Cardiac function and myocardial perfusion immediately following maximal treadmill exercise inside the MRI room

Abstract

Treadmill exercise stress testing is an essential tool in the prevention, detection, and treatment of a broad spectrum of cardiovascular disease. After maximal exercise, cardiac images at peak stress are typically acquired using nuclear scintigraphy or echocardiography, both of which have inherent limitations. Although CMR offers superior image quality, the lack of MRI-compatible exercise and monitoring equipment has prevented the realization of treadmill exercise CMR.It is critical to commence imaging as quickly as possible after exercise to capture exercise-induced cardiac wall motion abnormalities. We modified a commercial treadmill such that it could be safely positioned inside the MRI room to minimize the distance between the treadmill and the scan table. We optimized the treadmill exercise CMR protocol in 20 healthy volunteers and successfully imaged cardiac function and myocardial perfusion at peak stress, followed by viability imaging at rest. Imaging commenced an average of 30 seconds after maximal exercise. Real-time cine of seven slices with no breath-hold and no ECG-gating was completed within 45 seconds of exercise, immediately followed by stress perfusion imaging of three short-axis slices which showed an average time to peak enhancement within 57 seconds of exercise. We observed a 3.1-fold increase in cardiac output and a myocardial perfusion reserve index of 1.9, which agree with reported values for healthy subjects at peak stress. This study successfully demonstrates in-room treadmill exercise CMR in healthy volunteers, but confirmation of feasibility in patients with heart disease is still needed.

Low Cost Magnetic Resonance Imaging-Compatible Stepper Exercise Device for Use in Cardiac Stress Tests

“…Using a treadmill near the MRI, Jekic et al demonstrated a threefold increase in CO with exercise in healthy volunteers [16]. The main drawback of this treadmill system is the repositioning time between the exercise and imaging, which allows significant heart rate recovery in healthy subjects.…”

“…The response of cardiac hemodynamics to exercise stress has been previously studied with MRI [16,[24][25][26]. Using a treadmill near the MRI, Jekic et al demonstrated a threefold increase in CO with exercise in healthy volunteers [16].…”

“…In the context of MRI imaging, physical exercise stress poses significant challenges due to the limited space in the cylindrical cavity of the MR machine in which imaging takes place (the bore), the horizontal position of the subject during imaging, incompatibility of standard exercise equipment with the strong magnetic fields required for MR imaging and the sensitivity of MRI to motion artifacts. Therefore, most MRI-based physical exercise stress tests to date have used a paradigm in which exercise is performed outside of the MRI bore with a bicycle or treadmill; when the target level of exercise is reached, the subject stops exercising, relocates to a supine position on the MR table and is advanced into the bore for imaging [16,17]. The time lapse between exercising and imaging often allows for the subject's heart rate and CO to recover, especially for subjects with close to normal cardiac function.…”

Comparison of three artificial models of the magnetohydrodynamic effect on the electrocardiogram

“…Effective methods to produce a diagnostic quality ECG would be of great clinical benefit. There are three main applications during which this knowledge is useful: 1) MRI guided surgery (McVeigh et al 2006; Saikus and Lederman 2009; Lederman 2005; George et al 2011), 2) intracardiac electrophysiology (Susil et al 2002) and 3) stress testing by MRI (Cheng et al 2005; Jekic et al 2008, 2010). However, in order to develop a tool which can provide a useful ECG during MRI, realistic models of the MHD effect are required.…”

Diagnostic Performance of Treadmill Exercise Cardiac Magnetic Resonance: The Prospective, Multicenter Exercise CMR's Accuracy for Cardiovascular Stress Testing (EXACT) Trial

“…9 Our group recently developed a completely MR-compatible treadmill system that can be placed immediately next to the MR scanner table, minimizing the time to stress CMR image acquisition. 10,11 Although single-center data suggest feasibility of in-room exercise CMR, 12,13 prospective evaluation in a multicenter trial including both community and academic practices has been lacking. In this work we evaluated the diagnostic performance of exercise stress testing by CMR compared to SPECT as the reference standard with additional comparison to coronary angiography.…”