Impaired subendocardial perfusion in patients with metabolic syndrome

Background Metabolic Syndrome (MS) is associated to vascular damage, increased arterial stiffness, and impaired myocardial perfusion. Subendocardial viability ratio (SEVR) is a noninvasive estimation of myocardial workload, oxygen supply, and perfusion. The aim of the study was to describe the relation between arterial stiffness, SEVR, and cardio-metabolic risk factors. Methods A cohort of 55 patients, aged 59.9 ± 10.8 years, was studied; 28 subjects (50.9%) had metabolic syndrome. All patients underwent a clinical evaluation and blood venous sampling, to assess glico-lipid profile. Applanation tonometry was performed, to obtain pulse wave analysis and SEVR values. Results In the overall study population, SEVR showed negative associations with mean (r = −0.301; p = 0.026) and systolic (borderline relation, r = −0.257; p = 0.058) arterial pressure. Metabolic syndrome patients presented lower level of SEVR ( p = 0.012), even after adjusting for age, sex, and mean arterial pressure ( p = 0.040). Subdividing the study population by the number of metabolic syndrome components, SEVR significantly decreased as the number of Metabolic Syndrome components increased ( p for trend 0.005). In a logistic backward regression analysis, both metabolic syndrome and mean arterial pressure resulted significant predictors of SEVR, accounting for 18% of variance. Conclusion The reduced SEVR in metabolic syndrome patients could be an important pathophysiological determinant of the increased cardiovascular risk.

Ex vivo Validation of Noninvasive Epicardial and Endocardial Repolarization Mapping

Background: The detection and localization of electrophysiological substrates currently involve invasive cardiac mapping. Electrocardiographic imaging (ECGI) using the equivalent dipole layer (EDL) method allows the noninvasive estimation of endocardial and epicardial activation and repolarization times (AT and RT), but the RT validation is limited to in silico studies. We aimed to assess the temporal and spatial accuracy of the EDL method in reconstructing the RTs from the surface ECG under physiological circumstances and situations with artificially induced increased repolarization heterogeneity.Methods: In four Langendorff-perfused pig hearts, we simultaneously recorded unipolar electrograms from plunge needles and pseudo-ECGs from a volume-conducting container equipped with 61 electrodes. The RTs were computed from the ECGs during atrial and ventricular pacing and compared with those measured from the local unipolar electrograms. Regional RT prolongation (cooling) or shortening (pinacidil) was achieved by selective perfusion of the left anterior descending artery (LAD) region.Results: The differences between the computed and measured RTs were 19.0 ± 17.8 and 18.6 ± 13.7 ms for atrial and ventricular paced beats, respectively. The region of artificially delayed or shortened repolarization was correctly identified, with minimum/maximum RT roughly in the center of the region in three hearts. In one heart, the reconstructed region was shifted by ~2.5 cm. The total absolute difference between the measured and calculated RTs for all analyzed patterns in selectively perfused hearts (n = 5) was 39.6 ± 27.1 ms.Conclusion: The noninvasive ECG repolarization imaging using the EDL method of atrial and ventricular paced beats allows adequate quantitative reconstruction of regions of altered repolarization.

Comparison Between Invasive and Noninvasive Methods to Estimate Subendocardial Oxygen Supply and Demand Imbalance

Background Estimation of the balance between subendocardial oxygen supply and demand could be a useful parameter to assess the risk of myocardial ischemia. Evaluation of the subendocardial viability ratio (SEVR, also known as Buckberg index) by invasive recording of left ventricular and aortic pressure curves represents a valid method to estimate the degree of myocardial perfusion relative to left ventricular workload. However, routine clinical use of this parameter requires its noninvasive estimation and the demonstration of its reliability. Methods and Results Arterial applanation tonometry allows a noninvasive estimation of SEVR as the ratio of the areas directly beneath the central aortic pressure curves obtained during diastole (myocardial oxygen supply) and during systole (myocardial oxygen demand). However, this “traditional” method does not account for the intra‐ventricular diastolic pressure and proper allocation to systole and diastole of left ventricular isometric contraction and relaxation, respectively, resulting in an overestimation of the SEVR values. These issues are considered in the novel method for SEVR assessment tested in this study. SEVR values estimated with carotid tonometry by "traditional” and "new” method were compared with those evaluated invasively by cardiac catheterization. The “traditional” method provided significantly higher SEVR values than the reference invasive SEVR: average of differences±SD= 44±11% (limits of agreement: 23% – 65%). The noninvasive “new” method showed a much better agreement with the invasive determination of SEVR: average of differences±SD= 0±8% (limits of agreement: ‐15% to 16%). Conclusions Carotid applanation tonometry provides valid noninvasive SEVR values only when all the main factors determining myocardial supply and demand flow are considered.

Left atrial fibrosis: an essential hallmark in chronic mitral regurgitation

Chronic mitral regurgitation (MR) is the second valvular heart disease for incidence, which worsening severity gradually affects all cardiac chambers and leads to poor outcome if untreated. The recent development of minimally invasive surgical techniques and percutaneous intervention has reduced the operative risk, allowing a more confident referral of these patients for intervention. Therefore, there is a growing need of reliable markers to select the best therapeutic strategies and to identify the optimal timing for intervention. Myocardial fibrosis (MF) gradually occurs as a result of left atrial and ventricular (LA and LV) remodeling due to MR pressure and volume overload. It has been identifi ed as an index of clinical outcome and arrhythmic risk in patients with MR. Particularly, the assessment of LA fi brosis not only allows to define different MR etiology, but also was associated with prognosis and atrial fibrillation (AF) burden. Nowadays, noninvasive estimation of MF is possible through the use of advanced imaging modalities, particularly cardiac magnetic resonance and speckle tracking echocardiography. This review discusses the role of LA fibrosis as a diagnostic and prognostic marker in patients with MR and its quantification by noninvasive multimodality cardiac imaging.