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Chapter 14 Test — Premature Beats and Pauses: PACs, PVCs, Escape Beats and Compensatory Pauses
21 questions · 21 min · +4 / -1
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Question 1
Question 1
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A 40-year-old woman with palpitations undergoes 12-lead ECG monitoring. The arrowed beats in the tracing shown occur
early
in the cycle, have a
narrow
QRS (<120 ms), and each is preceded by a P wave whose shape differs from the sinus P waves. The most likely diagnosis of the arrowed beats is:
A.
Premature ventricular complexes
B.
Premature atrial complexes
C.
Junctional escape beats
D.
Mobitz I (Wenckebach) second-degree AV block
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Question 2
Question 2
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The 12-lead ECG shown is from a 55-year-old hypertensive man being investigated for palpitations. The lead II rhythm strip contains a premature ventricular complex — a wide, bizarre beat with no preceding P wave — which is followed by a pause before the next sinus beat. Which statement best characterises that post-ectopic pause?
A.
Non-compensatory (incomplete) pause — the sinus node has been reset
B.
Fully compensatory pause — the sinus node is not reset
C.
No true pause — the next sinus beat arrives exactly on time
D.
A pause with progressive PR lengthening in the beats that follow
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Question 3
Question 3
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All of the following are features of a premature ventricular complex (PVC), EXCEPT:
A.
Wide QRS complex (>120 ms)
B.
Absent preceding P wave
C.
Full compensatory pause
D.
Prolonged PR interval
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Question 4
Question 4
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All of the following may be seen in association with ventricular premature beats, EXCEPT:
A.
Fusion beat
B.
Narrow QRS complex
C.
AV dissociation
D.
Wide, bizarre QRS complex
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Question 5
Question 5
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Which of the following statements about a ventricular extrasystole (premature ventricular complex) is NOT true?
A.
It may fail to produce a palpable radial pulse
B.
It always indicates serious underlying heart disease
C.
It is associated with an abnormal, wide QRS complex
D.
It tends to be followed by a compensatory pause
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Question 6
Question 6
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A 50-year-old man 3 weeks after a myocardial infarction has frequent asymptomatic ventricular ectopics on monitoring and an ejection fraction of 35%. Which of the following is the most appropriate treatment?
A.
Flecainide
B.
Mexiletine
C.
Beta-blocker
D.
Immediate radiofrequency ablation of the ectopic focus
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Question 7
Question 7
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All of the following statements about pulsus bigeminus are true, EXCEPT:
A.
It must be distinguished from pulsus alternans
B.
It can be a sign of digitalis toxicity
C.
The compensatory pause is absent
D.
The rhythm is irregular
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Question 8
Question 8
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Which of the following ECG findings are manifestations of digitalis intoxication?
1. Ventricular bigeminy
2. Ventricular tachycardia
3. Atrial flutter
4. Atrial tachycardia with variable AV block
A.
1, 2 and 3
B.
1, 2 and 4
C.
1, 3 and 4
D.
2, 3 and 4
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Question 9
Question 9
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A 58-year-old woman on a cardiac monitor has an abrupt pause in her rhythm. On close inspection, the T wave of the beat immediately preceding the pause is
peaked and asymmetric
, unlike all her other T waves. The P-P interval containing the pause is not an exact multiple of the baseline P-P interval. What is the most likely cause of the pause?
A.
Sinoatrial exit block
B.
Sinus arrest with junctional escape
C.
Mobitz type II second-degree AV block
D.
Non-conducted (blocked) premature atrial complex
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Question 10
Question 10
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A 70-year-old man has intermittent pauses on his ECG. The baseline P-P interval is 900 ms. Each pause measures exactly 1800 ms, with a P wave and QRS entirely missing during it. Which diagnosis does this measurement point to?
A.
Sinoatrial exit block
B.
Sinus arrest
C.
Blocked premature atrial complex
D.
Sinus pause
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Question 11
Question 11
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A 76-year-old woman on a monitor has a 4-second pause that is terminated by a single
wide, bizarre QRS complex
with no related P wave. The intern asks whether to give IV lidocaine to suppress this "PVC". What is the correct action?
A.
Do not suppress the beat; identify and treat the cause of the pause
B.
Give IV lidocaine as suggested
C.
Give IV amiodarone instead, as it is safer
D.
Perform immediate synchronised cardioversion
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Question 12
Question 12
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A wide, bizarre ectopic beat is seen
sandwiched between two consecutive sinus beats
with no pause at all — the sinus rhythm marches through completely undisturbed. The beat immediately after the ectopic shows a slightly prolonged PR interval. What is this beat?
A.
A fusion beat
B.
An aberrantly conducted PAC
C.
An interpolated PVC
D.
A ventricular escape beat
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Question 13
Question 13
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An early beat on the ECG has a
wide QRS with an RBBB morphology
. Careful inspection shows an abnormal P wave deforming the T wave of the preceding beat, and the interval from the sinus R before the beat to the sinus R after it is
1.7 times
the baseline R-R interval. What is the diagnosis?
A.
Premature ventricular complex
B.
Ventricular escape beat
C.
Aberrantly conducted premature atrial complex
D.
Premature junctional complex with bundle branch block
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Question 14
Question 14
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A 44-year-old man with no symptoms of heart failure has 24-hour Holter monitoring showing a PVC burden of 24% (about 26,000 PVCs/day), all of identical morphology. Echocardiography now shows a dilated left ventricle with an ejection fraction of 36%. Coronary angiography is normal. What is the most appropriate management?
A.
Refer for catheter ablation of the PVC focus
B.
Start flecainide to suppress the ectopy
C.
Implant a cardiac resynchronisation therapy device
D.
Reassurance and repeat echocardiography in 5 years
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Question 15
Question 15
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A patient with an acute anterior MI and hypokalaemia has a PVC that falls directly on the
T wave
of the preceding beat, immediately followed by polymorphic ventricular tachycardia. This phenomenon corresponds to which Lown grade, and why is it dangerous?
A.
Grade 3 — multifocal PVCs indicating diffuse irritability
B.
Grade 4A — a couplet, indicating increased ectopic burden
C.
Grade 4B — a triplet, meeting the definition of non-sustained VT
D.
Grade 5 — R-on-T, striking the vulnerable period of repolarisation
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Question 16
Question 16
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A 32-year-old man with hypertrophic obstructive cardiomyopathy is being auscultated. During the examination he has a PVC. The systolic murmur in
the beat immediately following the compensatory pause
is noticeably louder. What is the mechanism?
A.
The PVC transiently increases afterload, worsening the obstruction
B.
The ectopic beat produces mitral regurgitation that persists into the next beat
C.
The longer filling time increases end-diastolic volume, so contractile force rises (Frank-Starling)
D.
The compensatory pause causes reflex vagal withdrawal and tachycardia
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Question 17
Question 17
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A 74-year-old man on digoxin for heart failure presents with nausea and palpitations. His ECG shows
early, narrow-QRS beats with inverted P waves in leads II, III and aVF
occurring just after each QRS, together with an atrial tachycardia showing variable AV block. What is the most likely explanation?
A.
Ventricular escape beats from sick sinus syndrome
B.
Premature junctional complexes due to digoxin toxicity
C.
Premature ventricular complexes due to hypokalaemia alone
D.
Premature atrial complexes from caffeine excess
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Question 18
Question 18
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In the rhythm strip shown, the arrowed beats are early and narrow-complex. Measuring from the sinus R wave
before
an arrowed beat to the sinus R wave
after
it gives an interval of about 1.6 times the baseline R-R interval. How is this pause best described, and what does it tell you?
A.
Non-compensatory pause — the ectopic impulse reset the sinus node
B.
Sinoatrial exit block — the pause is an exact multiple of the P-P interval
C.
Fully compensatory pause — the sinus node was not reset
D.
Interpolated beat — no pause is actually present
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Question 19
Question 19
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A 68-year-old woman on high-dose furosemide is admitted with weakness. Her monitor shows the pattern in panel C of the figure — every second beat is a wide, bizarre complex. Blood pressure is 118/74 mmHg and she is asymptomatic apart from fatigue. Serum potassium is 2.8 mEq/L. What is the most appropriate first step?
A.
Check and replace potassium and magnesium
B.
Insert a temporary transvenous pacemaker
C.
Start an intravenous lidocaine infusion to abolish the ectopy
D.
Arrange urgent catheter ablation of the ventricular focus
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Question 20
Question 20
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During telemetry, a patient has a run of
three consecutive PVCs
that terminates spontaneously and is followed by resumption of sinus rhythm. How should this be reported?
A.
Ventricular bigeminy
B.
Sustained ventricular tachycardia requiring immediate cardioversion
C.
A couplet (Lown grade 4A) — no further evaluation needed
D.
A triplet, which by definition constitutes non-sustained ventricular tachycardia
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Question 21
Question 21
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On a Holter recording, a patient's PVCs show
several different QRS morphologies
with
varying coupling intervals
from the preceding sinus beats. Compared with PVCs that are all identical with a fixed coupling interval, this finding is:
A.
Of no prognostic difference — only the total PVC count matters
B.
Diagnostic of an accessory pathway
C.
Less concerning — variable morphology indicates a benign, non-reentrant mechanism
D.
More concerning — it suggests multiple ectopic foci and diffuse myocardial irritability
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