Risks of Ventricular Arrhythmia and Heart Failure in Carriers of RBM20 Variants

BACKGROUND

Variants in RBM20 are reported in 2% to 6% of familial cases of dilated cardiomyopathy and may be associated with fatal ventricular arrhythmia and rapid heart failure progression. We sought to determine the risk of adverse events in RBM20 variant carriers and the impact of sex on outcomes.

METHODS

Consecutive probands and relatives carrying RBM20 variants were retrospectively recruited from 12 cardiomyopathy units. The primary end point was a composite of malignant ventricular arrhythmia (MVA) and end-stage heart failure (ESHF). MVA and ESHF end points were also analyzed separately and men and women compared. Left ventricular ejection fraction (LVEF) contemporary to MVA was examined. RBM20 variant carriers with left ventricular systolic dysfunction (RBM20LVSD) were compared with variant-elusive patients with idiopathic left ventricular systolic dysfunction.

RESULTS

Longitudinal follow-up data were available for 143 RBM20 variant carriers (71 men; median age, 35.5 years); 7 of 143 had an MVA event at baseline. Thirty of 136 without baseline MVA (22.0%) reached the primary end point, and 16 of 136 (11.8%) had new MVA with no significant difference between men and women (log-rank P=0.07 and P=0.98, respectively). Twenty of 143 (14.0%) developed ESHF (17 men and 3 women; log-rank P<0.001). Four of 10 variant carriers with available LVEF contemporary to MVA had an LVEF >35%. At 5 years, 15 of 67 (22.4%) RBM20LVSD versus 7 of 197 (3.6%) patients with idiopathic left ventricular systolic dysfunction had reached the primary end point (log-rank P<0.001). RBM20 variant carriage conferred a 6.0-fold increase in risk of the primary end point.

CONCLUSIONS

RBM20 variants are associated with a high risk of MVA and ESHF compared with idiopathic left ventricular systolic dysfunction. The risk of MVA in male and female RBM20 variant carriers is similar, but male sex is strongly associated with ESHF.

Metoprolol Improves Left Ventricular Longitudinal Strain at Rest and during Exercise in Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

Patients with obstructive hypertrophic cardiomyopathy (HCM) often experience symptoms of heart failure upon exertion despite having normal left ventricular (LV) ejection fractions. Longitudinal strain (LS) may be a more sensitive marker of systolic dysfunction in patients with LV hypertrophy. The aims of this study were to characterize LV segmental LS and global LS (GLS) at rest and during exercise and to assess if first-line treatment with β-blockers improves LV systolic performance.

METHODS

Twenty-nine patients with obstructive HCM and New York Heart Association functional class ≥ II symptoms were enrolled in a double-blind, placebo-controlled, randomized crossover trial. Patients received metoprolol 150 mg or placebo for two consecutive 2-week periods in random order. Echocardiographic assessment with speckle-tracking-derived LS was performed at rest and during peak exercise at the end of each treatment period.

RESULTS

During placebo treatment, resting values of segmental LS showed an apical-basal difference of -10.3% (95% CI, -12.7% to -7.8%; P < .0001), with a severely abnormal value of the basal segment of -9.3 ± 4.2%. Treatment with metoprolol was associated with more negative LS values of the apical segment (-2.8%; 95% CI, -4.2% to -1.3%; P < .001) and the mid segment (-1.1%; 95% CI, -2.0% to -0.3%; P = .007). During peak exercise there was a deterioration in LV GLS, but treatment with metoprolol was associated with more negative peak exercise LV GLS (-1.3 %; 95% CI, -2.6% to -0.1%; P = .03).

CONCLUSIONS

Systolic performance assessed by LV GLS showed impaired values at rest and during exercise, with severely depressed values of the basal and mid segments. Treatment with metoprolol improved LV GLS upon exercise, indicating a beneficial effect of β-blocker treatment on LV systolic function.

Effects of Metoprolol on Exercise Hemodynamics in Patients With Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

The relationship between exercise hemodynamics, loading conditions, and medical treatment in patients with obstructive hypertrophic cardiomyopathy (HCM) is incompletely understood.

OBJECTIVES

This study aimed to investigate the effect of metoprolol on invasive hemodynamic parameters at rest and during exercise in patients with obstructive HCM.

METHODS

This randomized, double-blind, placebo-controlled crossover trial enrolled 28 patients with obstructive HCM and New York Heart Association functional class ≥II. Patients were randomized to initiate either metoprolol 150 mg or placebo for 2 consecutive 2-week periods. Right-heart catheterization and echocardiography were performed at rest and during exercise at the end of each treatment period. The primary outcome was the difference in pulmonary capillary wedge pressure (ΔPCWP) between peak exercise and rest.

RESULTS

No treatment effect on ΔPCWP was observed between metoprolol and placebo treatment (21 ± 9 mm Hg vs 23 ± 9 mm Hg; P = 0.12). At rest, metoprolol lowered heart rate (P < 0.0001), left ventricular outflow tract (LVOT) gradient (P = 0.01), and increased left ventricular end-diastolic volume (P = 0.02) and stroke volume (SV) (+6.4; 95% CI: 0.02-17.7; P = 0.049). During peak exercise, metoprolol was associated with a lower heart rate (P < 0.0001), a lower LVOT gradient (P = 0.0005), lesser degree of mitral regurgitation (P = 0.004), and increased SV (+9 mL; 95% CI: 2-15 mL; P = 0.008).

CONCLUSIONS

In patients with obstructive HCM, exercise was associated with an abnormal rise in PCWP, which was unaffected by metoprolol. However, metoprolol increased SV at rest and peak exercise following changes in end-diastolic volume, LVOT gradient, and degree of mitral regurgitation. (The Effect of Metoprolol in Patients With Hypertrophic Obstructive Cardiomyopathy [TEMPO]; NCT03532802).

Randomized Trial of Metoprolol in Patients With Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

The use of β-adrenergic receptor blocking agents in symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM) rests on clinical experience and observational cohort studies.

OBJECTIVES

This study aimed to investigate the effects of metoprolol on left ventricular outflow tract (LVOT) obstruction, symptoms, and exercise capacity in patients with obstructive HCM.

METHODS

This double-blind, placebo-controlled, randomized crossover trial enrolled 29 patients with obstructive HCM and New York Heart Association (NYHA) functional class II or higher symptoms from May 2018 to September 2020. Patients received metoprolol or placebo for 2 consecutive 2-week periods in random order. The effect parameters were LVOT gradients, NYHA functional class, Canadian Cardiovascular Society (CCS) angina class, Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS), and cardiopulmonary exercise testing.

RESULTS

Compared with placebo, the LVOT gradient during metoprolol was lower at rest (25 mm Hg [interquartile range (IQR): 15-58 mm Hg] vs 72 mm Hg [IQR: 28-87 mm Hg]; P = 0.007), at peak exercise (28 mm Hg [IQR: 18-40 mm Hg] vs 62 mm Hg [IQR: 31-113 mm Hg]; P < 0.001), and postexercise (45 mm Hg [IQR: 24-100 mm Hg] vs 115 mm Hg [IQR: 55-171 mm Hg]; P < 0.0001). During metoprolol treatment, 14% of patients were in NYHA functional class III or higher compared with 38% of patients receiving placebo (P < 0.01). Similarly, no patients were in CCS class III or higher during metoprolol treatment compared with 10% during placebo treatment (P < 0.01). These findings were confirmed by higher KCCQ-OSS during metoprolol treatment (76.2 ± 16.2 vs 73.8 ± 19.5; P = 0.039). Measures of exercise capacity, peak oxygen consumption, and N-terminal pro-B-type natriuretic peptide did not differ between the study arms.

CONCLUSIONS

Compared with placebo, metoprolol reduced LVOT obstruction at rest and during exercise, provided symptom relief, and improved quality of life in patients with obstructive HCM. Maximum exercise capacity remained unchanged. (The Effect of Metoprolol in Patients with Hypertrophic Obstructive Cardiomyopathy [TEMPO]; NCT03532802).

Clinical effects of metoprolol in obstructive hypertrophic cardiomyopathy (TEMPO). A randomized, double-blinded, placebo-controlled crossover trial

Background

Treatment with beta blockers (BB) has been used for symptomatic relief in patients with obstructive hypertrophic cardiomyopathy (HCM) for decades. Even so, the guideline recommendation for the use of BB rests on expert opinions and observational cohort studies. Providing comprehensive high-quality data on the effects of BB in obstructive HCM is essential, especially in the context of newly developed pharmacological treatment strategies specifically targeting this disease (1).

Purpose

The study aimed to investigate the effects of metoprolol on left ventricular outflow tract (LVOT) obstruction, symptoms, and exercise capacity in patients with obstructive HCM.

Methods

This double-blinded, placebo-controlled, randomized crossover trial enrolled 30 patients with obstructive HCM and New York Heart Association (NYHA) class ≥ II symptoms from 1 May 2018 to 1 September 2020. Patients received metoprolol or placebo for two consecutive two-week periods in random order. The effect parameters were LVOT gradients, NYHA class, Canadian Cardiovascular Society (CCS) grading angina class, Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS), and cardiopulmonary exercise testing.

Results

Compared with placebo, the LVOT gradient during metoprolol was lower at rest (25 [15–58] mmHg versus 72 [28–87] mmHg; p=0.007), at peak exercise (28 [18–40] mmHg versus 62 [31–113] mmHg; p&lt;0.001), and post-exercise (45 [24–100] mmHg versus 115 [55–171] mmHg; p&lt;0.0001) (figure 1). During metoprolol treatment, 14% of patients were in NYHA class III compared with 38% on placebo (p&lt;0.01). Likewise, no patients were in CCS class ≥ III during metoprolol compared with 10% during placebo (p&lt;0.01). These findings were confirmed by a higher KCCQ-OSS score during metoprolol (76.2 (16.2) versus 73.8 (19.5), p=0.039) (figure 2). Peak oxygen consumption did not differ between study arms.

Conclusion

Compared with placebo, metoprolol reduced LVOT obstruction at rest and during exercise, provided symptom relief, and improved quality of life in patients with obstructive HCM. However, exercise capacity remained unchanged. Findings from the present study support the guideline recommendations that BB should be the first drug of choice in patients with obstructive HCM who develop symptoms.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Novo nordic foundation, Skibsreder Per Henriksen, R. og hustrus Foundation