One MCQ a day- 14.04.2015

Answer to the question on 13.04.2015:

Answer : A (Right ventricular outflow tract)

Explanation:

12-lead electrocardiographic (ECG) morphology helps in identifying the PVC origin

Left bundle branch block morphology with an inferior axis indicates an outflow tract origin of the PVCs, with a late precordial transition (>V3) pointing to an origin in the right ventricular outflow tract, and an early transition (V3) suggesting an origin from the aortic cusps, the left ventricular outflow tract, or the basal left ventricular epicardium.

Right bundle branch block PVC morphologies indicate a left ventricular origin, with positive concordance indicating a basal origin and a precordial transition to an R/S complex suggesting origin in the papillary muscle.

Intramural arrhythmias are more difficult to localize, and a specific pattern has not yet been described.

Ref:

1. Baman TS, Ilg KJ, Gupta SK, et al: Mapping and ablation of epicardial idiopathic ventricular arrhythmias from within the coronary venous system.Circ Arrhythm Electrophysiol 3:274–279,2010.

2. Good E, Desjardins B, Jongnarangsin K, et al: Ventricular arrhythmias originating from a papillary muscle in patients without prior infarction: A comparison with fascicular arrhythmias. Heart Rhythm 5:1530–1537, 2008.
3. Yokokawa M, Good E, Chugh A, et al: Intramural idiopathic ventricular arrhythmias originating in the intraventricular septum: Mapping and ablation. Circ Arrhythm Electrophysiol 5:258–263, 2012.

MCQ 14.04.2015

Treatment to decrease or eliminate frequency of premature ventricular contractions (PVC) is indicated in all of the following cases except

A. PVC triggering VT/VF

B. Frequent PVC causing nonresponse to cardiac resynchronization therapy

C. Asymptomatic occasional PVC

D. Very frequent PVC (>24% of QRS complexes on holter monitoring)

See below for answers

 

Explanation:

Treatment to decrease or eliminate PVCs should be considered in patients when an expected benefit in terms of symptoms or cardiac function exists. The categories of patients who should undergo treatment that targets PVCs can be summarized as follows:
• Patients with PVCs believed to be causing or contributing to LV dysfunction or dilatation
• Patients with symptomatically limiting PVCs • Patients with VT or VF for which a PVC trigger can be identified
• Patients in whom response to cardiac resynchronization therapy is limited by frequent PVCs
• Patients in whom deterioration of LV function may be expected, such as those with very frequent PVCs (>24%), may also be considered for therapy to reduce PVCs

Although clinical data regarding the last category are not yet definitive, PVC frequency in this range has been shown to often result in LV dysfunction, and a decision must be made on an individual basis between close follow-up of cardiac function versus prophylactic treatment to eliminate the PVCs.

Answer : C

(Ref: Cardiac Electrophysiology: From Cell to Bedside: 6th edition. Page 810)

Keywords: Cardiology review, Cardiology, Multiple choice questions, medical students, Electrophysiology

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