Endurance Interval Exercise, At Least in Short Term, Can Improve AF Time, Symptoms: Study

Deborah Brauser

January 14, 2016

TRONDHEIM, NORWAY – High-intensity, aerobic interval training may lead to symptom reductions and quality-of-life (QoL) improvements in patients with nonpermanent atrial fibrillation (AF), new research suggests[1].

In the small, randomized study of 51 AF patients in Norway, the group that underwent 12 weeks of thrice-weekly sessions of endurance training, consisting of 4-minute intervals of walking or running on a treadmill, showed significant reductions in both AF symptom frequency and severity vs those who continued their current exercise regimen (P=0.006 and 0.009, respectively).

They also had a reduction in AF mean time from 8.1% to 4.8%, as measured by an implanted loop recorder, whereas the control group's mean time increased from 10.4% to 14.6%. In addition, the interval-training group had significantly improved lipid levels, cardiac function, peak oxygen consumption (VO2peak), and "general health and vitality" as measured by QoL measures.

Lead author Dr Vegard Malmo (Norwegian University of Science of Technology, Trondheim, Norway) told heartwire from Medscape that he was "a bit surprised" by the large effect of exercise on both AF burden and secondary end points in such a short period of time, which implied that changes occurred "in electrophysiological properties."

The results were published online January 5, 2015 in Circulation.

"These are important and timely findings that are consistent with data from our group showing that gains in cardiorespiratory fitness are associated with significant abatement of arrhythmia burden both with and without rhythm-control strategies," write Dr Adrian D Elliott (Royal Adelaide Hospital, Australia) and colleagues in an accompanying editorial[2].

The editorialists, who were part of the recently published CARDIO-FIT trial, note that, together, the two studies show "empirical support for exercise training and physical activity as a key element in the treatment of patients with AF."

Paroxysmal or Persistent AF

All 51 participants had ECG-documented nonpermanent AF, which was defined as "paroxysmal (ie, self-terminating within 7 days) or persistent (ie, lasting more than 7 days or requiring cardioversion)."

For the 26 patients assigned to aerobic interval training, each interval aimed for 85% to 95% of their peak heart rate. The intervals were preceded by a 10-minute warmup at 60% to 70% maximum heart rate. There were also 3-minute "recovery" periods in between the intervals that aimed for the same 60% to 70% heart rate.

Although these patients began their regimens at the outpatient clinic at St Olavs Hospital in Trondheim, Norway, they could undergo one exercise session per week in their residence with the help of a heart-rate monitor.

The implanted loop recorders started measuring continuous AF time 4 weeks prior to the exercise intervention and stopped 4 weeks after the intervention ended.

At baseline and after the intervention period, the Norwegian version of the Short-Form 36 (SF-36) and the AF Symptoms and Severity Checklist (SSCL) were used, as were treadmill tests to measure VO2peak, blood samples to measure lipid levels, and MRI to measure ejection fraction (EF).

Decreased Burden

The interval-training group vs the control group showed significant differences in AF mean time (P=0.001). In the first group, 38% had decreased time in AF (decreased AF burden) vs 20% in the latter group. Increased AF burden was found in 12% vs 64%, respectively.

General health perception scores on the SF-36 improved from baseline by 4.4 points for the interval group (P<0.01), which was significantly better than the almost one-point decrease for the control group (P<0.0.5 for group comparison). Vitality scores improved by 8.2 points vs a 0.3 decrease, respectively, (P<0.001 for comparison).

In addition, compared with the control group, the exercise group had a significant increase in VO2peak (P<0.001) and in total and active left atrial emptying fraction (P<0.05); improved LVEF (P<0.05); decreased levels of triglycerides (P<0.01) and total (P<0.01) and LDL cholesterol (P<0.05); and a decrease in weight and body-mass index (both P<0.05).

Although not significant, there was also "a trend toward fewer cardioversions and hospital admissions" after interval training, report the researchers.

Overall, the study "supports the concept that interventions aimed at lifestyle and risk factors should be central in the management and prevention of AF," said Malmo.

However, he cautioned that because the study population was small and the intervention was short, the effects could be different in different patient populations and over time. He also noted that other studies have shown that extensive endurance exercise over many years can increase AF risk.

"Rising Wave of Evidence"

The editorialists note that several subtle points of the study should be examined, such as the facts that the patients were reasonably healthy and that the interval training did not significantly affect blood pressure or inflammation, "which are independent arrhythmogenic risk factors."

They agree with the study authors that larger trials are now needed with longer follow-ups.

"However, this study presents an exciting development for the treatment of AF and adds to the rising wave of evidence showing that in many patients, lifestyle change . . . provides an effective front-line strategy to reduce AF symptoms and provide a potent antiarrhythmic benefit."

The study was funded by grants from the Norwegian Council of Cardiovascular Disease, the Liaison Committee between the Central Norway Regional Health Authority and the Norwegian University of Science and Technology, the KG Jebsen Foundation, and SINTEF Unimed. Malmo, the other study authors, and Elliott report no relevant financial relationships. Disclosures for the coeditorialists are listed in the article.

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