LAUSR

A novel echocardiographic method to non-invasively determine myocardial work based on speckle-tracking derived longitudinal strain and blood pressure has recently been validated and offers new opportunities to study the mechanistic associations. Heart failure patients with prolonged electrical conduction (ie, left bundle branch block) exhibit reduced myocardial global work efficiency (GWE) due to an increase in global wasted work (GWW), which could be improved by biventricular pacing. We here investigated the association of ETI and myocardial work in a non-diseased population. The Characteristics and Course of Heart Failure STAges A/B and Determinants of Progression (STAAB) cohort study carefully characterized a representative sample of the population of a medium-sized town in Germany, aged 30–79 years and free from heart failure. Off-line analysis of the standardized, quality-controlled transthoracic echocardiograms regarding myocardial work yields the following parameters: global constructive work (GCW): work performed during shortening in systole and adding negative work during lengthening in isovolumic relaxation; global wasted work (GWW): negative work performed during lengthening in systole adding work performed during shortening in isovolumic relaxation; and global work efficiency (GWE): GCW/(GCW+GWW). We performed myocardial work analysis in 935 individuals from the sample of the first planned STAAB interim analysis who were in sinus rhythm, had preserved left ventricular ejection fraction and were free from significant valvular disease (51% female, 53±12 years). In linear regression including age, sex, heart rate, and ETI, we found increasing heart rate (64±10 bpm), QRS width (95±12 ms), QT interval (414±28 ms), and PQ interval (164±28 ms) associated with lower GWE (−0.11, −0.02, −0.03, and −0.001, respectively; all p<0.05) and higher GWW (+2.64, +0.29, +0.79, +0.16 mmHg%, respectively; all p<0.05). In subjects free of overt cardiac disease, GWE strongly associated with ETI. Prolonged atrio-ventricular and intra-ventricular coupling and repolarization was associated with an increase in wasted work, while constructive work was not affected. These findings not only suggest a positive effect on myocardial energetics by reducing the heart rate, but also advocate the concept of myocardial work as a bioassay that is responsive to subtle changes. Myocardial work holds promise to be further studied in diseased patient groups. German Ministry of Research and Education within the Comprehensive Heart Failure Centre Würzburg (BMBF 01EO1004 and 01EO1504)