JC M WCS 4

JC M WCS 4: SYNCOPE & IRREGULAR HEARTBEAT
Dr K Lee

Medicine

Thu 24-10-02
SYNCOPE

Definition - interruption of consciousness (vs. pre-syncope, near-syncope)

Causes (1) CV (2) on-CV - neuro, metab, psych

Cardiovascular (most common)

Cardiac arrhythmia - bradycardia, tachycardia

Mechanical / Structural - LV obstruction, low cardiac output (eg. aortic stenosis, ¯ contractility)

Vasovagal - neurocardiogenic (paradoxical response in ANS, functional, benign)

Orthostatic (D posture) - drug-induced, elderly patients (eg. VD - HT, IHD, heart failure)

Neurological

Epilepsy - generalised convusion (cerebral dysrrythmia)

TIA - reticular formation

CVA - ICP

* neuro deficits (eg. plegia, dysarthria, slurring) - if no neuro deficit, consider CV cause

Metabolic (prolonged)

Hypoglycemia (OHA-induced) / Hyperglycemic coma
Hyponatremia/ Hypernatremia
Hypothermia

* Need blood test, correct underlyling cause

CARDIAC PHYSIOLOGY

Cardiac action potential

RMP -80mv

Tendency for rapid repolarisation - phase 0

Peak @ +30mV

Repolarise - gradually to RMP (Phase 4)

CARDIAC ARRYTHMIA

Causes

Impulse formation prob
Impulse propagation prob

Mechanisms

Reentry - most common, dissociated p'ways, inhomogeneous conduction props, unidirectional block (eg. AVNRT, AVRT, A Flu, VT)

Triggered activity - extra impulses following normal impulses (single/ multiple)

Automaticity - present in cells, different rate (SAN 70, AVN 50, Purkinje 35/min) - automaticity of AVN + PF > SAN (pacemaker)

Normal automaticity

Abnormal automaticity

Eg. inappropriate sinus tachycardia, automatic atrial tachycardia

Classification

1. Bradyarrhythmia

SAN disease (sinus bradycardia, sinus node)

Sinus bradycardia
Sinus arrest - transient absence of SAN activity (N heartbeat with periods of stop)
SA block

AVN disease (heart block, no propagation, e- via myocardium, slower \ broader QRS)

1^o AVB - PR prolongation (N < 200 msec)
2^o AVB

Type I - Wenkebach phenomenon (periodical, progressive)
Type II - Intermittent failure of conduction

3^o AVB - complete AV dissociation

Treatment

Acute

Exclude reversible causes (hypothyroidism, drugs)
Intravenous drug (atropine, isoproterenol)
Temporary pacing (transcutaneous, transvenous)

Long term

Permanent pacemaker implantation

2. Tachyarrhythmia (rapid rate ® ¯ length diastole ® ¯ ventricular filling ® ¯ BF coronary a)

Supraventricular (origin above/at AVN)

SAN - sinus tachycardia (ST)
Atrial

PAC - premature atrial complex (baseline regular with atrial ectopic beats)
AT - atrial tachycardia (sinus pattern but > 100bpm, narrow QRS)
A Flu - atrial flutter ("saw-tooth" appearance)
AF - atrial fibrillation (HR + R-R interval totally irregular)

PSVT (paroxysmal SVT) - regular tachycardia with narrow QRS

AVRT - AV reentry tachycardia (accessory pathway present, usu congenital, retrograde P wave)

AVNRT - AV nodal reentry tachycardia (2 pathways within AVN itself, P wave fused with QRS \ hidden)

Ventricular (origin below level of AVN)

PVC - premature ventricular complex (QRS wider - depolarisation 2 ventricles sequentially rather than at same time)

VT - ventricular tachycardia (sustained PVC)

V flu - ventricular flutter (¯ CO, potentially lethal)

VF - ventricular fibrillation (v rapid \ no contraction, >5-10 min ® irreversible damage due to hypoxia, potentially lethal)

Treatment: stop arrythmia, restore/ maintain sinus rhythm

Acute

Haemodynamically stable ® pharmacological

IV Adenosine/ ATP (short t 1/2 < 10 sec, hyperpolarisation of ATP-sensitive K-channel in AVN, blocks AVN conduction)
IV AVN blockers (Verapamil, Diltiazem, Esmolol)

Haemodynamically unstable ® electrical

Non-pharmacological ® Vagal maenouevre (successful 10-20%, vagal tone = slow SVN conduction, stop SVT - eg. carotid sinus massage, Valsalva manouevre, gagging, ice water drink/ on face

Long-Term

Pharmacological

Oral AVN blockers (b -blockers, Ca-channel blockers, Digoxin)

Class I AAD

Class III AAD

Non-pharmacological

RFA (radiofrequency catheter ablation) - esp focal arrythmia ® PSVT, AT, A flu, AF, VT

CV (electrical cardioversion) followed by pharma ® A flu, AF

ICD (implantable cardioverter-defibrillator) ® VT/VF, (AF)

Surgery ® AF, VT

Specific

AT, A Flu, AF

Acute - IV AVN blockers (Diltiazem, Esmolol)/ Digoxin. Class I AAD/ Amiodarone + non-pharm (CV)

Long-term - Oral AVN blockers (b -blockers, Diltiazem), Digoxin, Class I ADD, Sotalol, Amiodarone + non-pharm (pacing, ICD, surg)

Note: anticoagulation may be required for prophylaxis of thromboembolism

VT, VF

Acute - IV Lignocaine/ Procainamide/ Amiodarone/ Bretylium + non-pharm (CV, defibrillation)
Long-term - Class I AAD, Sotalol, Amiodarone + non-pharm (ICD implant, RFCA, surg)

CLINICAL

Hx

Onset and/or termination (abrupt vs gradual) [abrupt ® genuine arrythmia]

Regularity/ rate

Frequency/ duration

Symptomatology

Functional ischemia ® chest pain, hemodynamic change ® dizziness, syncope, rapid rate ® SOB [genuine arrythmia]

SVT® polyuria after attack [acute distention of atrium ® (+) ANP]

Precipitating / relieving factors [coffee, emotion, PA]

Functional status/ Cardiac Sx in-between attacks [underlying structure heart disease?]

P/E

Evidence of structural heart disease eg. JVP, cardiomegaly, murmurs of VHD or HOCM, CHF [valvular heart disease ® atrial arrhythmia]

	HEART DISEASE
	YES	NO
Bradycardia	+++	+++
Atrial	+++	++
Ventricular	+++	+
PSVT	+	+++

+ = rare, ++ = occasional, +++ = common

History & Physical examination
ECG
24 hour ECG (Holter) - electrode, for intermittent arrhythmia (3% detection if only occasional event)
Event recorder - Pt activates when feels episode (can use w-m)
Electrophysiological study (catheter through BV to heart, can provoke arrhythmia and measure conduction physiology)

Psych

Vicious cycle: anxiety « arrhythmia/ tachycardia

Psychosomatic (disproportionate)

Stigmatisation

Sick role