too limited number of eligible patients

The purpose of this study is to determine whether left ventricular endocardial pacing exhibits a greater acute hemodynamic response during biventricular pacing in patients who do not show this response to standard cardiac resynchronization therapy.

Cardiac resynchronisation therapy (CRT) with biventricular pacemakers and implantable cardiac defibrillators (ICD) has proven to be a valuable therapy in selected patients with systolic heart failure, ameliorating both morbidity and mortality. However, with current selection criteria and implant technique, about 20 to 30 % of patients remain non-responders. Non-responders might be due to failing selection criteria or methodology in casu echocardiography. However, an important number of non-responders may result of sub-optimal positioning of the left ventricular lead, remote from the site of delayed activation. Endocardial left ventricular stimulation may ameliorate the shortcomings of epicardial stimulation. The advantage of an endocardial approach is the absence of phrenic nerve stimulation which regularly complicates epicardial pacing, a more predictable pacing threshold and much less restriction to position the lead in the area of interest. Transseptal left ventricular endocardial pacing has already been used in patients in whom standard epicardial pacing was not applicable.

Inclusion Criteria:

1. Age ≥18y
2. LVEF ≤35%
3. QRS-duration ≥0.12 seconds
4. NYHA functional class III or IV despite optimal medical therapy defined as use of angiotensin-converting enzyme inhibitors or angiotensin-II receptor blocker and beta-blockers unless they are not tolerated or contra-indicated
5. sinus rhythm or atrial fibrillation

Exclusion Criteria:

1. episode of acute heart failure ≤3 months
2. change in dosage of beta-blockers, angiotensin-converting enzyme inhibitors or angiotensin-II receptor blockers ≤3 months
3. unstable angina pectoris, acute myocardial infarction, percutaneous intervention or coronary bypass surgery ≤3 months
4. chronic atrial arrhythmias other than atrial fibrillation
5. any mechanical or biological valve prosthesis
6. atrial septal defect
7. right-to-left shunt
8. severe pulmonary hypertension (systolic pulmonary artery pressure >90 mmHg)
9. uncontrolled arterial hypertension
10. known allergy to sulphur hexafluoride
11. end-stage renal or hepatic disease
12. inability to provide written informed consent
13. pregnancy or childbearing potential without use of birth-control measurements
14. general contra-indications to magnetic resonance imaging