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Comparing hydrochlorothiazide and valsartan for treating high blood pressure in patients with hypertrophic obstructive cardiomyopathy

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What is this study about?

This study examines hypertrophic cardiomyopathy, a condition where the heart muscle becomes abnormally thick, which can make it harder for the heart to pump blood effectively. In some patients with this condition, the thickened muscle can block blood flow out of the heart, which is called obstructive hypertrophic cardiomyopathy. Many people with this heart condition also have high blood pressure, which is when the force of blood against the artery walls is too high. The study will compare two different medications used to lower blood pressure: hydrochlorothiazide, which is a water pill that helps the body get rid of extra salt and water, and valsartan, which works by relaxing blood vessels to make it easier for blood to flow through them.

The purpose of the study is to find out whether low dose hydrochlorothiazide causes less of an increase in the pressure difference across the blocked area of the heart compared to valsartan in patients who have both the obstructive heart condition and high blood pressure. Both medications are commonly used to treat high blood pressure, but doctors want to understand which one is better for patients with this specific heart condition. The study will measure the pressure gradient, which is the difference in pressure that occurs when blood tries to flow through the narrowed area of the heart.

This is a crossover study, which means that participants will receive both treatments at different times. The study is double-blind, meaning neither the participants nor the doctors will know which medication is being given at any particular time. Each treatment period will last for 30 days. During the study, measurements will be taken to see how each medication affects the blockage in the heart, blood pressure, heart function markers in the blood, and quality of life. Participants will need to be taking a medication called a betablocker at the highest dose they can tolerate before joining the study.

1 Initial treatment preparation

At the start of the study, your current blood pressure treatment will be reviewed. You should already be taking a beta-blocker medication at the highest dose you can tolerate, or have a medical reason why you cannot take this type of medication.

A beta-blocker is a medication that helps slow down your heart rate and reduce the force of your heart’s contractions.

Your blood pressure will be measured after you have not eaten for at least six hours. This is called fasting blood pressure.

2 First treatment period

You will be assigned to receive one of two medications: either hydrochlorothiazide or valsartan. The medication will be given as a tablet that you swallow by mouth.

Hydrochlorothiazide is a water pill that helps your body remove excess fluid and salt, which can lower blood pressure.

Valsartan is a medication that relaxes blood vessels to help lower blood pressure.

Neither you nor your doctor will know which medication you are receiving during this period. This is called a double-blind study design.

You will take the assigned medication for a specific period of time.

3 Monitoring during first treatment

During this treatment period, your heart function will be assessed. This includes measuring the pressure gradient in your heart, which is the difference in pressure as blood flows through the left ventricular outflow tract.

The left ventricular outflow tract is the path through which blood leaves the main pumping chamber of your heart.

You will have measurements taken at rest, which means while you are sitting or lying quietly.

Some measurements will be taken 30 to 60 minutes after you eat a standardized meal.

You may be asked to perform a Valsalva maneuver, which involves taking a deep breath and bearing down as if you are straining. This helps assess how your heart responds to changes in pressure.

Your blood pressure will be measured multiple times, including after eating.

Blood samples will be taken to measure substances in your blood, including NT-proBNP (a marker of heart stress), troponin (a marker of heart muscle damage), and interleukin-6 (a marker of inflammation).

4 Quality of life assessments

You will be asked to complete questionnaires about your symptoms and quality of life.

One questionnaire is called the Kansas City Cardiomyopathy Questionnaire, which asks about how your heart condition affects your daily activities.

Another questionnaire is the EQ5D5L, which asks about your overall health and well-being.

Your doctor will also assess your NYHA class, which is a way of describing how much your heart condition limits your physical activity.

5 Optional exercise test

If you participate in the exercise testing portion of the study, you will undergo a cardiopulmonary exercise test.

This test measures how well your heart and lungs work together during physical activity. You will exercise on a treadmill or stationary bike while your breathing and heart function are monitored.

The test measures peak oxygen consumption, which shows how much oxygen your body can use during maximum effort.

6 Washout period

After completing the first treatment period, there will be a break before starting the second treatment. This is called a washout period.

During this time, the first medication will be cleared from your body before you start the second medication.

7 Second treatment period

You will now receive the other medication that you did not take during the first treatment period. If you took hydrochlorothiazide first, you will now take valsartan, or vice versa.

This is called a crossover design, which means all participants receive both treatments at different times.

The medication will again be given as a tablet that you swallow by mouth.

You will take this second medication for the same length of time as the first treatment period.

8 Monitoring during second treatment

All the same measurements and assessments from the first treatment period will be repeated.

This includes heart function measurements at rest and after eating, blood pressure readings, blood tests, and the Valsalva maneuver.

The purpose is to compare how your body responds to each of the two different medications.

9 Repeat quality of life assessments

You will complete the same questionnaires about your symptoms and quality of life again.

Your NYHA class will be reassessed.

If you participated in the exercise testing portion, you will repeat the cardiopulmonary exercise test.

10 Safety monitoring throughout the study

Throughout both treatment periods, any side effects or health problems you experience will be recorded and monitored.

Serious health problems, called serious adverse events, will be carefully tracked and reported.

Your doctor will regularly check to ensure the study medications are safe for you.

11 Study completion

After completing both treatment periods and all required assessments, your participation in the study will be complete.

The results from both treatment periods will be compared to determine which medication has less effect on the pressure gradient in your heart while still controlling your blood pressure.

Who Can Join the Study?

  • You must have a diagnosis of HCM (a condition where the heart muscle becomes abnormally thick), confirmed according to current medical guidelines. This means having a thickened heart wall measuring 15 millimeters or more, or 13 millimeters or more if someone in your family has the same condition, and this thickening is not caused by other factors.
  • You must have a specific type of obstruction in your heart called SAM-associated LVOTO, which means a blockage in the path where blood leaves the heart. This blockage must show a pressure difference of at least 30 millimeters of mercury when measured at rest, 30 to 60 minutes after eating a standard meal.
  • Your blood pressure must be at least 135 over 85 millimeters of mercury when measured in a medical office after not eating for at least six hours. Either the top number or the bottom number must be increased.
  • You must be taking a heart medication called a cardioselective betablocker (a medicine that helps slow the heart rate and reduce its workload) at the highest dose you can tolerate, or you must be unable to take this medication due to side effects or medical reasons that make it unsafe for you.
  • You must be at least 18 years old.
  • If you are a woman, you must not be pregnant or breastfeeding. Additionally, you must either be unable to become pregnant, or if you can become pregnant, you must be using a highly effective birth control method (one that works more than 99% of the time) during the study period.
  • If you are a man, no additional birth control measures are required.
  • You must be willing and able to read and sign a consent form that explains the study, following all required guidelines.

Who Cannot Join the Study?

  • No exclusion criteria have been specified for this clinical trial in the available information.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name City Country Status
Medical University Of Vienna Vienna Austria
Medical University Of Graz Graz Austria

Other Sites

Site Name City Country Status
Landesklinikum Wiener Neustadt Vienna Austria
Kepler Universitaetsklinikum GmbH Linz Austria
Universitätsklinikum St. Pölten St. Poelten Austria

Want to learn more about this study or check if you can participate? Contact us.

Trial status

Country Status Recruitment Start
Austria Austria
Recruiting
12.01.2026

Trial locations

Investigated drugs:

Hydrochlorothiazide is a water pill (diuretic) that helps your body get rid of extra salt and water by making you urinate more. It is commonly used to treat high blood pressure. In this trial, it is being tested to see how it affects the heart in patients who have both high blood pressure and a thickened heart muscle that blocks blood flow.

Valsartan is a medication that relaxes blood vessels by blocking certain chemicals in your body that tighten blood vessels. This helps lower blood pressure and makes it easier for your heart to pump blood. In this trial, it is being compared with hydrochlorothiazide to see which medication works better for patients with high blood pressure and a specific heart condition that causes obstruction in the heart’s pumping chamber.

Investigated diseases:

Hypertrophic Cardiomyopathy – A condition where the heart muscle becomes abnormally thick, making it harder for the heart to pump blood effectively. The thickening most often occurs in the wall that separates the left and right sides of the heart. As the disease progresses, the thickened muscle can block blood flow out of the heart, causing the heart to work harder to pump blood. This obstruction can lead to shortness of breath, chest pain, and dizziness, especially during physical activity. The heart muscle may also become stiff, affecting its ability to relax and fill with blood properly. Over time, these changes can affect the heart’s rhythm and its overall ability to function normally.

Trial ID:
2024-520086-31-00
Protocol code:
NV-2025-01
Trial Phase:
Therapeutic confirmatory (Phase III)

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