Right Ventricular Energetics in Patients With Hypertrophic Cardiomyopathy and the Effect of Alcohol Septal Ablation

The Utility of Nuclear Imaging in Hypertrophic Cardiomyopathy: A Narrative Review

Hypertrophic cardiomyopathy (HCM) is the most common genetically inherited cardiac condition, characterized by clinical heterogeneity and a significantly increased risk of adverse cardiovascular outcomes, including sudden cardiac death. Current diagnostic methods primarily use echocardiography, often supplemented by cardiovascular magnetic resonance imaging (MRI), to assess the clinical profile of the disorder. Effective risk stratification protocols are essential for managing patients with HCM. These models rely on patient histories, imaging findings, and genetic information to evaluate the prognosis. Important factors in risk assessment include severe left ventricular hypertrophy (>30 mm), late gadolinium enhancement (>15%), or the presence of an apical aneurysm. However, these imaging techniques may lack sensitivity when it comes to detecting ischemia or microvascular dysfunction. Nuclear imaging methods, such as single-photon emission computed tomography (SPECT) and positron emission tomography (PET), offer a more comprehensive analysis of HCM. They provide valuable insights into the complex physiological mechanisms underlying the disease and facilitate early detection of functional abnormalities. This is particularly important for identifying high-risk phenotypes and understanding associated risk factors that may increase morbidity or mortality. This narrative review focuses on the role of nuclear imaging in the context of hypertrophic cardiomyopathy.

Right ventricular involvement in hypertrophic cardiomyopathy: evidence and implications from current literature

Objectives. In current guidelines, hypertrophic cardiomyopathy (HCM) is defined by hypertrophy of the left ventricle (LV). Less attention has been given to the right ventricle (RV) in patients with HCM. We wanted to provide an overview of current literature on RV involvement in HCM. Design. We performed a systematic search in PubMed and added additional articles by manual screening of references. The quality of the articles was assessed according to the GRADE system. Results. We identified 35 original articles on RV involvement in HCM. Based on these publications, RV hypertrophy occurs in 28-44% of HCM patients, depending on the cut-off value for hypertrophy and the method for assessment. Histological studies show the same structural changes in RV as are typically described in the LV cardiomyocyte hypertrophy and disarray, as well as fibrosis. These changes are similar, but less pronounced in the RV than in the LV. We discuss how HCM can impact the RV, either through a primary involvement similar to the LV or secondary to hemodynamic effects resulting from LV dysfunction. RV dysfunction in HCM is associated with higher mortality, partly due to an increased risk of ventricular tachycardia and sudden cardiac death. Conclusions. The evidence for RV involvement in HCM is limited. Multimodal imaging assessment of the RV should be included in the work-up of patients with HCM, and the added value of including RV function in the risk stratification algorithm should be further explored.

Biventricular reverse remodeling after successful alcohol septal ablation for obstructive hypertrophic cardiomyopathy

The aim of the present study was to investigate the long-term effects of alcohol septal ablation (ASA) on left ventricular (LV) and right ventricular (RV) remodeling in patients with obstructive hypertrophic cardiomyopathy (HC) using cardiovascular magnetic resonance (CMR). CMR was performed at baseline and 16 months after ASA in 38 patients with obstructive HC (mean age 48 ± 9 years) despite optimal medical treatment. ASA resulted in significant reductions of LV outflow tract gradient (mean 89 ± 22 vs 24 ± 12 mm Hg, p <0.001) and improvements in New York Heart Association functional class (p <0.001) during the follow-up period. LV remote mass and septal mass decreased from 98.34 ± 37.02 to 84.23 ± 34.71 g and from 77.56 ± 16.40 to 68.43 ± 14.02 g, respectively (p <0.001 for both) at 16-month follow-up. There were significant reductions of RV mass (mean 53.69 ± 7.12 vs 47.49 ± 6.17 g, p <0.001) and improvements in RV end-diastolic volume (mean 110.58 ± 22.47 vs 124.22 ± 24.17 ml, p <0.001) and the RV ejection fraction (p <0.001) during 16-month follow-up. Linear regression analysis showed that LV outflow tract gradient reduction was correlated significantly with LV remote mass reduction (r = 0.475, p = 0.003) and RV mass reduction (r = 0.535, p = 0.001) at 16-month follow-up. In conclusion, successful ASA can lead to positive biventricular reverse remodeling, showing significant reductions of RV and LV mass as well as increased RV and LV end-diastolic volumes during follow-up.

Right ventricular function in hypertrophic cardiomyopathy: A speckle tracking echocardiography study

Objective:

The aim of this study was to explore right ventricular (RV) mechanical function in patients with hypertrophic cardiomyopathy (HCM) by 2-D speckle tracking echocardiography (2-D-STE).

Methods:

Forty-three patients with HCM (mean age 48, 17 females) and 40 healthy subjects were consecutively included in this cross-sectional study. The diagnosis of HCM was based on the presence of typical clinical, electrocardiographic (ECG), and echocardiographic features. Patients with LV systolic impairment, significant valvular disease, history of coronary artery disease, hypertension, malignancy, and chronic obstructive pulmonary disease were excluded. Right and left ventricular (LV) function was assessed by tissue Doppler imaging (TDI) and 2-D-STE. Hypertrophic cardiomyopathy patients were divided into two groups according to ACC/ESC guidelines (LVOT gradient below and above 30 mm Hg). Student t-test was used to compare differences between groups. Non-parametric tests (Mann-Whitney U) were used in cases of abnormal distribution.

Results:

Hypertrophic cardiomyopathy patients had a significantly larger right atrium and RV diameters compared to controls. Mean pulmonary artery pressures (mPAB) were significantly higher in HCM patients (19.01±13.09 mm Hg vs. 8.40±4.50 mm Hg; p<0.001). Although RV Sm measure-ments were similar, RV strain measurements (-28.51±5.36% vs. -32.06±7.65%; p=0.016) were significantly lower in HCM patients. Left ventricular global longitudinal, radial, and circumferential strain values were also significantly different between the two groups (-20.50±3.58% vs. -24.12±3.40%; p<0.001, 38.18±12.67% vs. 44.80±10.15%; p=0.012, -21.94±4.28% vs. -23.91±3.95%; p=0.036 consecutively). Rotational movement of LV in each apical, mid-, and basal left ventricular segment was determined, and only mid-ventricular rotation of the HCM patients was more clockwise (-1.71±2.16 ° vs. 0.04±1.72 p<0.001). Although mPAP measurements were higher in HCM patients with significant LVOT obstruction (21.52±13.26 mm Hg vs. 12.31±10.53 mm Hg; p=0.049), none of the other TDI or 2-D-STE parameters was significantly different between groups.

Conclusion:

Speckle tracking echocardiography-derived right ventricular systolic function is impaired in HCM patients when compared with healthy subjects. However, RV systolic function is not affected form LVOT obstruction and left ventricular rotation dynamics in HCM patients.

Attenuated right ventricular energetics evaluated using ¹¹C-acetate PET in patients with pulmonary hypertension

PURPOSE

The right ventricle (RV) has a high capacity to adapt to pressure or volume overload before failing. However, the mechanisms of RV adaptation, in particular RV energetics, in patients with pulmonary hypertension (PH) are still not well understood. We aimed to evaluate RV energetics including RV oxidative metabolism, power and efficiency to adapt to increasing pressure overload in patients with PH using (11)C-acetate PET.

METHODS

In this prospective study, 27 patients with WHO functional class II/III PH (mean pulmonary arterial pressure 39.8 ± 13.5 mmHg) and 9 healthy individuals underwent (11)C-acetate PET. (11)C-acetate PET was used to simultaneously measure oxidative metabolism (k mono) for the left ventricle (LV) and RV. LV and RV efficiency were also calculated.

RESULTS

The RV ejection fraction in PH patients was lower than in controls (p = 0.0054). There was no statistically significant difference in LV k mono (p = 0.09). In contrast, PH patients showed higher RV k mono than did controls (0.050 ± 0.009 min(-1) vs. 0.030 ± 0.006 min(-1), p < 0.0001). PH patients exhibited significantly increased RV power (p < 0.001) and hence increased RV efficiency compared to controls (0.40 ± 0.14 vs. 0.017 ± 0.12 mmHg·mL·min/g, p = 0.001).

CONCLUSION

The RV oxidative metabolic rate was increased in patients with PH. Patients with WHO functional class II/III PH also had increased RV power and efficiency. These findings may indicate a myocardial energetics adaptation response to increasing pulmonary arterial pressure.