Rhythm recognition

Question 1

how is a three lead ECG attached?

Answer 1

White to right

smoke over fire on left ( Red over R ASIS and black/brown to L shoulder)

Question 2

Broad approach to interpreting an ECG?

Answer 2

Rate 
Rhythm 
Axis
Ischaemia (ST, TWI)
Intervals (QRS, QT, PR)
Matching p to QRS

Question 3

what is the normal rate of an ECG strip?

Answer 3

25mm/s
1 second = 5 large squares (25 small squares)

1 large square = 0.2s
1 small square = 0.04s

Question 4

Describe a junctional rhythm

Answer 4

ECG features of Junctional Escape Rhythm

• Junctional rhythm with a rate of 40-60 bpm
• QRS complexes are typically narrow (< 120 ms)
• No relationship between the QRS complexes and any preceding atrial activity (e.g. P-waves, flutter waves, fibrillatory waves)

Mechanism
Pacemaker cells are found at various sites throughout the conducting system, with each site capable of independently sustaining the heart rhythm. The rate of spontaneous depolarisation of pacemaker cells decreases down the conducting system:

SA node (60-100 bpm)
Atria (< 60 bpm)
AV node (40-60 bpm)
Ventricles (20-40 bpm)

Under normal conditions, subsidiary pacemakers are suppressed by the more rapid impulses from above (i.e. sinus rhythm). Junctional and ventricular escape rhythms arise when the rate of supraventricular impulses arriving at the AV node or ventricle is less than the intrinsic rate of the ectopic pacemaker.

Question 5

Describe Mobitz I and Mobitz II heart block

Answer 5

Definition of Mobitz I block (Wenckebach phenomenon)
Progressive prolongation of the PR interval culminating in a non-conducted P wave:

PR interval is longest immediately before dropped beat
PR interval is shortest immediately after dropped beat

Definition of Mobitz II block (Hay Block)
A form of 2nd degree AV block in which there is intermittent non-conducted P waves without progressive prolongation of the PR interval

If bundle branch block is present with 2:1 block it is more likely to be a MOBITZ II

Question 6

What are the two most common mimics of VF

Answer 6

1. Polymorphic VT

2. Preexcited AF (WPW)

Question 7

Describe accelerated idioventricular rhythm

Answer 7

idioventricular rhythm = arising from the ventricular myocardium with rate 30-40

accelerated idioventricular rhythm = after thrombolysis PCI - broad complex and faser rate 50-110. do not pose a serious risk, unlikely to develop into VT/VF

Question 8

what is usually the atrial rate in flutter?

Answer 8

300bpm

Question 9

what is a normal QT interval? QTc?

Answer 9

QT<440ms

QTc <0.46 for women, <0.44 for men

Question 10

Causes of long/short QT

Answer 10

short - hypercalcaemia, digoxin

long - low K/Mg/Ca/Temp, myocarditis,AMI, Class I+III antiarhythmics and antipsychotics