FFRCT May Herald a Paradigm Change in Evaluating Patients for Critical Myocardial Ischemia

Hello, and welcome to the February issue of Vascular Disease Management. There are several excellent articles and case reports in this edition. I have chosen to comment on the case report by Krievins and colleagues on the utilization of fractional flow reserve-computed tomography (FFR_CT) to identify critical myocardial ischemia in a patient with no cardiac symptoms. This patient presented with critical limb ischemia (CLI) that mandated urgent peripheral revascularization secondary to ischemia and a rapidly enlarging femoral pseudoaneurysm. In this case, FFR_CT was performed despite an elevated calcium score. The patient was noted to have critical multivessel coronary artery disease with abnormal FFR values in all of the major epicardial coronary arteries. The patient’s peripheral vascular disease was urgently treated with open surgical technique utilizing cardioprotective measures and medications. The patient was subsequently treated with multivessel coronary artery intervention in an elective setting. 

I have chosen to comment on this case presentation not only to highlight the potential of FFR_CT  to identify silent coronary ischemia and the arteries causing that ischemia, but to also highlight the need for some form of evaluation of silent myocardial ischemia in patients presenting with CLI. These patients often do not experience angina, as exercise is profoundly limited due to leg ischemia, and many have diabetes, which commonly results in impaired anginal warning. FFR_CT  is an excellent modality that identifies functional and anatomical abnormalities, but it may be limited in patients with critical renal impairment, as FFR_CT requires contrast administration and adequate imaging. Extensive coronary calcium or high resting heart rates may limit ideal imaging, but adequate results are often obtained even in patients with calcium scores previously deemed to preclude effective CTA angiography. In cases in which FFR_CT is not appropriate, procedures such as cardiac PET scans and infusion-based myocardial perfusion scans can be utilized to identify physiological ischemia in patients who cannot exercise. These scans only determine regional, not specific, artery-mediated ischemia. 

In my opinion, it is crucial that patients presenting with CLI are assessed for myocardial ischemia, not to determine if they will make it through a surgical or interventional procedure, but to improve subsequent survival, as several studies have demonstrated 2-year mortality rates of approximately 50% in patients who have presented with CLI, with the overwhelming majority dying from myocardial ischemia. Saving legs but allowing patients to die prematurely from potentially avoidable myocardial ischemic events is simply not an acceptable option in light of presently available technology. Evaluation of silent myocardial ischemia may result in immediate life-saving revascularization, but equally important, it can direct appropriate aggressive medical therapy to limit ischemia and to decrease the likelihood of atherosclerotic disease progression. If silent ischemia is identified, it may facilitate adherence to medical therapy and facilitate greater compliance with follow-up evaluations. Identification of silent ischemia may also prompt patients to seek medical attention earlier if symptoms do occur. 

The ability of interventionists and surgeons to revascularize critically ischemic limbs has improved with clearly demonstrated improved rates of limb salvage. We must now demonstrate that we can not only save limbs but can also improve life expectancy beyond what has been demonstrated with limb salvage alone. Reports demonstrate that critical coronary disease is present in far more than 50% of patients presenting with CLI. Myocardial ischemia is the most likely cause of premature death in these patients. In my opinion, it is no longer ethical to fail to evaluate these high-risk patients for myocardial ischemia and to initiate aggressive medical therapy or direct revascularization when critical myocardial ischemia is identified. FFR_CT may facilitate this paradigm change.