Differentials
Ventricular bigeminy
SIGNS / SYMPTOMS
Post-premature ventricular contraction (PVC) potentiation not present during sinus rhythm without PVCs.
Cannon a-waves seen in the jugular venous pulse.
INVESTIGATIONS
ECG and rhythm strip correlated with pulse show a premature ventricular beat after each normal beat.
Frequent premature ventricular contractions (PVCs)
SIGNS / SYMPTOMS
Non-perfused ventricular ectopy causing apparent sinus bradycardia.
Patients are usually asymptomatic.
Cannon a-waves may be seen in the jugular venous pulse.
INVESTIGATIONS
ECG and rhythm strip correlated with pulse. Specific ECG findings depend on the cause. However, ventricular beats occur earlier than normal.
Atrial fibrillation
SIGNS / SYMPTOMS
Apical versus peripheral pulse.
Irregular pulse rate.
INVESTIGATIONS
ECG shows absent P waves, presence of fibrillatory waves, and irregular QRS complexes. A rhythm strip may be useful.
Blocked premature atrial contractions (PACs)
SIGNS / SYMPTOMS
Atrial rate is fast but the ventricular rate is slow.
INVESTIGATIONS
ECG shows slight notching on preceding T-wave.
Ventricular tachycardia
SIGNS / SYMPTOMS
A-waves, variable S1, and variable pulse seen in jugular venous pressure.
INVESTIGATIONS
ECG shows atrioventricular (AV) dissociation with capture and fusion.
Cardiac tamponade
SIGNS / SYMPTOMS
Muffled heart sounds.
Sinus tachycardia.
Pulsus paradoxus (usually below 10 mmHg).
Elevated jugular venous pressure.
INVESTIGATIONS
ECG shows low voltage QRS or total electrical alternans.
Echocardiogram shows large pericardial effusion or chamber collapse and respiratory variation of ventricular filling.
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