Regional LV deformation in healthy individuals during isovolumetric contraction and ejection phases assessed by 2D speckle tracking echocardiography

Functional control of myosin motors in the cardiac cycle

Contraction of the heart is driven by cyclical interactions between myosin and actin filaments powered by ATP hydrolysis. The modular structure of heart muscle and the organ-level synchrony of the heartbeat ensure tight reciprocal coupling between this myosin ATPase cycle and the macroscopic cardiac cycle. The myosin motors respond to the cyclical activation of the actin and myosin filaments to drive the pressure changes that control the inflow and outflow valves of the heart chambers. Opening and closing of the valves in turn switches the myosin motors between roughly isometric and roughly isotonic contraction modes. Peak filament stress in the heart is much smaller than in fully activated skeletal muscle, although the myosin filaments in the two muscle types have the same number of myosin motors. Calculations indicate that only ~5% of the myosin motors in the heart are needed to generate peak systolic pressure, although many more motors are needed to drive ejection. Tight regulation of the number of active motors is essential for the efficient functioning of the healthy heart - this control is commonly disrupted by gene variants associated with inherited heart disease, and its restoration might be a useful end point in the development of novel therapies.

Abnormal left ventricular global strain during exercise-test in young healthy smokers

Background. It is unknown how much precociously the cigarette smoking (CS) may compromise the integrity of the cardiovascular (CV) system. Myocardial function can be routinely assessed by conventional echocardiography, but abnormalities are only detected when somewhat a remodelling has already occurred. These limitations could be overcome by strain imaging. Methods. We evaluated whether young smokers with normal left ventricular (LV) geometry, wall motion and ejection fraction may present abnormalities in myocardial deformation, both at rest and during physical effort. We selected 50 young smokers with no additional CV risk factors, and 60 non-smokers to undergo a standardized exercise-test. Consistently, we evaluated the CV adaptation to exercise by both conventional echocardiography and speckle-tracking analysis (2D-STE). Results. We found no difference between smokers and controls regarding baseline characteristics; as expected, smokers presented with lower HDL-cholesterol (p < 0.005), and higher fibrinogen, C-reactive protein (CRP), and interleukin-6 (p < 0.001). Conventional echocardiography parameters were not different between groups, while we detected a different behaviour of global longitudinal strain (GLS), global circumferential strain (GCS) and twist by 2D-STE during exercise-test. Indeed, GLS, GCS and twist behaved differently during exercise test in smokers with respect to controls. We found an association between CS, inflammation and LV mechanics changes uncovered by physical effort, and regression analysis confirmed that the intensity of the exposure to cigarette smoking, together with the inflammatory status (CRP, fibrinogen and Il-6) plasma levels, drive this impairment. Conclusions. We confirm strain imaging (2D-STE) as a very useful tool to identify early changes in cardiac mechanics, as adaptation to exercise; our findings may reflect a very precocious functional abnormality in active smokers, likely long before structural damage occurs.

Basal longitudinal strain predicts future aortic valve replacement in asymptomatic patients with aortic stenosis

AIMS

To evaluate the prognostic value of global longitudinal strain (GLS) and basal longitudinal strain (BLS) with the knowledge of coexisting coronary pathology evaluated by multi-detector computed tomography (MDCT) coronary angiography.

BACKGROUND

GLS and BLS are both sensitive markers of myocardial dysfunction and predictors of outcome in asymptomatic aortic stenosis. Aortic stenosis and ischaemic heart disease share risk factors and longitudinal function can be severely reduced in both conditions, why some of the previous findings of impaired regional longitudinal function in asymptomatic aortic stenosis could in fact be explained by silent ischaemic heart disease.

METHODS AND RESULTS

Prospective follow-up of 104 asymptomatic patients with moderate-severe aortic stenosis defined as an aortic valve area <1.5 cm(2). Patients underwent a thorough clinical work-up, advanced echocardiographic analysis and coronary angiography by MDCT. The combined endpoint was indication for aortic valve replacement (AVR) and sudden cardiac death. During a median follow-up of 2.3 years (interquartile range 1.7-3.6) 43 patients (41%) met the endpoint of indication for AVR. The basal (13.4 ± 3.1% vs. 15.7 ± 3.1%) and mid-ventricular segments (14.9 ± 2.7% vs. 16.2 ± 2.9%) were significantly reduced, but with sparing of the apical segments, in patients who later underwent AVR. In various multivariable Cox regression models, including only BLS, but not GLS, remained an independent predictor of AVR.

CONCLUSION

In contrast to GLS, reduced BLS is a significant predictor of future AVR in asymptomatic patients with aortic stenosis, independently of clinical characteristics, conventional echocardiographic measures, and coronary pathology.