ECG Interpretation Assignment: Case Studies and Analysis

This assignment presents the interpretation and analysis of four electrocardiograms (ECGs). The first ECG reveals a sinus rhythm with a rate of 75 bpm, indicating a bifascicular block, specifically right bundle branch block (RBBB) with left axis deviation. The second ECG shows a sinus rhythm at 100 bpm, indicating a left bundle branch block. The third ECG demonstrates sinus bradycardia at 33 bpm, identified as a second-degree heart block, Mobitz type 2. The final ECG also presents sinus bradycardia at 42 bpm, diagnosed as a second-degree heart block with Wenckebach phenomena. Each analysis includes a description of the rhythm, axis, intervals, and QRS patterns, along with interpretations based on established medical references. The analysis covers key aspects of ECG interpretation, including heart rate, cardiac axis, P waves, PR intervals, QRS complexes, and ST intervals, providing a comprehensive overview of the various cardiac conditions presented in the ECGs.

Electrocardiogram 1
Electrocardiogram interpretation.
Student’s name
Institutional Affiliation

ECG interpretation
2
ECG 1 ( ECGimagejaiden1)
Sinus rhythm with 75beaats per minute.
Left axis deviation.
P waves present normal, one for every QRS complex.
PR interval is normal at 120ms.
QRS complex, present, each preceded by a P wave. rSR pattern seen on lead II, V I and V II and
V III.
ST interval normal.
T waves normal inverted at aVR and VI which is normal.
Interpretation
Bifascicular Block- Right Bundle Branch Block (RBBB) with left axis deviation.
Analysis
There is sinus rhythm with a rate of 75bpm (normal rhythm is 60-100 bpm). The cardiac
axis is deviated to the left. The electrical depolarization wave is moving toward the left shown by
the positive R wave in lead I but negative in lead II and III. The PR interval is normal at 120 ms
(normal PR interval 120-200 ms) with normal P waves as the P wave corresponds to one QRS
complex. This shows each P wave is conducted leading to ventricular depolarization shown by a
QRS complex. The QRS complex pattern shows right bundle branch block as shown by the rSR’
pattern in right ventricular leads VI and VII. In a right bundle block no conduction occurs in the
right bundle branch but the septum is depolarized from right to left as usual causing an R wave in
VI. Then excitation spreads to the left ventricle causing an S wave in VI. Due to faulty
conduction the right ventricle depolarizes after the left causing a second R wave on VI. This
explains the RSR pattern on VI and VII (Hampton, J. 2013). A right bundle block is however

ECG interpretation
3
associated with a normal cardiac axis hence due to the left axis deviation a bifascicular block is
suspected.
ECG 2 (ECGimagejaiden2)
Sinus rhythm with 100 beats per minute.
Cardiac axis normal.
P wave present before each QRS complex.
Prolonged PR interval at 160ms.
QRS complex present each preceded by a P wave.
QRS interval normal at 120ms. M pattern present with deep S waves deep at lead VI, V2. S wave
absent on lead V6
ST segment elevated best seen at lead VI and V2.
T wave inverted at lead I, II, VI, V2
Interpretation
Left Bundle Branch Block.
Analysis
There is sinus rhythm with a rate of 100bpm (normal rhythm is 60-100 bpm). The cardiac axis is
normal. The electrical depolarization wave is moving toward lead I shown by positive R wave in
lead I, lead II and III. The PR interval is normal at 160 ms (normal PR interval 120-200 ms) with
normal P waves as the P wave corresponds to one QRS complex. This shows each P wave is
conducted leading to ventricular depolarization shown by a QRS complex. The QRS complex
pattern shows left bundle branch block as shown by the M pattern in lead opposite to right
ventricular leads VI and VII, and in left ventricular leads V6 and deep S waves in VI and VII. In
left bundle block no conduction occurs down the left branch so the septum is depolarized from

ECG interpretation
4
right to left causing a small Q wave in lead V1 and an R wave in V6. The right ventricle is
depolarized before the left. Despite the small muscle mass there is an R wave in VI and an S
wave in V6 appearing as a notch (M pattern). Left bundle block is also associated with T wave
inversion as seen in lead VI and VII (Hampton, J. 2013). The impression is a left bundle branch
block.
ECG 3 (ECGanalysis1brownyn)
Sinus rhythm with sinus bradycardia 33beats per minute.
Cardiac axis is normal.
P wave present. 2P wave per QRS.
PR interval constant, prolonged at 400ms.
QRS complex is normal
QRS interval at 100ms.
PR interval is prolonged at 400ms
The ST interval is normal.
There are large T waves in most leads.
Interpretation
Second degree heart block, Mobitz type 2
Analysis
There is a sinus rhythm with a sinus bradycardia of 33 beats per minute. There is a normal
cardiac normal. The electrical conduction starts with a P wave, two P waves per QRS. The PR
interval is prolonged at 400ms and it remains constant pointing to a morbitz type II heart block.

ECG interpretation
5
The QRS complex is normal with a normal interval. ST is normal with large T waves
(MacFariane et al., 2010)
ECG 4 (ECG2analysisbrownyn)
Sinus rhythm with sinus bradycardia 42 beats per minute.
Cardiac axis is normal.
P waves present, although not all translates to a QRS.
PR interval not constant, its lengthens progressively, conducts then lengthens. This cycle repeats
itself.
QRS complex is normal.
QRS interval normal at 120ms
The ST interval normal.
Interpretation
Second degree heart block “Wenckebach phenomena”.
Analysis
There is a sinus rhythm with a sinus bradycardia, 42 beats per minute. Every cycle starts with a P
wave, a QRS complex follows the P waves although not all P waves translates to a QRS. The PR
is not constant, it lengthens progressively, then conducts and lengthens again (MacFariane et al.,
2010)
.

ECG interpretation
6
References
Davidsons, J., (2014). Cardiovascular system. Principles and practices of medicine. Pg. 67-98,
22nd edition.
MacFariane et al., (2010). Comprehensive electrocardiology. Springer.
Hannibal, B., (2014). Electrode placement and Cardiac monitoring. Advanced critical care
AACN, 25, 2, 188-192
Hampton, J. (2013). ECG made easy.6 ed. pg 20-40.