• To compare efficacy of both therapies in relation to episode termination
• To compare the rate of total adverse events, cardiac and non cardiac, occurring during an observation period of 24 hours after treatment was applied

The purpose of this study is to determine whether intravenous amiodarone has less cardiac significant adverse events compared to intravenous procainamide in the acute treatment of haemodynamically well tolerated wide QRS tachycardia, the majority of them of probably ventricular origen.

Multicenter, prospective and randomized study in phase IV. A total of 302 patients will be included in the study within 40-50 institutions in Spain. Patients with regular and monomorphic tachycardia ≥ 120 bpm, QRS ≥ 120 ms and haemodynamically well tolerated will be randomized to receive iv amiodarone (single dosage: 5 mg/kg in 20 minutes) vs iv procainamide (single dosage: 10 mg/kg in 20 minutes). The study period will be 40 minutes from infusion initiation. Study variables include the presence of clinically cardiac significant adverse events: hypotension, syncope, heart failure, symptomatic sinus bradycardia, AV block, proarrhythmia and tachycardia acceleration (<20 lpm)and death. Total observation period will be 24 hours after the end of the infusion.

• Ventricular Tachycardia
• Wide QRS Tachycardia

• [No authors listed] ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death--Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death): Developed in Collaboration With the European Heart Rhythm Association and the Heart Rhythm Society. Circulation. 2006 Sep 5;114(10):1088-1132. Epub 2006 Aug 21. No abstract available.
• [No authors listed] Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Part 6: advanced cardiovascular life support: section 5: pharmacology I: agents for arrhythmias. The American Heart Association in collaboration with the International Liaison Committee on Resuscitation. Circulation. 2000 Aug 22;102(8 Suppl):I112-28. No abstract available.
• ECC Committee, Subcommittees and Task Forces of the American Heart Association. 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2005 Dec 13;112(24 Suppl):IV1-203. Epub 2005 Nov 28. No abstract available.

Inclusion Criteria:

• Patients with stable tachycardia ≥120 lpm, QRS ≥120 ms and haemodynamically well tolerated defined as: 1)Systolic blood pressure ≥90 mmHg, 2) absence of dyspnea at rest, 3)absence of peripheric hypoperfusion signs and 4)no severe angina.
• Age > 18 years
• Written inform consent obtained

Exclusion Criteria:

• Treatment with iv amiodarone or iv procainamide during the previous 24 hours
• QRS tachycardia <120 ms
• Patients with QRS ≥120 ms tachycardia with haemodynamic compromise that requires urgent cardioversion for termination
• Irregular tachycardia
• Tachycardia that is considered as supraventricular due to physician criteria (adenosine and/or vagal manoeuvres response)
• Patient that do not want to cooperate