Low myocardial energetic efficiency is associated with increased mortality in aortic stenosis

Impact of Metabolic Syndrome on Left Ventricular Deformation and Myocardial Energetic Efficiency Compared Between Women and Men: An MRI Study

BACKGROUND

Metabolic and hemodynamic alterations in metabolic syndrome (MetS) can cause a reduced myocardial energetic efficiency (MEE). Indexed MEE (MEEi), as a simple estimate of MEE, is emerging as a novel and useful imaging parameter.

PURPOSE

To investigate the impact of MetS on MEE and systolic myocardial strain and to assess any sex difference.

STUDY TYPE

Retrospective.

POPULATION

A total of 161 patients with MetS (female: n = 82, 52.2 ± 11.7 years; male: n = 79, 51.8 ± 10.6 years) and 77 healthy subjects (female: n = 46, 52.7 ± 8.2 years; male: n = 31, 54.1 ± 11.2 years). Patients with left ventricular (LV) ejection fraction <50% were excluded.

FIELD STRENGTH/SEQUENCE

A 3.0 T; balanced steady-state free precession sequence.

ASSESSMENT

LV volumes and mass (LVM) and global longitudinal strain (GLS) were obtained by MRI. Stroke volume (SV) divided by HR was used as a surrogate measure of MEE and normalized to LVM (MEEi).

STATISTICAL TESTS

Student's t-test or Mann-Whitney U-test; Multivariable linear regression (coefficient of determination, R² ). P < 0.05 was considered statistically significant.

RESULTS

For both males and females, MEEi and GLS were lower in MetS patients than in the normal controls. Among MetS patients, men had significantly higher LVM (59.7 ± 13.4 g/m² vs. 48.8 ± 11.3 g/m² ) and significantly lower MEEi (0.68 ± 0.23 mL/g/s vs. 0.84 ± 0.23 mL/g/s) and GLS (-11.7% ± 2.8% vs. -13.9% ± 2.7%) than women. After adjustment for clinical variables, male gender (β = -0.291) was found to be inversely correlated with MEEi. Multivariable analysis showed that MEEi (β = 0.454) were independently associated with GLS (adjusted R²  = 0.454) after adjustment for clinical and other MRI parameters.

DATA CONCLUSION

MEEi was significantly impaired in MetS without overt systolic dysfunction. There was a sex difference regarding the cardiac alterations in MetS, with men having significantly lower MEEi and GLS and significantly higher LVM than women. Further, MEEi was independently associated with GLS.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 3.

Determinants of improvement of left ventricular mechano-energetic efficiency in hypertensive patients

Background

Arterial hypertension, especially when coexisting with other cardiovascular risk factors, could determine an imbalance between myocardial energetic demand and altered efficiency, leading to an early left ventricular (LV) systolic dysfunction, even in terms of echo-derived mechano-energetic efficiency indexed for myocardial mass (MEEi). We aim to analyse an improvement in LV MEEi, if any, in a population of hypertensive patients with a long-term follow-up and to identify clinical, metabolic and therapeutic determinants of LV MEEi amelioration.

Materials and methods

In total, 7,052 hypertensive patients, followed-up for 5.3 ± 4.5 years, enrolled in the Campania Salute Network, underwent echocardiographic and clinical evaluation. LV MEEi was obtained as the ratio between stroke volume and heart rate and normalized per grams of LV mass and ΔMEEi was calculated as difference between follow-up and baseline MEEi. Patients in the highest ΔMEEi quartile (≥0.0454 mL/s/g) (group 1) were compared to the merged first, second and third quartiles (<0.0454 mL/s/g) (group 2). METS-IR (Metabolic Score for Insulin Resistance), an established index of insulin sensitivity, was also derived.

Results

Patients with MEEi improvement experienced a lower rate of major cardiovascular events (p = 0.02). After excluding patients experiencing cardiovascular events, patients in group 1 were younger (p < 0.0001), less often diabetic (p = 0.001) and obese (p = 0.035). Group 1 experienced more frequently LV mass index reduction, lower occurrence of LV ejection fraction reduction, and had a better metabolic control in terms of mean METS-IR during the follow-up (all p < 0.0001). Beta-blockers were more often used in group 1 (p < 0.0001) than group 2. A logistic regression analysis showed that younger age, lower mean METS-IR values, more frequent LV mass index reduction and therapy with beta-blockers were significantly associated with LV MEEi improvement, independently of presence of diabetes and obesity.

Conclusion

Metabolic control and therapy with beta-blockers could act in a synergic way, determining an improvement in LV MEEi in hypertensive patients over time, possibly confining cardiac damage and hampering progression toward heart failure.

Physiologic Range of Myocardial Mechano-Energetic Efficiency among Healthy Subjects: Impact of Gender and Age

BACKGROUND

Myocardial mechano-energetic efficiency (MEE) is the capability of the left ventricle (LV) to convert the chemical energy obtained from the cardiac oxidative metabolism into mechanical work. The aim of present study was to establish normal non-invasive MEE and MEEi reference values.

METHODS

In total, 1168 healthy subjects underwent physical examinations, clinical assessment, and standardized transthoracic echocardiographic (TTE) examination. MEE was obtained by TTE as the ratio between stroke volume (SV) and heart rate (HR): MEE = SV/HR [HR expressed in seconds (HR/60)]. Because MEE is highly related to left ventricular mass (LVM), MEE was then divided by LVM with the purpose of obtaining an estimate of energetic expenditure per unit of myocardial mass (i.e., indexed MEE, MEEi, mL/s/g).

RESULTS

The mean values of MEE and MEEi in the overall population were 61.09 ± 18.19 mL/s; 0.45 ± 0.14, respectively. In a multivariable analysis, gender, body surface area (BSA), diastolic blood pressure, left atrial volume indexed to BSA, E/e' and tricuspid annular plane systolic excursion (TAPSE) were the independent variables associated with MEE, while age, gender, BSA and TAPSE were the independent variables associated with MEEi.

CONCLUSIONS

The knowledge of age- and gender-based MEE and MEEi normal values may improve the global assessment of LV cardiac mechanics and serve as a reference to identify phenotypes at high risk of cardiovascular events.

Low mechano-energetic efficiency is associated with future left ventricular systolic dysfunction in hypertensives

Aims

In a hypertensive population with optimal blood pressure control with a long‐term follow‐up, we aimed at analysing possible predictors of left ventricular (LV) ejection fraction (LVEF) reduction, including indexed mechano‐energetic efficiency (MEEi), a well‐recognized echo‐derived parameter of LV performance.

Methods and results

The study population included 5673 hypertensive patients from the Campania Salute Network with a long‐term follow‐up, normal baseline LVEF (≥50%), and no prevalent cardiovascular (CV) disease. Patients developing LVEF impairment (LVEF < 50% or a reduction of at least 10 percentage points compared with baseline) were compared with patients with persistently normal LVEF. Optimal blood pressure control was achieved in about 80% of patients. Patients who experienced LVEF reduction were 2.41% during a long‐term follow‐up (mean duration 5.6 ± 3.9 years). At baseline, they were older (59.46 ± 11.58 vs. 53.40 ± 11.41, P < 0.0001) and showed higher LV mass index (53.3 ± 12.83 vs. 47.56 ± 9.58, P < 0.0001), left atrial (LA) volume index (14.4 ± 4.2 vs. 13.1 ± 2.8, P < 0.0001) and carotid intima–media thickness (1.99 ± 0.86 vs. 1.61 ± 0.73, P < 0.0001), lower MEEi (0.32 ± 0.08 vs. 0.34 ± 0.07, P = 0.037), and higher prevalence of CV events during follow‐up (13.9% vs. 3%, P < 0.0001) compared with patients with persistently normal LVEF. A logistic regression analysis, performed after running univariate analyses and selecting parameters significantly associated with LVEF reduction, showed that having a CV event [odds ratio (OR) 7.57, P < 0.0001], being in the lowest MEEi quartile (OR 2.43, P = 0.003), and having a larger LA volume index (OR 1.08, P = 0.028) were all parameters independently associated with the development of LV systolic dysfunction. A further logistic regression model, performed by excluding patients experiencing CV events, demonstrated that the lowest MEEi quartile was independently associated with the evolution towards LVEF reduction (OR 2.35, P = 0.004), despite significant impact of LA volume index (OR 1.08, P = 0.023) and antiplatelet therapy (OR 1.89, P < 0.01). Receiver operating characteristic curves showed that the model including MEEi had higher accuracy than the model without MEEi in predicting LVEF reduction (areas under the curve 0.68 vs. 0.63, P = 0.046).

Conclusions

Lower values of MEEi at baseline identify hypertensive patients more liable to develop LVEF reduction. In hypertensive setting, MEEi evaluation improves risk stratification for development of LV systolic dysfunction during long‐term follow‐up.