Validation of Myocardial Perfusion and Extracellular Volume Assessment Using Photon-Counting Computed Tomography (PCCT) Compared With Cardiac Magnetic Resonance (CMR) in Patients Undergoing Transcatheter Aortic Valve Implantation (TAVI)

Validering av genomblödning Och extracellulärvolym i hjärtmuskeln Med datortomografiundersökning Hos Patienter Som Ska genomgå Perkutan Aortaklaffbyte (TAVI)

Cardiovascular diseases are the leading cause of death worldwide, responsible for about 30% of all deaths. This substantial burden highlights the need for accurate diagnostic tools that help doctors detect heart disease early and understand it more fully. Recent advances in medical imaging offer promising opportunities to improve how heart conditions are diagnosed and treated.

One important development in computed tomography (CT), a widely used imaging technique, is photon counting computed tomography (PCCT). PCCT produces clearer and more detailed images of the heart while using lower radiation doses and smaller amounts of contrast agent, the dye injected into the bloodstream to make body tissues more visible. As PCCT is still a relatively new technology, its full potential in clinical heart imaging has not yet been fully explored.

This study includes patients with narrowing of the aortic valve, a condition that reduces blood flow from the heart and often requires treatment. These patients undergo cardiac CT before receiving a minimally invasive valve replacement procedure called transcatheter aortic valve implantation (TAVI). The study evaluates two diagnostic applications of PCCT:

Functional assessment: Blood flow to the heart muscle is examined during stress imaging, when the heart works harder, to determine whether narrowed coronary arteries significantly limit blood supply.

Tissue characterization: The heart muscle is analyzed to detect scarring or fibrosis by measuring the extracellular volume (ECV), the space between cells.

If successful, PCCT could provide detailed anatomical, functional, and tissue information in a single non invasive examination, offering a "one stop shop" for comprehensive heart assessment.

Inclusion Criteria:

• Patients referred for TAVI planning CTA. Both sexes are eligible; equal sex distribution is not required. Age ≥ 60 years.

Exclusion Criteria:

- Hemodynamic or rhythm related conditions: Systolic blood pressure < 90 mmHg. Bradycardia: < 45 beats/min. Persistent AV block II-III. Sick sinus syndrome. Prolonged QT interval. Atrial fibrillation. Severe heart failure: NYHA class IV.

Contrast or kidney relaterad factors: Previous allergic reaction to iodinated or gadolinium contrast or history of contrast induced nephropathy. Impaired renal function: eGFR < 45 mL/min/1.73 m².

Implants or devices: Metallic implants or devices in the imaging area, e.g., pacemaker. Medication: Persantin (dipyridamole), Theophyllamine, Fevarin (fluvoxamine).