NR 661 EXAM REVIEW 2026 QUESTIONS WITH
FULL ANSWERS AND SOLUTIONS
▶ L stands for. Answer: Left Arm (LA)
▶ F stands for. Answer: Left Leg (LL)
▶ Lead aVR. Answer: The right arm is positive and the other limbs are
negative.
▶ Lead aVL. Answer: The left arm is positive and the other limbs are
negative.
▶ Lead aVF. Answer: The left leg (or foot) is positive and the other limbs
are negative.
▶ Precordial Chest Unipolar Leads. Answer: All these electrodes are
positive and record the heart electricity in the horizontal plane. They include
leads: V1, V2, V3, V4, V5, and V6.
▶ V1. Answer: Fourth intercostal space, right sternal border.
▶ V2. Answer: Fourth intercostal space, left sternal border.
▶ V3. Answer: Equidistant between V2 and V4.
▶ V4. Answer: Fifth intercostal space, left midclavicular line.
▶ V5. Answer: Fifth intercostal space, anterior axillary line.
▶ V6. Answer: Fifth intercostal space, midaxillary line.
▶ The Electrocardiographic Grid and Waves. Answer: The EKG paper is a
graph paper with horizontal and vertical lines at 1-mm intervals. A heavy
line appears every 5mm.
▶ The horizontal axis represents time:. Answer: 1mm = 0.04 seconds
5mm = 0.2 seconds
,▶ The vertical axis represents:. Answer: voltage, measures in millivolts
(1/1000 part of a volt) but expressed in millimeters: 0.1mV-1mm.
▶ The tracing is marked on the paper by a stylus using _____.. Answer:
heat
▶ The running speed of an EKG machine is _____.. Answer: 25mm/sec
▶ The EKG machine must be properly standardized so that 1mV will
produce a deflection of _____.. Answer: 10mm
▶ Define Waveform. Answer: Refers to movement away from the
isoelectric line either upward (positive) deflection or downward (negative)
deflection.
▶ Define Segment. Answer: Line between two waveforms.
▶ Define Interval. Answer: Waveform plus a segment.
▶ Define Complex. Answer: Several waveforms.
▶ Atrial Depolarization. Answer: P wave
▶ P Wave. Answer: Is the first deflection after the diastole, produced by
atrial depolarization. It is smooth, round, not more than 2.5mm high and no
more than 0.11 sec. Positive in I, II, and V2 to V6.
▶ Ventricular Depolarization. Answer: QRS Complex, Q (q) Wave, R (r)
Wave, S (s) Wave
▶ QRS Complex. Answer: -Represents ventricular depolarization
(activation)
-The ventricle is depolarized from the endocardium to the myocardium, to
the epicardium
-Normal duration is no more than 0.1 sec (otherwise stated as "less than
.12 sec)
,▶ Q (q) Wave. Answer: The initial negative deflection produced by
ventricular depolarization.
▶ R (r) Wave. Answer: The first positive deflection produced by ventricular
depolarization.
▶ S (s) Wave. Answer: The first negative deflection produced by the
ventricular depolarization that follows the first positive deflection, (R) wave.
▶ Ventricular Repolarization. Answer: T Wave and U Wave
▶ T Wave. Answer: The first wave after the QRS complex has the
following characteristics:
-The deflection produced by ventricular repolarization
-It is slightly asymmetric
-No more than 5mm in height
▶ UWave. Answer: Is the deflection seen following the T wave but
preceding the diastole.
-Represents repolarization of Purkinje fibers
-Round and symmetric less than 1.5mm in height
-A prominent U wave is due to hypokalemia (low potassium, blood level)
▶ PR Segment. Answer: This segment is measured from the end of the P
wave to the beginning of the QRS Complex.
▶ ST Segment. Answer: This segment represents the time of ventricular
contraction and the beginning of repolarization of both ventricles. It is
measured from end of QRS to the beginning of the T wave.
From J point to the onset of the T wave.This segment is compared to the
PR segment to help identify myocardial ischemia or injury.
▶ PR Interval. Answer: Is defined as P wave and PR segment and is
measured from the beginning of P wave to the beginning of QRS complex.
The normal interval is 0.12-0.2 sec.
▶ QT Interval. Answer: It represents the total ventricular activity
(ventricular depolarization PLUS ventricular repolarization), and it is
measured from the beginning of QRS to the end of T wave. The normal
duration of this interval depends on the age and the HR.
, ▶ RR Interval. Answer: It is important to determine the HR and its
regularity.
This is the interval between two R waves.
▶ J (RST) Junction. Answer: Point at which QRS complex ends and ST
segment begins.
▶ Assesses the HR. Answer: -6 second Method
-Large Boxes Method
-Small Boxes
-Sequence Method
▶ Analyzing the EKG Strip. Answer: -Assesses the HR
-Assess Rhythm/Regularity
-Identify and examine the P waves
-Assess interval (PR, QRS,QT)
-Evaluate ST segments and T waves
-General Evaluation and Conclusion
▶ 6 second Method. Answer: The number of QRS Complexes between 6
sec marks on the EKG paper is multiplied by 10. Used generally for
estimating slow or irregular rhythms.
▶ Large Boxes Method. Answer: Count the number of large boxes
between two consecutive RR (one RR interval) and divide into 300 for the
ventricular rate; and count large boxes between two consecutive P waves
for the atrial rate. Used mainly in regular rhythms.
▶ Small Boxes. Answer: One minute have 1500 small boxes (0.04 sec).
Count the number of small boxes between an RR interval and divide into
1500. This method is more accurate and is used for regular rhythms only.
▶ Sequence Method. Answer: Select the R that falls on a dark vertical line.
Number the next consecutive dark line as 300, 150, 100, 75, 60, and 50.
Note where the next R wave falls in relation to the dark lines. That is the
heart rate.
FULL ANSWERS AND SOLUTIONS
▶ L stands for. Answer: Left Arm (LA)
▶ F stands for. Answer: Left Leg (LL)
▶ Lead aVR. Answer: The right arm is positive and the other limbs are
negative.
▶ Lead aVL. Answer: The left arm is positive and the other limbs are
negative.
▶ Lead aVF. Answer: The left leg (or foot) is positive and the other limbs
are negative.
▶ Precordial Chest Unipolar Leads. Answer: All these electrodes are
positive and record the heart electricity in the horizontal plane. They include
leads: V1, V2, V3, V4, V5, and V6.
▶ V1. Answer: Fourth intercostal space, right sternal border.
▶ V2. Answer: Fourth intercostal space, left sternal border.
▶ V3. Answer: Equidistant between V2 and V4.
▶ V4. Answer: Fifth intercostal space, left midclavicular line.
▶ V5. Answer: Fifth intercostal space, anterior axillary line.
▶ V6. Answer: Fifth intercostal space, midaxillary line.
▶ The Electrocardiographic Grid and Waves. Answer: The EKG paper is a
graph paper with horizontal and vertical lines at 1-mm intervals. A heavy
line appears every 5mm.
▶ The horizontal axis represents time:. Answer: 1mm = 0.04 seconds
5mm = 0.2 seconds
,▶ The vertical axis represents:. Answer: voltage, measures in millivolts
(1/1000 part of a volt) but expressed in millimeters: 0.1mV-1mm.
▶ The tracing is marked on the paper by a stylus using _____.. Answer:
heat
▶ The running speed of an EKG machine is _____.. Answer: 25mm/sec
▶ The EKG machine must be properly standardized so that 1mV will
produce a deflection of _____.. Answer: 10mm
▶ Define Waveform. Answer: Refers to movement away from the
isoelectric line either upward (positive) deflection or downward (negative)
deflection.
▶ Define Segment. Answer: Line between two waveforms.
▶ Define Interval. Answer: Waveform plus a segment.
▶ Define Complex. Answer: Several waveforms.
▶ Atrial Depolarization. Answer: P wave
▶ P Wave. Answer: Is the first deflection after the diastole, produced by
atrial depolarization. It is smooth, round, not more than 2.5mm high and no
more than 0.11 sec. Positive in I, II, and V2 to V6.
▶ Ventricular Depolarization. Answer: QRS Complex, Q (q) Wave, R (r)
Wave, S (s) Wave
▶ QRS Complex. Answer: -Represents ventricular depolarization
(activation)
-The ventricle is depolarized from the endocardium to the myocardium, to
the epicardium
-Normal duration is no more than 0.1 sec (otherwise stated as "less than
.12 sec)
,▶ Q (q) Wave. Answer: The initial negative deflection produced by
ventricular depolarization.
▶ R (r) Wave. Answer: The first positive deflection produced by ventricular
depolarization.
▶ S (s) Wave. Answer: The first negative deflection produced by the
ventricular depolarization that follows the first positive deflection, (R) wave.
▶ Ventricular Repolarization. Answer: T Wave and U Wave
▶ T Wave. Answer: The first wave after the QRS complex has the
following characteristics:
-The deflection produced by ventricular repolarization
-It is slightly asymmetric
-No more than 5mm in height
▶ UWave. Answer: Is the deflection seen following the T wave but
preceding the diastole.
-Represents repolarization of Purkinje fibers
-Round and symmetric less than 1.5mm in height
-A prominent U wave is due to hypokalemia (low potassium, blood level)
▶ PR Segment. Answer: This segment is measured from the end of the P
wave to the beginning of the QRS Complex.
▶ ST Segment. Answer: This segment represents the time of ventricular
contraction and the beginning of repolarization of both ventricles. It is
measured from end of QRS to the beginning of the T wave.
From J point to the onset of the T wave.This segment is compared to the
PR segment to help identify myocardial ischemia or injury.
▶ PR Interval. Answer: Is defined as P wave and PR segment and is
measured from the beginning of P wave to the beginning of QRS complex.
The normal interval is 0.12-0.2 sec.
▶ QT Interval. Answer: It represents the total ventricular activity
(ventricular depolarization PLUS ventricular repolarization), and it is
measured from the beginning of QRS to the end of T wave. The normal
duration of this interval depends on the age and the HR.
, ▶ RR Interval. Answer: It is important to determine the HR and its
regularity.
This is the interval between two R waves.
▶ J (RST) Junction. Answer: Point at which QRS complex ends and ST
segment begins.
▶ Assesses the HR. Answer: -6 second Method
-Large Boxes Method
-Small Boxes
-Sequence Method
▶ Analyzing the EKG Strip. Answer: -Assesses the HR
-Assess Rhythm/Regularity
-Identify and examine the P waves
-Assess interval (PR, QRS,QT)
-Evaluate ST segments and T waves
-General Evaluation and Conclusion
▶ 6 second Method. Answer: The number of QRS Complexes between 6
sec marks on the EKG paper is multiplied by 10. Used generally for
estimating slow or irregular rhythms.
▶ Large Boxes Method. Answer: Count the number of large boxes
between two consecutive RR (one RR interval) and divide into 300 for the
ventricular rate; and count large boxes between two consecutive P waves
for the atrial rate. Used mainly in regular rhythms.
▶ Small Boxes. Answer: One minute have 1500 small boxes (0.04 sec).
Count the number of small boxes between an RR interval and divide into
1500. This method is more accurate and is used for regular rhythms only.
▶ Sequence Method. Answer: Select the R that falls on a dark vertical line.
Number the next consecutive dark line as 300, 150, 100, 75, 60, and 50.
Note where the next R wave falls in relation to the dark lines. That is the
heart rate.
