The left atrium (LA) is emerging as a key element in the pathophysiology of several cardiac diseases due to having an active role in contrasting heart failure (HF) progression. Its morphological and functional remodeling occurs progressively according to pressure or volume overload generated by the underlying disease, and its ability of adaptation contributes to avoid pulmonary circulation congestion and to postpone HF symptoms. Moreover, early signs of LA dysfunction can anticipate and predict the clinical course of HF diseases before the symptom onset which, particularly, also applies to patients with increased risk of HF with still normal cardiac structure (stage A HF). The study of LA mechanics (chamber morphology and function) is moving from a research interest to a clinical application thanks to a great clinical, prognostic, and pathophysiological significance. This process is promoted by the technological progress of cardiac imaging which increases the availability of easy-to-use tools for clinicians and HF specialists. Two-dimensional (2D) speckle tracking echocardiography and feature tracking cardiac magnetic resonance are becoming essential for daily practice. In this context, a deep understanding of LA mechanics, its prognostic significance, and the available approaches are essential to improve clinical practice. The present review will focus on LA mechanics, discussing atrial physiology and pathophysiology of main cardiac diseases across the HF stages with specific attention to the prognostic significance. Imaging techniques for LA mechanics assessment will be discussed with an overlook on the dynamic (under stress) evaluation of the chamber.

Evaluation of cardiorespiratory coupling (CRC) usually requires the simultaneous recording of heart period(HP) variability, derived from the electrocardiogram (ECG), and respiration. ECG-derived respiration (ECGDR) exploits the cardiac axis movement due to respiration to estimate respiratory activity directly from the ECG. Since CRC indexes could theoretically be computed using ECGDR, a comparison with results obtained through a more precise monitoring of respiratory activity such as the respiratory flow (RF) is warranted. Therefore, a mixed unpredictability index (MUPI) of HP variability from respiratory dynamics, computed via local k-nearest-neighbor approach, was calculated using ECGDR and RF in patients with preserved functional capacity (PFC) and with reduced functional capacity (RFC) before and after cardiopulmonary exercise test (CPET) protocol. The MUPI computed from RF was found to be significantly increased in PFC patients after CPET protocol, while no effect could be observed when considering the ECGDR. Moreover, the correlation between the two MUPI indexes was limited. We conclude that indexes of CRC might require more direct measures of respiration than ECGDR to detect pathophysiological differences.

No abstract

Background Fabry disease (FD) is a rare x-linked lysosomal storage disease characterized by accumulation of glicosphingolipids in several organs, including the heart. Cardiac involvement manifests as left ventricular (LV) hypertrophy, often complicated by myocardial fibrosis. The impact of disease on functional capacity is not well defined, as well as the potential gender-related differences. Aim To evaluate the functional capacity in a cohort of FD patients with different degree of cardiac involvement. Methods Seventy-two patients were prospectively enrolled from March 2015 to December 2019. Patients underwent cardiac magnetic resonance (CMR) and cardiopulmonary exercise test (CPET) with cycle ergometer. In addition to standard CPET parameters, Chronotropic Index (CI) was calculated as (HR max − HR rest) / (HR max predicted − HR rest), adjusting with HR max predicted calculated as 119 + (HR rest/2) − (age/2) in case of beta-blockers treatment. Results CMR showed left ventricle (LV) hypertrophy (LV mass greater than normal reference value) in 36.1% of patients, LGE and reduced T1 values were detected in 30.6% and 59.7% of subjects respectively. Twenty-eight patients were males (39%), the median age was 40 (28–54) [median (25th–75th)] years and only 11 (15%) subjects were on beta-blockers. All subjects performed a maximal test [RQ max = 1.21 (1.14–1.26)] using a ramp protocol of 15 (15–20) Watt. The absolute peakVO2 was 18.2 (15.75–24.08) mL/min/kg, whilst the percentage of predicted peakVO2 was 67.7 (57.3–76.6)%. The chronotropic response of the overall population was characterized by reduced peak heart rate (HRmax) [80.3 (73.8–87.6)% of predicted], and diminished chronotropic index (CI) [0.67 (0.55–0.77) normal value: 0.80], but preserved heart rate reserve (HRR) [21 (12–28) bpm]. Ventilatory efficiency was preserved [VE/VCO2 = 25.70 (23.18–28.00)]. At gender analysis, men showed higher absolute peakVO2 [men vs females: 19.95 (17.20–28.28) vs 17.80 (15.50–21.28) mL/min/kg, p=0.02] but lower percentage of predicted [64.24 (52.58–70.61) vs 70.75 (59.05–78.02)%, p<0.001] than females. No differences between genders were observed in chronotropic response [HRmax = 138 (108–154) vs 142 (135–153) bpm, p=0.38; HRR = 22 (13–36) vs 20 (11–26), p=0.097; CI: 0.67 (0.51–0.76) vs 0.67 (0.58–0.79), p=0.33], whilst females showed a lower peak O2 pulse (VO2/HR) than males [men vs females: 12.08 (10.04–13.64) vs 7.76 (6.88–9.22), p<0.001], possibly related to gender differences in LV dimensions and stroke volume. Conclusions This large cohort of FD patients with different degree of cardiac involvement showed a significantly impaired functional capacity, mainly characterized by relevant chronotropic incompetence (independent from the use of beta-blockers), consistent with systemic autonomic dysfunction. The degree of chronotropic incompetence was similar between the genders, but females showed higher predicted peakVO2 despite a lower peak O2 pulse. FUNDunding Acknowledgement Type of funding sources: None.