Rhythm of the Heart Flashcards
Which conductive region of the heart is influenced by Parasympathetic and Sympathetic activity?
Sinus / Sinoatrial node
What is the “safety mechanism” of the Atrio-ventricular node?
Prevents high atrial rates being transmitted directly to the ventricles
What does the PR interval represent in the cardiac conduction pathway?
Reflects conduction through the Atrio-ventricular node
What does the QRS complex represent in the cardiac conduction pathway?
Reflects conduction through the ventricular myocardium
What is a normal PR interval in msec?
120 - 200 msec
What is a normal QRS interval in msec?
< 110 msec
What is normal sinus rhythm in adults and in children?
In adults: 60 - 100
In children: 100 - 120
What is fainting medically known as?
Vasovagal syncope
What is the effect of increased PNS activity on heart rate?
Decreases heart rate
What is the effect of increased SNS activity on heart rate?
Increases heart rate
What is the effect of decreased SNS activity on heart rate?
Decreases heart rate
What is the effect of decreased PNS activity on heart rate?
Increases heart rate
What is the effect of Adrenaline on HR?
Increases HR by increasing sympathetic activity
What is the effect of Salbutamol on HR?
Increases HR by increasing sympathetic activity
What is the effect of Beta-blockers on HR?
Decreases HR by decreasing sympathetic activity
What is the effect of Atropine on HR?
Increases HR by decreasing parasympathetic activity
What is Bradycardia defined as?
Heart rate less than 60 bpm
Atleast how many squares would seperate every QRS complex in Sinus Bradycardia?
300 / 60 = Atleast 5 squares
No more than how many squares would seperate every QRS complex in Sinus Tachycardia?
300 / 100 = No more than 3 squares
On an ECG, there are regular QRS complexes, spaced 6 squares apart. There is P wave in front of each QRS complex with normal delay. What does this mean?
Sinus Bradycardia
On an ECG, there are regular QRS complexes, spaced 6 squares apart. There is no P wave in front of each QRS complex with normal delay. What does this mean?
Heart block
On an ECG, there are irregular QRS complexes, spaced 7 squares apart. There are no P wave in front of each QRS complex with normal delay. What does this mean?
Slow atrial fibrillation
What is Brady-Tachy syndrome?
Intermittent episodes of slow and fast heart rates
How do we treat Brady-Tachy syndrome?
For the Bradycardia aspect: Pacemaker to speed up HR
For the Tachycardia aspect: Drugs to slow down HR
What are some causes for Sinus Bradycardia?
Athlete fitness
Certain medications which slow down heart rate, i.e. Calcium channel blockers, Beta blockers, Digoxin
Hypothyroidism
Of LBBB and RBBB, which one could be benign?
RBBB
On an ECG, there are regular QRS complexes, spaced 3 squares apart. The complexes are < 120 msec wide, and the HR is < 120 bpm. What does this mean?
Sinus Tachycardia (ST)
On an ECG, there are regular QRS complexes, spaced 3 squares apart. The complexes are >120 msec apart. What does this mean?
Ventricular Tachycardia (VT)
On an ECG, there are irregular QRS complexes, spaced 3 squares apart. What might this mean?
Atrial Fibrillation
How can you differentiate between Ventricular Tachycardia and Supraventricular Tachycardia?
Inject Adenosine, which blocks the atria. In SVT, the heart rate will slow down. In VT, it will not
What is the heart rate in Atrial Flutter?
300 bpm
What can exacerbate Torsades de Pointes?
Class I anti-arrhythmic drugs, and low K and low Mg
What is the treatment for Torsades de Pointes?
IV Magnesium
On an ECG, there are regular QRS complexes, spaced 3 squares apart. The complexes are < 120 msec wide, and the HR is > 140 bpm. What does this mean?
Supraventricular Tachycardia
