Coronary autoregulation and assessment of stenosis severity without pharmacological vasodilation

Area of Science:

• Cardiology
• Physiology

Background:

• Pharmacological stress agents are traditionally used to assess myocardial ischemia by evaluating coronary blood flow and myocardial perfusion.
• These agents aim to exhaust cardiac compensation mechanisms, but alternative methods are emerging.

Purpose of the Study:

• To review diagnostic modalities that quantify myocardial ischemia without pharmacological stress.
• To elucidate the theoretical underpinnings and clinical implications of vasodilator-free assessments.

Main Methods:

• Review of three modalities: myocardial contrast echocardiography, myocardial blood volume imaging, and invasive coronary pressure measurement.
• Focus on the instantaneous wave-free ratio (iFR) and its application in assessing coronary stenosis significance.
• Exploration of the physiological principles of coronary autoregulation and arteriogenesis.

Main Results:

• Three vasodilator-free modalities exist for quantifying myocardial ischemia.
• The instantaneous wave-free ratio (iFR) is clinically applicable and effective in determining the hemodynamic significance of coronary stenoses.
• Large randomized trials support the efficacy of iFR in over 4500 patients.

Conclusions:

• Myocardial ischemia can be assessed without pharmacological stress using specific imaging and pressure measurement techniques.
• The instantaneous wave-free ratio (iFR) offers a robust, evidence-based approach for functional stenosis assessment under resting conditions.
• Understanding coronary autoregulation and arteriogenesis is key to these vasodilator-free diagnostic strategies.