All patients
History: including arrhythmogenic medications/substances, pertinent family history
Physical examination
ECG/CXR
TTE
In selected patients
Exercise testing
Advanced imaging (CT/C-MR)
Electrophysiologic studies
Genetic testing
History: including arrhythmogenic medications/substances, pertinent family history
Physical examination
ECG/CXR
TTE
Exercise testing
Advanced imaging (CT/C-MR)
Electrophysiologic studies
Genetic testing
Based on ECG
Most important distinction is whether dysrhythmia is associated with underlying structural heart disease.
Idiopathic<unk>  Tachycardia:<unk>  outflow arrhythmias (RVOT > LVOT). Good prognosis, rarely associated with tachycardia-induced cardiomyopathy and sudden cardiac death (SCD).
Polymorphic<unk>  tachycardia: Inherited or acquired long QT syndrome, familial catecholaminergic PMVT
Increased risk of sudden cardiac death, consideration for ICD if symptomatic (syncope, arrest) or asymptomatic QTc > 550ms.
Arrhythmogenic Right<unk>  Cardiomyopathy: Fibro-fatty deposition in RVIT/RVOT/RV apex. Increased risk of SCD, consideration for catheter ablation with ICD backup.
Increased risk of sudden cardiac death, consideration for ICD if symptomatic (syncope, arrest) or asymptomatic QTc > 550ms.
Hypertension and LVH: warrants evaluation for ischemic heart disease, aggressive medical management of hypertension (including beta-blockade). Prognosis unclear.
Valvular disease: Highest incidence in AS and MR. No evidence that occurrence of<unk>  associated with SCD.
Ischemic heart disease: Monomorphic<unk>  around myocardial scars, active ischemia associated with both mono/polymorphic VT and VF. In ED, early<unk>  (<24h) after NSTEMI/STEMI common and not associated with adverse outcomes.
Hypertrophic cardiomyopathy; myocyte disarray produces arrhythmogenic substrate.<unk>  associated with increased risk of SCD.
Other conditions:
Non-ischemic dilated cardiomyopathy
Giant-cell myocarditis
Repaired TOF
Amyloidosis
Sarcoidosis
Chagas cardiomyopathy
Non-ischemic dilated cardiomyopathy
Giant-cell myocarditis
Repaired TOF
Amyloidosis
Sarcoidosis
Chagas cardiomyopathy
Nonsustained ventricular tachycardia
Assume any wide-complex tachycardia is ventricular tachycardia until proven otherwise 
Wide-complex tachycardia
Regular
Narrow-complex tachycardia
Monomorphic ventricular tachycardia
Accelerated idioventricular rhythm
PSVT with aberrant conduction: