CHD patients do not need to rule out high-intensity exercise

By Ingrid Grasmo, medwireNews Reporter

Findings from a retrospective study show that patients with coronary heart disease (CHD) who engage in high-intensity exercise have a similarly low risk for a cardiovascular event as those engaging in moderate-intensity exercise.

The findings are important as exercise performed at higher relative intensities has been shown to elicit greater increases in aerobic capacity and cardioprotective effects than moderate continuous training (MCT). However, concerns exist surrounding vigorous exercise and the associated increased acute risk for sudden cardiac death and myocardial infarction in susceptible individuals.

In a commentary accompanying the report in Circulation, Steven Keteyian (Henry Ford Hospital, Detroit, Michigan, USA) says the findings should be considered preliminary, given that the study is underpowered to accurately determine the safety of high-intensity interval training (HIIT). In addition, patients were not prospectively randomized so it is not possible to determine the isolated effect of HITT on safety.

"[The study] highlights that more work remains relative to better understanding the nature and scope of exercise training in the care of patients with cardiovascular disease," says Keteyian.

Analysis of data from 4846 CHD patients from four Norwegian cardiac rehabilitation centers who completed a total of 175,820 combined high- and moderate-exercise training hours revealed one fatal cardiac arrest per 129,456 exercise hours of MCT and two nonfatal cardiac arrests during 46,364 hours of HIIT.

HIIT consisted of a warm-up for a minimum of 10 minutes at 60-70% peak heart rate (PHR) before working for four 4-minute intervals at 85-95% PHR. During the moderate exercise sessions, patients worked continuously at an intensity at or below 70% PHR.

No myocardial infarctions were observed among any of the patients in the study.

Given that the number of HIIT hours was 36% of the total number of MCT hours, complication rates were calculated as one per 129,456 MCT hours and one per 23,182 HIIT hours.

"When considering earlier indications that adaptation in exercise capacity and cardiac function show a dose-response relationship, or display an intensity-threshold for adaptation to occur, HIIT should be considered in future rehabilitation programs among CHD patients," say Øivind Rognmo (Norwegian University of Science and Technology [NTNU], Trondheim, Norway) and colleagues.

However, Keteyian says the findings also show that MCT is potentially safer than HIIT given the relatively lower complication rate for MCT.

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