Microvascular Resistance Reserve and Prognosis After Heart Transplantation

Area of Science:

• Cardiology
• Transplant Medicine
• Vascular Physiology

Background:

• Impaired microcirculatory function post-heart transplant is linked to acute cellular rejection.
• Microvascular resistance reserve (MRR) is a novel index for microvascular function, yet unvalidated in transplanted hearts.

Purpose of the Study:

• To investigate the prognostic impact of MRR in heart transplant recipients.
• To assess if MRR can predict adverse outcomes like death or acute cellular rejection.

Main Methods:

• Prospective enrollment of 154 heart transplant recipients.
• Invasive coronary physiological assessment including MRR, index of microcirculatory resistance, and fractional flow reserve 1 month post-transplant.
• Primary outcome: composite of death or biopsy-proven acute cellular rejection (grade ≥ 2R).

Main Results:

• 22.1% of patients exhibited impaired microcirculatory function (MRR ≤3.0).
• Impaired MRR was associated with significantly increased risk for death or acute cellular rejection (adjusted HR: 5.31).
• MRR independently predicted adverse outcomes, irrespective of epicardial stenosis or elevated microcirculatory resistance.

Conclusions:

• Early assessment of microcirculatory function using MRR identifies heart transplant patients at high risk for death or acute cellular rejection.
• MRR serves as a valuable prognostic marker in heart transplantation.
• Findings support the routine use of MRR in post-transplant cardiac assessment.