Hypertrophic cardiomyopathy (HCM) is a common heart condition in which the heart muscle becomes abnormally thick. In non-obstructive HCM, blood flow out of the heart is not blocked, but many patients still experience chest pain, breathlessness and limitation of daily activities. This may be because the small blood vessels within the thickened heart muscle do not supply enough blood and oxygen, particularly during exercise or stress.
Current treatment options for symptomatic non-obstructive HCM are limited.
This study will test a small device called the coronary sinus reducer (CSR), which is placed into a vein of the heart using a catheter. The CSR is designed to improve blood flow to areas of heart muscle that are short of blood supply.
Fifty adults with non-obstructive HCM, ongoing symptoms and reduced blood supply on a heart MRI scan will take part.
Participants will be randomly assigned to receive either CSR implantation or a placebo procedure. Neither participants nor the follow-up research team will know which procedure was performed until the 6-month follow-up assessments are complete.
The investigators will use detailed heart MRI scans to measure blood flow, a smartphone app to record daily symptoms, coronary sinus blood tests to look for biochemical evidence of reduced oxygen supply, and invasive coronary physiology measurements to assess the small blood vessels of the heart. The main aim is to find out whether the CSR improves blood flow and reduces symptoms. The results may identify a new treatment option for patients with non-obstructive HCM and improve understanding of the disease.
Non-obstructive hypertrophic cardiomyopathy (LVOT gradient ≤30 mmHg at rest on echocardiography)
Ongoing symptoms despite current medical therapy
Significant perfusion defects (≥ 2 myocardial segments) on stress perfusion CMR
Age < 18 years
Left ventricular impairment LVEF <55%
Severe renal impairment (Estimated glomerular filtration rate <30mL/min/1.73m2)
Right atrial pressure ≥ 15 mmHg
Parallel
Coronary sinus reducer
DeviceThe Shockwave Reducer (coronary sinus reducer) is intended to create a controlled narrowing that increases coronary sinus pressure and redistributes venous blood flow from epicardial to subendocardial regions, thereby improving myocardial perfusion in areas of microvascular ischaemia.
Placebo procedure
Procedure/SurgeryParticipants in the placebo group will not have the device implanted, but will remain sedated in the catheter laboratory for 15-30 minutes so that the experience is similar and blinding is maintained.
Daily symptom frequency during blinded 6-month follow-up
Patient-reported. ORBITA-app daily symptom reporting.
The change in ratio of stress MBF in ischaemic versus non-ischaemic myocardial subsegments at 6 months comparing CSR and placebo groups
Quantitative stress perfusion CMR.
Coronary sinus lactate concentration during adenosine stress
Coronary sinus blood samples obtained during adenosine stress and analysed immediately using a standard blood gas analyser to determine lactate concentration.
Coronary sinus pH during adenosine stress
Coronary sinus blood samples obtained during adenosine stress and analysed immediately using a standard blood gas analyser to determine pH.
MacNew Heart Disease Health-related Quality of Life Questionnaire
Global score range 1 to 7; higher scores indicate better health-related quality of life.
Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS)
The Kansas City Cardiomyopathy Questionnaire (KCCQ-23) Clinical Summary Score will be derived. Score range 0 to 100; higher scores indicate better health status.
Stress myocardial blood flow (MBF) in ischaemic, non-ischaemic myocardial segments, and globally
Quantitative stress perfusion CMR. Myocardial blood flow will be quantified in mL/g/min.
Rest myocardial blood flow (MBF) in ischaemic, non-ischaemic myocardial segments, and globally
Quantitative stress perfusion CMR. Myocardial blood flow will be quantified in mL/g/min at rest.
Myocardial perfusion reserve (MPR) in ischaemic, non-ischaemic myocardial segments, and globally
Quantitative stress perfusion CMR. Myocardial perfusion reserve will be calculated as the ratio of stress myocardial blood flow to rest myocardial blood flow.
Endocardial:epicardial perfusion ratio
Quantitative stress perfusion CMR.
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