Hypertrophic cardiomyopathy is characterized by alterations of the mitochondrial calcium uniporter complex proteins: insights from patients with aortic valve stenosis versus hypertrophic obstructive cardiomyopathy.

Introduction: Hypertrophies of the cardiac septum are caused either by aortic valve stenosis (AVS) or by congenital hypertrophic obstructive cardiomyopathy (HOCM). As they induce cardiac remodeling, these cardiac pathologies may promote an arrhythmogenic substrate with associated malignant ventricular arrhythmias and may lead to heart failure. While altered calcium (Ca2+) handling seems to be a key player in the pathogenesis, the role of mitochondrial calcium handling was not investigated in these patients to date. Methods: To investigate this issue, cardiac septal samples were collected from patients undergoing myectomy during cardiac surgery for excessive septal hypertrophy and/or aortic valve replacement, caused by AVS and HOCM. Septal specimens were matched with cardiac tissue obtained from post-mortem controls without cardiac diseases (Ctrl). Results and discussion: Patient characteristics and most of the echocardiographic parameters did not differ between AVS and HOCM. Most notably, the interventricular septum thickness, diastolic (IVSd), was the greatest in HOCM patients. Histological and molecular analyses showed a trend towards higher fibrotic burden in both pathologies, when compared to Ctrl. Most notably, the mitochondrial Ca2+ uniporter (MCU) complex associated proteins were altered in both pathologies of left ventricular hypertrophy (LVH). On the one hand, the expression pattern of the MCU complex subunits MCU and MICU1 were shown to be markedly increased, especially in AVS. On the other hand, PRMT-1, UCP-2, and UCP-3 declined with hypertrophy. These conditions were associated with an increase in the expression patterns of the Ca2+ uptaking ion channel SERCA2a in AVS (p = 0.0013), though not in HOCM, compared to healthy tissue. Our data obtained from human specimen from AVS or HOCM indicates major alterations in the expression of the mitochondrial calcium uniporter complex and associated proteins. Thus, in cardiac septal hypertrophies, besides modifications of cytosolic calcium handling, impaired mitochondrial uptake might be a key player in disease progression.

The clinically effective use of cardiac markers by restructuring laboratory profiles at Cardiology wards.

Background: Laboratory overutilization is associated with diagnostic error and potential patient risk. We applied a demand management strategy in collaboration with the local Department of Cardiology to reduce the cardiac markers high-sensitive troponin T (hsTropT) and N-terminal pro brain natriuretic peptide (NTproBNP) in laboratory ordering profiles (LOPs). The present study aimed to retrospectively evaluate the implemented strategies. Methods: Strategies included educational measures and evidence-guided, active test de-selection from all cardiology ward LOPs, and/or permanent removal from LOPs. Tests remained available at all times. We evaluated overutilization by reductions in monthly orders, and assessed differences in 30-day all-cause readmission rate and length of patients' hospital stay. Results: Overall, we observed a mean reduction of 66.1% ± 7.6% (n = 277 ± 31) in hsTropT tests. Educational measures effectively reduced NTproBNP orders by 52.8% ± 17.7% (n = 60 ± 20). Permanent removal of tests from LOPs additionally decreased orders to a final extent of 75.8% ± 8.0% (n = 322 ± 31) in NTproBNP tests. The 30-day readmission rate and overall length of hospital stay did not increase. Conclusions: Our results indicate that cardiac markers in routine care are subject to extensive overutilization when used within LOPs. Educational measures are an effective strategy to overcome the overutilization of cardiac markers but may be more effective when combined with the removal of cardiac markers from LOPs.