Exercise as it relates to Disease/Cardiovascular effects of aerobic training strategies for heart failure patients

What is the background to this research?
Heart failure affects around 100 000 Australians. Heart failure happens when your heart muscle gets damaged, then becomes weak and doesn’t pump blood properly. Once your heart is damaged, it can’t heal, the damage is permanent. Damage to the heart can be caused either by a heart attack, or by long-term health problems like high blood pressure, diabetes or heart disease. It can also be caused by cardiomyopathy, a disease of the heart muscle. Cardiomyopathy means your heart is unable to pump an adequate supply of blood around the body. Heart failure significantly impairs an individual’s ability to function on a day to day basis, everyday tasks can be exhausting. Through medicine and lifestyle interventions, symptoms may be improved.

Symptoms of heart failure



 * Feeling weak and tired
 * being breathless
 * swollen ankles, legs, or stomach
 * weight gain
 * losing your appetite
 * dizziness
 * coughing

Treatments for heart failure
Traditionally there are two main forms of treatment for heart failure: Medication and Lifestyle changes.

Medications include the following :


 * ACE inhibitors - lower blood pressure and reduce strain on your heart. They also may reduce the risk of a future heart attack.
 * Aldosterone antagonists - trigger the body to remove excess sodium through urine. This lowers the volume of blood that the heart must pump.
 * Angiotensin receptor blockers - relax your blood vessels and lower blood pressure to decrease your heart’s workload.
 * Beta blockers - slow your heart rate and lower your blood pressure to decrease your heart’s workload.
 * Digoxin - makes the heart beat stronger and pump more blood.
 * Diuretics (fluid pills) - help reduce fluid buildup in your lungs and swelling in your feet and ankles.
 * Isosorbide dinitrate/hydralazine hydrochloride - helps relax your blood vessels so your heart doesn’t work as hard to pump blood.

Lifestyle changes include the following :


 * Dietary changes
 * Physical Activity changes

The study by Wisloff et, al. focuses only on the lifestyle change of Physical activity changes

Location and researchers
This research is coming from Norway, out of the university of science and technology. The lead researcher Ulrik Wisloff has a reputation for advocating strongly for the benefits of HITT training across a range of applications. All patients were taken from the cardiology department at St Olav’s Hospital Trondheim. Lead researcher Ulrik Wisloff has a reputation for his vocal support of high intensity interval training over other forms of training across a range of applications. This means he has some pre-existing bias in favour of this style of training.

Funding
The study was supported by grants from:
 * The Norwegian Council of Cardiovascular Disease,
 * The Foundations for Cardiovascular and Medical Research at St. Olav’s University Hospital Torstein Erbo’s foundation
 * The National Institutes of Health
 * The American Diabetes Association
 * The United States Department of Agriculture

There do not appear to be any sponsorship or funding links that would lead to conflict of interest or influence the reliability of the science reported in this study given that none of these organisations have a vested interest in which outcome is more beneficial for reducing heart failure symptoms.

What kind of research was this?
This was a randomised control trial, randomised control studies are the most academically rigorous way for determining a cause and effect relationship. Other study designs like observational or non-randomised studies can show some associations or trends between an intervention and an outcome but struggle to rule out external factors and bias. Meta studies can be beneficial as they look at reanalysing previous studies but their validity depends on the quality of the original data. The key focus of a randomised control trial is reduction of bias, making the study more reliable.

What did the research involve?
The study recruited 27 patients with post infarction heart failure, none of the patients had had a myocardial infarction within the last 12 months. None of the patients were fitted with a pacemaker. The patients were stratified by gender and age then randomised by random number generator to the following groups; Aerobic Interval training, Moderate continuous training or Control (AIT, MCT, Control). During the intervention period training was done three times a week, all workouts were done at home for the control group. Both the aerobic interval training and the moderate continuous training groups trained twice a week under supervision and once per week at home. VO2 peak testing was done both before and after the intervention. The researchers determined work economy as oxygen uptake at a standard submaximal workload. The study was controlled such that the intervention groups were isocaloric, meaning they had the same overall energy cost. The aerobic interval training group trained at intervals of 90-95% of peak heart rate as measured in the peak testing. The moderate continuous training group performed exercise at a continuous 70-75% peak heart rate. All of the groups trained on a treadmill where the speed and inclination of the treadmill was adjusted to maintain heart rate.

The research methods were fairly solid overall, however, they could have been made more statistically significant by recruiting a higher number of participants.

What were the basic results?
The researchers made claims through reported data showing statistically significant changes in test scores for pre and post intervention data. The major finding of the present study was that aerobic interval training was superior to moderate continuous training and the control group in patients with post-infarction heart failure with regard to the following.

Reversal of Left Ventricular Remodelling
Left ventricular diameter was measured by ultrasound

Aerobic Capacity
Measured through VO2 peak testing on a treadmill

Endothelial Function
Dilation of the brachial artery was measured by ultrasound

Quality of Life
Quality of life was measured by the MacNew Heart Disease Health-Related Quality of Life questionnaire

What conclusions can we take from this research?
The study demonstrates that high-intensity training relative to the individual’s maximal oxygen uptake is safe and achievable even in elderly patients with chronic heart failure and severely impaired cardiovascular function. The study shows that the intensity of exercise may be an important factor for reversing left ventricular remodelling, improving aerobic capacity, and improving quality of life in patients with post-infarction heart failure. These findings could have important implications for exercise prescription in post cardiac event rehabilitation programs. And provides a useful pilot for future studies.

These conclusions align with current research by Ellingson et,al and Haykowsky et, al.

Practical advice
It's important to note that each of the patients was being medicated in addition to the physical activity interventions, therefore it is recommended that all patients stay on their medications whilst doing any form of lifestyle intervention. From the data in this journal it is recommended that aerobic interval training protocols should be prescribed over moderate intensity protocols for patients recovering from heart failure.

Further reading and resources
The following sources will be helpful for readers wanting to learn more about Heart failure and the treatments and interventions available to reduce symptoms:


 * https://www.heartfoundation.org.au/your-heart/heart-conditions/heart-failure-the-facts