Treatment of Rhythm Disorders - ALWAYS TREAT THE ORIGINAL CAUSE BEFORE ESTABLISHING SINUS RHYTHM. TREATING UNDERLYING CAUSE MAY AUTOMATICALLY TREAT ARRYTHMIA. 

SINUS TACHYCARDIA
- Treat the underlying cause (i.e.: hypoovolaemia, pain, thyrotoxicosis, anxiety, heart failure)

ATRIAL PREMATURE COMPLEX
- This is when there is an extra systolee. It can cause a 'missed beat' sensation and is not really cause for concern. The QRS is normal, but P wave is abnormal/missing because the impulse starts from place other than SA node. 
- Treatment: 'reassurance' + beta-block  / verapamil (if need be)

ATRIAL FLUTTER
What is it?: It is rapid 'saw tooth' atrial activity --> 250-350bpm. Usually 2:1, 3:1, 4:1 ratio with ventricular rate.
ECG: 'saw toothed'
Aetiology: Re-entry circuit within atrium
Complication: Atrial fibrillation, Ventricular tachycardia (i.e.: Atrial rate slows so much that impulses reach AV node at their repolarised state)
Treatment (follow tree): 
	- Serious: DC Cardioversion / Artifical pacemaker (capture atrial rhythm)
	- Not Serious: Pharmacological therapy
		- Slow ventricular rate:
			- beta-blockers (oral/IV)
			- diltiazem (oral) / verapamil (IV)
			- digoxin
				- not urgent: maintenance dose
				- urgent: 1.5mg / 24 hrs --> maintenance dose
		- Return sinus rhytm
			- amiodarone: 5mg/kg/0.3 - 2hrs + 10-15mg/kg/24hrs

		- Prevent relapse (only if recurrent attacks): amiodarone
ATRIAL FIBRILLATION
What is it?: irregularly irregular atrial rate: 350-600bpm. Often fluctuates between AF & flutter
ECG: discrete p waves not visible (i.e.: looks like VF but P waves affected)
Aetiology: multiple re-entry circuit within atrium. Causes: atrial enlargement (i.e.: MR, MS, thyrotoxicosis, HTN). 
Complication: 1) low CO due to rapid ventricular rates (i.e.: impulse reaches ventricle in its repolarised state), 2) thrombus formation --> thromboembolism (risk = 5% / yr - depending on risk factors). 
Treatment (similar to flutter): 
	- Slow ventricular rate:
		- beta-blockers
		- diltiazem
		- digoxin
	- Return sinus rhythm if AF rate control does not work:
		- DC cardioversion is done if atrial thrombus is excluded. If thrombus present --> perform 3-6 wks of anticoagulation --> pharmacological cardioversion)
		- pharmacological cardioversion: Class III antiarthymics: sotalol, amiodarone, Class IC: flecanide. 
	- Continue anticoagulation for 4 wks after returning sinus rhythm

	- Prevent relapse (only if recurrent attacks): amiodarone, sotalol

	- Anticoagulation in AF: Indicated if attack > 24hrs or if recurrent attacks
		- Treatment of choice: warfarin (reduce risk by 2/3), aspirin (20-25%)
			- High risk groups: warfarin with INR 2-3
			- Moderate risk groups: warfarin or aspirin
			- Low risk groups: aspirin 75-300mg/day

		- Refer to lecture notes for info on high/low/moderate-risk patients


AT THIS STAGE, REVISE THE PHARMACOLOGICAL ASPECTS OF CLASS III & CLASS IV ANTIARRYTHMICS + DIGOXIN + WARFARIN. KNOW D/I, C/I, SIDE EFFECTS. Lecture notes covers well. 

SUPRAVENTRICULAR TACHYCARDIA
What is it?: Paroxysmally the atrial rate becomes fast: 140-250bpm
ECG: sometimes an inverted P wave due to caudocranial direction of activation
Aetiology: re-entry circuit (Fig 12.15 Lilly pp 258) --> AV nodal re-entrant circuit or Wolf Parkinson White Syndrome. 
Treatment: (follow tree):
	- Acute: 
		- Vagal manouver (carotid sinus massage, valsalva): Reduce AV node conduction and break the re-entry rhythm
		- Drugs: 
			- Adenosine (IV): 6mg --> 12mg 2mins later (if necessary) --> 18mg 2mins later (if necessary)
			- Verapamil (avoid if on beta-blocker or LVF): 1mg/min --> 15mg. 
		- DC Cardioversion
	- Chronic: 
		- transcatheter ablation
		- Sotalol (80-160mg twice/day)

	Adenosine actually binds to surface receptors --> activates K+ channels + inhibits adenylate cyclase --> 10 sec half life, so side effects (i.e.: headache, bronchoconstriction, hypotension, chest pain) are only transient. C/I: asthma. D/I: theophylline + caffeine antagonise adenosine receptors (so need higher doses) + dypyridamole

VENTRICULAR ECTOPICS
What is it?: Somewhere in the ventricle an ectopic focus fires. Normal in healthy people.
ECG: QRS with no preceding P wave
Treatment: none

VENTRICULAR TACHYCARDIA
What is it?: The ventricle fires at an abnormally high rate: 100-200bpm. Defined as more than 3 VPBs in a row. Two categories: 1) sustained (>30secs + symptoms), 2) nonsustained (<30secs)
ECG: shows numerous QRS complexes
Aetiology: Numerous ventricular foci fire off. Associated with serious heart disease (AMI etc). 
Complication: VF, haemodynamic consequences (syncope, hypotension, chest pain etc)
Treatment:
	- Acute: 
		- Sustained: DC Cardioversion + Class III antiarrthymics (sotalol / amiodarone)
		- Non-sustained: amiodarone 5mg/kg/IV over 20-180mins --> 10-15mg/kg/24hrs
	- Prevent relapse:
		- internal defibrillator, b-blockers, amiodarone
	- Prophalyxis: dont worry about prevention if VT occurs within 48hrs of AMI. 

VENTRICULAR FIBRILLATION
What is it?: Irregular ventricle beats
ECG: choatic QRS with various widths + amplitudes
Aetiology: multiple re-entry circuits (like AF). AMI / Ischaemia / Electrocution
Complication: Death due to haemodynamic consequences
Treatment: 
	- Acute: DC Cardioversion + adrenaline + CPR + treat the cause
	- Prevent relapse: Class III: amiodarone, sotalol, bretyllium. internal defribrillator, b-blockers, amiodarone
	- Prophalyxis: dont worry about prevention if VF occurs within 48hrs of AMI.