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Chapter 7
Detailed Answers to Assess Your Understanding
1.
b: The lead used to assess the ECG affects the appearance of the QRS complexes.
2.
b: In lead II the deflection of the QRS complex is characteristically positive or upright.
3.
c: Analyzing the QRS complex helps identify how the electrical impulse is being carried through
the ventricles.
4.
a: The normal duration of the QRS complex is 0.06 to 0.10 seconds.
5.
d: An upright (in lead II) narrow QRS complex indicates that the electrical impulse originated at
or above the AV node and was carried through the ventricles in a normal manner.
6.
a: The R wave is the first positive deflection in the QRS complex.
7.
c: Early beats that arise from the atria produce normal QRS complexes.
8.
c: The amplitude of QRS complexes is higher in the precordial leads than the limb leads.
9.
c: Intraventricular conduction defect causes the QRS complexes to appear abnormal. It is usually
due to right or left bundle branch block.
10.
b: Low voltage or abnormally small QRS complexes are seen in obese patients.
11.
c: Bundle branch block is the most common cause of intraventricular conduction defect.
12.
a: Bundle branch blocks may be partial or complete.
13.
d: Aberrant conduction occurs when the impulse reaches one of the bundle branches while it is
still refractory.
14.
c: Early beats that arise from the ventricles produce QRS complexes that look different than
those that arise above or at the AV junction.
15.
a: Idioventricular rhythm has wide, bizarre-looking QRS complexes.
16.
b: With ventricular tachycardia the QRS complexes are wide and bizarre-looking.
17.
d: With the most severe form of AV heart block the QRS complexes are slower than the P wave
rate because there is complete blockage of the AV node.
18.
b: Ventricular fibrillation is seen as a chaotic wavy line on the ECG.
19.
d: Asystole is seen as a flat line on the ECG.
20.
a: The extra QRS complexes are originating from the ventricles.
21.
c: The most likely cause of the patient’s extra beats is ischemia.