Investigating the potential of the isometric handgrip exercise as a test of cardiovascular reactivity to blood pressure fluctuations

BACKGROUND: In the perioperative setting, blood-pressure fluctuations can cause adverse outcomes, underscoring the need to identify vulnerable patients preoperatively. Imaging-based cardiovascular diagnostic tests are rapidly evolving, yet few are developed with anaesthesia in mind. This highlights an opportunity to develop techniques that evaluate the cardiovascular response to changes in blood pressure, but early feasibility studies in healthy controls are needed before clinical application. In combination with cardiovascular magnetic resonance (CMR) imaging, the isometric handgrip test has the potential to comprehensively assess how the heart and ascending aorta respond to transiently elevated blood pressure. We investigated the effect of an isometric handgrip exercise on myocardial tissue features with atrial, ventricular, and aortic function and coupling in healthy adults, assessed by CMR. METHODS: In a single-centre observational study, 45 healthy adults underwent a CMR exam. Following acquisition of non-invasive blood pressure as well as cardiac and aortic rest images, participants sustained a grip of a dynamometer at 30% of their maximal strength. After a 2.5 min adjustment period, identical images were acquired. Myocardial blood volume and oxygenation were measured using parametric mapping and oxygenation-sensitive imaging. Furthermore, aortic function was assessed via vascular strain and flow parameters, while atrial and ventricular function were assessed through long-axis shortening. Coupling was calculated from atrial, ventricular and aortic parameters. RESULTS: The isometric handgrip exercise improved left ventricular and left atrial systolic (-18.4±2.6% to -19.3±3.3%, p < 0.05 and 36.2±6.4% to 39.6±7.9%, p < 0.01) and late diastolic function (4.4 ± 1.7% to 5.1 ± 1.6%, p = 0.04 and -11.5 ± 4.5% to -14.8 ± 5.3%, p < 0.01), assessed by long-axis shortening. Aortic strain, reflecting vascular elasticity, decreased (31.0±11.3% to 26.1±12.3%, p < 0.01). The ventricular-arterial systolic coupling index dropped (31.0 ± 11.3% to 26.1 ± 12.3%, p < 0.01), while atrio-ventricular coupling remained unchanged. While myocardial blood volume did not change (T1: 1193±25ms to 1194±22ms, p = 0.77), myocardial oxygenation decreased (-2.9% [95%CI: -4.4, -1.3], p = 0.02). CONCLUSIONS: The isometric handgrip exercise effectively increased afterload and elicited augmented cardiovascular function and myocardial oxygen demand in healthy adults. Our data demonstrate the physiological changes expected from increased afterload in healthy hearts. Future studies in patient cohorts are warranted to investigate if it has potential as diagnostic tool for preoperative stress testing.