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

Study Overview
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Brief Summary
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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.

Detailed Description
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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 .

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

Conditions
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Chronic Heart Failure

Intervention / Treatment
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* Device: Tailored pacemaker settings


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Standard pacemaker settings<br>Standard pacemaker settings will be programmed and the patient will complete a symptom limited exercise tolerance test with metabolic gas exchange | |
| Experimental: Tailored pacemaker settings<br>The pacemaker settings will be altered to match optimal heart rate range with respect to cardiac contractility, as determined by echocardiography. This will be programmed and the patient will complete a symptom limited exercise tolerance test with metabolic gas exchange. | Device: Tailored pacemaker settings<br>* Tailored pacemaker settings, optimised for cardiac contractility: Pacemaker settings, optimised for cardiac contractility as determined by echocardiography, will be programmed<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Exercise Time | Exercise duration in seconds | Assessed following the second treadmill test, 1 week later | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Peak Oxygen Consumption (pVO2) | Peak Oxygen Consumption (pVO2) measured by metabolic gas exchange | Assessed following the second treadmill test, 1 week later |