Physical Activity and Ventricular Arrhythmias

The purpose of the study is to determine the effect of aerobic interval training in patients with an implantable cardioverter defibrillator (ICD) on physical fitness, quality of life and the amount of serious ventricular arrhythmic events on short and long term.

In this study, participants will be randomly assigned to either take part in the exercise program or serve as control and live as usual. At baseline study visit, study researchers will review medical records to collect various information, including the reason for needing an ICD, the type and settings of the ICD, medication use and medical history etc. All participants will undergo blood collection, complete a questionnaire to assess quality of life and undergo examination with echocardiography and ECG. The ICD will be programmed accordingly to international guidelines regarding ICD-therapy and optimal monitoring, before each participant complete an exercise treadmill test to determine VO2 peak. They will wear a Holter monitor to record heart activity 48 hours before the test and 24 hours after the test. All participants will then be observed for 2 months before being randomly assigned to either intervention or control. During this observation period, they will wear a fitness activity tracker wristband to evaluate degree of physical activity and a Holter monitor to register number of premature ventricular contractions. Participants taking part in the interval training group will perform aerobic interval training 4 x 4 minutes intervals, 3 times a week for 12 weeks (week 1-12), whereas participants taking part in the control group will carry on with usual daily life with no lifestyle recommendations. All participants will then undergo a new period of observation (week 13-20) and repeat the tests and examinations performed at baseline and during the observation period prior to intervention/control.

Aerobic interval training during 12 weeks 3 times a week: 4 x 4 minutes intervals at an intensity of 90-95% of VO2 peak and active breaks of 3 minutes between intervals.

Baseline and the last 4 weeks of intervention period plus 4 first weeks after intervention period (week 9-16)

Baseline and the last 4 weeks of intervention period plus 4 first weeks after intervention period (week 9-16)

Evaluated by number of episodes with monitored ventricular tachycardias without ICD-therapy (registered on ICD)

Evaluated by number of episodes with monitored ventricular tachycardias without ICD-therapy (registered on ICD)

Evaluated by number of episodes with monitored ventricular tachycardias without ICD-therapy (registered on ICD)

Baseline and the last 4 weeks of intervention period plus 4 first weeks after intervention period (week 9-16)

Evaluated by number of premature ventricular contractions (registered on a 72 hours Holter monitoring)

Evaluated by number of premature ventricular contractions (registered on a 72 hours Holter monitoring)

Evaluated by number of premature ventricular contractions (registered on a 72 hours Holter monitoring)

Baseline and the last 4 weeks of intervention period plus 4 first weeks after intervention period (week 9-16)

Evaluated by changes in left ventricular dimensions and systolic/diastolic function assessed by echocardiography and blood values (NT-proBNP and troponin T)

Assessed by number of steps daily registered with fitness activity tracker wristband (worn for 1 week)

Evaluated by changes in total cholesterol, HDL-cholesterol, LDL-cholesterol (all in mmol/L) as a measure of cardiac risk

Evaluated by measuring changes in SDNN, SDANN 5, ASDNN 5 and RMSSD registered on a 72 hours Holter monitoring

Changes in number of premature ventricular contractions during a single bout of high intensity exercise (VO2 peak test)

Inclusion Criteria: Patients with ICD and dilated cardiomyopathy or coronary heart disease as cause for implantation ICD implanted at St Olavs hospital, Trondheim In case of difficulties with patient inclusion for the study, the criteria might be broadened to include patients with idiopathic ventricular arrhythmia as cause for implantation. Exclusion Criteria: inability to accomplish the exercise program due to serious comorbidity or to participate in regular training within the next 3 months due to other reasons signs of severe cardiac ischemia or persistent ventricular tachycardia during individualized treadmill O2 peak test, which after individual assessment is to be found at risk comorbidity where endurance training at more than moderate intensity is discouraged severe cardiac valve disease planned surgery within the next 3 months inability to give informed consent

Individual participant data for all primary and secondary outcome measures will be made available after deidentification and publication