[02.06] CM - Disorders of Rhythm_Bradycardias V2.pdf

RCA in 55 to 60 percent of people

From which coronary artery does the SA nodal artery arise in the majority of individuals?

LCx in 40 to 45 percent of people

From which coronary artery does the SA nodal artery arise in 40 to 45 percent of individuals?

60 to 100 beats per minute

What is the normal resting heart rate of the sinoatrial node?

Autonomic nervous system

Which nervous system division controls the sinoatrial node resting rate?

Parasympathetic innervation

Which autonomic division mostly controls the resting sinoatrial node rate?

Slow calcium currents

On which electrical currents is the rapid phase 4 depolarization of sinoatrial cells dependent?

Phase 4 depolarization

Which phase of the action potential in sinoatrial cells exhibits the most rapid depolarization making it the dominant pacemaker?

Fatigue, exercise intolerance, and syncope

What are three major symptoms with which most sinoatrial nodal disease patients present?

ECG, Holter, and telemetry

What are three standard electrocardiographic workups for sinoatrial nodal disease?

ECG watches

What is an example of wearable devices used for diagnosing sinoatrial nodal disease?

Treadmill test

Which diagnostic test is used specifically to evaluate chronotropic incompetence?

2D Echo and electrophysiology study

What are two imaging and electrical diagnostic procedures used to work up sinoatrial nodal disease?

History and physical examination

What are the two most important initial clinical evaluations to perform when a patient presents with bradycardia?

Reversible causes

What must a clinician accurately elicit and identify when evaluating a patient with bradycardia?

Hypothyroidism

Which endocrine condition is listed as a medical condition associated with sinus bradycardia?

Sleep apnea

Which respiratory disorder during sleep is associated with sinus bradycardia?

Hypoxia

What state of low oxygen tissue delivery is associated with sinus bradycardia?

Hypothermia

What state of abnormally low body temperature is associated with sinus bradycardia?

Increased intracranial pressure

Which neurological elevation in pressure is associated with sinus bradycardia?

Lyme disease

Which tick-borne infectious disease is associated with sinus bradycardia?

Myocarditis

What inflammation of the heart muscle is associated with sinus bradycardia?

COVID-19

Which viral pandemic disease is listed as a medical cause of sinus bradycardia?

Vagal reflex

Which neural reflex, triggered by cough or pain, is associated with sinus bradycardia?

Beta-adrenergic receptor blockers

Which class of antihypertensive medications is associated with sinus node dysfunction?

Clonidine and methyldopa

What are two centrally acting antihypertensive agents associated with sinus node dysfunction?

Nondihydropyridine calcium channel blockers

Which subclass of calcium channel blockers is associated with sinus node dysfunction?

Amiodarone and sotalol

What are two Class III antiarrhythmic medications associated with sinus node dysfunction?

Dronedarone

Which antiarrhythmic drug, related to amiodarone, is associated with sinus node dysfunction?

Flecainide and propafenone

What are two Class IC antiarrhythmic medications associated with sinus node dysfunction?

Procainamide and quinidine

What are two Class IA antiarrhythmic medications associated with sinus node dysfunction?

Ivabradine

Which specific hyperpolarization-activated cyclic nucleotide-gated channel blocker antiarrhythmic is associated with sinus node dysfunction?

Donepezil

Which psychiatric medication used in Alzheimer's disease is associated with sinus bradycardia?

Lithium

Which psychiatric mood stabilizer used in bipolar disorder is associated with sinus bradycardia?

Opioid analgesics

Which class of strong pain relievers is associated with sinus node dysfunction?

Phenothiazine antiemetics and antipsychotics

Which class of antiemetics and antipsychotics is associated with sinus node dysfunction?

Phenytoin

Which anti-seizure medication is associated with sinus node dysfunction?

Selective serotonin reuptake inhibitors

Which antidepressant drug class is associated with sinus node dysfunction?

Tricyclic antidepressants

Which older class of antidepressants is associated with sinus node dysfunction?

Propofol

Which common intravenous anesthetic drug is associated with sinus node dysfunction?

Cannabis

Which recreational or medicinal substance is listed as associated with sinus node dysfunction?

Digoxin

Which cardiac glycoside is associated with sinus node dysfunction?

Muscle relaxants

Which musculoskeletal class of therapeutic drugs is associated with sinus node dysfunction?

Type I SA block

Which sinus node exit block subtype is defined by a fixed delay out of the sinus node?

Type II SA block Mobitz I

Which sinus node exit block subtype is defined by progressive delay and then intermittent failure to propagate to the atrium?

Group beating

What specific ECG beating pattern produces a regularly irregular heart rhythm in Type II SA Block Mobitz I?

Absence of P wave

What ECG finding denotes the occurrence of a sinus node exit block on a telemetry strip?

Failure to propagate signal out of the sinus node

What does a sinus node exit block physically mean compared to an AV block?

Type II SA block Mobitz II

Which sinus node exit block subtype is defined by a fixed delay with intermittent failure to conduct?

Multiple of the first interval

What is the mathematical relationship of subsequent blocked intervals to the first interval in Mobitz II SA block?

Complete SA block

Which sinus node exit block is noted as being difficult to diagnose on a standard ECG?

Tachy Brady Syndrome

What syndrome is defined by high heart rates, most commonly atrial fibrillation, alternating with symptomatic bradycardia or offset pauses?

Pacemaker implantation

What therapeutic intervention is often considered for Tachy Brady Syndrome because rate-control medications exacerbate bradycardia?

Isoelectric flat interval

What type of interval on an ECG represents a prolonged pause following atrial fibrillation in Tachy Brady Syndrome?

Transient cerebral hypoperfusion

What physiological drop in brain blood flow is caused by long pauses in Tachy Brady Syndrome?

Syncope, brief unresponsiveness, and sudden falls

What are three clinical presentations of transient cerebral hypoperfusion caused by pauses in Tachy Brady Syndrome?

Blank stares

What term describes the brief unresponsiveness or sudden vacant look during a prolonged tachy-brady pause?

Chronotropic Incompetence

What is the clinical term for the inability of the heart to increase its rate to meet activity or metabolic demand?

85 percent of age-predicted maximal heart rate

What percentage of age-predicted maximal heart rate must a patient fail to achieve during a stress test to diagnose chronotropic incompetence?

220 minus age multiplied by 0.85

What is the mathematical formula used to calculate 85 percent of age-predicted maximal heart rate?

208 minus 0.7 multiplied by age

What mathematical formula defines the overall maximum heart rate?

Heart rate instability

What abnormality during exercise, along with failure to achieve submaximal heart rate, characterizes chronotropic incompetence?

Sinus Node Fibrosis

What is the most common cause of sinus node dysfunction in older adults?

Age-associated increase in fibrotic tissue

What normally occurring process in the SA node of older adults leads to sinus node fibrosis?

Acute inferior or posterior myocardial infarction

In patients with which two acute infarct locations is sinus bradycardia commonly seen?

ST-segment elevation in leads II, III, and aVF

What are the classic ECG findings of an acute inferior STEMI?

Reciprocal ST-segment depression in V1 to V3

What ECG findings in the anterior chest leads suggest a posterior myocardial infarction?

ST-segment elevation in V7 to V9

What ECG findings in posterior leads confirm a posterior myocardial infarction?

Bezold-Jarisch reflex

Which reflex describes an increase in vagal tone that can exacerbate sinus bradycardia during myocardial ischemia?

Morphine and beta blockers

Which two commonly administered medications can exacerbate bradycardia during acute myocardial infarction?

RCA involvement

Ischemia of the SA nodal artery is most typically associated with acute coronary syndrome involving which coronary artery?

Transient

What is the typical duration of SA node dysfunction caused by acute coronary artery syndrome?

Improves or resolves

What happens to the associated bradycardia as myocardial perfusion is restored through angioplasty?

Carotid sinus hypersensitivity and neurally mediated bradycardia

Which two conditions prominently feature sinus bradycardia associated with the cardioinhibitory variant of vasovagal syncope?

Pacemaker implantation

How does carotid sinus hypersensitivity with recurrent syncope and a predominant cardioinhibitory component respond to therapy?

Carotid Sinus Massage

What does the abbreviation CSM stand for?

Forty years old

At what age is CSM indicated as a Class I recommendation for syncope of unknown origin compatible with a reflex mechanism?

Asystole or hypotension

What two physiological findings during CSM confirm Carotid Sinus Syndrome by reproducing spontaneous symptoms?

Carotid Sinus Syndrome

What does the abbreviation CSS stand for?

Observe

What should a clinician do next if the treatment for a reversible cause of SA nodal dysfunction is effective or unnecessary?

Structural heart disease

What should a clinician check for next if there is no reversible cause identified for SA nodal dysfunction?

Transthoracic echocardiography

What is the Class IIa imaging modality of choice to evaluate for suspected structural heart disease in sinus node dysfunction?

Infiltrative cardiomyopathy, endocarditis, and congenital heart disease

What are three structural conditions evaluated on a 2D Echo for sinus node dysfunction?

CT scan, MRI, and PET scan

What are three advanced imaging modalities indicated (Class IIa) if echocardiography reveals structural abnormalities?

Exercise ECG testing

What diagnostic test is indicated (Class IIa) for symptomatic sinus node dysfunction if the symptoms are exercise-related?

Ambulatory ECG monitoring

What diagnostic monitoring is a Class I recommendation if sinus node dysfunction symptoms are not exercise-related?

Electrophysiology study

What diagnostic study is a Class IIb recommendation if symptoms are not exercise-related and ambulatory monitoring is non-diagnostic?

Permanent pacing

What is the Class I indication for sinus node dysfunction when reversible causes are ruled out and no reasonable alternative exists?

Single chamber ventricular pacing

What pacing modality is considered (Class IIa) if there is infrequent pacing or significant comorbidities?

Single chamber atrial pacing

What pacing modality is indicated (Class I) if there is normal AV conduction and a reason to avoid an RV lead?

Dual chamber pacing

What is the most commonly implanted Class I pacing modality for sinus node dysfunction?

1.8 percent

What is the annual risk of developing a complete heart block in a patient with sinus node dysfunction?

Pacemaker cardiomyopathy

What long-term complication can high ventricular pacing induce, prompting programming to minimize ventricular pacing?

Oral theophylline

Which oral medication can be tried (Class IIb) if symptoms are likely or uncertain to correlate with bradycardia?

Observe and look for other causes

What should be done if a patient's symptoms do not correlate with bradycardia during evaluation?

Class III

What class of recommendation is permanent pacing if the symptoms do not correlate with bradycardia?

Symptomatic chronotropic incompetence

Which exercise-related sinus node dysfunction is a specific indication for permanent pacing?

Slow conduction

What is the specialized function of the AV node to create a delay between atrial and ventricular activation?

Spontaneous depolarization during phase 4

What electrical activity do AV nodal cells exhibit, similar to SA nodal cells but at a slower rate?

Slower phase 0 depolarization

What type of phase 0 depolarization, dependent on calcium influx, characterizes AV nodal cells?

Calcium influx

What ion influx drives the slower phase 0 depolarization of AV nodal cells?