Robustness of T1 and ECV mapping radiomics features: a between-session evaluation in young athletes

Funding Acknowledgements

Type of funding sources: None.

Introduction

Radiomics of cardiac MRI T1, T2 and extracellular volume (ECV) maps has the potential to add biomarkers that can aid in the detection and diagnosis of myocardial diseases. Recently, the feasibility of CMR mapping based radiomics to classify various myocardial diseases was demonstrated [1-6]. However, reproducibility studies have reported sensitivity of radiomics to acquisition parameters and processing steps involved concluding that only a limited number of features may be reproducible [7-8]. As CMR mapping guidelines recommend to use site-specific normal values [9], radiomics features derived likely also need careful site-specific evaluation to benchmark disease-related feature alterations.

Purpose

We aimed to assess the between-session reproducibility of radiomics features in a longitudinal dataset of MOLLI T1 and ECV maps obtained in young athletes at 1.5T.

Materials and methods

This study included data from 17 healthy subjects (15-20y; informed consent obtained) with data acquired two years apart [10] considered for this purpose as test-retest data since a prior standard analysis showed near identical average T1 (t1: 977±16 ms, t2: 982±20ms) and ECV (t1: 23.4±1.3%, t2: 23.4±1.5%). T1 mapping data was acquired on a 1.5T system (Ingenia, Philips) using MOLLI 5s(3s)3s. After motion correction and T1 and ECV map calculation [11], the left ventricular myocardium was manually delineated by two readers independently (3D Slicer [12]). In total 44 images (short and long axis) were included for each time point. The radiomics analysis resulted in 96 features per image (7 feature families, ‘shape’ excluded; no filters applied; Pyradiomics, [13]). The concordance correlation coefficient (CCC) was calculated to assess reproducibility, and features with CCCs ≥ 0.7 were considered reproducible. A coefficient of variation (CV) below 15% was considered low.

Results

Only a limited number of radiomics features had high CCC (T1: 6/96 ECV 0/96) or a low CV (T1: 32/96, ECV:30/96) in the between-session analysis. The inter-reader evaluation showed that the effect of the delineation on the results was limited. Features that were most robust in the between-session analysis were ‘first order (total)energy’ for T1 maps and ‘glcm_Autocorrelation’ for ECV maps (table 1). These results in young healthy subjects confirm previous test-retest reports [9-10]. Features with low CCC levels or high CV may however still be useful when discriminating between patient with myocardial diseases if the difference is larger than the confidence interval assessed via this reproducibility analysis.

Conclusion

In these healthy subjects, a strong variability in reproducibility of radiomics features of T1 and ECV mapping can be noted. Nonetheless, these variability measures are informative to determine features that are likely most robust when discriminating between health and disease and can be used as a benchmark towards radiomics AI-based diagnostic approaches. Top ranked features for either T1 or ECV

Personalized remotely guided preventive exercise therapy for a healthy heart: protocol and design of the PRIORITY study

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation – Flanders (FWO)

Introduction

Approximately half of the heart failure population has heart failure with preserved ejection fraction (HFpEF), a chronic disease starting with cardiovascular risk factors such as hypertension, diabetes and obesity (stage A) which can further emerge in a structural heart disease without (stage B) or with (stage C) signs or symptoms. Structured exercise therapy is recommended as a Class IA intervention in national and international guidelines and, as such, should be offered to all patients. Yet, in current practice, exercise therapy is often only offered within a secondary prevention program. At present, there exists no comprehensive preventive care program that includes structured exercise for patients in the early stages of heart failure, when cardiovascular risk factors are present, but cardiac remodeling and dysfunction might still be reversible or even preventable.

Purpose

PRIORITY aims to investigate the use of remotely guided exercise therapy as a preventive clinical and cost-effective treatment in the HFpEF continuum. This includes both prevention of progression of asymptomatic diastolic dysfunction towards symptomatic HFpEF (= primary prevention) and delaying progression of symptomatic HFpEF (= secondary prevention).

Methods

A randomized controlled multicenter trial will be conducted in 450 patients (men and women, aged 35-80 years) with heart failure (n = 180 stage A, 180 stage B, 90 stage C). Participants are being recruited from 3 different hospitals and the general population during a 16-month period which started in September 2021. Patients will be randomized (1:1) to usual care or to the PRIORITY exercise intervention (i.e. a combination of supervised with remotely guided home-based training sessions). Training prescription is based on the EXPERT tool and includes person-tailored endurance and dynamic strength training. During one year, participants will receive 18 supervised exercise sessions supplemented with a structured progressive home-based exercise program. Outcomes will be assessed at baseline, 4 months, one and two-years. Primary outcome is the proportion of patients with a clinically relevant improvement in peak oxygen uptake at one-year. Secondary outcomes include vascular health, muscle metabolism, change in electrocardiographic parameters and physical fitness parameters (muscle strength, body composition). Further, big data of physical activity collected during the trial will be used to develop models using machine-learning algorithms which can predict physical activity uptake and changes in fitness to facilitate the creation of more personalized interventions and better tailored exercise prescription.

Conclusion

We anticipate that the PRIORITY study will contribute to better prevention of heart failure thanks to an early easily accessible person-tailored exercise intervention.

The prevalence and clinical significance of a reduced ventricular ejection fraction in asymptomatic young elite endurance athletes

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Health and Medical Research Council of Australia

Background

Ventricular ejection fraction (EF) is the most widely used parameter to evaluate ventricular systolic function. Endurance athletes presenting with a reduced ventricular EF often raise the question of an underlying dilated or arrhythmogenic cardiomyopathy. The clinical significance of a reduced EF in athletes remains to be elucidated.

Purpose

To investigate the prevalence and clinical significance of a reduced EF in asymptomatic endurance athletes.

Methods

Two hundred eighteen asymptomatic young elite endurance athletes were evaluated at baseline. Cardiac magnetic resonance imaging (CMR) was performed to assess cardiac volumes, left ventricular and right ventricular EF (LVEF and RVEF), mass and fibrosis. Athletes with reduced EF (ATrEF) were defined as those having LVEF<50% and/or RVEF<45%. Ventricular systolic and diastolic function were assessed by trans-thoracic echocardiography. A 12-lead ECG and 24-hour holtermonitoring assessed electrical alterations and arrhythmias. In 145 athletes, LV and RV contractile reserve was evaluated by exercise CMR. Cardiopulmonary testing was performed in all athletes to measure maximal oxygen uptake (VO2max).

Results

Thirty-one ATrEF (14.2%) were compared to 187 athletes with a preserved EF (ATpEF). ATrEF were more frequently males (93 vs 77% male, p=0.033) but did not differ from ATpEF with regard to age (18.8±2.1 vs 18.3±2.1 years, p=0.25). Ten athletes had an isolated reduced LVEF, 10 had an isolated reduced RVEF and 11 had both a reduced LVEF and RVEF. ATrEF had similar end-diastolic volumes and cardiac mass but differed by higher end-systolic volumes.

Peak exercise LVEF and RVEF determined by exercise CMR remained lower in ATrEF (68±3 vs 73±4% and 62±6 vs 69±5%, p<0.001) but contractile reserve was greater (ΔLVEF 18±5 vs 14±4% and ΔRVEF 19±5 vs 15±5%, p<0.01).

A reduced EF was not associated with lower exercise capacity, in fact VO2max was higher in ATrEF than in ATpEF (65±6 vs 62±9mL/kg/min, p=0.020) and the percentage of predicted VO2max by the Wasserman equation were similar (151±14 vs 149±21%, p=0.533).

Fibrosis was present in 3 ATrEF and 18 ATpEF (9.7 vs 9.6%, p=0.993) and was isolated to the RV hinge-points in all but 3 ATpEF who had midmyocardial LV lateral wall fibrosis. LV systolic strain (-17.5±2.0 vs -19±2.1%, p<0.001) was lower in ATrEF whereas RV free wall systolic strain (-24.9±3.7 vs -25.1±3.5%, p=0.776) was similar. Diastolic function was normal in all ATrEF and ATpEF. Pathologic T-wave inversions were present in 2 ATrEF and 13 ATpEF (6.5 vs 7%, p=0.999). Ventricular premature beats (VPB) were infrequent but more prevalent in ATrEF than in ATpEF (2[0-18] vs 1[0-2]/24h, p=0.025; 16.1 vs 2.7% >100/24h, p=0.006).

Conclusion

A reduced ventricular EF is common in asymptomatic young elite endurance athletes, is more frequent in males but is not associated with structural, functional or electrical abnormalities apart from a minor excess in VPB.

Modest association between peak exercise blood pressure and ambulatory hypertension in endurance athletes

Funding Acknowledgements

Type of funding sources: None.

Background

An exaggerated blood pressure (BP) response to exercise may be an early indicator of hypertension. However, it is common in endurance athletes and the association between systolic blood pressure (SBP) during exercise and hypertension is not well established in this group.

Purpose

To establish whether there is an association between exercise-induced hypertension (EIH) and clinical hypertension in endurance athletes.

Methods

250 current and former endurance athletes (16-80 years, 75% male) performed a maximal exercise test on a cycle ergometer with BP measured every 2 min. Athletes were diagnosed with EIH based on international guidelines (SBP ≥210mmHg males, ≥190mmHg females). The relationship between SBP and workload was determined by linear regression analysis. Office hypertension was identified from either supine SBP ≥140mmHg or diastolic BP ≥90mmHg, or if treated for hypertension. Gold-standard 24-hour ambulatory blood pressure monitoring (ABPM) was performed in a subset of 42 athletes with EIH and 9 athletes with a normotensive response to exercise (NRE).

Results

On average, peak exercise SBP values were universally high (221±26mmHg in males and 199±21mmHg in females). 71% of athletes (70% of males and 74% of females) met criteria for EIH of which 12% had a peak SBP≥250mmHg. EIH and NRE groups were of similar age, sex, body mass index (BMI) and fitness (Figure 1). The strongest determinant of peak exercise SBP was exercise workload (R=0.78, P<0.001), which remained significant after adjusting for age, sex, BMI and antihypertensive medication (p<0.001) In the full cohort, resting SBP was higher in the EIH group (EIH: 128±13mmHg vs NRE: 122±15mmHg, P=0.006 – Figure 1), however there was a similar prevalence of office hypertension between the EIH (19%) and NRE (15%) groups (P=0.59). This prevalence remained similar (EIH: 13% vs NRE: 10%, P=0.49) after excluding those being treated for hypertension (n=15). In the subset of athletes who underwent 24h ABPM (n=51), there were no diagnoses of clinical hypertension in NRE (n=9, Figure 1). Of the 42 athletes with EIH, a majority (n=32, 76%) were normotensive on ABPM. In the 10 athletes with EIH and hypertension on ABPM, the majority were classified with Grade 1 hypertension (n=5) or daytime hypertension (n=3). Interestingly only two of these athletes would have been identified with office BP measures (see Figure 2).

Conclusion

EIH is common in endurance athletes and is strongly associated with peak exercise workloads suggesting this may be a reflection of superior cardiovascular fitness. In a small proportion of athletes, EIH may be associated with mild hypertension.

Prevention of heart failure in type 2 diabetes by exercise intervention: protocol and design of the PROTECTION study

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): research Foundation - Flanders (FWO)

Introduction

Cardiac dysfunction is highly prevalent in patients with type 2 diabetes mellitus (T2DM), leading to increased risk of cardiac morbidity and premature death. Previous research underscored the high prevalence of a disturbed global longitudinal strain (GLS), a marker to predict this cardiac dysfunction, in both symptomatic and asymptomatic T2DM patients. Exercise-based therapy is recommended in the management of patients with type 2 diabetes. However, it remains unclear i) which type of exercise therapy to have the biggest effect on GLS and ii) which factors modify the effect of exercise therapy on GLS.

Purpose

The PROTECTION study will i) investigate the impact of exercise volume and intensity on GLS to optimize exercise prescription in T2DM and will ii) assess which patient-specific factors influence the change in GLS and physical fitness as a result of exercise intervention in T2DM.

Methods and analyses

The PROTECTION study is composed of two work packages (WP). In WP 1, 100 T2DM adults (50% male, aged 30-75 years) will be randomized to a usual care group or one of the three supervised exercise intervention groups (see Table 1) for a duration of 26 weeks. Outcome measures will be performed at baseline, 13, 26 and 52 weeks of follow-up. The primary outcomes are GLS and cardiac dimensions. Secondary outcomes include health-related physical fitness, blood biomarkers and physical activity behavior. Data will be analyzed by two-way ANOVA repeated measures. A two-tailed P-value <0.05 will be considered statistically significant.

Parallel with the randomized controlled trial, a longitudinal intervention study (WP2) involving 107 adults (50% male, aged 30-75 years) with T2DM will be conducted. All participants will engage in a supervised intervention for 26 weeks, including a high volume of moderate intense physical activity (see Table 1). The main objective of this work package is to define determinants of change in GLS during an exercise intervention. Moreover, the interaction between diet-exercise, habitual physical activity-exercise and phenotype-exercise on change in GLS will be studied in great detail. Patient-specific data will be analyzed by multivariate regression analysis. A two-tailed P-value <0.05 will be considered statistically significant.

Conclusion

It is anticipated that the PROTECTION study will contribute to a better understanding on i) which exercise characteristics are preferred to maximally improve GLS in T2DM and on ii) the determinants of the responsiveness of GLS and physical fitness to exercise in T2DM.

T1 and ECV mapping texture analysis distinguishing hypertrophic cardiomyopathy from athletes heart better than median values

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ph.D fellowship of the Research Foundation Flanders (FWO). The Master@Heart trial is funded by the FWO.

Introduction

Differentiating intensive training induced hypertrophy from hyperthropic cardiomyopathy (HCM) is important to identify those young athletes at risk of sudden cardiac death. Swoboda and colleagues demonstrated that T1 and ECV mapping can aid such a differentiation between athletic and pathological hypertrophy, particularly in subjects with indeterminate wall thickness (1).

Recently texture analysis (TA) methods of CMR data have demonstrated improved diagnostic accuracy over conventional qualitative analysis in various heart diseases. Only few studies have applied TA to T1 and ECV mapping data (2-4). Here we aimed to demonstrate that a TA approach provides superior capacity to distinguish HCM from athlete’s heart over average native T1 and ECV values.

Purpose

It was our hypothesis that a texture analysis of T1 and ECV mapping images would identify features that could discriminate between a HCM and athlete’s heart with a higher classification accuracy (CA) than average T1 and ECV values.

Methods

This study included data from 97 subjects diagnosed with HCM (acc. to guidelines; 5) and 28 athletes that took part in the Master@Heart trial (an ongoing study assessing the beneficial effects of long-term endurance exercise for the prevention of coronary artery disease, 6).  Long and short axis T1 mapping data was acquired on a 1.5T Philips Ingenia system using MOLLI (seconds scheme). After offline motion correction and T1 and ECV map calculation (7), the left ventricular myocardium was manually delineated (3D Slicer; 8). Texture analysis of the masked images resulted in 194 features (Pyradiomics, standard settings; 9). The dataset was then split (75/25%) for training and testing purposes keeping images from the same subject within the same set. A fast correlation based filter rank was applied to the training data to derive relevant features. A further reduction to only two features was based on the CA of a support vector machine (SVM) learning method (linear kernel; cost 0.9 regression loss epsilon 0.1; leave-one-out). Finally, ROC analysis on the test data was used to determine the diagnostic accuracy for the following predictors: (1) median T1 and ECV (2) two most relevant features (training) (3) combination of (1) and (2) (ROC AUC statistics (10)).

Results

The two most relevant features were the histogram feature ECV energy and the gray level size zone matrix (GLSZM) feature native T1 zone entropy, a measure of heterogeneity in the texture pattern.

A model to distinguish HCM from athletes based on these features outperformed the model using only median T1 and ECV values with both higher sensitivity and specificity (table 1) and a significantly  higher AUC in the ROC analysis (p < 0.05, figure 1). Combining these two features with median values did not improve the CA further. 

Conclusion

Texture analysis of motion-corrected T1 and ECV mapping images out-performs classical analysis based on average values in distinguishing HCM from athlete"s heart.

Hinge point fibrosis in athletes is not associated with structural, functional or electrical consequences: a comparison between young and middle-aged elite endurance athletes

Background

The health benefits of extensive endurance training have been debated due to the report of myocardial fibrosis (MF), arrhythmias and temporary post-race cardiac impairment in middle-aged and veteran athletes. The extent of these changes is unknown in elite young athletes.

Purpose

To assess the prevalence of MF and its structural, functional and electrical impact in highly trained young endurance athletes (YA, 15–23 years) as compared to middle-aged athletes (MA, 30–50 years). We hypothesised that MF would be more frequent in MA and associated with more structural, functional and electrical abnormalities.

Methods

We prospectively assessed 197 YA and 34 MA. All had ECG, maximal oxygen consumption (VO2max) testing, cardiac magnetic resonance imaging (CMR), echocardiography and 24h-holter. Indexed left ventricular and right ventricular end diastolic volume (LVEDVi, RVEDVi), ejection fraction (LVEF, RVEF), left ventricular mass (LVMi), and MF defined as delayed gadolinium enhancement were assessed by CMR. LV and RV free wall strain (LVSL, RVfwSL) were assessed by 2D speckle tracking echocardiography. Ventricular premature beats (VPB) and non-sustained ventricular tachycardia (nsVT) were assessed by 24h-holter.

Results

YA and MA (18±2 vs 38±5 years [p<0.01]; 78% vs 80% male [p=0.99]) with an elite level of fitness (VO2max 61±8 vs 54±10 mL/min/kg [p<0.01]; % predicted VO2max 150±20 vs 158±30 [p=0.02]) had a large variance in LV and RV remodelling (Figure 1). MF was seen in 28 athletes (12.5%) and more prevalent in MA than in YA (23.5 vs 10.5%, p=0.048). MF was limited to the hinge points in all 8 MA with MF and 17 YA. 3 YA had LV lateral wall subepicardial MF. 27 of 187 (14.4%) male athletes had MF compared to 1 of 50 (2%) female athletes (p=0.01).

MF+ MA(A) and YA(B) as well as MF− MA(C) and YA(D) had similar structural remodelling (LVEDVi 110±14 vs 118±14 vs 113±19 vs 110±16 mL/m2; RVEDVi 120±14 vs 128±17 vs 117±19 vs 125±23mL/m2; LVMi 77±11 vs 83±14 vs 81±14 vs 77±15g/m2, p>0.05). LVEF, LVSL and RVSL were similar (59±3 vs 58±5 vs 61±6 vs 58±6%; −18.8±2 vs −18.8±2 vs −19.8±2 vs −19.3±2%; −26.3±2.4 vs −24.4±2.4; −26.3±3 vs −25.8±3.5% respectively, p>0.05). LVEF <50% was seen in 19 (8.2%) athletes (0 [0%] vs [5%] 1 vs 1 [3.8%] vs 17 [9.6%]; p=0.51). RVEF was higher in D compared to C without further differences between groups (54±4 vs 54±6 vs 53±6 vs 57±5, p=0.005). RVEF<45% was seen 21 (9.1%) athletes (0 [0%] vs 1 [5%] vs 0 [0%] vs 20 [11.3%]; p=0.14). Abnormal T-wave inversion was similar (12.5 vs 5 vs 7.4 vs 6.2%, p=0.93) as was the prevalence of >100VPB/24h (12.5 vs 5 vs 11.1 vs 5.1%, p=0.42). 2 athletes had nsVT, both in D. All had similar exercise capacity (% predicted VO2max 157±26 vs 152±15 vs 147±24 vs 158±32%; p=0.11).

Conclusion

Hinge-point fibrosis was more prevalent in MA, possibly due to repeated hemodynamic stress during exercise, but is not associated with structural, functional or electrical consequences.

Figure 1. Cardiac remodelling in elite athletes

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fonds voor Wetenschappelijk Onderzoek (FWO)

P970 Significant differences in atrial structural and functional parameters leading to differing mechanisms of atrial fibrillation in athletes compared to non-athletes

Methods

36 endurance athletes in sinus rhythm, with a previous history of AF (ATH-AF) were compared to age and gender matched endurance athletes with no prior history of AF (ATH), non athletes with paroxysmal AF (NONATH-AF) and age and gender matched healthy controls (CONTROL). A detailed transthoracic echocardiogram was performed with all groups in sinus rhythm, with detailed left atrial (LA) and left ventricular (LV) measurements, including strain analysis.

Results

All athletes had increased LA and LV size when compared with healthy controls (Table 1). Non athletes with paroxysmal AF had increased LA size when compared with controls. However, indexed LA/LV ratio was preserved in athletes and similar to healthy individuals, whilst AF patients had significantly increased LA/LV ratio. Athletes with AF had higher e’ velocity and lower E/e’, whereas e’ was reduced and E/e’ elevated in non-athlete AF patients.

Athletes had impaired LA reservoir and contractile strain, and reduced LV global longitudinal strain (GLS) compared with healthy controls.

Conclusions

Compared to healthy controls, athletes have reduced LA and LV strain, with preserved LV diastolic function and LA/LV ratio. In contrast, altered diastolic function with differential increase in LA volume was observed in AF patients. The increased risk of AF in athletes is likely mediated by different mechanistic processes other than an atrial myopathy consequent to diastolic dysfunction as observed in non-athletes with AF.

Table 1. LA and LV parameters Parameter ATH-AF ATH NONATH-AF CONTROL P value LVEDV indexed (ml/m2) 84 ± 12 79 ± 14 57 ± 10 51 ± 13 <0.001 LVESV indexed (ml/m2) 35 ± 6 34 ± 7 25 ± 8 27 ± 33 0.02 LV ejection fraction (%) 58 ± 4 56 ± 4 56 ± 10 58 ± 8 0.586 LV global longitudinal strain (%) 19.2 ± 1.7 18.9 ± 2.1 21 ± 3.1 21.7 ± 2.9 <0.001 e’ vel (cm/s) 10 ± 2 10 ± 3 8 ± 2 9 ± 2 0.007 E/e’ 5.7 ± 1.3 5.9 ± 1.8 9.1 ± 3.3 7.5 ± 1.5 <0.001 LAV max indexed (ml/m2) 45 ± 11 43 ± 12 38 ± 11 27 ± 8 <0.001 Indexed LAV/LVEDV ratio 0.5 ± 0.1 0.6 ± 0.2 0.7 ± 0.2 0.5 ± 0.1 <0.001 LA reservoir strain (%) 27.2 ± 4.8 28.2 ± 3.7 27.9 ± 8.4 33.2 ± 7.0 <0.001 LA conduit strain (%) 14.2 ± 4.5 14.4 ± 4.0 14.9 ± 5.5 16.6 ± 6.3 0.182 LA contractile strain (%) 13.0 ± 3.1 13.8 ± 3.6 13.0 ± 5.1 16.6 ± 3.1 <0.001 LV = left ventricular, LAV = left atrial volume, LA = left atrial

Implantation of a dual chamber pacemaker in a patient with persistent left superior vena cava

A patient underwent dual chamber pacemaker implantation by puncture of the left subclavian vein. During the procedure we observed persistence of the left superior vena cava. A "J-shaped" atrial lead was used for ventricular pacing with excellent long-term results. This technique can be a valuable alternative when confronted with the problem of persistent left superior vena cava during pacemaker implantation.