This study is a single arm, prospective, feasibility, multi-centre, observational study. Participants will be suitable for a Cardiac Resynchronisation Therapy (CRT) implant using Wireless Stimulation Endocardially for Cardiac Resynchronization Therapy, known as the WiSE-CRT device system as well as requiring a pacemaker implant which will also be leadless. Some of these participants may also require an AV Node ablation.

The purpose of this study is to assess the safety and efficacy of these two cardiac devices implanted in the order of operator preference (all implants undertaken on the same day or in a number of up to 4 separate sequenced implants/procedures).

Heart Failure is a serious condition in which the heart is unable to pump enough blood to meet the body's demands. Some heart failure occurs when the heart chambers pump in a desynchronised manner, reducing the amount of blood pumped with each heartbeat.

The National Institute for Health and Care Excellence (NICE) recommends Cardiac Resynchronisation Therapy (CRT) for a subset of these patients. Patients undergoing CRT receive a special implantable pacemaker with an additional lead via the coronary sinus (CS) to synchronise the pumping of the heart chambers (ventricles). CRT works by pacing both the left & right ventricles to ensure they pump at the same time. This in turn, reduces heart failure symptoms.

CRT is an effective treatment for many patients, but limitations prevent some patients from benefiting:

• 5-10% of patients are considered untreated due to acute/chronic issues with the CS lead
• 30% of patients do not respond/improve

The WiSE-CRT System is an implantable pacing system capable of delivering pacing energy to the heart without using a pacing lead. It was designed to address the persistent limitations of current CRT systems. The WiSE-CRT System operates alongside a co-implanted pacemaker or CRT system and replaces the pacing function of the CS lead.

Intracardiac pacemakers are miniaturized, self-contained, pacing systems implanted directly inside the right ventricle of the heart, eliminating the need for a device pocket and pacing lead inserted into a vein.

By co-implanting both the European conformity certificated (CE marked) WiSE-CRT system and a leadless intracardiac pacemaker, this pilot study will assess the safety and efficacy of implanting a totally leadless system, thereby avoiding both acute and chronic complications associated with the implant of transvenous pacing leads.

This study is a single arm, prospective, multi-centre, observational study. Participants will have initial pre-implant screening baseline measurements prior to implantation of the first system, then will be followed up immediately post implant, then at 1 month & 6 months post implant.

Inclusion Criteria:

Male or Female, aged 18 years or above. Participant is willing and able to give informed consent for participation in the study.

Additionally, participants will be enrolled and classified from one of two distinct groups:

GROUP A: De novo totally leadless CRT

• implant in whom the physician believes a totally leadless approach would be beneficial (e.g. wish to avoid lifelong transvenous lead implant, anatomical constraints, history of device infection). Examples of this could include:
• symptomatic atrial fibrillation (AF) and an uncontrolled heart rate who are candidates for AV node ablation (irrespective of QRS duration and ejection fraction), in whom the physician believes a leadless pacing approach would be beneficial.
• high degree atrioventricular block who has an indication for permanent pacing, with an ejection fraction ≤50%, are expected to require ventricular pacing more than 40% of the time and in whom the physician believes a leadless approach would be beneficial.
• Other indications for leadless pacing including venous obstruction, pocket issues, infection risk (eg: chronic dialysis), etc.

GROUP B: Upgrade chronic intracardiac pacemaker to CRT

o Patient with existing intracardiac pacemaker with greater than 20% right ventricular (RV) pacing, who have developed symptomatic heart failure.

Exclusion Criteria:

• Female participant who is pregnant, lactating or planning pregnancy during the course of the study
• Inability to comply with the study follow-up or other study requirements
• History of chronic alcohol/drug abuse and currently using alcohol/drugs
• Non-ambulatory (or unstable) NYHA class 4
• Life expectancy less than 12 months
• Any other significant disease or disorder which, in the opinion of the Investigator, may either put the participants at risk because of participation in the study, or may influence the result of the study, or the participant's ability to participate in the study.
• Enrolled in another clinical study that could confound the results of this study (note: patients enrolled in complementary study are eligible for enrolment)

Adult patients appropriate for these devices