Arrhythmias

Stem Breakdown:

Acute-onset left leg pain and coldness: This suggests a sudden loss of blood flow, which is concerning for an acute arterial occlusion.
Pale and pulseless leg: These findings confirm that the limb is ischemic due to an arterial blockage.
History of chronic atrial fibrillation: Atrial fibrillation increases the risk of thromboembolism, which can lead to arterial embolism.
Option Analysis:

A) Deep vein thrombosis: Deep vein thrombosis (DVT) affects the veins, not arteries, and typically causes swelling, pain, and warmth in the affected limb, not coldness or pulselessness.
B) Acute arterial embolism: This is the correct diagnosis. Davidson and Harrison explain that acute arterial embolism is a sudden blockage of an artery, often due to an embolus originating from the heart (e.g., in atrial fibrillation). The "5 Ps" of acute arterial occlusion are Pain, Pallor, Pulselessness, Paresthesia, and Paralysis.
C) Chronic venous insufficiency: Chronic venous insufficiency causes leg swelling, varicose veins, and skin changes, but it does not cause sudden limb ischemia or a pulseless leg.
D) Peripheral neuropathy: Peripheral neuropathy causes numbness, tingling, and weakness, but it does not cause acute pain or loss of pulses.

Stem Breakdown:

Recurrent episodes of chest pain, palpitations, and shortness of breath: These symptoms suggest a tachyarrhythmia, such as paroxysmal supraventricular tachycardia (PSVT).
ECG showing PSVT: PSVT is a common type of arrhythmia characterized by sudden onset and termination, often due to reentrant circuits in the atrioventricular (AV) node.
Option Analysis:

A) Beta-blockers: Beta-blockers can be used to control the rate in some arrhythmias, but they are not the first-line treatment for terminating acute PSVT episodes.
B) Adenosine: This is the correct answer. Davidson and Harrison recommend adenosine as the first-line treatment for acute PSVT because it temporarily blocks AV nodal conduction, terminating the reentrant circuit responsible for PSVT. It is highly effective and works within seconds.
C) Calcium channel blockers: Calcium channel blockers (e.g., verapamil, diltiazem) can be used to slow AV nodal conduction in PSVT, but they are typically second-line agents after adenosine.
D) Amiodarone: Amiodarone is used to treat ventricular arrhythmias and atrial fibrillation but is not the first-line treatment for acute PSVT. It has a longer onset of action compared to adenosine.

ECG abnormalities: T-wave inversion, ST depression and prolonged QTc interval

During episodes of AF, the atria beat rapidly but in an uncoordinated and ineffective manner. The ventricles are activated irregularly at a rate determined by conduction through the AV node. This produces the characteristic ‘irregularly irregular’ pulse. The ECG shows normal but irregular QRS complexes; there are no P waves.

Reference: Davidson 23rd , Page : 473 , Box : 16.24

Explanation: see question no: 7

Reference: Davidson 23rd; P-133

Reference: Davidson 23rd , Page : 482
Explanation : Adenosine effects are greatly potentiated by dipyridamole and inhibited by theophylline.

Reference: Davidson 23rd , Page : 481
Explanation : Amiodarone is probably the most effective drug currently available for controlling paroxysmal AF.

Explanation: Absent a wave in JVP is found in Atrial fibrillation, Tricuspid regurgitation produces giant v waves

Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death in young athletes. Davidson explains that in HCM, abnormal thickening of the heart muscle, particularly the interventricular septum, can obstruct blood flow and predispose to fatal arrhythmias. Harrison emphasises the importance of screening athletes with family histories of sudden cardiac death or unexplained syncope for HCM.

Explanation:

Explanation: All are the causes of bradycardia, Option A, B, D are pathological cause.