The heart as a spring, the measurement of myocardial bounce to assess left ventricular function on cardiac MR

Abstract

Little has been reported on the left ventricular myocardial distension (bounce) and its utility to assess cardiac function. The purpose of this study is to determine whether myocardial bounce at end diastole is reproducibly visualized by blinded observers and to determine whether it corresponds to systolic and diastolic function. 144 Consecutive cardiac MR exams between September and December 2017 were selected for analysis. The bounce was graded by two blinded observers, and the change in LV diameter pre and post bounce was measured. The bounce was defined as the rapid change in LV volume that occurs at the end of diastole during atrial contraction just prior to systolic ejection. Inter-reader agreement was summarized using Cohen's kappa. Spearman's rank correlation coefficient was used to evaluate associations between bounce grade and cardiac physiology parameters. Overall agreement was good with unweighted kappa = 0.69 (95% CI 0.60-0.79). Bounce grade was significantly correlated with the average change in LV diameter before and after the bounce (Spearman's rho = 0.76, p < 0.001). Median diameter changes were 0.0, 1.9, and 4.2 mm in grades 0 (no bounce), 1 (small bounce), and 2 (normal), respectively. The bounce lasted 8 to 12 ms in all patients. Bounce grade was significantly correlated with LV EF (Spearman's rho = 0.43, p < 0.001). Median EF was 44%, 51%, and 58% in grades 0, 1, and 2, respectively. Of the 87 patients who had E/A ratio or E/e' ratio measured, bounce grade was also significantly correlated with E/A ratio (r = - 0.24, p = 0.034) and E/e' ratio (r = - 0.24, p = 0.022), with lower grades having higher ratio values on average (Table 4). Of the 15 patients with a bounce grade of 0 by one or both readers and EF ≥ 50%, 8 had E/A ratio measurements and 7 had E/e' ratio measurements. The E/A ratio values ranged from 1 to 2.7 (median 1.5). The E/e' ratio values ranged from 4.8 to 9.6 (median 7.7). The simple observation of a normal myocardial bounce during cine loop review of cardiac MR exams was predictive of normal diastolic and systolic cardiac function. Lack of myocardial bounce was highly associated with both systolic and diastolic dysfunction. The subpopulation of patients with loss of myocardial bounce and normal ejection fraction appear to represent patients with early diastolic dysfunction. Further studies with more diastolic dysfunction MRs are needed to examine this relationship. This study suggests changes to the myocardial bounce seen on cardiac MR may be a simple useful tool for detecting cardiac dysfunction. This study is not to replace, but rather aid the clinical diagnosis and management of both diastolic and systolic dysfunction.

Keywords: Assessment of cardiac function; Cardiac MRI; Diagnosis and management of systolic and diastolic dysfunction; Heart failure; Myocardial bounce; Systolic and diastolic function.