Novel non-invasive left ventricular pressure-strain loop imaging demonstrates reduced myocardial work in cardiomyopathy with significant regional variation in non-ischemic cases

Abstract

Background: Non-invasive left ventricular (LV) pressure-strain loop imaging is a novel method of calculating myocardial work (MW). The total area within the pressure-strain loop represents global MW (Figure1A). Myocardial shortening during systole and lengthening during isovolumic relaxation is classified as constructive work (CW) while myocardial lengthening during systole and shortening during isovolumic relaxation is classified as wasted work (WW).

Purpose: Non-ischemic (CMPN-ISC) and ischemic cardiomyopathy (CMPISC) heart disease etiology influences management, prognosis as well as electromechanical correlates in heart failure. Differences in global MW and regional MW in patients with CMPN-ISC and CMPISC were assessed.

Methods: Strain analysis was performed in 34 patients divided into: 1) Controls (n=10); 2) CMPN-ISC (n=10) (EF<40%; no evidence of significant coronary artery disease); 3) CMPISC (n=14) (EF<40%; coronary artery stenosis) immediately prior to coronary angiography. Dedicated MW software normalized standard LV pressure curves to brachial systolic cuff pressure and isovolumic and ejection duration. MW efficiency (GWE) was derived from the percentage ratio of: CW/(CW+WW). Segmental wasted work between septal and lateral segments were compared between CMPN-ISC and CMPISC.

Results: Significantly higher global MW and GWE (p<0.05) was observed in controls. CMPISC demonstrated the lowest global MW (780mmHg%) but was not significantly different to CMPN-ISC (1054mmHg%). CMPN-ISC WW was significantly higher (p<0.05) compared to CMPISC (259 vs 185 mmHg%). Regional septal WW was significantly higher (p<0.05) in CMPN-ISC (459mmHg%) vs lateral WW (174mmHg%) (Figure1C). There was no significant difference between septal (198mmHg%) and lateral (161mmHg%) WW in CMPISC.