Bowditch Revisited: Defining the Optimum Heart Rate Range in Chronic Heart Failure

Bowditch Revisited: Defining the Optimum Heart Rate Range in Chronic Heart Failure

The investigators are examining the relationship between heart rate and heart contraction in patients with heart failure and pacemakers, aiming to improve quality of life.

Heart rate lowering is a cornerstone of the management of chronic heart failure (CHF) and the degree of lowering is closely related to improvements in longevity, hospitalisation rate and heart function. The investigators have shown that increasing heart rates using pacemakers does not increase exercise capacity in CHF patients. This might be because the optimal heart rate range for contraction is narrower for patients with CHF. At higher heart rates, heart contraction might be less strong. The investigators now want to examine the relationship between heart rate and heart contraction in patients with heart failure and pacemakers. Tailored pacemaker heart rate setting's, individually optimised for heart contractility as assessed by cardiac ultrasound, will be investigated to examine the effects on exercise tolerance .

Inclusion Criteria:

• stable CHF
• Cardiac Resynchronisation Therapy (CRT) device for >3 months,
• able to walk on treadmill

Exclusion Criteria:

• unable to walk on treadmill,
• unstable angina pectoris
• uncontrolled heart rate
• prescribed calcium channel blocker
• significant aortic stenosis
• significant airways disease