Bradyarrythmias: Disorders of the Sinoatrial Node

Question 1

Autonomic Nervous System

Answer 1

Regulates the rate of phase 4 diastolic depolarization and thus the firing rate of both primary (SA node) and subsidiary pacemaker.

Question 2

2 most common causes of pathologic bradycardia

Answer 2

SA node dysfunction

AV conduction block

Question 3

Only reliable therapy for symptomatic bradycardia in the absence of extrinsic and reversible etiologies (inc vagal tone, hypoxia, Hypothermia)

Answer 3

Permanent pacemaking

Question 4

Where is the SA node?

Answer 4

Sulcus terminalis on the epicardial surface at the right atrial superior vena cava junction

Question 5

Where does the SA nodal artery arise from?

Answer 5

right coronary artery (55-60%)

left circumflex artery (40-45%)

Question 6

Slow conduction within SA node explained by

Answer 6

Absence of I(Na) and poor electrical coupling

Question 7

Most common causes of extrinsic SA node dysfunction

Answer 7

Drugs and autonomic nervous system influences

Question 8

Other extrinsic causes of SA node dysfunction

Answer 8

Hypothyroidism, sleep apnea, Hypothermia, Hypoxia, and increased intracranial pressure (cushing’s response) and endotracheal suctioning via activation of the vagus nerve

Question 9

Inflammatory disorders that are associated with SA nodal disease ( sinus bradycardia, sinus arrest and exit block)

Answer 9

Pericarditis, Myocarditis, Rheumatic Heart Disease

Question 10

Infiltritative disorder in patients typically in the ninth decade of life
Deposition of amyloid protein in the atrial myocardium

Answer 10

Senile amyloidosis

Question 11

Ophthalmoplegia
Pigmentary degeneration of the retina
Cardiomyopathy

Answer 11

Kearns-Sayre Syndrome

Question 12

Coexisting diseases that may hasten deposition of fibrous tissue in SA node

Answer 12

CAD
DIabetes Mellitus
Hypertension 
Valvular diseases
Cardiomyopathies

Question 13

Incidence of persistent atrial fibrillation or atrial flutter in SA node dysfunction increases in the ff condition

Answer 13

Advanced age
Hypertension 
Diabetes mellitus 
Left Ventricular Dilation 
Valvular Heart Disease
Ventricular Pacing

Question 14

ECG manifestation of SA node dysfunctin

Answer 14

sinus bradycardia
Sinus pauses
sinus arrest
sinus exit block 
tachycardia (in SSS) 
Chronotropic incompetence

Question 15

Chronotropic incompetence

Answer 15

inability to increase the heart rate in response to exercise

Question 16

Normal IHR after administration of 0.2 mg/kg of propofol and 0.04 mg/kg atropine

Answer 16

117.2 - (0.53 x age)
in beats/min
low IHR is indicative of SA disease

Question 17

Sinus node recovery time

Answer 17

longest pause after cessation of overdrive pacing of the right atrium near the SA node (normal <1500 ms or sinus cycle length <550 ms)

Question 18

Sinoatrial conduction time (SACT)

Answer 18

1/2 the difference between intrinsic sinus cycle length and a noncompensatory pause after a premature atrial stimulus <125 ms

Question 19

Pacemaker implantation

Answer 19

primary therapeutic intervention in patients with symptomatic SA node dysfunction

Question 20

Which class/es of antiarrythmic drugs promote SA node exit block

Answer 20

Class I and Class III

Question 21

These drugs increase SNRT in patients with SA node dysfunction

Answer 21

Beta blockers and calcium channel blockers

Question 22

These IV drugs may be used to increase the heart rate acutely

Answer 22

Atropine and Isoproterenol

Question 23

This drug may be used acutely or chronically to increase heart rate but has liabilities when used in patients with tachycardia-bradycardia syndrome and in patients with structural heart disease

Answer 23

Theophylline

Question 24

Most commonly programmed modes of implanted singe and dual chamber pacemaker

Answer 24

VVIR

DDDR

Question 25

Complications of transvenous pacemaker implantation

Answer 25

``` HIPCaDL Hematoma Infection Pneumothorax Cardiac perforation Diaphragmatic/Phrenic nerve stimulation Lead dislodgement ```

Question 26

Limitations of chronic pacemaker therapy

Answer 26

Infection Erosion Lead failure Abnormalities (Inappropriate programming or interaction with native electrical cardiac function)

Question 27

Twiddler's syndrome

Answer 27

Rotation of the pacemaker pulse generator in its subcutaneous pocket

Question 28

``` Collection of symptoms that include neck pulsation, fatigue Palpitations cough Confusion Exertional Dyspnea Dizziness Syncope Elevation in jugular venous pressure canon A waves stigmata of congestive heart failure ```

Answer 28

Pacemaker syndrome

Question 29

Stigmata of CHF

Answer 29

edema rales third heart sound

Question 30

Most common causes of pathologic bradycardia

Answer 30

SA node dysfunction, AV conduction block

Question 31

Composed of a cluster of small fusiform cells in the sulcus terminalis on the epicardial surface of the heart at the right atrial-superior vena caval junction

Answer 31

SA node

Question 32

Alternate definition of chronotropic incompetence

Answer 32

Failure to reach 85% of predicted maximal heart rate at peak exercise or failure to achieve a heart rate > 100 beats per min with exercise or maximal heart rate less than 2 SD below that of age matched control population.

Question 33

Normal IHR after administration of 0.2 mg/kg propanolol and 0.04 mg/kg atropine

Answer 33

117.2 - (0.53* age) in beats per min