Cardiac Arrhythmias

Cardiac Arrhythmias
By:Elise Georgi Morris, M.D.

Objectives
* Identify common arrhythmias encountered by the family physician
* Discuss arrhythmia etiologies
* Discuss initial primary care work-up and treatment
* Practice questions

Normal Sinus Rhythm
Implies normal sequence of conduction, originating in the sinus node and proceeding to the ventricles via the AV node and His-Purkinje system.
EKG Characteristics: Regular narrow-complex rhythm

Sinus Bradycardia
* HR< 60 bpm; every QRS narrow, preceded by p wave
* Can be normal in well-conditioned athletes
* HR can be<30 bpm in children, young adults during sleep, with up to 2 sec pauses

Sinus bradycardia--etiologies
* Normal aging
* 15-25% Acute MI, esp. affecting inferior wall
* Hypothyroidism, infiltrative diseases
(sarcoid, amyloid)
* Hypothermia, hypokalemia
* SLE, collagen vasc diseases
* Situational: micturation, coughing
* Drugs: beta-blockers, digitalis, calcium channel blockers, amiodarone, cimetidine, lithium

Sinus bradycardia--treatment
* No treatment if asymptomatic
* Sxs include chest pain (from coronary hypoperfusion), syncope, dizziness
* Office: Evaluate medicine regimen—stop all drugs that may cause
* Bradycardia associated with MI will often resolve as MI is resolving; will not be the sole sxs of MI
* ER: Atropine if hemodynamic compromise, syncope, chest pain
* Pacing

Sinus tachycardia
* HR > 100 bpm, regular
* Often difficult to distinguish p and t waves

Sinus tachycardia--etiologies
* Fever
* Hyperthyroidism
* Effective volume depletion
* Anxiety
* Pheochromocytoma
* Sepsis
* Anemia
* Exposure to stimulants (nicotine, caffeine) or illicit drugs
* Hypotension and shock
* Pulmonary embolism
* Acute coronary ischemia and myocardial infarction
* Heart failure
* Chronic pulmonary disease
* Hypoxia

Sinus Tachycardia--treatment
* Office: evaluate/treat potential etiology :check TSH, CBC, optimize CHF or COPD regimen, evaluate recent OTC drugs
* Verify it is sinus rhythm
* If no etiology is found and is bothersome to patients, can treat with beta-blocker

Sinus Arrhythmia
* Variations in the cycle lengths between p waves/ QRS complexes
* Will often sound irregular on exam
* Normal p waves, PR interval, normal, narrow QRS

Sinus arrhythmia
* Usually respiratory--Increase in heart rate during inspiration
* Exaggerated in children, young adults and athletes—decreases with age
* Usually asymptomatic, no treatment or referral
* Can be non-respiratory, often in normal or diseased heart, seen in digitalis toxicity
* Referral may be necessary if not clearly respiratory, history of heart disease

Sick Sinus Syndrome
* All result in bradycardia
* Sinus bradycardia (rate of ~43 bpm) with a sinus pause
* Often result of tachy-brady syndrome: where a burst of atrial tachycardia (such as afib) is then followed by a long, symptomatic sinus pause/arrest, with no breakthrough junctional rhythm.

Sick Sinus Syndrome--etiology
* Often due to sinus node fibrosis, SNode arterial atherosclerosis, inflammation (Rheumatic fever, amyloid, sarcoid)
* Occurs in congenital and acquired heart disease and after surgery
* Hypothyroidism, hypothermia
* Drugs: digitalis, lithium, cimetidine, methyldopa, reserpine, clonidine, amiodarone
* Most patients are elderly, may or may not have symptoms

Sick sinus syndrome--treatment
* Address and treat cardiac conditions
* Review med list, TSH
* Pacemaker for most is required

Paroxysmal Supraventricular Tachycardia
* Refers to supraventricular tachycardia other than afib, aflutter and MAT
* Occurs in 35 per 100,000 person-years
* Usually due to reentry—AVNRT or AVRT

PSVT
* Initial eval: Is the patient stable?
* Determine quickly if sinus rhythm
* If not sinus and unstable, cardioversion
* Unstable sinus tachycardia---IV beta-blocker, and treat cause
* Sxs of instability would include: chest pain, decreased consciousness, short of breath, shock, hypotension—unstable sxs require shock
* If stable, determine whether regular rhythm (sinus or PSVT) vs irregular (afib/flutter, MAT)? p waves (MAT vs. AF)?
* If regular, determine whether p waves are present, if can’t see---administer adenosine (6mg, can give 2 doses) or CSM or other vagal maneuvers)

* CSM or adenosine commonly terminate the arrhythmia, esp, AVRT or AVNRT
* Can also use CCB or beta blockers to terminate, if available
* Counsel to avoid triggers, caffeine, Etoh, pseudoephedrine, stress
* No p waves —junctional tachycardia, AVRT or AVNRT, Afib
* AVRT and AVNRT: can have retrograde p waves and short RP interval
* Abnormal p waves morphology: MAT

Atrial Fibrillation
* Irregular rhythm
* Absence of definite p waves
* Narrow QRS
* Can be accompanied by rapid ventricular response

Atrial Fibrillation—causes and associations
* Hypertension
* Hyperthyroidism and subclinical hyperthyroidism
* CHF (10-30%), CAD
* Uncommon presentation of ACS
* Mitral and tricuspid valve disease
* Hypertrophic cardiomyopathy
* COPD
* OSA
* ETOH
* Caffeine
* Digitalis
* Familial
* Congenital (ASD)

Atrial fibrillation--assessment
* H & P—assess heart rate, sxs of SOB, chest pain, edema (signs of failure)
* If unstable, need to cardiovert
* Echocardiogram to evaluate valvular and overall function
* Check TSH
* Assess for RVR
* Assess onset of sxs—in the last 24-48 hours? Sudden onset? Or no sxs?

Atrial fibrillation--management
* Rhythm vs Rate control—if onset is within last 24-48 hours, may be able to arrange cardioversion—use heparin around procedure
* Need TEE if valvular disease (high risk of thrombus)
* If unable to definitely conclude onset in last 24-48 hours: need 4-6 weeks of anticoagulation prior to cardioversion, and warfarin for 4-12 weeks after

Atrial Fibrillation
* Cardioversion: synchronized (w/QRS) delivery of current to heart; depolarizes tissue in a reentrant circuit; afib involves more cardiac tissue, but cardiovert
* Defibrillation: non-synchronized delivery of current

Atrial fibrillation--management
* Rate control with chronic anticoagulation is recommended for first line approach for majority of patients; overall Afib is a stable rhythm
* Beta-blockers (atenolol and metoprolol) or calcium channel blockers (verapamil or diltiazem) recommended. Digoxin not recommended for rate control
* Anticoagulation: LMWH and then warfarin; can use aspirin for anticoagulation if CI to warfarin, not as effective

Atrial fibrillation--management
* Goal INR of 2.5 (2.0-3.0)
* Rhythm control---second line approach, if unable to control rate or pt with persistent sxs
* Can also consider radiofrequency ablation at pulm veins
* P wave from another atrial focus
* Occurs earlier in cycle
* Different morphology of p wave
* Benign, common cause of perceived irregular rhythm
* Can cause sxs: “skipping” beats, palpitations
* No treatment, reassurance
* With sxs, may advise to stop smoking, decrease caffeine and ETOH
* Can use beta-blockers to reduce frequency

1st Degree AV Block
* PR interval >200ms
* If accompanied by wide QRS, refer to cardiology, high risk of progression to 2nd and 3rd deg block
* Otherwise, benign if asymptomatic

2nd Degree AV Block Mobitz type I (Wenckebach)

* Progressive PR longation, with eventual non-conduction of a p wave
* May be in 2:1 or 3:1
Wenckebach, Mobitz type I
* Usually asymptomatic, but with accompanying bradycardia can cause angina, syncope esp in elderly—will need pacing if sxs
* Also can be caused by drugs that slow conduction (BB, CCB, dig)
* 2-10% long distance runners
* Correct if reversible cause, avoid meds that block conduction

2nd degree block Type II (Mobitz 2)
* Normal PR intervals with sudden failure of a p wave to conduct
* Usually below AV node and accompanied by BBB or fascicular block
* Often causes pre/syncope; exercise worsens sxs
* Generally need pacing, possibly urgently if symptomatic

3rd Degree AV Block

* Complete AV disassociation, HR is a ventricular rate
* Will often cause dizziness, syncope, angina, heart failure
* Can degenerate to Vtach and Vfib
* Will need pacing, urgent referral
* Extremely common throughout the population, both with and without heart disease
* Usually asymptomatic, except rarely dizziness or fatigue in patients that have frequent PVCs and significant LV dysfunction
* No treatment is necessary, risk outweighs benefit
* Reassurance
* Optimize cardiac and pulmonary disease management

Non-sustained Ventricular tachycardia
* Defined as 3 or more consecutive ventricular beats
* Rate of >120 bpm, lasting less than 30 seconds
* May be discovered on Holter, or other exercise testing

Non-sustained ventricular tachycardia
* Need to exclude heart disease with Echo and stress testing
* If normal, there is no increased risk of death
* May need anti-arrhythmia treatment if sxs
* In presence of heart disease, increased risk of sudden death
* Need referral for EPS and/or prolonged Holter monitoring

Ventricular fibrillation
* Defibrillation

Practice Questions—Case studies

References

Cardiac Arrhythmias.ppt