Titin truncating variant cardiomyopathy and related sarcomere insufficiency causes high energy demand resulting in mitochondrial dysfunction, autophagosome formation, and apoptosis

Background/Objectives

Titin truncating variants (TTNtv) are the most prevalent genetic cause of dilated cardiomyopathy (DCM), resulting in upregulation of cardiac transcripts of oxidative phosphorylation (1,2). However, the underlying molecular mechanism(s) and cellular consequences of these findings remain unknown.

Methods and results

To gain insight into the metabolic changes and cellular consequences of a TTNtv, metabolic, mitochondrial, and survival pathways were studied in human TTNtv DCM hearts and isolated cardiomyocytes of TTNtv mice. TTNtv resulted in a significant increase of cardiac transcripts of glycolysis, citric acid cycle, mitochondrial fission, autophagy, and apoptosis when comparing RNAseq in 24 TTNtv and 27 mutation-negative DCM cardiac biopsies. Furthermore, a decrease in the area of myofibrils in human TTNtv hearts (TTNtv vs. mutation-negative DCM: 46%, and 62%, P=0.001), and an increase of mitochondrial (49% and 31%, P=0,001) and autophagosome areas (4% and 2%, P=0.002) was observed using transmission electron microscopy (TEM). Similar patterns of cardiomyocyte disorganization and stress could be seen in TTNtv hearts of mice even without a phenotype. Additionally, observed swollen mitochondria by TEM and decreased quantity of OXPHOS proteins by immunoblotting in murine TTNtv hearts indicate mitochondrial stress. Mitochondrial oxygen consumption at baseline and the maximum respiration in TTNtv cardiomyocytes of mice increased by a factor of 1.8 and 1.5 respectively (both P≤0.05), compared to WT. Furthermore, palmitate oxidation in TTNtv cardiomyocytes increased by 1.3 fold (P=0.005) compared to WT mice, suggestive of increased energy demand in TTNtv.

Conclusion

Myofibrillar insufficiency in human TTNtv DCM augments the cardiac oxygen and energy consumption, leading to pronounced morphological and functional mitochondrial decompensation. Swelling, damage and fission of mitochondria is further characterized by autophagosome formation and increased apoptosis pathways in TTNtv hearts.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Double-Dose consortium by Dutch Cardiovascular Alliance (DCVA)

Left atrial strain at CMR is a strong independent prognostic predictor in DCM, superior to LV-GLS, LVEF and LAVI, and incremental to LGE

Background

The left atrium (LA) is an early sensor of left ventricular (LV) dysfunction. LA size and new-onset atrial fibrillation (AF) are associated with an increased risk of mortality and heart failure (HF) progression in patients with dilated cardiomyopathy (DCM). Whether abnormal LA strain measured at cardiac magnetic resonance (CMR) – a new technology to study atrial function – may predict overall outcome in DCM – either or not leading to new onset AF – remains completely unknown.

Purpose

To determine the prognostic value of CMR derived LA strain in DCM patients.

Methods

A total of 488 DCM patients (age 54 [46–62] years, 61% male) undergoing CMR were prospectively enrolled in the Maastricht Cardiomyopathy Registry between 2004 and 2018. Outcome consisted of the combination of sudden or cardiac death, HF hospitalization or life-threatening arrhythmias. LA reservoir (passive LA filling), conduit (passive LV filling), and booster strain (active LV filling) were measured using feature tracking strain analysis of the 2- and 4-chamber long-axis cines (Figure 1). Given the non-linearity of continuous variables, cubic spline analysis was performed to dichotomize.

Results

Seventy out of 488 DCM patients (14%) reached the endpoint (follow-up 6 [4–9] years). Age, NYHA class ≥3, late gadolinium enhancement (LGE) presence, LV ejection fraction (EF), LA volume index (LAVI), LV global longitudinal strain (GLS), and LA reservoir and conduit strain were univariably associated with worse outcome (all p-values <0.02). LA conduit strain was superior to reservoir strain to predict outcome. LA conduit strain, NYHA class ≥3 and LGE remained associated in the multivariable model (Figure 2A), while age, NTproBNP, LVEF, LA ejection fraction, LAVI and LV-GLS did not. Adding LA conduit strain to NYHA class and LGE significantly improved the calibration, accuracy, and reclassification of the prediction model (p<0.05). In patients without known AF and sinus rhythm (n=425) during CMR, 10% developed new-onset AF (paroxysmal or persistent) at long-term. Higher age, male sex, NYHA class ≥3, higher LAVI and impaired booster strain were all univariably associated with new-onset AF. Age and impaired booster strain remained as independent predictors of new-onset AF in the multivariable analysis (Figure 2B).

Conclusions

LA conduit strain on CMR is a strong independent prognostic predictor in DCM, superior to LV-GLS, LVEF and LAVI, and incremental to LGE. In addition, LA booster strain is an independent predictor of new-onset AF.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Netherlands Cardiovascular Research Initiative, an initiative with support of the Dutch Heart Foundation

CMR derived left ventricular intraventricular pressure gradients identify different patterns associated with prognosis in patients with dilated cardiomyopathy

Introduction

The direction of blood flow in the left ventricle (LV) is determined by intraventricular pressure gradients (IVPGs) between apex and base, which are altered when cardiac function declines. New cardiac magnetic resonance (CMR) post-processing software enables estimating LV-IVPGs. To date, the prognostic value of CMR derived IVPGs in patients with dilated cardiomyopathy (DCM) remains unknown.

Methods

DCM patients from the Maastricht Cardiomyopathy Registry, who underwent a CMR, were included. The software estimates the LV-IVPGs (between apex and base) by using the myocardial movement and velocity of a reconstructed 3D-LV model (derived from feature-tracking strain analysis of 2-, 3- and 4-chamber cine images). The primary outcome was a combined endpoint of heart failure (HF) hospitalisations, life-threatening arrhythmias and (sudden) cardiac death.

Results

In total, 447 DCM patients were included (age 55 interquartile range [46–63] years; 60% male). During a median follow-up of 6 [4–9] years, 66 patients (15%) reached the primary endpoint. In 168 patients (38%), a temporary pressure reversal from base-apex to apex-base during the systolic-diastolic transition was observed (figure). After correction for covariates that were univariably associated with outcome (p<0.100, age, NYHA-class≥3, and left atrial (LA) conduit strain), flow reversal from base-apex to apex-base in the diastole was independently associated with outcome in the total cohort (HR 2.91, 95%-Confidence interval (95%-CI) [1.16–7.32], p=0.023; Table). In patients without pressure reversal (N=279) in the systolic-diastolic transition, IVPG during the total cardiac cycle (HR 0.88 [0.81–0.96], p=0.003), the systolic ejection force (HR 0.92 [0.87–0.97], p=0.003), and the E-wave decelerative force “C” (passive diastolic filling, HR 0.85 [0.74–0.97], p=0.013) were predictors of outcome, independent of other covariates (age, sex, NYHA class ≥3, LV ejection fraction, late gadolinium enhancement, LV longitudinal strain, LA volume index and LA conduit strain, table).

Conclusion

CMR-derived LV-IVPG analysis showed pressure reversal in the systolic-diastolic transition in one-third of DCM patients, and flow reversal was an independent predictor of worse outcome in these patients. In patients without this pressure reversal, LV-IVPG during the total cardiac cyle, the systolic ejection force, and the E-wave decelerative force were predictors of outcome, independent of all evauluated clinical and imaging parameters.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Netherlands Cardiovascular Research Initiative (initiative with support of the Dutch Heart Foundation) and CVON (She-PREDICTS, grant 2017-21 & CVON-DCVA Double Dosis 2021)

Clinical presentation, disease course, and outcome of COVID-19 in hospitalized patients with and without pre-existing cardiac disease: a cohort study across 18 countries

AIMS

Patients with cardiac disease are considered high risk for poor outcomes following hospitalization with COVID-19. The primary aim of this study was to evaluate heterogeneity in associations between various heart disease subtypes and in-hospital mortality.

METHODS AND RESULTS

We used data from the CAPACITY-COVID registry and LEOSS study. Multivariable Poisson regression models were fitted to assess the association between different types of pre-existing heart disease and in-hospital mortality. A total of 16 511 patients with COVID-19 were included (21.1% aged 66-75 years; 40.2% female) and 31.5% had a history of heart disease. Patients with heart disease were older, predominantly male, and often had other comorbid conditions when compared with those without. Mortality was higher in patients with cardiac disease (29.7%; n = 1545 vs. 15.9%; n = 1797). However, following multivariable adjustment, this difference was not significant [adjusted risk ratio (aRR) 1.08, 95% confidence interval (CI) 1.02-1.15; P = 0.12 (corrected for multiple testing)]. Associations with in-hospital mortality by heart disease subtypes differed considerably, with the strongest association for heart failure (aRR 1.19, 95% CI 1.10-1.30; P < 0.018) particularly for severe (New York Heart Association class III/IV) heart failure (aRR 1.41, 95% CI 1.20-1.64; P < 0.018). None of the other heart disease subtypes, including ischaemic heart disease, remained significant after multivariable adjustment. Serious cardiac complications were diagnosed in <1% of patients.

CONCLUSION

Considerable heterogeneity exists in the strength of association between heart disease subtypes and in-hospital mortality. Of all patients with heart disease, those with heart failure are at greatest risk of death when hospitalized with COVID-19. Serious cardiac complications are rare during hospitalization.

Age is the main determinant of COVID-19 related in-hospital mortality with minimal impact of pre-existing comorbidities, a retrospective cohort study

BACKGROUND

Age and comorbidities increase COVID-19 related in-hospital mortality risk, but the extent by which comorbidities mediate the impact of age remains unknown.

METHODS

In this multicenter retrospective cohort study with data from 45 Dutch hospitals, 4806 proven COVID-19 patients hospitalized in Dutch hospitals (between February and July 2020) from the CAPACITY-COVID registry were included (age 69[58-77]years, 64% men). The primary outcome was defined as a combination of in-hospital mortality or discharge with palliative care. Logistic regression analysis was performed to analyze the associations between sex, age, and comorbidities with the primary outcome. The effect of comorbidities on the relation of age with the primary outcome was evaluated using mediation analysis.

RESULTS

In-hospital COVID-19 related mortality occurred in 1108 (23%) patients, 836 (76%) were aged ≥70 years (70+). Both age 70+ and female sex were univariably associated with outcome (odds ratio [OR]4.68, 95%confidence interval [4.02-5.45], OR0.68[0.59-0.79], respectively;both p<  0.001). All comorbidities were univariably associated with outcome (p<0.001), and all but dyslipidemia remained significant after adjustment for age70+ and sex. The impact of comorbidities was attenuated after age-spline adjustment, only leaving female sex, diabetes mellitus (DM), chronic kidney disease (CKD), and chronic pulmonary obstructive disease (COPD) significantly associated (female OR0.65[0.55-0.75], DM OR1.47[1.26-1.72], CKD OR1.61[1.32-1.97], COPD OR1.30[1.07-1.59]). Pre-existing comorbidities in older patients negligibly (<6% in all comorbidities) mediated the association between higher age and outcome.

CONCLUSIONS

Age is the main determinant of COVID-19 related in-hospital mortality, with negligible mediation effect of pre-existing comorbidities.

TRIAL REGISTRATION

CAPACITY-COVID ( NCT04325412 ).

Myocardial strain overrules left ventricular ejection fraction and late gadolinium enhancement extent in predicting MACE in CMR-proven acute myocarditis

Funding Acknowledgements

Type of funding sources: None.

Background

Cardiac magnetic resonance (CMR) plays a major role in both the diagnostic process and prognostic stratification in acute myocarditis. Presence of late gadolinium enhancement (LGE) and left ventricular (LV) ejection fraction (EF) are known predictors of major adverse cardiovascular events (MACE). However, in daily clinical practice it remains challenging to distinguish ‘the good from the bad’. The prognostic value of CMR feature tracking (FT) derived strain, with respect to LGE and LVEF, remains unclear.

Purpose

To evaluate the incremental prognostic value of left atrial (LA) phasic function, LV and right ventricular (RV) strain using CMR-FT in patients with CMR-proven acute myocarditis.

Methods

In this multicenter observational study, patients with CMR-proven acute myocarditis were included and followed with regard to MACE including all-cause mortality (ACM), heart-failure hospitalizations (HFH), and life-threatening arrhythmias (LTA). Using FT-derived strain, LV global longitudinal strain (GLS), circumferential strain (GCS), and radial strain (GRS), RV GLS and LA phasic function were measured. Uni- and multivariable analysis including clinical and CMR parameters were performed to assess the association with MACE.

Results

A total of 162 patients were included (75% male, 41 ±17 years). MACE occurred in 29 patients (18%, ACM n = 18, HFH n = 7, LTA n = 11) during a median follow-up of 5.5 (2.2-8.3) years. Forty-six percent had a STEMI-like presentation (combination of chest pain, elevated troponin, and ST-elevation, n = 74). LGE was present in 90% of patients and mean LVEF was 51 ± 12%. Patients with LVEF &lt;50% had a significantly worse prognosis compared to patients with LVEF ≥50% (p &lt; 0.0001, Figure A). When we categorized the study population into subgroups of quartile values of LV GLS, patients with LV GLS worse than 18% had a significant worse outcome compared to the other subgroups (p &lt; 0.05, Figure B). Subgroups of LGE extent did not show significantly different associations with outcome (p = 0.458, Figure C). Cox regression analysis showed that LV strain and LA phasic function were univariably associated with MACE, whereas RV GLS and LGE extent were not. All univariable associated strain parameters were separately included in a multivariable model, including age, sex, STEMI-like presentation, and LVEF. LV GLS (HR 1.08, p = 0.01), LV GCS (HR 1.15, p = 0.02), and LV GRS (HR 0.98, p = 0.02) were independent predictors of MACE.

Conclusions

LV strain parameters are independent and incremental predictors of prognosis in patients with acute myocarditis, while RV strain and LA phasic function are not. Therefore, LV strain is a promising novel parameter for risk stratification in acute myocarditis.