Non-invasive CMR-Based Quantification of Myocardial Power and Efficiency Under Stress and Ischemic Conditions in Landrace Pigs

Background: Myocardial efficiency should be maintained stable under light-to-moderate stress conditions, but ischemia puts the myocardium at risk for impaired functionality. Additionally, the measurement of such efficiency typically requires invasive heart catheterization and exposure to ionizing radiation. In this work, we aimed to non-invasively assess myocardial power and the resulting efficiency during pharmacological stress testing and ischemia induction.Methods: In a cohort of n = 10 healthy Landrace pigs, dobutamine stress testing was performed, followed by verapamil-induced ischemia alongside cardiac magnetic resonance (CMR) imaging. External myocardial power, internal myocardial power, and myocardial efficiency were assessed non-invasively using geometrical and functional parameters from CMR volumetric as well as blood flow and pressure measurements.Results: External myocardial power significantly increased under dobutamine stress [2.3 (1.6–3.1) W/m2 vs. 1.3 (1.1–1.6) W/m2, p = 0.005] and significantly decreased under verapamil-induced ischemia [0.8 (0.5–0.9) W/m2, p = 0.005]. Internal myocardial power [baseline: 5.9 (4.6–8.5) W/m2] was not affected by dobutamine [7.5 (6.9–9.0) W/m2, p = 0.241] nor verapamil [5.8 (4.7–8.8) W/m2, p = 0.878]. Myocardial efficiency did not change from baseline to dobutamine [21% (15–27) vs. 31% (20–44), p = 0.059] but decreased significantly during verapamil-induced ischemia [10% (8–13), p = 0.005].Conclusion: In healthy Landrace pigs, dobutamine stress increased external myocardial power, whereas myocardial efficiency was maintained stable. On the contrary, verapamil-induced ischemia substantially decreased external myocardial power and myocardial efficiency. Non-invasive CMR was able to quantify these efficiency losses and might be useful for future clinical studies evaluating the effects of therapeutic interventions on myocardial energetics.

Seasonal Organization of Haemodynamics in Skiers with Sports Ranks Living in the Arctic Zone of the Russian Federation

This paper analyses the results of a correlation analysis of haemodynamic parameters in 38 male skiers with the ranks of First- and Second-Class Sportsman aged between 18 and 22 years. Stroke volume, heart rate, cardiac output, myocardial efficiency index, myocardial stress index, left ventricular power index, and total peripheral resistance were determined 4 times a year (autumn, winter, spring and summer). It was found that not only the haemodynamic parameters, but also the connections between them change during the year. For instance, in skiers with sports ranks, stroke volume prevails in the structure of cardiac output, especially in autumn and winter, which indicates a significant chronotropic reserve of the cardiovascular system. Myocardial efficiency index is provided by the value of stroke volume. A correlation between myocardial efficiency index and left ventricular power index in skiers can be observed in autumn and, especially, in winter. The value of total peripheral resistance negatively affects cardiac output, stroke volume, myocardial stress index, heart rate, and left ventricular power index.

How to measure left ventricular myocardial work by pressure–strain loops

Myocardial work is calculated from non-invasive left ventricular pressure and strain by speckle tracking echocardiography. Myocardial work provides diagnostic information beyond what is achieved from left ventricular ejection fraction and strain since it incorporates afterload, and provides a measure of myocardial efficiency. The method can be used to calculate global as well as segmental work. The work method was recently shown to be of clinical value in selection of patients for cardiac resynchronization therapy. Several other clinical applications are currently tested.

Acute response to cardiac re-synchronization therapy: ventricular properties adaptation?

Background Cardiac re-synchronization therapy (CRT) reduces mortality and hospitalization in patients with heart failure, reduced left ventricular ejection fraction (LVEF) and left bundle branch block (LBBB). However, there is no conclusive evidence on baseline parameters able to discriminate responder vs non-responder patients. Purpose In this study, we tested whether echocardiographic parameters describing LV dyssynchrony and efficiency may predict an acute LV recovery after CRT and whether lead position can modify such relationship. Methods We enrolled 65 consecutive patients (75% males, aged 71.2±10.5 years) referred for CRT according to current guidelines; 45% had an underlying ischaemic cardiopathy and 1/3 of them presented diabetes mellitus. We performed a CRT-off and CRT–on 2D and 3D echocardiography during devices optimization (time between programming change 10/12 min). We evaluated ventricular dyssynchrony by speckle-tracking analysis based on temporary uniformity of strain (TUS) 3D longitudinal and circumferential. We also derived non-invasive myocardial efficiency (Effic) by interaction between pressure work index (PWI), representing an estimation of myocardial oxygen consumption, and mechanical external work. We indicated as concordant those patients presenting a LV lead position (defined from a chest X-ray using 2 orthogonal views) in the same segment as the latest systolic 3D circumferential strain curves. Results In the CRT-on phase, a non-statistically significant raise in LVEF was observed [from 0.37 (0.28–0.46) to 0.41 (0.34–0.47), p=0.27]. No improvement in both longitudinal and circumferential 3D TUS was demonstrated during CRT-on (p=0.44 and 0.47, respectively). Conversely, the gain in Effic from CRT-off to CRT-on phase was overall significant (from 0.43±0.14 to 0.50±0.16; p<0.001). After switching to CRT-on, the increase in longitudinal 3D TUS was higher in concordant compared to discordant patients (from 0.83±0.08 to 0.87±0.07 vs 0.88±0.11 to 0.87±0.12, respectively), but without significant interaction (interaction p 0.24). No interaction was also found between variations of PWI after switching to CRT-on and LV lead position (concordant: from 12.99±4.18 to 12.84±2.99 ml/min/100g; discordant: from 13.58±3.89 to 13.95±3.97 ml/min/100g; interaction p 0.75). Conclusions Effic was overall acutely augmented during CRT-on phase in patients with LV dysfunction undergoing cardiac re-synchronization. In the acute phase, no significant relationship between LV changes in speckle-tracking analyses after CRT and LV lead position was found. 2-way ANOVA for myocardial efficiency Funding Acknowledgement Type of funding source: None

559 An analysis of myocardial efficiency in patients with severe asymptomatic mitral regurgitation

Funding Acknowledgements None declared. Background and Aims It is difficult to determine left ventricular systolic performance in patients with severe mitral regurgitation (MR) since left ventricular ejection fraction (EF) could be preserved until the end stages of the disease. Myocardial efficiency describes the amount of external work (EW) done by the left ventricle per unit of oxygen consumed (mVO2). In the present study, we aimed to investigate MEf in patients with asymptomatic severe MR using a novel echocardiographic method. Methods: A total of 27 patients with severe asymptomatic MR and 26 healthy volunteers were included in this cross-sectional study. EW was measured using stroke volume and blood pressure, while mVO2 was estimated using double product and LV mass. Results: There were no differences between the groups with regards to EF (66%±5% vs. 69%±7%), while MEf was significantly reduced in patients with severe MR (25%±11% vs. 44%±12%, p < 0.001) (Table 1). This difference was maintained even after adjustment for age, gender and body surface area (adjusted :0.44, 95%CI: 0.39–0.49 for controls and adjusted :0.24, 95%CI: 0.19–0.29 for patients with severe MR). Further analysis showed that this reduction was due to an increase in total mVO2 in the severe MR group (Figure 1). Conclusions: Myocardial efficiency was significantly lower in patients with asymptomatic severe MR and preserved EF. Table 1 Parameter Control Group (n = 26) Severe Mitral Regurgitation (n = 27) P Value Age (y) 36.5 ± 8.9 41.3 ± 14.2 0.23 Gender (%Male) 9 (35%) 10 (37%) 1.0 BSA (m2) 1.82 ± 0.20 1.76 ± 0.18 0.64 LV End-Diastolic Volume (ml) 83.13 ± 18.88 121.91 ± 37.63 <0.001 LV End-Systolic Volume (ml) 28.07 ± 9.57 45.30 ± 17.42 <0.001 Left Ventricular Ejection Fraction (%) 0.69 ± 0.07 0.66 ± 0.05 0.29 Systolic Mitral Velocity (cm/s) 7.88 ± 1.14 8.07 ± 1.81 0.66 Stroke Work (j) 1.14 ± 0.21 1.15 ± 0.36 0.91 Minute External Work (j) 65.96 ± 14.71 70.17 ± 23.15 0.85 mVO2 (ml.min-1.100g-1) 6.79 ± 1.93 9.48 ± 4.71 0.02 Total mVO2 (j) 166.58 ± 77.14 346.46 ± 202.71 <0.001 Myocardial Efficiency (%) 44 ± 12 25 ± 11 <0.001 Table 1. Demographic, anthropometric, echocardiographic and mechanoenergetic data for study groups. BSA, body surface area; LV, left ventricle; mVO2, myocardial oxygen consumption. Abstract 559 Figure 1