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Microcirculatory PerfusionDIRECT-HEARTNCT07135700

Hemodynamic Evaluation and Assessment of DIRECT myocaRdial and Sublingual Capillary Perfusion in Thoracic Surgery Patients on Cardiopulmonary Bypass

An observational study of Microcirculatory Perfusion, run by Academisch Medisch Centrum - Universiteit van Amsterdam (AMC-UvA) at 1 site in Netherlands.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

After cardiac surgery, some people may experience problems with their circulation or how well the heart pumps. This can occur because the smallest blood vessels in the heart do not function properly. Read more about this study

Who is it for?
Any age
Conditions the study is for
Microcirculatory Perfusion
How many people
30 participants
Where
1 siteNetherlands
Study dates
2 Nov 2026to 1 Oct 2029
Phase
Observational
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages Any age
  • All sexes
  • No healthy volunteers
  • Child, Adult, Older adult

Study population: The patients are selected from the surgical waiting list. Since we aim to include only elective adult patients with minimal comorbidities and a low or intermediate European System for Cardiac Operative Risk Evaluation (EuroSCORE) II (i.e., low or intermediate risk of in-hospital mortality), a significant number of patients are eligible. On our department, we perform approximately 20 cardiac surgeries per week, with valve surgeries representing a relatively large portion. The distribution of surgeries varies from week to week. However, a significant proportion of patients cannot be included due to the need for concomitant coronary revascularization or a history of such procedures

Who may be able to join

  • Adult patients (18 years or older)
  • Use of central cannulated CPB through median sternotomy
  • Patients undergoing valve surgery or a supracoronary ascending aorta replacement
  • Good LVEF and RVF
  • LAVI < 50 ml/m2, and right atrial volume index (RAVI) < 45 ml/m2,

Who cannot join

  • Patients with significant coronary artery disease (i.e., CAD-RADS ≥ 4, and/or stenosis of ≥ 70% as observed in coronary angiogram) or previous infarctions, including ST-elevated myocardial ischemia (STEMI) or non-ST-elevated myocardial ischemia (N-STEMI)
  • Patients with echocardiographically observed regional wall motion abnormalities, hypokinesis, or akinesis in the coronary territories
  • Patients undergoing left atrial appendage amputation (LAAA)
  • Patients with AF
  • High-risk patients, as defined by a EuroSCORE II ≥ 8%

Trial locations and contacts

1 site in 1 country. Contact the study team or a site near you to ask about taking part.

Bahaeddin Ufuk Baldan, DR MD contact

+31640001607

b.u.baldan@amsterdamumc.nl

Netherlands1 site, 1 recruiting
  • Amsterdam Univeristy Medical Center

    Amsterdam, North Holland, 1105 AZ

    Ufuk Baldan, MD, +31640001607, b.u.baldan@amsterdamumc.nl

    Recruiting

Other trials in Netherlands

About this study

After cardiac surgery, some people may experience problems with their circulation or how well the heart pumps. This can occur because the smallest blood vessels in the heart do not function properly. When these vessels don't work correctly, organs and tissues don't receive enough oxygen and nutrients, which can lead to circulatory problems and organ damage.

Typically, treatments focus on improving the larger blood vessels, such as blood pressure and heart function, but the investigators don't yet know enough about the smallest blood vessels. In this study, the investigators measure blood flow using a special camera (a microscope) at two locations: under the tongue and directly on the heart. Measurements under the tongue are already performed more frequently, but measurements directly on the heart are still new.

Read more

If the investigators can demonstrate that differences in cardiac blood flow can also be observed under the tongue, it will become easier to conduct research on microcirculation. The use of the device is safe, and measurements are performed under strict supervision and control by experienced physicians and researchers.

Ultimately, the investigators hope to use this knowledge to better prevent or treat complications after cardiac surgery.

The aim of this research is to investigate whether measurements of blood flow in the smallest blood vessels (microcirculation) on the heart provide the same information as measurements of microcirculation under the tongue.

This appears to be describing a clinical study comparing sublingual and epicardial microcirculation monitoring techniques to potentially establish a less invasive method for assessing cardiac microvascular function in post-surgical patients.

Read the detailed description

Congruence of micro- and macrocirculation is essential in participants during the postcardiotomy period to maintain hemodynamic stability [1,2]. At the capillary (i.e. microcirculatory) level, gas and nutrient exchange occurs, while macrocirculation facilitates these exchanges by ensuring that blood flows with appropriate pressure and velocity. A mismatch in this relationship, where the capillary perfusion does not correlate with the macrocirculatory parameters, is frequently observed in patients with shock or heart failure [3,4]. This discrepancy is often caused by capillary leak or hemodilution. To date, treatment has primarily focused on correcting macroscopically observed variables or values derived from them and resulting in pressure- or flow-dependent therapies.

While sublingual capillary perfusion measurements provide systemic insights, direct myocardial capillary perfusion assessment offers a direct and regional perspective. Unlike systemic capillary beds, myocardial perfusion is directly influenced by filling pressures, such as left ventricular end-diastolic pressure (LVEDP) [5]. Impaired myocardial capillary perfusion can lead to a cascade of cardiac dysfunction, including reduced oxygen delivery, inadequate nutrient exchange and making it vulnerable to ischemia or hibernation [1].

Current literature has examined intra- and postoperative sublingual (i.e., systemic) capillary perfusion following cardiac surgery [5]. Cardiopulmonary bypass (CPB), commonly used in many types of heart surgeries, inherently disrupts capillary perfusion due to its extracorporeal nature. The use of CPB alone triggers systemic inflammation, reperfusion injury and hemodilution, leading to the accumulation of metabolic waste products, formation of free oxygen radicals and perfusion alternations [7]. Additionally, the participants undergo an invasive cardiac procedure, accompanied by anesthesia and other contributing factors that negatively impact the capillary perfusion [8]. These alterations manifest in differences in microcirculatory parameters, including total vessel density (TVD), perfused vessel density (PVD), proportion of perfused vessels (PPV), microvascular flow index (MFI), and heterogeneity index (HI) [9].

Additionally, unloading the left ventricle (LV) unloading is posited to be critical for improving myocardial circulation. LV unloading is a promising concept that theoretically could improve capillary perfusion by reducing LVEDP and hence myocardial work. LV unloading could be particularly important for heart failure patients in acute cardiogenic shock. It may help promote myocardial circulation and prevent pulmonary edema. However, there is currently no robust scientific evidence to support these benefits and remains a subject of debate and philosophical discourse within the medical community [11-13].

To address this, the investigators aim to investigate whether capillary perfusion changes induced by CPB flow alterations, measured at sublingual and myocardial sites, provide consistent results. Additionally, the investigators will assess the effect of LV unloading on the capillary perfusion. The investigators will employ a handheld IDF-microcamera to perform real-time measurements of capillary perfusion. The investigators hypothesize that during hemodynamic alternations via CPB-flow sublingual and myocardial capillary perfusion measurements will show minimal differences and correlate with each other. This would supporting the validity of sublingual capillary perfusion measurements as a reliable, non-invasive proxy for the myocardial capillary perfusion status. Furthermore, the investigators anticipate an improvement in solely myocardial of both sublingual and myocardial capillary perfusion with LV unloading. These findings will significantly advance our understanding of the interaction between macro- and microcirculatory systems, providing a foundation for the use of sublingual measurements in both clinical and research settings. Ultimately, this could simplify monitoring techniques, enhance perioperative management, and help elucidate the mechanisms underlying persistent hemodynamic instability, guiding the development of more effective strategies to optimize postoperative outcomes

Keywords
cardiac surgery, microcirculation, capillary perfusion

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

Study groups in NCT07135700
Study groupRoleWhat they receive
Cardiac surgery patientsIn order to be eligible to participate in this study, a participant must meet all of the following criteria: * Adult patients (18 years or older) * Use of central cannulated CPB through median sternotomy * Patients undergoing valve surgery or a supracoronary ascending aorta replacement * Good LVEF and RVF * LAVI < 50 ml/m2, and right atrial volume index (RAVI) < 45 ml/m2,

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. TVD (Total Vessel Density)

    The number of small blood vessels (< 20 μm) in a given area. (Vessel density in #/area)

    Measured: Intraoperatively

  2. PVD (Perfused Vessel Density)

    The number of small blood vessels that show perfusion, defined by a flow score of 2 or higher (moderate to normal flow). (Perfusion vessel density in #/area)

    Measured: Intraoperatively

  3. PVD (Perfused Vessel Density)

    The ratio of total vessel length to the length of perfused vessels. (Ratio)

    Measured: Intraoperatively

  4. MFI (Microvascular Flow Index)

    A semi-quantitative measure that evaluates flow in the capillary perfusion. (Flow score)

    Measured: Intraoperatively

  5. HI (Heterogenity Index)

    The degree of variation in capillary perfusion flow between different areas, calculated as the difference between the highest and lowest MFI, divided by the average MFI. (Variation index)

    Measured: Intraoperatively

Secondary outcomes (11)
  1. Demographic information: Age

    Reported in years.

    Measured: Preoperatively

  2. Demographic Information: Gender

    Categorized as male/female/other.

    Measured: Preoperatively

  3. Demographic Information: Body Mass Index (BMI)

    Calculated as weight (kg) divided by height squared (m²). Reported in kg/m²

    Measured: Preoperatively

  4. Demographic Information: Medical History

    Presence or absence of pre-existing conditions, such as hypertension, diabetes, prior heart surgeries; each condition reported as a separate categorical variable (yes/no).

    Measured: Preoperatively

  5. Demographic Information: Comorbidities

    Presence or absence of vascular disease other than coronary artery disease, kidney dysfunction, pulmonary disease; each as separate categorical variables.

    Measured: Preoperateively

  6. Surgical Variables: Type of Underlying Pathology

    Described separately for valve regurgitation, valve stenosis, aneurysm; categorical variable.

    Measured: Preoperatively

  7. LV Unloading Variables: TVD (Total Vessel Density, # vessels per area)

    Capillary perfusion parameters measured separately, as they have different units and scales, consistent with primary objectives:

    Each perfusion parameter is reported separately for conditions with and without LV unloading.

    Measured: Intraoperatively

  8. LV Unloading Variables: PVD (Perfused Vessel Density, # vessels per area)

    Capillary perfusion parameters measured separately, as they have different units and scales, consistent with primary objectives:

    Each perfusion parameter is reported separately for conditions with and without LV unloading.

    Measured: Intraoperatively

  9. LV Unloading Variables: PPV (Proportion of Perfused Vessels, ratio)

    Capillary perfusion parameters measured separately, as they have different units and scales, consistent with primary objectives:

    Each perfusion parameter is reported separately for conditions with and without LV unloading.

    Measured: Intraoperatively

  10. LV Unloading Variables: MFI (Microvascular Flow Index, semi-quantitative score)

    Capillary perfusion parameters measured separately, as they have different units and scales, consistent with primary objectives:

    Each perfusion parameter is reported separately for conditions with and without LV unloading.

    Measured: Intraoperatively

  11. LV Unloading Variables: - HI (Heterogeneity Index, variation ratio)

    Capillary perfusion parameters measured separately, as they have different units and scales, consistent with primary objectives:

    Each perfusion parameter is reported separately for conditions with and without LV unloading.

    Measured: Intraoperatively

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted22 Aug 2025
  2. Study start2 Nov 2026 (estimated)
  3. Primary completion1 Jun 2028 (estimated)
  4. Study completion1 Oct 2029 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Observational
Observational model
Case-control
Time perspective
Prospective
Enrolment
30 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07135700
Sponsor's protocol ID
DIRECT-HEART
Acronym
DIRECT-HEART
Status last verified
Oct 2026
First submitted
13 Aug 2025
Last updated
4 Nov 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
Undecided: Depending on the outcome

Questions about this trial

What is this clinical trial studying?

An observational study of Microcirculatory Perfusion, run by Academisch Medisch Centrum - Universiteit van Amsterdam (AMC-UvA) at 1 site in Netherlands.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 5 inclusion and 5 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 4 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in Netherlands. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Bahaeddin Ufuk Baldan, DR MD (+31640001607, b.u.baldan@amsterdamumc.nl), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

TVD (Total Vessel Density) (time frame: Intraoperatively). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 4 Nov 2026.

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