The purpose of this pilot study is to evaluate the progression of ventricular dysfunction in patients with ventricular dysfunction within the permanent pacing population.

The interventricular synchrony is one of the components of a proper cardiac function. When there is no synchrony -as in left bundle block (LBBB)- the clinic consequences should have little importance in patients with a healthy heart or a great importance in patients suffering heart failure (HF), specially in those with severe grade of HF, the benefit of cardiac resynchronization by pacing both ventricles or left ventricle (LV)should means healthy improvement in patients. All previous studies done in HF, are in patients with symptomatic HF. The importance of stop progression of latent HF in patients with asymptomatic ventricular dysfunction (VD)in permanent pacing indication patients. Pacing may accelerate HF progression by dissincronyzing ventricles. ACE inhibitors studies in asymptomatic VD gave positive results.

The PreVent-HF is an international, multicenter, prospective, randomized, single-blinded pilot trial specifically designed to evaluate as main objective the progression of VD in permanent pacing population.

Inclusion Criteria:

• Meet Class I and/or Class IIa implantation criteria for permanent cardiac pacing according to the guidelines given by the American College of Cardiology (ACC)/American Heart Association(AHA).

Exclusion Criteria:

• Expected ventricle stimulation <80% of the time
• Impossibility of dual chamber stimulation in the absence of AF
• Severe heart failure (NYHA Functional class III-IV) previous to indication for pacing device implant
• Patient needs revascularization within 3 months
• Myocardial infarction in the last 3 months
• Cardiac surgery performed in the last 3 months
• Hypertrophic cardiomyopathy
• Constrictive pericarditis
• Bad echo window
• Previous system implanted (ICD or pacemaker)
• Aortic stenosis
• Patient has a mechanical right heart valve
• Patient <18 years
• Pregnancy
• Patient has medical conditions that would preclude the testing required by the protocol, or limit study participation
• Life expectancy <1year
• Patient is unwilling or unable to cooperate or give written informed consent.
• Patient is or will be inaccessible for follow-up at the study center.
• Patients who are participating or planning to participate in other clinical trials during the clinical study

Video tapes are provided by the central study organization and are labelled by numbers. The tapes are sent to the echocardiography core laboratory (Malaga, Spain) and are read by the Director of the Echo Core Lab (J.J. Gomez-Doblas). The echo examiner is blinded as to the point of time of the recording and assignment of treatment, although the presence of a LV lead may be adumbrated by visible artefacts.