Myocardial Work Index: A Marker of Left Ventricular Contractility in Pressure- or Volume Overload-Induced Heart Failure

Figure 1. (A) Morphological features of the study groups measured by echocardiography. Upper panel: Representative 2D echocardiographic images of the two heart failure models and a Sham‐operated animal (red lines: myocardial wall thickness, white lines: end‐diastolic diameter). While the left ventricular (LV) end‐diastolic diameter was markedly enlarged in aortocaval fistula (ACF, n = 12) group, it was only mildly increased in transverse aortic constriction (TAC, n = 12) compared to their corresponding control (Shama and Shamt, n = 12/12). The relative wall thickness was decreased in ACF, while it was increased in TAC. LV fractional shortening was significantly lower in both HF groups. On the other hand, LV ejection fraction was maintained in ACF, while it was significantly lower in TAC compared to their corresponding Sham. [Statistics: Student's unpaired t‐test]. (b) Markers of left ventricular (LV) fibrosis and wall stress. Upper panel: Representative histological samples of the two heart failure models and a Sham‐operated animal. The area of interstitial and perivascular fibrosis was unaltered in the aortocaval fistula (ACF, n = 6) model compared to its Sham operated control (Shama, n =…

Figure 2. Left ventricular (LV) functional parameters. (A) Representative pressure‐volume loops of the study groups. Preload recruitable stroke work, a load‐independent marker of contractility, showed distinct changes in haemodynamic overload states: aortocaval fistula (ACF, n = 12) demonstrated significantly deteriorated values, while the transverse aortic constriction (TAC, n = 12) group had maintained LV contractility. (b) In contrast with these findings, global longitudinal strain was only mildly decreased in the ACF group while it was markedly lower in TAC compared with their corresponding sham (Shama and Shamt, n = 12/12). (c) Representative pressure‐strain loops of the study groups. The changes of global myocardial work index (GMWI) showed a pattern resembling to PRSW: in ACF, GMWI was significantly lower, while it was preserved in TAC compared with their control. [Statistics: Student's unpaired t‐test].

Figure 3. Correlation of left ventricular (LV) contractility and LV deformation parameters. Global longitudinal strain (GLS) did not correlate with preload recruitable stroke work (PRSW). Conversely, global myocardial work index (GMWI) demonstrated strong correlation with PRSW, a gold standard load‐independent parameter of LV contractility in the pooled study population (n = 48). [Statistics: Pearson's correlation coefficient analysis].

Figure 4. Correlation between global longitudinal strain (GLS) and markers of LV wall stress and fibrosis. GLS showed a significant correlation with atrial natriuretic peptide (ANP; n = 24) as well as area of myocardial interstitial fibrosis (n = 39) in the pooled study population. [Statistics: Pearson and Spearman correlation coefficient analysis].