Objectives: This study aimed to assess the feasibility and diagnostic accuracy of a dynamic handgrip exercise (DHE) stress test to induce ischemia-related wall motion abnormalities detected by fast strain-encoded (fSENC) cardiac magnetic resonance (CMR).

Background: Pharmacological stress CMR is a well-established diagnostic tool for the non-invasive detection of myocardial ischemia. DHE as a promising physiologic maneuver may however represent a viable, cheaper and safer alternative to pharmacological stressors. Combined with different imaging modalities, the utility of DHE for the detection of myocardial ischemia has been recently demonstrated. fSENC allows for the rapid assessment of segmental myocardial strain with a high sensitivity. We therefore hypothesized that fSENC after DHE may accurately identify significant stenosis in patients with suspected or known coronary artery disease (CAD). 

Methods: We prospectively enrolled patients with suspected or known CAD to undergo an extended stress CMR protocol applying fSENC following a DHE for 2 minutes. Quantitative coronary angiography served as the reference standard. Luminal narrowing of either >50% in left main/proximal LAD or >90% in any other vessel was defined as significant stenosis. Longitudinal strain was quantified in fSENC images at rest and after DHE. Results were visualised in colour-coded maps. Rest and DHE fSENC-maps were directly compared to identify a subendocardial impairment of strain.

Results: In total, 106 predominantly male patients were included (67.7 ± 10.4 years, 83.0% men). DHE was safely completed by all patients and did not cause any major side effects. 15 patients (14.2%) reported muscular fatigue in their forearms and/or hands. GLS increased significantly after DHE (rest: -17.9 ± 2.7%; HG: -18.7 ± 3.0%; p < 0.001). Furthermore, the response of segmental longitudinal strain to DHE was significantly different between non-ischemic and ischemic segments (LS-non-ischemic: -0,8 ± 3,6%, LS-ischemic: 3,4 ± 3,9%; p < 0,001). Coronary angiography revealed 43 patients (41.0%) with significant lesions. fSENC performed after DHE correctly identified inducible ischemia in 36 of these patients thus providing a high diagnostic accuracy (sensitivity 81.8% [67-92], specificity 88.7% [78-95], positive predictive value 83.7% [72-91]; negative predictive value 87.3% [79-93]).

Conclusions: DHE-fSENC appears to be a safe and feasible drug and needle-free stress test with a high diagnostic accuracy in the detection of significant coronary artery stenosis.