Effectively Screening PAD Patients for CLI

Hello and welcome to the September edition of Vascular Disease Management. I have decided to comment on the submission by Dainis Krievins and colleagues about the high prevalence of asymptomatic ischemia-producing coronary stenosis in patients with critical limb ischemia: anatomic and functional assessment with coronary CT-derived fractional flow reserve (FFRCT).

There has been great debate as to what constitutes an ideal cardiovascular evaluation of patients presenting with peripheral arterial disease (PAD). Most of this debate has been centered around the evaluation of patients with planned vascular interventional or surgical procedures. These studies have primarily been centered around the safety of proceeding with the surgery or intervention but have not addressed the issue of avoiding subsequent long-term cardiovascular mortality. I think the debate should widen to include all patients diagnosed with any form of PAD as multiple studies have demonstrated that PAD is associated with high rates of subsequent cardiovascular mortality. The poor long-term survival is predomi- nately secondary to subsequent ischemic cardiac events. Patients with PAD may not experience angina secondary to diminished exercise capacity or faulty angi- nal warning related to diabetes mellitus which is highly prevalent in this patient cohort. In my opinion the debate should not center on whether or not the patient will survive a surgical or interventional procedure out to thirty days, but should also center on patient survival in the ensuing five-year period.

Present screening methods utilized to evaluate patients with PAD have substantial limitations. Exercise based studies are suboptimal in most patients as exercise capacity is limited. Studies utilizing chemical provocation only determine if there is ischemia at a single point in time and do not have the capability of distinguishing those patients who have completely normal coronary anatomy and do not require extensive follow-up from those who have significant coronary disease but may not yet have associated ischemia but need careful subsequent monitoring. Chemical provocation is poorly tolerated by many patients. CTA alone provides anatomical definition but does not reveal the physiological significance of lesions. CTA is limited by the need to administer iodinated contrast (which has risk of allergic reactions and contrast induced nephropathy) and is of limited utility in those with markedly elevated calcium scores because of blooming artifact. Coronary angiography is invasive, is associated with bleeding risk and the risk of contrast administration, is expensive, and doesn’t give physiological information without the risk associated with traversing the coronary arteries. FFRCT is associated with the same risk as CTA but has the advantage of providing not just anatomical delineation but physiological significance of the coronary obstructive disease as well. FFRCT has been validated in patients with coronary symptoms to correlate with invasive physiological studies. I suspect that the FFRCT studies may be less accurate in patients with congestive heart failure but those patients may warrant invasive investigation based on congestive heart failure. FFRCT will have limitations where there is severe coronary calcification. It is my opinion that FFRCT has great promise in evaluating patients with no symptoms from underlying coronary artery disease. The images of obstructive coronary disease when shown to the patient can motivate behavioral change improving medication and follow-up compliance. The physiological data may lead to appropriate revascularization.

This report in patients presenting with critical limb ischemia and no coronary symptoms demonstrated evidence of asymptomatic ischemia producing coronary artery stenoses in 77% of the entire cohort with multivessel ischemia noted in 42%. The study is limited as the patient cohort is small, is single center, and is limited to patients presenting with critical limb ischemia. Larger multicenter studies are needed including patients with asymptomatic PAD, those with claudication only, and those with aneurysmal disease. Long term follow-up is necessary to determine if this modality can influence what is presently dismal five-year morbidity and mortality outcomes. I believe that this relatively non-invasive technology has profound potential to improve what are presently suboptimal outcomes in patients presenting with PAD.