Abstract
BackgroundMyocardial energetic efficiency (MEE), is a strong predictor of CV events in hypertensive patient and is reduced in patients with diabetes and metabolic syndrome. We hypothesized that severity of insulin resistance (by HOMA-IR) negatively influences MEE in participants from the Strong Heart Study (SHS).MethodsWe selected non-diabetic participants (n = 3128, 47 ± 17 years, 1807 women, 1447 obese, 870 hypertensive) free of cardiovascular (CV) disease, by merging two cohorts (Strong Heart Study and Strong Heart Family Study, age range 18–93). MEE was estimated as stroke work (SW = systolic blood pressure [SBP] × stroke volume [SV])/“double product” of SBP × heart rate (HR), as an estimate of O2 consumption, which can be simplified as SV/HR ratio and expressed in ml/sec. Due to the strong correlation, MEE was normalized by left ventricular (LV) mass (MEEi).ResultsLinear trend analyses showed that with increasing quartiles of HOMA-IR patients were older, more likely to be women, obese and hypertensive, with a trend toward a worse lipid profile (all p for trend < 0.001), progressive increase in LV mass index, stroke index and cardiac index and decline of wall mechanics (all p < 0.0001). In multivariable regression, after adjusting for confounders, and including a kinship coefficient to correct for relatedness, MEEi was negatively associated with HOMA-IR, independently of significant associations with age, sex, blood pressure, lipid profile and central obesity (all p < 0.0001).ConclusionsSeverity of insulin resistance has significant and independent negative impact on myocardial mechano-energetic efficiency in nondiabetic individual from a population study of American Indians.Trial registration number NCT00005134, Name of registry: Strong Heart Study, URL of registry: https://clinicaltrials.gov/ct2/show/NCT00005134, Date of registration: May 25, 2000, Date of enrolment of the first participant to the trial: September 1988
Highlights
Myocardial energetic efficiency (MEE), is a strong predictor of CV events in hypertensive patient and is reduced in patients with diabetes and metabolic syndrome
We developed a simple method for non-invasive, ultrasound-guided estimation of myocardial mechano-energetic efficiency per gram of Left ventricular (LV) mass (MEEi), which has been prognostically validated [4, 5]
This study demonstrates that in non-diabetic participants of the Strong Heart Study (SHS) cohort with normal ejection fraction and free of prevalent CV disease, insulin resistance is a significant contributor of the variance of myocardial mechano-energetic efficiency per gram of LV mass
Summary
Myocardial energetic efficiency (MEE), is a strong predictor of CV events in hypertensive patient and is reduced in patients with diabetes and metabolic syndrome. Cuff systolic blood pressure (SBP) may be used as a surrogate of peak-systolic pressure, under the assumption that the kinetic energy is negligible at least in resting conditions. The efficiency of the left ventricle in pumping blood into the arterial tree (LV pump performance) may be defined as the ratio between the developed external work (i.e. SW) and the amount of energy produced for each contraction [2]. The ratio between external work delivered by cardiomyocytes and the amount of total energy produced at each beat is, a measure of myocardial mechano-energetic efficiency (MEE)
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