The myocardial bridge (MB) is a muscle band found sporadically above the coronary artery (CA) in humans and certain animals such as the dog, cat and sheep. The purpose of our study was to compare the structure of the MB muscle with that of tissue from the subepicardial myocardium. The histological studies included toluidine blue staining of 1-µm-thick sections and Gomori’s trichrome staining of canine cardiac samples. The MB muscle of the dog heart is characterized by a distinctive spatial arrangement, with individual fibers separated by substantial elements of intercellular connective tissue in cross-section. Longitudinally, the long, slender fibers are aligned continuously with intermediation of intercalated disks lying peφendicular to the long axis of the fibers. In other regions of the left ventricular subepicardial myocardium, each myocyte is tightly packed in transverse view. There is great variation in the thickness (0.11-2.24 mm, average 0.45 mm) of MBs and the distance (24-236 µm, average 103 µm) between MBs and the left anterior descending coronary artery (LAD) among the 13 affected dogs examined, with no apparent relationship between the occurrence of MBs and either age or sex. These results on MB alignment suggest that the MB muscle generates force along the long axis of the fiber orientation as skeletal muscle does, and with minimal constriction of the CA; if so, the function of MB myocytes may differ from that of common cardiac myocytes, as does the structure. Then, the long-supposed downward compressive force of MBs on the LAD would be minimal in most cases; however, when the MB produces a systolic narrowing of the LAD known as the milking effect, the degree of lateral compression and its influence should depend not only on the substantial size of the MB muscle but also on the distance between the MB muscle and LAD. The environment surrounding the LAD may be a crucial factor in determining whether the MB influences the induction of heart disorders or not.

with left ventricular (LV) dysfunction exacerbates the V/Q mismatch, leading to progressively lower endtidal CO2 pressures (PETCO2). 7 Thus, EOV severity can be evaluated by detecting PETCO2 and V E, which indicate reduced pulmonary blood flow in patients with LV dysfunction, exacerbating the V/Q mismatch. During CPX, EOV appears as a loop (EOV loop) formed by graphing the 2 parameters, PETCO2 and V E. Hence, we hypothesized that the size of this loop during CPX would be larger in patients with severe cardiac disorders and would be associated with prognosis. Consequently, we investigated the correlation between area of the EOV loop and patient prognosis. Methods Patient Selection This cohort was retrieved from the Gunma Prefectural Cardiovascular Centre Database, established in 2002 for patients who newly visited the hospital. A total of 2,043 patients who underwent symptom-limited maximal CPX between 2010 and 2016 were analyzed. Inclusion criteria were: previous or present HF symptoms (NYHA functional class II-III, ACC/AHA classification stage C), documentation of LV systolic dysfunction (LV ejection fraction

Patients with a relatively greater minVE/VCO in comparison with peak VO had impaired cardiac output as well as restricted pulmonary blood flow increase during exercise, partly due to accumulated pleural effusion.

Background: Cardiopulmonary exercise testing (CPX) is used in the prognostic evaluation of patients with heart failure with reduced ejection fraction (HFrEF). In these patients, the ventilation feedback system is dysfunctional, and overactive peripheral chemoreceptors may be responsible for the early appearance of the respiratory compensation point (RCP) after the anaerobic threshold (AT). The mechanism of RCP appearance remains unknown and very few studies have reported the relationship between RCP and heart failure. We hypothesized that the duration between the RCP and AT (RCP-AT time) can predict the severity of cardiac disorders and prognosis in patients with HFrEF. Methods and Results:We enrolled 143 patients with HFrEF who underwent symptom-limited maximal CPX between 2012 and 2016. During a median follow-up of 1.4 years, cardiovascular death occurred in 45 participants (31%). The patients who died had a significantly shorter RCP-AT time and lower hemoglobin (Hb) levels than those who survived (P<0.001 and P=0.01, respectively). Cox regression analyses revealed RCP-AT time and Hb level to be independent predictors of cardiovascular death in patients with HFrEF (P<0.001 and P=0.018, respectively).Conclusions: RCP-AT time can better predict prognosis in patients with HFrEF than the magnitude of increase in oxygen consumption within the isocapnic buffering domain (∆V O2 AT-RCP). It may be useful as a new prognostic indicator in these patients.

Background:The increase in stroke volume during inotropic stimulation in patients with heart failure with reduced ejection fraction (HFrEF) is called the "pump function reserve." Few studies have reported on the relationship between pump function reserve and HF prognosis. In HFrEF patients who have pump function reserve, stroke volume increases during exercise. Simply put, the pulse pressure change (∆PP) during cardiopulmonary exercise testing (CPX) is closely related to the prognosis of patients with HFrEF. We hypothesized that ∆PP could predict disease severity and cardiovascular death in patients with HFrEF. Methods and Results:A total of 224 patients with HFrEF who underwent symptom-limited maximal CPX between 2012 and 2016 were enrolled. During a median follow-up of 1.5 years, cardiovascular death occurred in 54 participants (24%). Patients who died demonstrated a lower ∆PP between rest and peak exercise (∆PP [peak−rest]) than those who survived (P<0.001). Cox regression analyses revealed that ∆PP, slope of the relationship between minute ventilation and carbon dioxide production, and B-type natriuretic peptide level were independent predictors of cardiovascular death in patients with HFrEF (P=0.001, 0.021, and <0.001, respectively).Conclusions: ∆PP (peak−rest) can accurately predict cardiovascular death in patients with HFrEF and may be a useful new prognostic indicator in these patients.