Author + information
- Heiko Stern, MD, PhD,
- Lenika Calavrezos,
- Christian Meierhofer, MD,
- Eva Steinlechner,
- Jan Müller, PhD,
- Alfred Hager, MD, PhD,
- Stefan Martinoff, MD,
- Peter Ewert, MD, PhD and
- Sohrab Fratz, MD, PhD∗ ()
- ↵∗Department of Pediatric Cardiology and Congenital Heart Disease, Deutsches Herzzentrum München, Lazarettstrasse 36, 80636 Munich, Germany.
In patients with aortic regurgitation (AR), exercise testing plays a pivotal role in clinical decision making according to American College of Cardiology/American Heart Association guidelines. However, it is unclear exactly how AR behaves during exercise, as it has only been estimated but not measured so far. Using cardiac magnetic resonance (CMR), it is theoretically possible to measure AR and cardiac volume changes during exercise. Studies in patients with other cardiac diseases have combined exercise and CMR by using complex, cumbersome, and expensive ergometers (1–3).
Therefore, the first aim of this study was to establish a simple and adequate form of exercise during CMR studies. We designed a steady-state submaximal exercise test, because it is known that most hemodynamic changes occur at submaximal exercise levels (4). Additionally, acquiring blood-flow and cardiac-volume data by CMR requires a certain amount of time during a hemodynamic steady-state.
The second aim of this study was to investigate the change of AR and left ventricular (LV) volumes during steady-state submaximal exercise in patients with asymptomatic isolated AR without any cardiac medication.
To this end, we designed and built an exercise apparatus (patent utility no. 202013006749.7) to easily enable steady-state submaximal exercise over longer periods of time during CMR scanning. The apparatus is intrinsically auto-normative, as the workload depends only on the length and weight of the subject's legs, which are attached to a rope passing over a pulley fixed to a specially designed aluminum frame mounted onto the magnetic resonance table. The patients stroke their legs 72 times/min as directed by a metronome.
Healthy volunteers underwent 2 cardiopulmonary tests to determine steady-state submaximal and peak oxygen uptake (VO2) by the new submaximal exercise apparatus and by routine symptom-limited maximal bicycle exercise. Submaximal VO2 was median 24% (range 17% to 37%) of peak VO2 (8.6 ml/kg/min [range 7.2 to 13.7 ml/kg/min] and 40 ml/kg/min [range 33 to 54 ml/kg/min]).
To investigate the change of AR and LV volumes, all healthy volunteers and patients with isolated AR were studied by a standard cardiac 1.5-T CMR scanner during rest and steady-state submaximal exercise. LV end-diastolic and end-systolic volumes and aortic forward and backward flow were measured in a routine fashion, as previously described (5) (Table 1).
In patients with isolated AR, the amount of AR decreased clearly and uniformly during exercise. This finding may impact clinical decision making, because according to American College of Cardiology/American Heart Association guidelines, exercise testing is used as a selection criterion to provoke symptoms during exercise. However, as shown in our study, AR decreases during exercise. Additionally, AR at rest correlated with increase of cardiac index during submaximal exercise (R2 = 0.64; p = 0.001).
We believe that submaximal exercise is an important, but underused, tool to study hemodynamic changes if myocardial perfusion is not the objective, because most hemodynamic changes occur at lower levels of exercise (4). Furthermore, submaximal exercise offers longer observation time and can be tolerated by ill patients.
Please note: Lenika Calavrezos has received a Kaltenbach scholarship from the Deutsche Herzstiftung. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- American College of Cardiology Foundation
- Holverda S.,
- Rietema H.,
- Westerhof N.,
- et al.
- Astrand P.O.,
- Cuddy T.E.,
- Saltin B.,
- Stenberg J.