Table 4.
Summary of various techniques used for assessing coronary physiology.
| Technique | Invasive /Non-invasive & Method | Advantages | Disadvantages | ||
|---|---|---|---|---|---|
| Surrogate indices of coronary/myocardial blood flow in the catheterization laboratory | |||||
| Coronary flow velocity reserve (CFVR) |
Thermodilution/Doppler coronary wire | Can assess coronary stenosis and microcirculation | Cannot distinguish between microvascular disease and coronary stenosis Affected by hemodynamic conditions |
||
| Fractional Flow reserve (FFR) |
Pressure sensitive coronary wire | Can assess significance of coronary stenosis. Robust evidence base for FFR guided revascularization. Reproducible. |
Cannot assess microcirculation. Influenced by conditions causing high microvascular resistance | ||
| Instantaneous wave_Free ratio (iFR) |
Pressure sensitive coronary wire | Good correlation with FFR at extreme values of FFR at assessing coronary stenoses. Avoids the use of adenosine. Recent large trials prove non-inferiority with FFR |
Cannot assess microcirculation. Not very accurate at intermediate values of FFR. | ||
| Index of microcirculatory resistance (IMR) | Thermodilution | Can assess microcirculation. | Cannot assess coronary stenoses. | ||
| Non-invasive methods of myocardial flow quantification | |||||
| Positron emission tomography (PET) | Non-invasive, uses radioactive tracer | Able to quantify regional myocardial blood flow accurately | Limited clinical utility as not available for decision making in the catheterization laboratory. Not widely available |
||
| Cardiac magnetic resonance (CMR) | Non-invasive, no ionizing radiation | High spatial resolution. CMR sequences have been shown to be able to calculate myocardial blood flow. |
Non-volumetric ventricular imaging, relatively complex post processing steps. Limited clinical utility as not available in the catheterization laboratory. Still a research tool. |
||
| Invasive methods of coronary flow quantification in the catheterization laboratory | |||||
| TIMI myocardial perfusion grade (TMPG) | Invasive but no need for coronary wire | Easily available, semi-quantitative tool for assessing myocardial perfusion. | Can be subjective. It is a crude method | ||
| Doppler wire method of coronary flow calculation | Doppler coronary wire | Coronary flow calculation using flow velocity from Doppler wire | Operator dependent. Lacks reproducibility |
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| Thermodilution method of volumetric coronary flow measurement | Continuous thermodilution | Volumetric coronary blood flow measurements | Cannot distinguish between coronary stenosis and micro circulation. Need for specially designed infusion catheter | ||