Myocardial Mass Determination by FFRct and Absolute Coronary Blood Flow

Although knowledge about the myocardial mass (in grams) of the different territories belonging to the major coronary arteries, is of clinical importance to estimate risk of coronary interventions (PCI, CABG) and to determine area of necrosis after myocardial infarction, no invasive methodology has been available so far for reliable assessment of mass.

Especially in the setting of percutaneous coronary intervention (PCI), it would be valuable to have information about the absolute and relative myocardial mass distal to the location where the intervention is planned. Such information is valuable for risk estimation and can also be helpful in multivessel disease to determine the most adequate way of revascularization.

Both MRI and CT scanning have claimed to be able to estimate myocardial mass non-invasively, but by the lack of any gold standard, none of these methods could be validated in vivo so far.

A relatively new development in CT technology is the calculation of fractional flow reserve (FFR) by CT scanning, according to a sophisticated algorithm developed by Heartflow Inc. One of the baseline assumptions in that algorithm is that myocardial mass is proportional to resting blood flow, which seems a plausible assumption from a rational physiological point of view.

More recently, invasive calculation of absolute blood flow has become possible as well as resistance measurement of the (microcirculation of the) myocardium.

Using that invasive technology (explained in the appendix to this protocol), it can be assumed that measuring absolute maximum blood flow in a coronary artery as well as fractional flow reserve for different territories or for different spots within one major coronary artery, provides a basis for relative mass calculation. The background for performing the present study is to compare these mass calculations by CT scanning and by invasive measurements, thereby corroborating both methods.

Inclusion criteria

• Presence of multivessel coronary disease with an indication for multivessel FFR and/or PCI or patients with single vessel disease scheduled for FFR/PCI of that single coronary artery
• Availability of a coronary CT scan performed prior to the scheduled invasive investigation. The time difference between the CT scan and the invasive exam should be less than 3 months.
• Focal lesions only
• Normal left ventricular function
• Age < 75 years
• Note: previous uncomplicated PCI in any of the coronary arteries is permitted

Exclusion criteria

• Inability to give informed consent
• Diffuse coronary disease
• Tortuous or calcified arteries interfering with reliable invasive FFR assessment
• Previous myocardial infarction or ejection fraction less than 60% by echocardiography or ventriculography or less than 50% by nuclear methods
• Atrial fibrillation interfering with high quality coronary CT scanning
• Contra-indications for CT scanning
• Left main stenosis
• Age > 75 years
• Pregnancy or desired pregnancy in the future