Differentials
Supraventricular tachycardia with aberrancy
SIGNS / SYMPTOMS
None.
INVESTIGATIONS
ECG; electrophysiological study: failure to meet criteria for ventricular tachycardia; absence of fusion or capture beats; absence of atrioventricular dissociation.
Supraventricular tachycardia with pre-excitation
SIGNS / SYMPTOMS
None.
INVESTIGATIONS
ECG, electrophysiological study: failure to meet criteria for ventricular tachycardia; absence of fusion or capture beats; absence of atrioventricular dissociation.
Electrical artefact
SIGNS / SYMPTOMS
None.
INVESTIGATIONS
Evidence of underlying sinus rhythm on ECG discernible through electrical noise (motion artefact).
Evidence of arrhythmia isolated to specific leads on 12-lead ECG (tremor).
Sepsis or fever
SIGNS / SYMPTOMS
Raised temperature, malaise, rigors, symptoms of underlying infection.
INVESTIGATIONS
ECG shows underlying sinus rhythm or sinus tachycardia.
Appropriate cultures may show presence of infecting agent.
Panic/hyperventilation
SIGNS / SYMPTOMS
Anxiety or panic, fear of imminent death, paraesthesiae, chest pain, numbness, faintness, dizziness, sweating.
INVESTIGATIONS
ECG shows underlying sinus rhythm.
Hospital Anxiety and Depression Scale anxiety score >11.
Hyperthyroidism
SIGNS / SYMPTOMS
Tremor, anxiety, weight loss but good appetite, diarrhoea, eyelid retraction and lid lag, fatigue, heat intolerance, goitre.
INVESTIGATIONS
ECG shows underlying sinus rhythm or atrial fibrillation.
Raised thyroxine/triiodothyronine and low thyroid-stimulating hormone levels.
Acute haemorrhage
SIGNS / SYMPTOMS
Low blood pressure, abdominal pain with haematemesis and/or melaena, haemorrhage from other sites, history of likely cause of blood loss: for example, trauma or post-operative.
INVESTIGATIONS
ECG shows underlying sinus tachycardia.
Ultrasound or CT may show internal bleeding source and/or collection of blood.
Phaeochromocytoma
SIGNS / SYMPTOMS
Headache, sweating, palpitations, fluctuating hypertension, anxiety, nausea, vomiting, weight loss, heat intolerance, tremors, chest and abdominal pain.
INVESTIGATIONS
ECG shows underlying sinus tachycardia.
Increased plasma and 24-hour urine adrenaline (epinephrine)/noradrenaline (norepinephrine)/metanephrine levels.
Glucagon stimulation test positive.
Clonidine suppression test positive.
CT, MRI, or m-iodobenzylguanidine scans show tumour in adrenal gland.
Pericarditis
SIGNS / SYMPTOMS
Tachycardia and friction rub; jugular venous distension and pulsus paradoxus indicate pericardial effusion causing tamponade.
INVESTIGATIONS
ECG shows diffuse concave-up ST-elevation, associated PR depression.
Chest x-ray may show enlarged cardiac silhouette (globular heart) if pericardial effusion present.
Echocardiogram may show pericardial effusion.
Caffeine, alcohol, amphetamine use
SIGNS / SYMPTOMS
History of recent use or high intake.
Tremor, agitation, signs of intoxication.
INVESTIGATIONS
ECG shows underlying sinus tachycardia.
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