DefinitionDefinition Characterized by transient loss of consciousness

Due to temporary and self terminating global cereberal hypoperfusion

In recent studies, syncope has been shown to account for approximately 1% of ED visits and is the sixth most common cause for hospitalization of patients older than 65 years.

Establishing a definitive cause for this common problem in the ED is hampered by its transient and episodic nature and by the fact that the affected patient has usually completely recovered by the time of examination. Moreover, multiple potential causes are present in 18% of patients with syncope.

Characterized by transient loss of consciousness Due to temporary and self terminating global cereberal

hypoperfusion

In recent studies, syncope has been shown to account for approximately 1% of ED visits and is the sixth most common cause for hospitalization of patients older than 65 years.

Establishing a definitive cause for this common problem in the ED is hampered by its transient and episodic nature and by the fact that the affected patient has usually completely recovered by the time of examination. Moreover, multiple potential causes are present in 18% of patients with syncope.

Causes of Nonsyncopal Attacks (Commonly Misdiagnosed as

Syncope)

Causes of Nonsyncopal Attacks (Commonly Misdiagnosed as

Syncope)

Disorders without any impairment of consciousness Falls   Cataplexy   Drop attacks   Psychogenic pseudosyncope   Transient ischemic attacks of carotid origin

Disorders with partial or complete loss of consciousness   Metabolic disorders, including hypoglycemia, hypoxia,

hyperventilation with hypocapnia   Epilepsy   Intoxications   Vertebrobasilar transient ischemic attack

Disorders without any impairment of consciousness Falls   Cataplexy   Drop attacks   Psychogenic pseudosyncope   Transient ischemic attacks of carotid origin

Disorders with partial or complete loss of consciousness   Metabolic disorders, including hypoglycemia, hypoxia,

hyperventilation with hypocapnia   Epilepsy   Intoxications   Vertebrobasilar transient ischemic attack

Causes of SyncopeCauses of Syncope

Age-Dependent Causes of Syncope

Mayo Clinic: 1996-1998 (n=1,291)

Age-Dependent Causes of Syncope

Mayo Clinic: 1996-1998 (n=1,291)<65 years<65 years

n=607n=60765 years65 years

n=684n=684

13%

43%

3%

17%

24%

30%23%

10%18%

19%

Cardiogenic Vasovagal CHS Undetermined OtherCardiogenic Vasovagal CHS Undetermined Other

SYNCOPE: Natural HistorySYNCOPE: Natural History

Kapoor: Medicine, 1990Kapoor: Medicine, 1990

102030405060

0 1 2 3 4 5 0 1 2 3 4 5

Year of follow-up

%

CardiogenicUndeterminedNoncardiac

Mortality Sudden Death

Emergency Department Risk Stratification of Patients With Syncope of Unknown Cause

Emergency Department Risk Stratification of Patients With Syncope of Unknown Cause

High-risk group High-risk group Intermediate-risk Intermediate-risk group group

Low-risk group Low-risk group

Chest pain Chest pain

Signs of chronic heart Signs of chronic heart failurefailureModerate/severe valvular Moderate/severe valvular diseasediseaseHistory of ventricular History of ventricular arrhythmiasarrhythmiasElectrocardiographic/cardiac Electrocardiographic/cardiac monitor findings of ischemiamonitor findings of ischemiaProlonged QTc (>500 ms)Prolonged QTc (>500 ms)Trifascicular block or pauses Trifascicular block or pauses between 2 and 3 sbetween 2 and 3 sPersistent sinus bradycardia Persistent sinus bradycardia between 40 and 60 between 40 and 60 beats/minbeats/minAtrial fibrillation and Atrial fibrillation and nonsustained ventricular nonsustained ventricular tachycardia without tachycardia without symptomssymptomsCardiac devices (pacemaker Cardiac devices (pacemaker or defibrillator) with or defibrillator) with dysfunction dysfunction

Age =50 yAge =50 yWith history of CAD, MI, CHFWith history of CAD, MI, CHFwithout active symptoms or without active symptoms or signs while taking cardiac signs while taking cardiac medicationsmedicationsBundle-branch block or Q Bundle-branch block or Q wave without acute changeswave without acute changesFamily history of premature Family history of premature (<50 y), unexplained (<50 y), unexplained sudden deathsudden deathSymptoms not consistent Symptoms not consistent with a reflex-mediated or with a reflex-mediated or vasovagal cause vasovagal cause

Cardiac devices without Cardiac devices without evidence of dysfunction evidence of dysfunction

Physician’s judgment that Physician’s judgment that suspicion of cardiac suspicion of cardiac syncope is reasonable syncope is reasonable

Age <50 yAge <50 yWith no history ofWith no history of  Cardiovascular disease  Cardiovascular disease  Symptoms consistent   Symptoms consistent with reflex-mediated or with reflex-mediated or vasovagal syncopevasovagal syncopeNormal findings on Normal findings on cardiovascular examinationcardiovascular examinationNormal electrocardiographic Normal electrocardiographic

findingsfindings

85-year-old patient with valvular heart disease and congestive heart failure.

85-year-old patient with valvular heart disease and congestive heart failure.

Atrial tachycardiaAtrial tachycardia

Generally has an atrial rate 150 to 200 bpm P-wave countour is different than the sinus

P wave Each P-wave can conduct to the ventricle

as long as atrial rate is not excessive and the AV node is not depressedAs atrial rate increases there is increased AV

block Can be seen in dig toxicity

Generally has an atrial rate 150 to 200 bpm P-wave countour is different than the sinus

P wave Each P-wave can conduct to the ventricle

as long as atrial rate is not excessive and the AV node is not depressedAs atrial rate increases there is increased AV

block Can be seen in dig toxicity

51-year-old female with palpitations.

Regular Rate 142 bpm

No clear P waves before QRS – Not sinus rhythm

Retrograde P-waves, with short RP interval

Mechanism of ReentryMechanism of Reentry

An impulse initiated in the SA node passes through both the AV node and the accessory pathway

A premature atrial impulse occurs and reaches the accessory pathway when it is refractory, but conduction occurs through the AV node

The impulse takes sufficient time to circulate through the AV node to allow the accessory pathway to recover initiating reentry

Mechanisms of Supraventricular Tachycardia

AVNRT – the AV node is divided into two pathways and the activation of the atria and ventricle is synchronous so the retrograde P-wave is buried. Account for 60% of SVT. Usu are 150-200 bpm

Orthodromic AVRT – mechanism seen on previous slide. Usually, L atrium is the first site retrograde atrial activation. Accounts for 30% of SVT

Widened QRS

Antidromic AVRT – activation occurs in the opposite direction resulting in wide complex tachycardia that is indistinguishable from V tach

Regular Rate 166 bpm

No clear P waves before QRS – Not sinus rhythm

Wide QRS 160 ms

RBBB pattern

DDx of regular wide complex tachycardia

1) V. Tach

2) SVT w/ aberrant conduction or preexisting block

- Sinus tachycardia - A. flutter - AVRT/AVNRT - A. tachycardia

Retrograde P-waves associated with the QRS complex

Regular, Ventricular Rate 150 bpm

Wide QRS complex 180 ms

1) V. Tach

2) SVT w/ aberrant conduction or preexisting block

- Sinus tachycardia - A. flutter - AVRT/AVNRT - A. tachycardia

DDx of regular wide complex tachycardia (WCT)

A question of aberrancyA question of aberrancy Occurs when a supraventricular

impulse encounters persistant refractoriness in part of the ventricular conduction system Refractory period RR interval

Aberration can result from a shortened RR interval and refractory period (1) or a lengthened RR interval and refractory period (2)

Always initially assume wide QRS is ventricular 80% of WCT are VT

Triphasic rsR’ in V1 and qR in V6 favor aberrancy

If the QRS morphology is similar to sinus rhythm, then WCT unlikely ventricular in origin

Occurs when a supraventricular impulse encounters persistant refractoriness in part of the ventricular conduction system Refractory period RR interval

Aberration can result from a shortened RR interval and refractory period (1) or a lengthened RR interval and refractory period (2)

Always initially assume wide QRS is ventricular 80% of WCT are VT

Triphasic rsR’ in V1 and qR in V6 favor aberrancy

If the QRS morphology is similar to sinus rhythm, then WCT unlikely ventricular in origin

1

2

The Thyroid and the Heart

The Thyroid and the Heart

Thyroid Hormone Actions on the Heart

Thyroid Hormone Actions on the Heart

Embryolgically the thyroid and the heart share a close relationship

Cardiac myocyte cannot convert T3 to T4

Appears that thyroid hormone increases the release of calcium by sarcoplasmic reticulum

Embryolgically the thyroid and the heart share a close relationship

Cardiac myocyte cannot convert T3 to T4

Appears that thyroid hormone increases the release of calcium by sarcoplasmic reticulum

Hemodynamic Alterations in Thyroid Disease

Hemodynamic Alterations in Thyroid Disease

T3 has direct effects on vascular smooth muscle cells as well increase in NO releases decreases systemic vascular resistance In Hypothyroidism there is an increase in SVR

and pts have diastolic hypertension Decrease in SVR decreases MAP which leads to

stimulation renin-angiotensin system Leads to an increase in preload In total, there is an increase in CO CO may more than double in hyperthyroidism and

can decrease by 30 to 40% in hypothyroidism

T3 has direct effects on vascular smooth muscle cells as well increase in NO releases decreases systemic vascular resistance In Hypothyroidism there is an increase in SVR

and pts have diastolic hypertension Decrease in SVR decreases MAP which leads to

stimulation renin-angiotensin system Leads to an increase in preload In total, there is an increase in CO CO may more than double in hyperthyroidism and

can decrease by 30 to 40% in hypothyroidism

HyperthyroidismHyperthyroidism

Exercise intolerance as cardiac functional reserve is compromised

Palipitations - common for HR>90 bpm Angina due to increase in CO and cardiac

contractility leading to ischemia Atrial fibrillation occurs in 2-20 percent of

patients Heart failure usually related to rate related

phenomenon

Exercise intolerance as cardiac functional reserve is compromised

Palipitations - common for HR>90 bpm Angina due to increase in CO and cardiac

contractility leading to ischemia Atrial fibrillation occurs in 2-20 percent of

patients Heart failure usually related to rate related

phenomenon

HypothyroidismHypothyroidism

BradycardiaIncrease in SVR Decrease in COIncrease in LDLMore likely to have ischemic

cardiomyopathy

BradycardiaIncrease in SVR Decrease in COIncrease in LDLMore likely to have ischemic

cardiomyopathy