prolongation of PR interval > 200ms
Second-degree heart block - underlying conduction disease
Mobitz type I: progressive prolongation of PR interval, leading to dropped QRS
Mobitz type II: randomly dropped QRS
Third-degree heart block - complete dissociation between P waves and QRS complexes on ECG
Bradyarrhythmias clinical features
Asymptomatic
Fatigue, lethargy
Dizziness, pre-syncope
Syncope
Pulmonary oedema
Chest pain
Shock
Impaired consciousness
Four cardinal features that suggest an unstable arrhythmia
Syncope
Myocardial ischaemia (chest pain)
Heart failure
Shock
Bradyarrhythmias pharmacological management
Pharmacological therapy - used in an attempt to increase the heart rate
Atropine (antimuscarinic): reversible antagonist of muscarinic acetylcholine receptors, blocks the action of the vagus nerve on the SAN & AVN -> leads to increased SAN electrical activity and increased conduction through the AVN
Given as IV bolus, which can be repeated
Isoprenaline (non-selective beta-adrenoreceptor agonist): positive inotropic and chronotropic effects on the heart via beta-receptors, leads to an increase in HR and improved contractility
Given as IV infusion
Pacing
Delivers electrical stimuli to the heart via pacing leads
May be required in an emergency setting, following MI or a long-term option in patients with bradyarrhythmias
Temporary pacing - transcutaneous, epicardial & transvenous
Permanent pacing - permanent electronic device that is inserted under the skin (pacemaker box is attached to wires which are inserted into the heart via the transvenous route )
Permanent pacemakers
Three main types of pacemaker
Single chamber - single lead implanted into the right atrium/ventricle
Dual chamber - two leads implanted, one in the right atrium & one in right ventricle
Biventricular (cardiac resynchronisation) - left ventricular and right ventricular pacing
-Used in heart failure
Stable angina
Atherosclerosis affecting the coronary arteries, narrowing the lumen and reducing blood flow to the myocardium
Symptoms only come on with exertion and are always relieved by rest or glyceryl trinitrate (GTN)
Angina baseline investigations
Physical examination
ECG
FBC – anaemia
U&Es, LFTs – required before starting medications
Lipid profile
TFTs
HbA1C & fasting glucose (diabetes)
Angina specialist investigations
Cardiac stress testing – assessing the patient’s heart function during exertion, can involve having the patient exercise/giving medication (dobutamine)
- Options for assessing cardiac function = ECG, echo, MRI or myocardial perfusion scan
CT coronary angiography – involves injecting contrast and taking CT imaged timed with heart contractions (gives detailed view of coronary arteries, highlighting any narrowing)
Invasive coronary angiography – catheter is inserted into the patient’s brachial/femoral artery -> directed to coronary arteries under x-ray guidance, where contrast is injected to visualise coronary arteries = GOLD STANDARD
Angina principles of management
R – refer to cardiology
A – advice them about the diagnosis, management & when to call an ambulance
M – medical treatment
P – procedural or surgical interventions
S – secondary prevention
Referrals sent to rapid access chest pain clinic
Angina medical management
1) Immediate symptomatic relief
2) Long-term symptomatic relief
3) Secondary prevention of CVD
Angina immediate symptomatic relief
Sublingual glyceryl trinitrate in the form of spray/tablets
GTN causes vasodilation, improving the blood flow to the myocardium
Take GTN when symptoms start, take second dose after 5 mins if symptoms remain, take third dose after 5 mins if symptoms remain, call ambulance after a further 5 mins if symptoms remain
SE: headaches, dizziness
Angina long-term symptomatic relief
Beta blocker
Calcium-channel blocker (diltiazem/verapamil – both avoided in HFrEF)
Specialist may consider – long-acting nitrates (isosobide mononitrate), ivabradine, nicorandil, ranolazine
Angina secondary prevention
Aspirin 75mg once daily
Atorvastatin 80mg once daily
ACE inhibitor (if diabetes, HTN, CKD, HF present)
Already on a beta blocker for symptomatic relief
Angina surgical interventions
Percutaneous coronary intervention (PCI) – catheter into patient’s brachial/femoral artery & guided to coronary arteries, contrast injected, areas of stenosis can be treated by dilating a balloon to widen the lumen (angioplasty) & inserting a stent to keep it open
Coronary artery bypass graft (CABG) – involves opening the chest along the sternum, with a midline sternotomy incision, graft vessel is attached to the affected coronary artery, bypassing the stenotic area
- Saphenous vein
- Internal thoracic artery
- Radial artery
PCI: faster recovery, lower rate of strokes as a complication, higher rate of requiring repeat revascularisation (further procedures)