Cardiac Axis Quiz
Questions: 16 · 10 minutes
1. An ECG shows a positive QRS in lead I, a negative QRS in aVF, and a negative QRS in lead II. Which classification best fits?
Normal-axis quadrant
Right axis deviation
Left axis deviation
Extreme axis deviation
2. If the mean QRS vector points toward a limb lead's positive electrode, what pattern is generally expected in that lead?
A predominantly negative QRS complex
A predominantly positive QRS complex
An absent QRS complex
A QRS complex determined only by the T-wave direction
3. An ECG has a wide QRS complex and an abnormal frontal-plane axis. Which statement is most accurate?
The axis alone identifies the precise cardiac disorder.
A wide QRS makes frontal-plane axis description impossible.
Only the T-wave axis should be assessed when the QRS is wide.
The axis still describes mean ventricular depolarization direction, but its cause requires the full ECG and clinical context.
4. In the positive-dominant method, what makes a QRS complex net positive in a particular lead?
Its total upward deflection is greater than its total downward deflection.
Its QRS duration is shorter than 120 milliseconds.
Its T wave points in the same direction as its R wave.
Its tallest deflection crosses at least one large ECG square.
5. Lead I is nearly equiphasic, and aVF is strongly positive. Which approximate QRS axis is most consistent with these findings?
A horizontal rightward axis near 0°
An inferior vertical axis near +90°
A mildly superior-left axis near −30°
A superior vertical axis near −90°
6. The QRS complexes in both lead I and aVF are predominantly negative. What does the quadrant method indicate?
A normal vertical axis
Extreme axis deviation
Right axis deviation only
Left axis deviation only
7. Lead I is unexpectedly negative and aVR is strongly positive on an otherwise surprising tracing. What should be checked before concluding that severe axis deviation is present?
Whether the limb electrodes were placed or connected correctly
Whether the patient had eaten before the ECG
Whether the T waves are taller than the P waves
Whether the paper speed changed the electrical axis
8. Lead I and lead aVF both have predominantly positive QRS complexes. Which axis category does the basic quadrant method indicate?
Left axis deviation
Right axis deviation
Extreme axis deviation
Normal-axis quadrant
9. Lead I has the strongest positive QRS, while aVF is nearly equiphasic. What is the best approximate axis estimate?
+120°
+60°
0°
−90°
10. A QRS complex is most positive in lead aVL. Which frontal-plane angle is the closest estimate?
About −30°, aligned with aVL
About +90°, aligned with aVF
About +30°, opposite the aVL direction
About −150°, opposite the lead III direction
11. A limb lead has a nearly equiphasic QRS, with similar upward and downward deflections. What is the best initial inference?
The axis must point directly toward that lead's positive pole.
The axis is approximately perpendicular to that lead, with another lead needed to choose between two directions.
The axis must be exactly 180 degrees from that lead.
The tracing cannot contain any useful axis information.
12. In lead I, the R wave measures 8 mm upward and the S wave measures 3 mm downward, with no meaningful Q wave. What is the approximate net QRS deflection?
+11 mm, found by adding both magnitudes
−5 mm, treating the S wave as dominant
+5 mm, calculated as 8 mm minus 3 mm
+3 mm, using only the S-wave magnitude
13. In the standard hexaxial reference system, a QRS vector aligned most closely with lead II points toward approximately which angle?
+60°
0°
−30°
+150°
14. A QRS complex is most positive in lead III and relatively smaller in the other limb leads. Which axis estimate is closest?
−30°
0°
+60°
+120°
15. The QRS is predominantly negative in lead I and positive in aVF. Which quadrant classification applies?
Normal-axis quadrant
Left axis deviation
Extreme axis deviation
Right axis deviation
16. Lead I is positive, aVF is negative, and lead II remains positive. Using the common adult convention, where is the QRS axis most likely located?
Extreme superior-left sector, from about −90° to −180°
Rightward sector, from about +90° to +180°
Slightly leftward sector, from about −30° to 0°
Inferior normal sector, from about +30° to +90°